Date: Wed, 19 Jul 1995 10:43:57 -0400 From: SidLloyd@aol.com Subject: AeroCanard flys! Just got a phone call from Jeff Russell, owner of AeroCad and manufacturer of Cozy IV pre-fab parts and their own kit- the Aerocanard (basically a slightly wider in the rear Cozy IV). He had an exciting first flight of the Aerocanard and now has about 3 hours on it. His first flight initially went well. Rotation speed was as expected and climb rate was excellent at about 1700 fpm. The larger ailerons gave him roll rates closer to the Bearkut than the Cozy and the larger rudders were very authoratative. The excitement came when he touched down. Landing speed was about 85 knots and when he began braking there was an immediate and violent shudder in the right main gear. It was pulling him to the right and he applied hard left brake to compensate. He estimates that the main gear was vibrating through an amplitude of about 6 inches. The right tube blew but the tire remained on the rim. Upon examination, there was no damage done to the airframe or the tire. The only damage was the blown tube. In checking the right rotor, it was discovered that it had at least 1/16" runout! The left rotor had 1/32". *Lesson learned - always check brake rotor runout prior to first flight. He had done high speed taxi tests with no problem but of course hadn't got up to this speed. Cleveland says their maximum allowable runout is 20 thousandths. I think that is way too much. Aren't auto brake rotors around 3 thousandths or so? Anyway, he will continue testing when the new Cleveland rotors are received (and measured for runout!) He only expanded the flight envelope to about 150 during the flight but reported that it was extremely stable and responsive. Sid Date: Wed, 19 Jul 1995 13:15:13 -0400 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) Subject: Re: SHADOW'S OBITUARY Over the past few months I have been investigating the braking capacity of the Cozy MK IV and I find it to be inadequate. Keith's unfortunate accident prompted me to investigate the MK III braking system and I find that it uses the same components. The Cleveland brakes recommended for both the MK III and the MK IV are rated for a maximum kinetic energy capacity of 192,000 ft lbs per wheel (384,000 ft lbs total). Keith says he was operating within the recommended C of G range and at a weight of 1600 lbs. His take off trim speed was set at 80 kts which is what Nat recommends for the MK IV (A Message from Nat... " I usually wait until I see 80 kts. And then I rotate, regardless of c.g.") The total energy that Keith had, was 453,327 ft lbs or some 18% over the maximum rated capacity for those brakes. It is small wonder that something like this happened. How does someone design an aircraft with hard data, Max take off weight, rotation speed etc, and include brakes that are clearly out of spec. Isn't this negligence? Keith has a broken aeroplane because of this. To compound the situation these same brakes are used in the design of the MK IV. Now when you do the calculations for the MK IV the aborted take off energy at gross weight (2050 lbs) is 580,825 ft lbs which is some 51% above the maximum capacity. The result in either case is either the accident that Keith had, or a potential wheel fire. Incidentally Keith has also had one of those in the past, and wheel fire directly under a fuel tank is no fun. (Note: The max aborted take off weight using the Clevelands is 1355 lbs for the MK III & MK IV alike. 170 lb pilot and 130 lb of fuel. This makes it a single place aeroplane dosn't it?) The availability of high dissipation brakes may have precluded Nat from designing an appropriate system for the three place but Matco do have a heavyweight unit that will meet the requirement for the MK IV. I am expecting a MANDATE from Co-z Development Corp. to this effect. For those of you who are interested in incorporating adequate braking for the MK IV I suggest that you give J.D.Newman (Infinity Aerospace) a call (619) 448 5103 (72124.347@compuserve.com) he sells the whole kit at a good price: There have been a couple of posts saying Nat recommends retracting the nose gear or take off roll should be increased. If these are not rumour then these should be in the POH as appropriate procedure, shouldn't they? This is my $0.02 worth. Phillip Johnson Date: Wed, 19 Jul 95 13:33:59 EDT Subject: Brakes for a Cozy MKIV Dear Mr. Newman; I am presently in the early stages of constructing a COZY MKIV. It has been brought to my attention that you sell a heavy duty brake kit which could be used in this aircraft. I would be very interested in receiving any information (either via e-mail or snail-mail) you have on this kit, notably; 1) Who is the manufacturer? 2) What is the kit (or seperate component) price? 3) What is included in the kit (wheels, tubes, tires, brakes, etc.)? 4) What is the rated energy absorption for these brakes? Thank you very much for your time and attention. My home address is: Marc J. Zeitlin 47 Flint Rd. Acton, Ma. 01720 Please send any mail to that address. Thanks again. -- Marc J. Zeitlin E-Mail: marcz@an.hp.com Date: Wed, 19 Jul 1995 15:34:56 -0400 From: SidLloyd@aol.com Subject: CozyIV brakes In early discussions with AeroCad, I decided to go with the magnesium/aluminum 600X6 Cleveland wheel & brake kit that the Defiant uses (available from Wick's, pn:CWB199-133X). The brakes are double puck. It did cost a little more than the 500X5 kit as specified in the plans. I measured the difference in radius and mounted them (if I remember correctly) 1.5" higher on the gear struts in order to maintain the same takeoff AOA. Yes, it adds some weight, but I believe it is worth the trade-off. A also exchanged the vertical master cylinders for some horizontal ones to fit my brake setup. BTW- they have a static capacity of 2500#. I don't have the other specs, but the single puck 600X6 has a static capacity of 1500#, limit load of 6000#, and kinetic energy rating capacity of 200,000 foot/lb. I would assume the Defiant ones would be commensurately higher. Sid From: Lee Devlin Subject: Cozy brakes Date: Wed, 19 Jul 95 17:05:29 MDT Phillip wrote: > Isn't this negligence? Keith has a broken aeroplane because of > this. .. That's 'legal talk' here in the U.S. and I'm not sure I like the implication of it. Maybe you think that Nat should pay for the airplane? (and maybe some emotional distress too?) Keith already stated that he was 500' past the safe stopping distance when he aborted so he had about 1000' of runway to stop the plane which was moving at over 90 mph. That's very much akin to making a hot landing into a 1000' strip. No matter how big a set of brakes you put on it, there's a limit to how fast that energy can be absorbed. I am very sorry for Keith's loss and think that his posting was full of good information for us to think about and I'm happy he chose to share it with us. But to blame it all on the insufficiency of the brakes misses other important points that Keith made in his posting. If I had my Colt moving at 90 mph, it would be impossible to stop it in 1000' and its aerodynamics are a lot more similar to a barn door than they are to a slippery aiplane like the Cozy. > The availability of high dissipation brakes may have precluded Nat > from designing an appropriate system for the three place but Matco do > have a heavyweight unit that will meet the requirement for the MK IV. > I am expecting a MANDATE from Co-z Development Corp. to this effect. If you want to use Matco, you should read the recent posting that a builder put on r.a.homebuilt about the Seawind. (If your read the whole thing you'll be glad you're not building one.) Here's a very small excerpt related to Matco: :9. The brakes are very poor. The Seawind uses Matco brakes. Have you ever :heard of these brakes. Cleveland, maybe, but Matco??. Must be a reason, :could it be that they are cheaper. Imagine that. Anyway, the Matco's are :designed for a 2200 lb. airplane, not a 3500 lb. airplane. (We use :Cleveland's). > For those of you who are interested in incorporating adequate braking > for the MK IV I suggest that you give J.D.Newman (Infinity Aerospace) > a call (619) 448 5103 (72124.347@compuserve.com) he sells the whole > kit at a good price: Isn't Infinity the company that was selling retractable gear for any 'EZ style' aircraft before they even test flew them? I've been thinking about the ft-lb rating of the brakes and I'm wondering how these things get so hot so as to melt gear and blow tires, etc.. Maybe one of you guys can help me with my calculations. Say a brake needs to handle about 300,000 ft-lb of kinetic energy. I assume that rating is a thermal limit on the disks. There are 770 ft-lb of mechanical energy per BTU so that's about 385 BTU that needs to be dissipated per brake. The specific heat capacity of steel is .116 BTU/lb-F. Assuming you have about .5 lb of steel in the disk/pad interface (which seems about right for a 6" disk as steel's specific gravity is .283 lb/in^3), its temperature rise should only be around 80 degrees F (and that's assuming no losses!). I think this number is off by at least a factor of 5. I've gone through this several different ways and still come up with low temperature rise numbers. Maybe the temperature gradients are much higher than I am thinking. Anyone see a mistake? Lee Date: Wed, 19 Jul 1995 22:07:57 -0500 From: Tom Barclay Subject: brakes Tho I am given to levity, my Cozy will *always* be toward the max of front cg conditions; so brakes are a subject near and dear to my heart, feet, ankles, ribs, etc. Not to be in the least funny about this, Lee; did your calculations take into account the total braking _system_, i.e., heat gain in tires due to friction with the runway? I'd suspect some rather large gains are possible thru induction-like effects with tire friction. I look forward to better-learned comments. Tom Barclay Date: Thu, 20 Jul 1995 00:55:21 -0400 From: Danky01@aol.com Subject: cozy IV brakes Phillip wrote: > Isn't this negligence? Keith has a broken aeroplane because of > this. .. Lee wrote: >That's 'legal talk' here in the U.S. and I'm not sure I like the >implication of it. Maybe you think that Nat should pay for the >airplane? < lots of stuff deleted> Ok guys lets all take a deep breath and count to 10 please. Thank you To summarize, Keith Spreuer and Phillip Johnson are of the opinion that the cozy brakes are too small. Lee Devlin's calculations would indicate the brakes are adequate. Sid Lloyd and Jeff Russell are using larger brakes, so it seems they also think the spec brakes are too small. Keith also has one less airplane today, man that must hurt bad!! We could argue over the math forever and a day or we could do some true to life testing here. I say we find a cozy 3 and a cozy 4 load them to gross, put them on the longest runway we can find, run them up to 80 KTAS and stand on the brakes as hard as we can. Measure how many feet it takes to stop. It would seem that there are enough of both of these flying that we could find some volunteers and report it to this news group for all to read. Now for my guess. I guess that the brakes are too small.It seems to me that I have read about other canard or cozy builders that have had the same problem as Keith has experienced. I would hope that the person doing this test would do it with the wheel pants off, the first time, so they can see if the discs are red hot at the end of the runway. If I am wrong and the brakes pass this test then put the pants back on ( after the brakes cool all the way down ) and do the test again. Most of the canards that I have seen flying have very tight wheel pants and very little ventilation in them. This could be a major factor in the performance of the brakes. I would also like to see a test of a cozy with the larger brakes, measure the stopping distance from 80 KTAS at gross and compare this to the standard spec brakes stopping distance. All tests must be at the same weight. It would also be good to know how much more the defiant type brakes weigh than the cozy IV brakes. If we knew all of this ( I know this is asking a lot ) we then could measure the tradeoffs and decide which way to go. Sid, maybe you could talk to Jeff Russell about some of this?? Any volunters out there with a cozy 3 or 4 feel like testing ??? Kyle Dansie Date: Thu, 20 Jul 1995 09:44:37 -0400 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) Subject: Cozy Brakes Ok guys I'll explain my motive for using the term negligence. I know Keith reasonably well and I don't believe that he would sue for an issue like this, I'm a Brit and we don't sue for anything, in fact I left Nat a get out intentionally when I said "The availability of high dissipation brakes may have precluded Nat from designing an appropriate system for the three place" In the past I have had the same response from Nat that Keith has had i.e. "put down, told that 1200 (possibly an exaggeration) other builders didn't have my problem," My real concern is that brakes are available that do meet the requirement and there are many more people out there building Cozy's than those in this group. Many of these builders are the Vanilla builders i.e. no change acceptable. These builders will continue to install inadequate brakes unless Nat issues a directive. Nat receives a copy of most of the posts from this group and I hope the choice of words "negligence" will make him do something because the next accident victim may not be as complacent as Keith. In doing this I hope to reach out to all of the builders, MK III's and MK IV's, not just those in the group. Kyle Suggests some testing, good idea but we shouldn't have to do this. Cleveland say, when they give out their figures, that they are inadequate. Ron Kid says "This is a HOMEBUILT airplane that we build in our garages!" If alternative brakes were not available I would not have raised the issue but since they are available ...... Lee Devlin writes > are very poor. The Seawind uses Matco brakes. Have you ever :heard > of these brakes. Cleveland, maybe, but Matco??. Must be a reason, > :could it be that they are cheaper. Imagine that. Anyway, the > Matco's are :designed for a 2200 lb. airplane, not a 3500 lb. > airplane. (We use :Cleveland's)." Matco used to be sold under the name of Roseham or a name similar to that. They came from the light weight ultralight arena but over the years they have been developing heavier and heavier duty brakes. Their latest brake is a three puck device and is very substantial unlike the older units that were known for their lack of performance. A friend of mine uses these on a long eze and finds them very powerful and free of fade. Lee also writes > Isn't Infinity the company that was selling retractable gear for > any 'EZ style' aircraft before they even test flew them? Yes Infinity is the company selling retracts but no they had flown them before they started selling them. There was a development phase between prototype and production. Didn't Nat do this when he sold the MK IV plans? I remember ordering what I was led to believe was a full set of plans only to receive section one with no explanation. I have come to expect this as normal. Remember this is Phil writing this so you can all expect me to be direct and not diplomatic. I'm looking for rational argument and debate not a slanging match. Phillip Johnson. From: Marc J. Zeitlin Subject: Re: Cozy brakes Date: Thu, 20 Jul 95 10:58:31 EDT People; I spent a bit of time last night going through the Wicks and Aircraft Spruce catalogs, looking at brakes, wheels, etc. Of course, the only Cleveland brakes without a energy absorption rating were the "6.00x6 Defiant double puck" brakes, but IF we can do some scaling, we can probably estimate about a 300K ft-lb rating, given the ratings of the other brakes, and the weight of a Defiant. One of us should probably give Cleveland a call. With respect to Matco, they used to be Rosenhan, which has been around a long time. I've never used their stuff, but other than one bad report from Seaturbine regarding the seriously overloaded brakes on the Seawind, I've not heard anyone say anything bad about them - I think we need to hear more about their use in a REASONABLE installation. Lee wrote: >Say a brake needs to handle about 300,000 ft-lb of kinetic energy. "a brake needs to handle about 300,000 ft-lb of kinetic energy". (That's a joke, son - we need a bit of humor in this topic!!!). >................... I >assume that rating is a thermal limit on the disks. There are 770 ft-lb >of mechanical energy per BTU so that's about 385 BTU that needs to be >dissipated per brake. Well, its 778.2 ft-lb/BTU according to Marks Handbook, but that's picking nits. >............. The specific heat capacity of steel is .116 >BTU/lb-F. Assuming you have about .5 lb of steel in the disk/pad >interface (which seems about right for a 6" disk as steel's specific >gravity is .283 lb/in^3) That seems low for weight of the disk - after looking at the replacement disks in Wicks last night, I'd guess closer to 2 lbs/disk. The Defiant kit weighs in at about 15 lbs for the wheels, disks, brakes, pads, etc. (not including the master cylinders). >.................., its temperature rise should only be around 80 >degrees F (and that's assuming no losses!). I think this number is off >by at least a factor of 5. I've gone through this several different >ways and still come up with low temperature rise numbers. Maybe the >temperature gradients are much higher than I am thinking. Anyone see a >mistake? Well, let's assume the 0.5 lb rotor (assuming all the heat goes into the rotor, which it doesn't). Then: 385 BTU = .116 BTU/lb-F * 0.5 lb * dT deg F dT = 6,638 deg F This is a bit more than 80 deg F :-). With the 2 lb rotor system: dT = 1,659 deg F Only slightly more palatable - obviously, this is NOT what's happening. If we assume (also not correct, but probably closer) that the energy heats up the disk, the pads, the brake, and the wheel, we get: 385 BTU = .116 BTU/lb-F * 15 lb * dT deg F dT = 221 deg F Now, this is too low, but at least we're in the right order of magnitude. The rotor and brake heats up more, and the wheel less, and there's dissapation to the air while all the heating is going on. -- Marc J. Zeitlin E-Mail: marcz@an.hp.com From: Lee Devlin Subject: Re: Cozy brakes Date: Thu, 20 Jul 95 10:01:58 MDT Marc wrote: > This is a bit more than 80 deg F :-). > > With the 2 lb rotor system: > > dT = 1,659 deg F > > Only slightly more palatable - obviously, this is NOT what's happening. > If we assume (also not correct, but probably closer) that the energy > heats up the disk, the pads, the brake, and the wheel, we get: > > 385 BTU = .116 BTU/lb-F * 15 lb * dT deg F > > dT = 221 deg F > > Now, this is too low, but at least we're in the right order of > magnitude. The rotor and brake heats up more, and the wheel less, and > there's dissapation to the air while all the heating is going on. Thanks for finding my mistake, Marc. Multipling where I should have been dividing...sheesh. The entire braking process, given a speed of 90 mph with a distance of 1000', must take less than 15 seconds to be successful (assuming uniform decelleration). That means that the rate of energy absorbtion is about 92,400 BTU/hr. That's on par with the heating rate of a household furnace. I suspect with such a short amount of time, it's not possible to heat up all of the surrounding mass so there will be a pretty steep temperature gradient in the parts making up the braking system. It seems to me that increasing the rating of the braking system is most easily done by adding material (thickness) to the rotors. It's a matter deciding how much weight you want to carry around that you will need only in the case of an emergency. You could also leave off the wheel fairings for additional cooling but you'll lose 10-15 mph of cruise speed. The real crux of the problem is that we have a very high speed mass (the plane) with small wheels that need to get rid of a lot of energy in a very short time. As most of you are aware, the kinetic energy is proportional to the square of the landing speed so a plane moving at 90 mph will have about 60% more energy than one that touches down at 70 mph, the weights being equal. Since we need a lot of runway to take off already, a long landing roll is not really a limitation since we wouldn't intentionally put it down on a 1000' strip because we couldn't take off from it. It does however, make a big difference in the case of a forced landing or aborted takeoff. This is one of the trade-offs I realize I am making to go fast. Retracting the nose gear offers an interesting option for the Cozy. I know from experience that trying to apply the brakes when the plane is floating doesn't work well because you have very little normal force between the wheel/ground interface. If you were to deliberately retract the nosewheel, the force of the wing will push the mains down on to the surface as well as give you a third point in which to absorb braking friction. There'd be some loss of control, but it may be more acceptable than the alternative. It's probably only useful on a hard surface, however, due to a increased possiblity of flipping the aircraft in the case of an off-airport landing. I have a friend with a Lancair who flies it out of a 2400 paved strip. In the first year, he went through 4 pairs of tires from putting flat spots on the them so this problem is not unique to the Cozy. Lee Devlin Date: Thu, 20 Jul 1995 13:07:24 -0400 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) Subject: Re Cozy Brakes The heat energy is lost from more than the just disc and wheel. A significant part of the heat is dissipated through the calliper itself. The calliper is in a better airstream than much of the disk and the multiple pucks, conduct away much of the heat into the calliper from which the heat is extracted through forced air cooling. Heavy duty brakes use multiple pucks for this reason. At the end of the day I guess that the brake manufacturers, be they Cleveland, Matco or whoever, know what limits the capacity and design accordingly. When they give a max limit it means that it should not be exceeded. The POH gives the landing speed for 1800 lb as 70 kts IAS. This is assumed to be IAS not TAS or GS. At 1900 lbs which is the maximum landing weight given in the POH the landing speed increases to about 73 kts IAS. So with the exception of Canadian winters, airports at or below sea level and windy days. The GS is going to be higher than this figure. Thus the landing energy is no less than 224,000 ft lbs per wheel which is in excess of the 192,000 quoted for the standard brakes. A braking system should be designed with some safety margin since as they age things are only going to get worse. BTW does any one know what limits the max landing weight on the Cozy? Is it the brakes, landing gear or what? Phillip Johnson From: Lee Devlin Subject: Cozy Brakes Date: Thu, 20 Jul 95 14:05:13 MDT Phillip wrote: > Heavy duty brakes use multiple pucks for this reason. At the end of > the day I guess that the brake manufacturers, be they Cleveland, Matco > or whoever, know what limits the capacity and design accordingly. When > they give a max limit it means that it should not be exceeded. > The POH gives the landing speed for 1800 lb as 70 kts IAS. This is > assumed to be IAS not TAS or GS. At 1900 lbs which is the maximum > landing weight given in the POH the landing speed increases to about > 73 kts IAS. So with the exception of Canadian winters, airports at or > below sea level and windy days. The GS is going to be higher than this > figure. Thus the landing energy is no less than 224,000 ft lbs per > wheel which is in excess of the 192,000 quoted for the standard > brakes. A braking system should be designed with some safety margin > since as they age things are only going to get worse. These are all good points. My field's altitude is 4650 ft. This means that I'll probably have an extra 10% of ground speed which is the real number I need to use to calculate energy. I also have 15% less cooling from convection due to a lower air pressure. Another thing no one has yet mentioned which works in our favor is that the aircraft has significant wind resistance and rolling resistance at 90 mph. For instance, how much power does it take to move a Cozy at 90 mph? 20 HP? 30HP? A motorcycle needs about 30 HP or more to go 90 mph and it has only about 1/4-1/2 the weight of a Cozy. The rate of power dissipation from the brakes (which is around 35 HP per wheel based on the 87,500 BTU/hr given in one of my earlier postings) is offset by the wind resistance and rolling resistince of the aircraft. This should be subtracted from the total energy that needs to be absorbed by the brakes. Granted, it drops off dramatically with speed, but then so does kinetic energy. Initially, it could be as high as the energy that the brakes are absorbing. I think the real question to be answered is how the specification of the energy rating is derived. Is it done on a test stand with a maximum allowable temperature rise? How much time is it allowed to absorb the energy? What effect does convection play in the test? All of these things are important to determining if the brakes are going to be sufficient or not. I apologize to the rest of the group if this discussion is bordering on pedantic, but I am finding it quite useful as I'll be in the market for wheels/brakes very soon. Lee Devlin From: Marc J. Zeitlin Subject: Cozy Brakes (fwd) Date: Thu, 20 Jul 95 16:52:06 EDT Lee writes: >Another thing no one has yet mentioned which works in our favor is that >the aircraft has significant wind resistance and rolling resistance at >90 mph. Don't count on this for too much. >...... For instance, how much power does it take to move a Cozy at 90 >mph? 20 HP? 30HP? Well, 180 HP gets you 220 mph, and drag power varies as the cube of the speed (to a first order approximation). So, you're looking at about 10-15 HP. >.............. A motorcycle needs about 30 HP or more to go 90 mph >and it has only about 1/4-1/2 the weight of a Cozy. Drag is what counts here, not weight. Runways are pretty flat - no potential energy change. >............... The rate of power >dissipation from the brakes (which is around 35 HP per wheel based on >the 87,500 BTU/hr given in one of my earlier postings) is offset by the >wind resistance and rolling resistince of the aircraft. This should be >subtracted from the total energy that needs to be absorbed by the >brakes. Granted, it drops off dramatically with speed, but then so does >kinetic energy. Initially, it could be as high as the energy that the >brakes are absorbing. The brakes don't absorb energy linearly, even if the decelleration is constant. They will absorb ~28 times as much energy in the first second of deceleration as in the last second. In the first second, they'll be absorbind an average of 132 HP/wheel, while in the last second, they'll ber absorbing about 5 HP/wheel. (If anyone cares to see the exact #'s, I can provide them, or I can leave it as an exercise for the student :-) ). Looks like the drag power absorbed is ~5% of the power absorbed by the brakes (12 HP/264 HP). Something, but not enough to count on for a lot of stopping power. Witness how poorly ShadowFax slowed down with only aerodynamic braking. This is, of course, the whole point of slippery aircraft :-). -- Marc J. Zeitlin E-Mail: marcz@an.hp.com (Smail3.1.28.1 #7) id m0sZ3Yt-0002lLC; Thu, 20 Jul 95 16:55 CDT with Novell_GroupWise; Thu, 20 Jul 1995 16:56:58 -0500 Date: Thu, 20 Jul 1995 17:01:13 -0500 From: Scott Christensen Subject: hp for 90MPH Marc writes: >Well, 180 HP gets you 220 mph, and drag power varies as the >cube of the speed (to a first order approximation). So, you're >looking at about 10-15 HP. 220 mph is not on the ground, so this is overlooking friction of the wheels. Scott From: Marc J. Zeitlin Subject: Cozy Brakes (fwd) Date: Thu, 20 Jul 95 23:38:52 EDT I wrote: >The brakes don't absorb energy linearly, even if the decelleration is >constant. They will absorb ~28 times as much energy in the first second >of deceleration as in the last second. In the first second, they'll be >absorbing an average of 132 HP/wheel, while in the last second, they'll >ber absorbing about 5 HP/wheel. (If anyone cares to see the exact #'s, >I can provide them, or I can leave it as an exercise for the student >:-) ). I should be more careful. Divide these #'s by two - I forgot to. (Thanks, Lee, for pointing that out). It's about 66 HP/wheel and 2.5 HP/wheel. >Looks like the drag power absorbed is ~5% of the power absorbed by the >brakes (12 HP/264 HP). This changes to ~10%. -- Marc J. Zeitlin E-Mail: marcz@an.hp.com Date: Fri, 21 Jul 1995 09:32:21 -0400 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) Subject: Re Cozy Brakes The aero dynamic drag indeed varies as the cube of the power for the same condition of lift. But on landing there is little or no lift so induced drag is further reduced. However on landing the landing brake is extended so this throws a spanner in the works with respect to estimating drag. Likewise the comparison of a motor cycle on the street Vs a landing cozy on a smooth runway is questionable. On another topic I managed to dig out the data on the Matco brakes and they are as follows: Matco 3 puck 338,000 ft lbs Matco 2 puck 283,000 ft lbs Cleveland 192,000 ft lbs At max landing weight of 1900 lbs then, for Lee, and anyone expecting to visit Lee at his elevation, they will need a landing speed of 80 kts. Their landing Kinetic energy is 270,000 ft lbs per brake but because of rolling resistance, drag etc this figure could be less if it were not for the loss in cooling caused by altitude (Thanks Lee I had forgotten that one). The latter two effects could offset each other. This suggests a minimum of the two puck design. My personal feeling is that the severity of Keith's accident could have been reduced significantly if the three puck device had been installed. I shall be using the three puck model in my Cozy since most airports in my area are typically 3000 to 3500 ft. One last point. The Matco design is a low profile so if you burst the tyre, the wheel rim protects the brake. I understand that the Cleveland can get ground away. I have not checked this for the Cleveland, this is hear say only, don't flame on this one. Phillip Johnson Date: Mon, 24 Jul 1995 08:29:42 -0400 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) Subject: Re Cozy Brakes Marc Writes > Does anyone other than Infinity sell the Matco brakes? I don't see > them in Aircraft Spruce or Wicks. Also, do they make a set to go > on 6.00x6 wheels as well as 5.00x5 ? I'm not sure but I called Matco on Friday evening to get hard data, and they said that Aircraft Spruce sold their product. I have not seen them in last years catalogue but maybe they have them in the new one which is issued at Oshkosh. Im not sure about the 6.00x6 wheels I think they probably do make them. Cleveland do make them and they have the double puck. Why do you want larger wheels, they will give more drag? Do you land on rough strips? BTW I looked in the late Steve Whitmans book on landing gear design. He has a section on brakes. He refers to the FAR's and they say that, for light aircraft there is no OBLIGATION to design for sufficient capacity for an aborted take off so I was wrong on that count. However the FAR's do ask for CONSERVATISM when designing the braking capacity for the worst case landing condition. They also recommend a complete strip down and check of the breaking system if the capacity is exceeded. (This is every landing over 1350 lbs using Clevelands.) Sorry to labour the point, but I wanted to be objective unlike my first post. Phillip Johnson Date: Wed, 26 Jul 1995 10:05:04 -0400 From: KSPREUER@aol.com Subject: Fwd: Cozy brakes In a message dated 95-07-26 01:46:55 EDT, K SPREUER writes: << Just for the record I have no thoughts of any law suite resulting from my accident. I do believe that with adequate brakes and 1000' I could stop given immediate reaction. I think the Matco brakes in the Seawind report must be a smaller model of Matco's line. I think Nat did reccomend the heavy duty brakes for the Cozy 3 place later on in the design but did not make it mandatory. I do believe the heavy duty are still too small for the Mark IV. Regardless of how much runway is left you should not be limitted by fading of the brakes. >> --------------------- Forwarded message: Subj: Re: Cozy brakes Date: 95-07-26 01:46:55 EDT From: K SPREUER Just for the record I have no thoughts of any law suite resulting from my accident. I do believe that with adequate brakes and 1000' I could stop given immediate reaction. I think the Matco brakes in the Seawind report must be a smaller model of Matco's line. I think Nat did reccomend the heavy duty brakes for the Cozy 3 place later on in the design but did not make it mandatory. I do believe the heavy duty are still too small for the Mark IV. Regardless of how much runway is left you should not be limitted by fading of the brakes. Date: Sat, 29 Jul 1995 18:50:48 -0700 (PDT) From: Eric Westland Subject: Brakes... I have followed the discussion on brakes with interest as I went with the recommended Clevelands. I am not qualified to comment on any of the calculations you folks have presented, but it has brought up a couple of questions as well as a comment. First, are the specifications for the Cleveland, Matco and Infinity brakes ever been independently confirmed or are we taking the word of the same people competing to sell us brakes? Secondly, I have some faith in the Cleveland and Matco numbers as they have been around for a while, but I question the Infinity numbers. I have never even seen their product and for all I know, it may be better than advertised, but they caught my eye when the stated that their Infinity 1 canard plane has a top speed of "460 m.p.h." (Kitplanes, Dec. 94). This is more than 100 m.p.h. faster than anything else in the homebuilt aircraft directory. Makes one wonder. Finally, a comment. I have resisted participating in any of the discussions concerning Nat. Nat can take care of himself when presented with information and if I have a question for him, I just pick up the phone. Never the less, I have no doubt whatsoever that Nat has recommended to us the best brakes that are available and that if something comes along later that is better, he will let us know. This has consistently been his practice and while none of us are perfect, Nat does a great job at making sure our planes are as safe, simple and as affordable to fly as they can be. Eric Date: Sun, 30 Jul 1995 21:04:57 -0400 From: KSPREUER@aol.com Subject: Re: Brakes... In a message dated 95-07-29 22:02:32 EDT, you write: > >First, are the specifications for the Cleveland, Matco and Infinity >brakes ever been independently confirmed or are we taking the word of the >same people competing to sell us brakes? > Just a couploe of points. Infinity does not make brake, they are a distributor for Matco. The numbers I've quoted are the advertised numbers by the manufactures. Verified?? I don't know. It would be nice if Nat recommended larger brakes. I don't know if he will or not. As I have noted before there is a large degree of not invented here syndrone. That is beside the point. There is not nearly enough history on the Mark IV (28%) heavier than Longs or 3 place Cozys. My note is to give early warning to those savey enough to listen to bitter experience. This is an ideal place to be a little conservative. It may be some time and maybe several accidents later before Nat decides to recommend larger brakes. In the mean time hundreds of builders are spending time and labor installing brakes that in my opinion are too small. Date: Mon, 31 Jul 1995 03:48:14 -0400 From: StetsonE@aol.com Subject: Matco Brakes With all the talk about brakes lately, I thought the reprint below might be informative. It's an article from the October 1992 edition of the Canard Pusher Newsletter about Matco brakes. It was written by Mike Melvill, who some of you probably know is a long-time employee of RAF, and now Scaled Composites: ------------------- Our airplane was the first Long-EZ to use the "heavy duty" Cleveland brakes, the 3/8" thick discs and the large diameter brake pad actuator. In fact, we flew for several years with these brakes before George Varga did the research through Cleveland's data sheets to come up with the current so called "heavy duty" brakes. The brakes we had came off Peter Garrison's "Melmoth" after it was destroyed in a bizarre accident at Orange County airport back in 1981 or '82. Recently, I installed some new brakes. These are designed by a VariEze builder/flyer, Phil Mattingly, who bought the business from Fred Rosenhaan. These brakes are quite different from the Cleveland design in that the 3/8" heavy duty disc is simply a flat disc that bolts to the wheel rim in 3 places. The brake assembly is a double puck arrangement, that is, each brake uses 4 brake pads and these are actuated by two hydraulic piston assemblies. The brakes are very powerful, smooth and, best of all, they seem to last a long time. I installed them 15 months ago, have over 250 hours of flight time on them and I still have not had to replace the brake linings! For me, that is remarkable. It seems I was always replacing the linings on my Clevelands. I have been extremely pleased with these Matco wheels and brakes (the wheels are slightly narrower than Cleveland 500x5 wheels and fit the Lamb tires better). You will have to purchase the whole set, including wheels, brakes and axles. Phil tells me this brake is standard equipment on some Glasair models and on the Venture. ------------------- I also recall an article within the past year in Sport Aviation (I think) about Matco, their products and history. Stet Elliott Perpetual Long-EZ builder Date: Wed, 2 Aug 1995 02:38:52 -0400 (EDT) From: Tech Support - Rick Subject: Brake thoughts I've talked to people throughout the Rutan community about the brake issues. Here they are almost unanimous. The Matco brakes will outbrake(?) anything Cleveland puts out. Life expectancy is about the same. However, changing the pads on the Matco's are a Royal Pain in the Behind! Cleveland are much easier in this regard. Most Vari-Eze owners don't like the fast stopping power of the Matco's, however the Long and Cozy crowd love them. Go figure. Basically, it boils down to preference and how short a field you will be landing in for most flights. Rick -002 More on this later. Date: Thu, 3 Aug 1995 11:34:47 -0400 From: Marcnadine@aol.com Subject: Re: Brake thoughts (Defiant type) Rick -002 writes: >The Matco brakes will outbrake(?) anything Cleveland puts out. Life >expectancy is about the same. When I was at OSH I hear that some builders were going to the Cleveland 6" brakes used on the DEFIANT with four pads per brake and the low-profile tires. . Do you know how they differ? Marc P. N425CZ Date: Thu, 3 Aug 1995 11:54:36 -0400 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) Subject: Re[2]: Brake thoughts (Defiant type) The four pads per brake are two puck devices. The Matco is a three puck device with six pads per brake. The six inch is a good wheel and will definitely give a better ride, but you pay for it in weight, cost and increased drag. Phillip Johnson PS not withstanding my above comments, the 6 inch Cleveland will meet the braking requirements. It becomes a judgement call and where you feel happiest. Cleveland parts are more readily available than Matco but more and more manufactures are using the Matco. Velocity are now using the three puck Matco so I guess there are here to stay. ______________________________ Reply Separator _________________________________ Subject: Re: Brake thoughts (Defiant type) Author: Marcnadine@aol.com at smtp_gway Date: 3/8/95 11:34 AM Rick -002 writes: >The Matco brakes will outbrake(?) anything Cleveland puts out. Life >expectancy is about the same. When I was at OSH I hear that some builders were going to the Cleveland 6" brakes used on the DEFIANT with four pads per brake and the low-profile tires. Date: Fri, 4 Aug 1995 01:16:52 -0400 (EDT) From: Tech Support - Rick Subject: Re: Brake thoughts (Defiant type) > > When I was at OSH I hear that some builders were going to the Cleveland 6" > brakes used on the DEFIANT with four pads per brake and the low-profile > tires. > . > Do you know how they differ? To be honest , No, I don't know about that design, but be warned, the bigger tires besides adding drag will cause a more pronounced canard dip in rain if you are building a GU canard. Reference Varieze owners experience and LOng's. Otherwise be careful of the incidence of the aircraft with the larger wheels and brakes. Plus, you will use up more runway with the larger tires. Just a few thoughts on the subject. Rick -003 Date: Fri, 4 Aug 1995 08:17:14 -0400 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) Subject: Re: Brake thoughts (Defiant type) Rick wrote: > Plus, you will use up more runway with the larger tires. Why do you use up more runway? Is this on take off, landing, or both? I don't understand. Phillip Johnson Date: Fri, 4 Aug 1995 14:08:59 -0700 From: craigb@gargamel.ptw.com (Craig R. Bowers) Subject: Re: Brake thoughts (Defiant type) > Rick wrote: > > > Plus, you will use up more runway with the larger tires. > > Why do you use up more runway? Is this on take off, landing, or both? > I don't understand. > > Phillip Johnson > > This is the first time that I thrown my $0.02 in, but here goes. It would seem to me that if the size of the main gear tires were increased that the AC would be setting at a lower angle-of-attact when on the ground. This being true it seems to me that more airspeed would be required in order to generate enough lift to rotate. I don't beleave that the speed differance would be great, but I am not sure. As for landing. With the nose wheel on the ground and the AC at this new lower angle-of-attact the wing and canard should be generating less lift and the brakes may be more effective. This would only be true right after touch down. In an earlyer posting someone said that testing of the different brake systems would yield some good information. I agree, BUT PLEASE be very careful. In my 11 years working at Edwards AFB I saw a few AC damaged in heavy braking tests by fire. All ways have available several fire extinguishers. Also do expect to blow a tire. That way if it does not happen at least you were ready. Thanks for hearing me out. Craig. _________________________________________________________________________ / | Craig R. Bowers | | | |__________________| | | | | SNAIL MAIL: P.O. Box 725 E_MAIL: craigb@pargamel.ptw.com | | Lancaster, CA | | 93584-0725 | | | | VOICE: (805) 256-4504 | | | | | | | |_________________________________________________________________________| Date: Fri, 4 Aug 1995 19:39:13 -0400 From: Marcnadine@aol.com Subject: Re: 3 Brake thoughts (Defiant type) Marc P. -WRITES: >> When I was at OSH I hear that some builders were going to the Cleveland 6" >> brakes used on the DEFIANT with four pads per brake and the low-profile >> tires. Rick-003 WRITES . >> Do you know how they differ? > To be honest , No, I don't know about that design, but be warned, the >bigger tires besides adding drag will cause a more pronounced canard dip >in rain if you are building a GU canard. Reference Varieze owners >experience and LOng's. Otherwise be careful of the incidence of the >aircraft with the larger wheels and brakes. Plus, you will use up more >runway with the larger tires. >Just a few thoughts on the subject. >Rick -003 The setup I saw at OSH was on a Mark IV using 15x6.00-6 low-profile light-weight 6 ply tires and Velocity wheel pants. This Cozy owner did not mention any problems, the drag this with this system should not be much more than the standard system without pants. Marc P. N525CZ Date: Sat, 5 Aug 1995 07:49:47 -0400 From: SidLloyd@aol.com Subject: Re: Brake thoughts (Defiant type) In a message dated 95-08-04 18:55:46 EDT, craigb@gargamel.ptw.com (Craig R. Bowers) writes: >It would seem to me that if the size of the main gear tires were >increased that the AC would be setting at a lower angle-of-attact >when on the ground. This being true it seems to me that more >airspeed would be required in order to generate enough lift to rotate. >I don't beleave that the speed differance would be great, but I am not >sure. Good point. I thought of that when I put them on. I mounted them up higher to keep the Cozy at the same AOA by measuring the difference between the 600X6 and the 500X5. I think it was an inch or so. Also, I doubt that there will be any difference in airspeed. I suspect that getting the aerodynamics right on the wheel pants will make much more difference thant the slightly bigger wheels. What actually convinced me to go to the bigger wheels was noticing that Cessna 150s have 600X6's on them, are much lighter (hmm, that is I think they are), and land MUCH slower. I also had ideas of landing on grass strips but after my flight in Ron's Cozy and seeing how fast a 110 mph landing is, I plan to stay on LONG paved runways! Sid Date: Sun, 6 Aug 1995 10:24:06 -0400 (EDT) From: Tech Support - Rick Subject: Re: Brake thoughts (Defiant type) On Fri, 4 Aug 1995, Phillip Johnson wrote: > Rick wrote: > > > Plus, you will use up more runway with the larger tires. > > Why do you use up more runway? Is this on take off, landing, or both? > I don't understand. > > Phillip Johnson > This is on T/O especially, due to the increased rooling resistance. Reference for this is especially Long's when they went from Lamb to the 5.00x5 tires. Their T/o distance increased 200 ft. Rick -003 Date: Tue, 8 Aug 1995 12:47:10 -0400 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) When I wrote > Why do you use up more runway? Is this on take off, landing, or > both? > I don't understand. I assumed the builder would adjust the length of the gear leg to compensate for the increased tire size. Rick now writes: > This is on T/O especially, due to the increased rooling resistance. > Reference for this is especially Long's when they went from Lamb to > the 5.00x5 tires. Their T/o distance increased 200 ft. Is this true? Does a larger tyre have greater rolling resistance? I am not knowledgeable in this area but intuitively I feel the converse is true. Granted the larger tyre has more contact area because of the larger radius but the sidewalls are deformed less and I always understood that the sidewalls caused the major loses. When I was a kid I made many model cars that ran down smooth inclines and I always found that the ones with larger wheels went further suggesting less friction. I would not have thought the rotational moment of inertial of the larger wheels accounted for that sort of difference so I concluded that the rolling resistance was less. The point is somewhat moot for me since I shall be using the Matco 5 inch wheels but I am interested strictly from the academic aspects. When the Long Eze's increased their take off roll using the big tires did they compensate for the gear leg length or did they result in a reduced wing angle of attack as mentioned in the many posts on this subject? In other words, are we comparing apples with apples? Please, I'm looking for rational discussion and debate not an argument. Phillip Johnson Subject: Brakes (Oh No, Not AGAIN!!!) Date: Fri, 6 Oct 1995 16:08:10 -0400 (EDT) From: "Randy Smith" Ok, since Chuck W. brought up the Brake thing again... I have an idea. How hard/effective would it be to install a brake line pressure modulator (aka Anti-lock brakes) on the Mk IV to improve its braking distance? Seems to me that this would have more benefit (improved wet pavement handling) that just putting bigger brakes on the thing. Aside from the added complexity to add the speed sensors in the wheel and a little weight, it should be a simple thing to do. Perhaps even a system that modulated the pressure all the time (and not just when it senses skidding) would alieviate the need for the speed sensors. Just a thought that passed through my mind as I was daydreaming about flying my MV IV over SC. -Randy --* --- -* **-* *-** -*-- -* Crash Rescue Team 7 - Don't PANIC! _____|_____ AT&T Randy.Smith@ColumbiaSC.attgis.com -(X)- Global Support Center Voice 803-939-7648, V+ 633-7648 ___o/o\o___ West Columbia, SC 29170 "I am the way, the truth, and the life..." -JC From: Marc J. Zeitlin Subject: Brakes (Oh No, Not AGAIN!!!) (fwd) Date: Fri, 6 Oct 95 16:24:30 EDT Randy Smith writes: >I have an idea. How hard/effective would it be to install a brake line >pressure modulator (aka Anti-lock brakes) on the Mk IV........... I remember seeing some sort of review or advertisement in a recent Sport Aviation or Kitplanes (pretty precise here, huh?) which talked about an Anti-Lock brake system for homebuilts - someone had one on a Lancair, I think, and claimed they were wonderful. Not cheap, though, and not light, either. My admittedly poor memory has something on the order of a few thou, and 10-20 lbs. in it. I've actually got to admit that in this case, as Nat says, the V.E., L.E., Cozy design has a built in emergency brake (dropping the nose) which apparently works VERY well, costs little, and weighs and costs nothing (until you have to fix the nose after using it - a reasonable price, I'd say). The problem, of course, is that retracting your LG is not the first thing on your mind during an aborted takeoff or long landing. Maybe it's worth practicing once or twice during SLOW taxi testing? That said, with Chapter 9 looming, I still haven't decided which wheel and brake system to use......... -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Sat, 7 Oct 1995 17:25:22 -0400 From: RonKidd@aol.com Subject: Re: Brakes (Oh No, Not AGAIN!!!) (fwd) Marc, I don't think that I would practice the "emergency brake" technique. The minimum damage you will have (at any speed) is a cracked nose and probably stripped gear in your retract mechanism to boot. Not a fun thing to replace when your airplane is all finished and shiny. I speak from experience! I got in the bad habit of cranking my nose gear up about one turn after refueling (so the bird would be "nose heavy") rather than parking it on the nose as they will leak fuel out of the strake vents and or fill caps and put blue stains all over your nice white paint. I went in and paid for the fuel and entered the airplane to taxi out. I did not notice the nose was slightly lowered. It immediatly stripped out, dropped to the ground, damaging the nose, the rod end etc. I could not get parts for repair as it was a Sat. I had to rent a car (in central Georgia) drive back to Columbus Ohio. The following weekend I drove back (10 hours) fixed it and flew back home. In all it ended up costing about $400.00 and 20 hours of driving time! What do they say in the AOPA column? Oh yeah, NEVER AGAIN! Ron Date: Mon, 9 Oct 1995 01:06:22 -0400 From: KSPREUER@aol.com Subject: Re: Brakes (Oh No, Not AGAIN!!!) (fwd) >I've actually got to admit that in this case, as Nat says, the V.E., >L.E., Cozy design has a built in emergency brake (dropping the nose) >which apparently works VERY well, costs little, and weighs and costs >nothing (until you have to fix the nose after using it - a reasonable >price, I'd say). The problem, of course, is that retracting your LG is >not the first thing on your mind during an aborted takeoff or long >landing. Maybe it's worth practicing once or twice during SLOW taxi >testing? > Dropping the nose does work very well, but I wouldn't practice it. There is some damage each time and a possibility of striping teeth on the retract gear. It should also be noted that the ratchet mechanism sold as an option to lock the gear up or down will delay the ability to react to emergency use. My 2 cents on anti-lock brakes: I've never skidded the tires in 7 years. Maybe it ice and snow it would be a different story but I wouldn't spend the time, weight, complexity or money for that one. From: Lee Devlin Subject: Anti-lock brakes Date: Mon, 9 Oct 95 15:52:29 MDT I would question the advisability of anti-lock brakes on the Cozy. The problem that gave rise to the initial discussion was quite different from the problems that anti-lock brakes solve. In general, an anti-lock mechanism provides two functions: 1.) it maintains the static coefficient of friction between the tire and the road surface (which is higher than the dynamic coefficient of friction), and 2.) it helps to maintain direction control using the steering which is otherwise ineffective if the tires are skidding with respect to the road surface. One of the items that would be *lost* with an anti-lock brake system on a Cozy is directional control (i.e. differential braking) during hard deceleration. Skidding or brake lock-up is the opposite of the problem brakes overheating and begining to fade. Another interesting fact is that on dry pavement, a skilled driver using conventional brakes can stop in less distance than is possible with anti-lock brakes. Lee Devlin Date: Tue, 10 Oct 1995 13:21:43 -0400 From: Phillip.Johnson@Lockheed.on.ca (Phillip Johnson) Subject: Re: Brakes (Oh No, Not AGAIN!!!) Hey chaps, the problem with the brakes is that they are under capacity. This means that the brake will almost certainly fade not skid. Skidding could only be induced at the early stages of the braking process because the temperature rise, in the later stages, will reduce the effectiveness thereby making it impossible to skid. Skidding, although not desirable, is controllable unlike brake fade. The ideal brake should be capable of inducing skidding at any stage of the braking process. Notice I say capable, because the optimum braking is obtained just prior to skidding. ABS on under capacity brakes will only induce fade and potential wheel fires. Note: Contrary to popular belief, higher capacity brakes of the same lining material, run cooler, for the same braking energy, than lower capacity brakes. Although the same energy is expended the increase in thermal mass causes a lower temperature to be induced. This statement is valid for brakes using the same lining material. If ceramic brake linings are used, the operating temperature is allowed to be higher before fade occurs. This is OK if you have metal suspension system such as with retracts, but is bad news for composite gear. Phillip Johnson