Date: Sat, 19 Sep 1998 23:17:37 -0400 From: Bill Theeringer Subject: COZY: Flat tire Bob; I noticed a crack around the hub of my stock Brock nose wheel at Oshkosh this year. I decided to replace the whole thing - tire, tube, hub, both wheel halves, bearings and bolt, since Ken was there and had an assembly, and I had over 1,000 hours on mine. When I took the tube out of the tire a bunch of little pieces of black rubber fell out. It looked like a mouse had ben resident there, if you know what I mean. They were little soft cylinders. Further inspection revealed the tube to be severely chaffed, both sides, about 1/3 of the circumference and confined to the outermost areas. The tire was also chaffed but not as severe. I always carry 50 psi in the nose, although JD says it should be 70. It's amazing it held pressure given its condition. A few weeks ago I replaced both of the main tires and tubes. They were the Michelin 500 X 5 six ply that JD has and had been on for 5 years. They were still good with acceptable tread but I did it anyway. Might as well be 3 for 3. The tubes were in excellent condition as we had installed them with plenty of talcum powder, but I accidently cut a one during installation so I replaced them both. Should we carry 70 psi in the nose? JD says yes. Bill Theeringer N29EZ See our award winning Long EZ with Jim Newmans excellent retractable gear at http://www.flash.net/~infaero/infgear.htm Composite Aircraft Accessories HOME: 805-964-5454, SHOP: 805-964-5453 E Mail: Composite_Aircraft_Accessories@Compuserve.com PO Box 21645 Santa Barbara, CA 93121 "Once you have tasted flight, you will walk with your eyes turned skywards, for there you have been and there, you will long to be" Leonardo DaVinci (1452-1519) Date: Sun, 20 Sep 1998 14:54:28 -0400 From: Bill Theeringer Subject: COZY: Tire Pressure Reply-To: cdenk@ix.netcom.com Bill Theeringer writes <70 PSI in main tires> What does the manufacturer (Michelin) in print, brocures or instructions, (a letter or verbal doesn't count) for maximum pressure, don't exceed that!!! That is not what I wrote. What I wrote is "I always carry 50 psi in the nose, although JD says it should be 70." Michelin specifies a normal pressure of 40 psi with 50 psi being max acceptable for heavy loads in their 500 X 5 six ply aircraft tire. I always carry 50. The issue of 70 psi in the _nose tire_ has come about because JD contacted the manufacturer, has their data in writing, and has found a misprint in the Spruce Catalog which set the incorrect number to start with. All this is of course verbal to me via JD so you might want to contact him for all the particulars. Bill Theeringer N29EZ From: "Nat Puffer" Subject: Re: COZY: Tire Pressure Date: Sun, 20 Sep 1998 12:48:00 -0500 Dear Bill, There is a history of the Brock 4 inch nosewheel failing. The first failure close hand was on Uli Wolters Cozy at Sun & Fun in 1986. The wheel actually broke. A year or so later, we had one go flat on landing. Part of the problem is the weak design, and part of the problem is that the tube has to be distorted for the valve to come out the side. Even if the wheel itself doesn't fail, the tube can. At any rate, since that date, we have been recommending to Cozy builders that they buy the Cleveland cast aluminum 4" wheels, a much stronger design, in stock at Wicks and Aircraft Spruce. A huge quantity of these wheels were produced for the main gear on the BD5, but they had integral brake discs. Bud Meyers at Wicks discovered the source and came up with the idea of machining off the brake disc so they could be used for the nosewheel. We haven't heard of any wheel or tube failures with this wheel. We still have a Brock wheel we took off one of our airplanes when we replaced it with a Cleveland. I hope all Cozy builders are using this wheel which we have recommended in our plans. Hope this might help someone. Regards, Nat ---------- > From: Bill Theeringer > To: All > Subject: COZY: Tire Pressure > Date: Sunday, September 20, 1998 1:54 PM > > Reply-To: cdenk@ix.netcom.com > > Bill Theeringer writes <70 PSI in main tires> > What does the manufacturer (Michelin) in print, brocures or instructions, > (a letter or > verbal doesn't count) for maximum pressure, don't exceed that!!! > > That is not what I wrote. What I wrote is "I always carry 50 psi in the > nose, although JD says it should be 70." > > Michelin specifies a normal pressure of 40 psi with 50 psi being max > acceptable for heavy loads in their 500 X 5 six ply aircraft tire. I > always carry 50. The issue of 70 psi in the _nose tire_ has come about > because JD contacted the manufacturer, has their data in writing, and has > found a misprint in the Spruce Catalog which set the incorrect number to > start with. All this is of course verbal to me via JD so you might want to > contact him for all the particulars. > > Bill Theeringer > N29EZ Date: Sun, 20 Sep 1998 16:00:50 -0400 From: David Domeier Subject: Re: COZY: Tire Pressure Bill, re "That is not what I wrote. What I wrote is "I always carry 50 psi in the nose, although JD says it should be 70." I had 2 flat nose tires on one trip, one in Rochester, NY, and one at OSH some years back on my LEZ. I credited the first one to old inner tube rubber and second one to old inner tube rubber also, since that tube was scrounged up at a John Deere tractor place in Rochester. I believe rubber wears out whether it is used or not. The 50 vrs 70 psi in the nose tire is interesting. That little bugger gets quite a jolt on touch down and it could be 70 psi would be better. Let us know if you find out more on this subject. JD is pretty knowledgeable and he's probably right. dd From: cdenk@ix.netcom.com Date: Sun, 20 Sep 1998 18:39:31 -0500 (CDT) Subject: Re: COZY: Tire Pressure I have a MkIV (10 inch) nose tire. As turning off the runway at Sioux Fall, South Dakota, it went flat. Since we always carry a spare nose wheel and tire, since it is not a common size, that was no big thing. Since we were pushing weather to get home that night after Leaving Riverton, Wyoming that morning, I had the FBO mechanic change the tire while we ate lunch. After getting home and examining the failure, I found a radial split in the tube. A call to McCreery tire (the only manufacturer of that size), revealed that the tubes are extruded as a long helix, cut and butt glued together. They said the butt joint was a difficult at best joint, and occasionally there is a defect. I recommend carrying a nose tire and tube everywhere. When time comes to replace the nose tire and tube, I use the spare, and buy a new spare. The main tires are very common, and I feel a replacement either new or used would likely be available at most airports. My Cosy is probably the most nose heavy EZ, and I carry either 50 or 60 psi in the nose and main tires, and haven't had any issues at that pressure. Excessive pressure can cause less traction for braking or turning, and don't know of a good reason to carry more. A bigger issue is to low pressure, which can cause pinched tubes, damaged sidewalls, and more likely hydroplaning whe wet. Tire pressures should be checked about 4 times a year, and for sure anytime the temperatures decrease in as the cooler seasons approach. When rolling the plane on level pavement, you should get a feel for the effort required with correct tire pressures. Date: Wed, 23 Sep 1998 22:15:30 -0700 From: "LCDR James D. Newman" Subject: COZY: Re: Flat Tire Hi Bill, Carl, Dave and All, > Bill Theeringer wrote: > I always carry 50 psi in the nose, although JD says it should be 70. It's amazing it held pressure given its condition. > A few weeks ago I replaced both of the main tires and tubes. They were the Michelin 500 X 5 six ply that JD has and had been on for 5 years. They were still good with acceptable tread but I did it anyway. Might as well be 3 for 3. The tubes were in excellent condition as we had installed them with plenty of talcum powder, but I accidently cut a one during installation so I replaced them both. > Should we carry 70 psi in the nose? JD says yes. > Carl Denk wrote: > What does the manufacturer (Michelin) in print, brochures or instructions, (a letter or verbal doesn't count) for maximum pressure, don't exceed that!!! Whooa, easy big fella. When Bill stated "JD says yes", you can bet your bottom dollar that I knew what I was talking about (after designing 5 kinds of retractable landing gear for customers which are now in production, you kinda remember *things*); AND, that I backed it up by showing him documentation of the tire pressures for both the nose and main tires he has on his Long-EZ-RG. Also remember, this is just e-mail. As I've said before, you never need to worry about me. > Bill Theeringer wrote: > That is not what I wrote. What I wrote is "I always carry 50 psi in the nose, although JD says it should be 70." > Michelin specifies a normal pressure of 40 psi with 50 psi being max acceptable for heavy loads in their 500 X 5 six ply aircraft tire. I always carry 50. The issue of 70 psi in the _nose tire_ has come about because JD contacted the manufacturer, has their data in writing, and has found a misprint in the Spruce Catalog which set the incorrect number to start with. All this is of course verbal to me via JD so you might want to contact him for all the particulars. Actually, the documentation I showed Bill (4.5+ years ago) for the 8" diameter Long-EZ McCreary nose tire PSI is in the tire section of the "Landing Gear Design for Light Aircraft" book by Ladislao Pazmany which states on page 55 that this tire pressure should be 70 PSI, and this tires Static Service Load Rating is 430 lbs. at this PSI (I don't know the Bottom Load as I type tonight, but is probably around 1171 lbs.). So based on this fact, the PSI misprint spoken of is in the owners manual. Therefore, when you only put in 40 PSI per the owners manual, the pressure dropping off just a little causes the tube to turn on the wheel cutting the stem, and many other problems occur, that are all well documented over the years concerning this nose tire and tube at 40 PSI. Note: a minor problem when/if you do pump the nose tire up to 70 PSI [try it, you'll like it :-)] is that it might not fit into your nose wheel well since it will be slightly larger in diameter and could rub against the back of the nose wheel well below the FS 40 Long-EZ instrument panel bulkhead making it a little difficult to retract and extend the nose strut. Just extend the opening slightly. Another note (food for thought): from FAR Part 23.479, using a Limit Load Factor of 3.00, a Landing Weight (LW) of 1325 lbs. could impose over 953 lbs. of load on the *nose* strut and tire from a hard 3 point landing with the aircraft loaded at the _fwd._ CG (worst case scenario); 800 lbs. LW, 576 lbs. nose strut and tire load; 900 lbs. LW, 720 lbs. load; 1500 lbs. LW, 1079 lbs. load; 1700 lbs. LW, 1223 lbs. load; 2050 lbs. LW, 1475 lbs., and at 2200 lbs. LW, 1583 lbs. load. So max Landing Weight for this tire is about 1625 lbs. Also, at 800 lbs. LW, the *main* tires load (at the _aft_ CG worst case scenario) see over 1980 lbs. total load on both main gear tires; 900 lbs. LW, 2227 lbs. load; 1325 lbs. LW, 3279 lbs.; 1500 lbs. LW, 3712 lbs. load; 1700 lbs. LW, 4207 lbs. load; 2050 lbs. LW, 5073 lbs., and at 2200 lbs. LW, 5444 lbs. total load on both main tires. The documentation I showed Bill about the main 5.00 X 5 - 6 ply tires was from Michelin, and you can see it on their web site. This tire has a Static Service Load Rating of 1285 lbs. (each), and a 3500 lbs. Bottom Load (each) at 50 PSI. You can also see the 5.00 x 5 - 6 ply tire pressure and specs in the "Tire and Rim Association" ratings book, or in any of the other vendors sales catalogs: i.e. - Aircraft Spruce, Wicks, etc. [How am I doing Carl? ;-)] Also, the 11.5" diameter 8 ply Lamb size tire I use for my *nose* strut, and some tandem canards use for their mains, is also 70 PSI and has a Static Service Load Rating of 850 lbs. (again, I don't know the Bottom Load tonight, but is probably around 2315 lbs.). As you can see, using this tire for the *mains* like some of the tandem canards do limits their max LW to about 1871 lbs., which creates a load of 4629 lbs. on both main gear tires (worst case scenario). The 10" diameter Cozy MK-IV and AeroCanard McCreary nose tire pressure should also be 70 PSI, and it's Static Service Load Rating is 500 lbs. Again, I don't have this tires Bottom Load Rating tonight, but it's probably around 1362 lbs., which would be a max LW of 1895 lbs. at a max _fwd._ CG (worst case scenario). So, all I'm trying to say is, as you can see from the worst case scenarios, if you don't have the nose tire at 70 PSI, and the 5.00 X 5 mains at 50 PSI, the tires are not doing the work they should for you. > Dave Domeier wrote: > I believe rubber wears out whether it is used or not. Correct. And Michelin tells me that aircraft tires (at least there's), are made from a more pure rubber than car tires, so air leaks through the tube more easily than car tires [it seems to me this occurs more from non use {not flying} :-)]. At any rate, this (using a purer rubber) explains why aircraft tires 'seem' to go flat more often, so check them a LOT more -- take-off roll will be greater with low tires, and low pressure tires cause higher loads on your plane from hard landings. The gear landing loads are designed around tires full of air. Braking would be worse too with low tires. > JD is pretty knowledgeable and he's probably right. Thanks Dave, I try. All, HTH. Infinity's forever, JD From: cdenk@ix.netcom.com Date: Thu, 24 Sep 1998 20:47:25 -0500 (CDT) Subject: COZY: TIRE PRESSURES AND REUSING TUBES Quoted from McCreary Tire and Rubber printed brocure: For 5.00 x 5 6 ply Airhawk or AirTrac tires: Inflation pressure = 50 psi. Maximum load = 1285 lbs per tire. For Airtrac Special Purpose tires 10x3.5, 4 Ply, Inflation Pressure = 60 Psi. Maximum Load = 460 lbs. "USED AIRCRAFT TUBES" Aircraft tubes are made of natural rubber and are made slightly undersize, so they will fit easily into a new tire. Aircraft-tire plies are made of nylon, and tires will "grow" slightly, in service. The tube will also grow, and will eventually take a permanent set to the (now) larger inside tire dimension. If this now larger tube is later put into a new tire, it may be too large for the inside-tire cavity, with the result that the tube may have folds in it. In service, these folds may eventually wear through and destroy the tube's ability to hold air. A slow wearing-through will result in a slow ,leakage of air, and the pilot will be alerted to the problem before it becomes too serious. However, if the tube is torn in a particular takeoff, the tire will probably go flat in mid-air, without the pilot having realized what is wrong. When he touches down on a flat tire with no forewarning, his aircraft may be extremely difficult to control. Considering the cost of a new inner-tube, the risks are hardly worth taking.