---------------------------------------------------------- TeamGrumman-List Digest Archive --- Total Messages Posted Fri 04/17/09: 11 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:59 AM - Re: Squeaking nose gear (flyv35b) 2. 06:37 AM - Re: Squeaking nose gear (SteveR) 3. 07:02 AM - Re: strange compression test. (flyv35b) 4. 07:08 AM - Re: Re: Squeaking nose gear (flyv35b) 5. 07:44 AM - Re: Squeaking nose gear (SteveR) 6. 07:50 AM - Re: Re: Squeaking nose gear (cloudvalley@comcast.net) 7. 11:20 AM - Re: strange compression test. (teamgrumman@AOL.COM) 8. 12:39 PM - Re: strange compression test. (budzz89) 9. 12:46 PM - Re: Squeaking nose gear (grumpyparts) 10. 12:50 PM - Re: Squeaking nose gear (SteveR) 11. 01:45 PM - Re: Squeaking nose gear (grumpyparts) ________________________________ Message 1 _____________________________________ Time: 05:59:27 AM PST US From: "flyv35b" Subject: Re: TeamGrumman-List: Squeaking nose gear I'd say there is a very high probability that the squeaking noise you are hearing is due to a delaminated torque tube. No lubrication was required anywhere on the strut/torque tube installation. You will need to have someone help you bounce the plane up and down while you get under the panel and put your fingers across both sides of the torque tube joint on the socket and also at the outboard ends near the fuselage sidewall. Do this on both sides. Delaminated torque tubes can be rebuilt. A failed joint will put additional load on the opposite site and if that side fails you will end up with the prop in the ground! Cliff A&P/IA ----- Original Message ----- From: "SteveR" Sent: Thursday, April 16, 2009 9:34 PM Subject: TeamGrumman-List: Squeaking nose gear > > > The nose gear in an AA5 Traveler I've been flying lately started squeaking > after a rain shower (the plane is kept outside currently). The squeak is > coming from the nose gear torque tube area (very near the firewall). I > think maybe it just needs to be lubricated as I read about this elsewhere. > Would anyone agree with that? I'm new to Grummans so I'm not sure if the > squeaky nose gear is common or not. Bouncing the nose up and down > slightly makes it squeak fairly loud. > > What is the proper procedure and lubricant to use on the torque tube/nose > gear strut junction, assuming that is where the squeak is coming from? > Does the nose gear strut have to be removed from the torque tube in order > to lubricate it? > > Or if I'm going in completely the wrong direction, I'd be glad to hear > about that too. Thanks for any help. > > Steve > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=239660#239660 > > > ________________________________ Message 2 _____________________________________ Time: 06:37:55 AM PST US Subject: TeamGrumman-List: Re: Squeaking nose gear From: "SteveR" Cliff, thanks for your help, I really appreciate it. I think we'll ground the plane until we know for sure what the problem is. If anyone has any diagrams of the torque tube assembly that would help us know what to look for, they would be greatly appreciated. This is where I got the information on lubricating the strut and torque tube: http://www.grumman.net/cgrcc/aa5.html > The nosegear demands maintenance and must be lubricated and adjusted strictly by the book. (Not many shops even have the book.) In particular, the strut inside the torque tube should be free of corrosion and well lubricated. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=239688#239688 ________________________________ Message 3 _____________________________________ Time: 07:02:31 AM PST US From: "flyv35b" Subject: Re: TeamGrumman-List: strange compression test. > Both times, the compression on #2 fell off dramatically at 20 to 15 BTDC. > Compression came back up slightly to 60/80 at TDC. On the other side, > ATDC, compression fell off slightly and then went back up before going > back down. Compression is normally checked at TDC. Are you saying you held the prop stationary at 20 and 15 BTDC or where you moving the piston upwards at the time you noticed the drop in compression? Checking the compression while the piston is moving upwards doesn't really tell you much. You can "generate" higher numbers and even see 80/80 or higher depending on how fast you are moving the piston. Also, many times compression will fall off right after TDC and then come back up shortly later, especially if there is bore wear from the top ring at the top of the stroke and wear in the piston ring land. > At 25 hours, the cylinder was pulled, sent to Lycon for inspection. > Valves/seats were recut, rings were honed, cylinder was rehoned. The > plane was flown again for 10 hrs and the compression tested. The > compression fall-off wasn't as bad, but, it was still there. Plane was > flown for another 15 hours. At 50 hours, I removed the cylinder and > replaced it with another new cylinder. How do you hone the rings? > The owner has about 5 hours on it and I'll be checking it again. > > Note: when the cylinder was pulled, the piston was removed to the point > where I could remove the wrist pin. The top of the piston was scuffed in > a "V" shape from about 1 inch below the rings to the ring grooves. At the > grooves, the scuffing was about 1 inch wide. I did not remove the piston > and look inside. I sent the cylinder to Lycon today. > > Has anyone ever heard of this before? Not quite sure what the scuffed area looks like. I assume you are talking about scuffing on the piston skirt at the 12 o'clock position as it is installed? Does the scuffing go all the way to the bottom of the skirt and the point of the "V" start there and get wider as it approaches the oil ring land? Was the piston scuffed on the bottom side at the 6 o'clock position? Why not just pull the cylinder off the piston when removing it and then remove the pin and piston? That way you can inspect all of the cylinder bore and the head area. Normally, if scuffing occurs it will be on the skirt at the 12 and 6 o'clock positions. This can be pretty severe on a new engine that has tight clearances when takeoff power is applied without the engine being warmed up adequately. The aluminum piston expands faster than the steel cylinder and starts to scuff. Since it sounds like you didn't change the piston with the new cylinder, I'd want to check the cylinder bore diameter vertically and horizontally with a dial bore gauge and compare that to the piston skirt diameter in both directions. There might be a clearance issue. The scuffed area as you described it sounds abnormal and might be due to incorrectly made parts. Maybe the cylinder is not round near the top and the rings can't conform to the bore, resulting in a loss of compression. Lycon should be able to take some measurements and tell you if there is a problem. Lastly, what about a dynamic cranking compression test. Did you do that on this engine? I guess that wouldn't show up the problem if it only occurs at 20-15 BTDC and not at the very top of the stroke. Cliff ________________________________ Message 4 _____________________________________ Time: 07:08:20 AM PST US From: "flyv35b" Subject: Re: TeamGrumman-List: Re: Squeaking nose gear Good information but not intended to replace the maintenance manual info. The lubrication Aviation Consumer is referring to is where the nose fork is mated to the nose strut. This area is where lots of non Grumman shops and mechanics know very little about and they ignore the maintenance here and get the fork tension washer installation and adjustment screwed up and the nose wheel shimmys. I wouldn't fly the plane until you find out if the torque tube is OK. I'd also buy a maintenance and parts manual from Fletchair, especially if you mechanic doesn't have a set. Cliff ----- Original Message ----- From: "SteveR" Sent: Friday, April 17, 2009 6:37 AM Subject: TeamGrumman-List: Re: Squeaking nose gear > > > Cliff, thanks for your help, I really appreciate it. I think we'll ground > the plane until we know for sure what the problem is. If anyone has any > diagrams of the torque tube assembly that would help us know what to look > for, they would be greatly appreciated. > > This is where I got the information on lubricating the strut and torque > tube: > > http://www.grumman.net/cgrcc/aa5.html > > >> The nosegear demands maintenance and must be lubricated and adjusted >> strictly by the book. (Not many shops even have the book.) In >> particular, the strut inside the torque tube should be free of corrosion >> and well lubricated. > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=239688#239688 > > > ________________________________ Message 5 _____________________________________ Time: 07:44:28 AM PST US Subject: TeamGrumman-List: Re: Squeaking nose gear From: "SteveR" Thanks again Cliff. The owner might have the manual, I'll check with him. I found the information below (last paragraph) which describes the torque tube assembly. I'm having trouble understanding which part(s) might be delaminated. It sounds to me like everything is bolted or welded, which I know isn't right. Once I'm under there with a light, and a helper is bouncing the nose, will it be pretty obvious? And finally, if it is a delaminted torque tube, can you recommend any good shops for rebuilds? I am in the Oklahoma City area, any local experts that anyone could recommend would be greatly appreciated. Here is the paragraph I found somewhere else...I'm having trouble understanding where to look for delaminations here: The torque tube assembly is made up of three parts: the T connector, the horizontal tube(s), and the sidewall mounting bracket(s). The T connector has a tube in it which connects to the nose gear strut and is bolted to the floor and firewall. It is welded to the horizontal tubes which on the other ends are welded to the sidewall mounting brackets. The mounting brackets are bolted to the sidewalls. Thanks again for the help, Steve Ruse Read this topic online here: http://forums.matronics.com/viewtopic.php?p=239703#239703 ________________________________ Message 6 _____________________________________ Time: 07:50:47 AM PST US From: cloudvalley@comcast.net Subject: Re: TeamGrumman-List: Re: Squeaking nose gear Hi Cliff! =C2-Ah yes the torque tube. We had a problem with that also.smile Brian Preston ----- Original Message ----- From: "flyv35b" Sent: Friday, April 17, 2009 7:08:51 AM GMT -08:00 US/Canada Pacific Subject: Re: TeamGrumman-List: Re: Squeaking nose gear Good information but not intended to replace the maintenance manual info. The lubrication Aviation Consumer is referring to is where the nose fork is mated to the nose strut. =C2-This area is where lots of non Grumman shops and mechanics know very little about and they ignore the maintenance here and get the fork tension washer installation and adjustment screwed up and the nose wheel shimmys. I wouldn't fly the plane until you find out if the torque tube is OK. =C2 -I'd also buy a maintenance and parts manual from Fletchair, especially if you mechanic doesn't have a set. Cliff ----- Original Message ----- From: "SteveR" Sent: Friday, April 17, 2009 6:37 AM Subject: TeamGrumman-List: Re: Squeaking nose gear > > > Cliff, thanks for your help, I really appreciate it. =C2-I think we'll ground > the plane until we know for sure what the problem is. =C2-If anyone has any > diagrams of the torque tube assembly that would help us know what to look > for, they would be greatly appreciated. > > This is where I got the information on lubricating the strut and torque > tube: > > http://www.grumman.net/cgrcc/aa5.html > > >> The nosegear demands maintenance and must be lubricated and adjusted >> strictly by the book. =C2-(Not many shops even have the book.) In >> particular, the strut inside the torque tube should be free of corrosion >> and well lubricated. > > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=239688#239688 > > > > > > > > > > =========== - =========== MS - =========== e - =C2- =C2- =C2- =C2- =C2--Matt Dralle, List Admin. =========== ________________________________ Message 7 _____________________________________ Time: 11:20:22 AM PST US Subject: Re: TeamGrumman-List: strange compression test. From: teamgrumman@AOL.COM Cliff Wrote: Compression is normally checked at TDC. Are you saying you held the prop stationary at 20 and 15 BTDC or where you moving the piston upwards at the time you noticed the drop in compression? Checking the compression while the piston is moving upwards doesn't really tell you much. You can "generate" higher numbers and even see 80/80 or higher depending on how fast you are moving the piston. Also, many times compression will fall off right after TDC and then come back up shortly later, especially if there is bore wear from the top ring at the top of the stroke and wear in the piston ring land. Reply: All of the compression measurements were made with the piston static at the various cranking positions from 30 BTDC to 30 ATDC in 5 degree increments. I started checking compressions at 30, 20, 10, 0, 10, 20, 30 cranking degrees many years ago to build a data base of compression behavior based on engine time. Compression at TDC was only 60/80 (or thereabouts. Sometimes as low as 45, sometimes as high as 65). When I checked compressions BTDC I noticed a dramatic change in compression that was not expected. Then I did a compression survey and noticed that somewhere in the 20 BTDC range, there was a compression peak (75/80) and then a dramatic fall-off to TDC. I had the owner go to another shop and have them repeat the test to see if they found something weird. Their results were the same as mine. Cliff Wrote: How do you hone the rings? Reply: The rings were lapped into the cylinder. Cliff Wrote: Not quite sure what the scuffed area looks like. I assume you are talking about scuffing on the piston skirt at the 12 o'clock position as it is installed? Does the scuffing go all the way to the bottom of the skirt and the point of the "V" start there and get wider as it approaches the oil ring land? Was the piston scuffed on the bottom side at the 6 o'clock position? Why not just pull the cylinder off the piston when removing it and then remove the pin and piston? That way you can inspect all of the cylinder bore and the head area. Reply: I didn't remove the piston from the cylinder. I rarely do that. Lycon does all my engine work. The scuffed area looks like a "V" about 1 inch high and 1 inch wide at the oil ring. Note: This scuffing was not evident when I sent the cylinder assembly to Lycon for tear-down and inspection at 25 hours. Lycon didn't find anything specific about the cylinder that would cause a problem. The compressions were better after Lycon worked on the cylinder, but not perfect. I've removed a lot of cylinders and if there is scuffing (and there usually is) it looks like uniform scratches from the rings to the end of the piston skirt. This scuffing is confined to a small area just below the oil rings. Cliff Wrote: Normally, if scuffing occurs it will be on the skirt at the 12 and 6 o'clock positions. This can be pretty severe on a new engine that has tight clearances when takeoff power is applied without the engine being warmed up adequately. The aluminum piston expands faster than the steel cylinder and starts to scuff. Reply: I always wait until the oil temp is above 100 degrees before adding power. New, used, or abused. Cliff wrote: Since it sounds like you didn't change the piston with the new cylinder, I'd want to check the cylinder bore diameter vertically and horizontally with a dial bore gauge and compare that to the piston skirt diameter in both directions. There might be a clearance issue. The scuffed area as you described it sounds abnormal and might be due to incorrectly made parts. Maybe the cylinder is not round near the top and the rings can't conform to the bore, resulting in a loss of compression. Lycon should be able to take some measurements and tell you if there is a problem. Reply: It may sound like that, but, as far as I'm concerned, the pistons and cylinders are a unit. I never mix or match. A new cylinder 'assembly' was installed. Ken (Lycon) is going to inspect the cylinder/piston assembly just-in-case this shows up again on an other cylinder. The new assembly I received from Lycon had been torn down, inspected, and measured before they sent it to me to install. Cliff wrote: Lastly, what about a dynamic cranking compression test. Did you do that on this engine? I guess that wouldn't show up the problem if it only occurs at 20-15 BTDC and not at the very top of the stroke. Reply: Like I said in earlier posts, I am doing dynamic testing of cranking pressures to build a database of new vs old, roller vs flat tappet cams, low compression vs high compression, etc. For example: Compressions on a Lycon overhauled O320 with high compression pistons are in the 140-145 range. Compression on a roller cam are in the 125 range. Cranking pressure on the subject cylinder was only a point below the other cylinders. Had the engine felt smooth in flight, and reached red line in straight and level flight like it did with the old engine and a bad cam, I wouldn't have thought anything about it. The engine just didn't feel right. If Lycon finds something I'll post it. If the new cylinder is better, I'll post that too. ________________________________ Message 8 _____________________________________ Time: 12:39:53 PM PST US Subject: TeamGrumman-List: Re: strange compression test. From: "budzz89" GrummanDude wrote: > Cliff Wrote: > Compression is normally checked at TDC. Are you saying you held the > prop > stationary at 20 and 15 BTDC or where you moving the piston upwards at > the > time you noticed the drop in compression? Checking the compression > while > the piston is moving upwards doesn't really tell you much. You can > "generate" higher numbers and even see 80/80 or higher depending on how > fast > you are moving the piston. Also, many times compression will fall off > right > after TDC and then come back up shortly later, especially if there is > bore > wear from the top ring at the top of the stroke and wear in the piston > ring > land. > > Reply: > All of the compression measurements were made with the piston static at > the various cranking positions from 30 BTDC to 30 ATDC in 5 degree > increments. I started checking compressions at 30, 20, 10, 0, 10, 20, > 30 cranking degrees many years ago to build a data base of compression > behavior based on engine time. Compression at TDC was only 60/80 (or > thereabouts. Sometimes as low as 45, sometimes as high as 65). When I > checked compressions BTDC I noticed a dramatic change in compression > that was not expected. Then I did a compression survey and noticed > that somewhere in the 20 BTDC range, there was a compression peak > (75/80) and then a dramatic fall-off to TDC. I had the owner go to > another shop and have them repeat the test to see if they > found > something weird. Their results were the same as mine. > > Cliff Wrote: > How do you hone the rings? > > Reply: The rings were lapped into the cylinder. > > Cliff Wrote: > Not quite sure what the scuffed area looks like. I assume you are > talking > about scuffing on the piston skirt at the 12 o'clock position as it is > installed? Does the scuffing go all the way to the bottom of the skirt > and > the point of the "V" start there and get wider as it approaches the oil > ring > land? Was the piston scuffed on the bottom side at the 6 o'clock > position? > Why not just pull the cylinder off the piston when removing it and then > remove the pin and piston? That way you can inspect all of the > cylinder > bore and the head area. > > Reply: I didn't remove the piston from the cylinder. I rarely do > that. Lycon does all my engine work. The scuffed area looks like a > "V" about 1 inch high and 1 inch wide at the oil ring. > > Note: This scuffing was not evident when I sent the cylinder assembly > to Lycon for tear-down and inspection at 25 hours. Lycon didn't find > anything specific about the cylinder that would cause a problem. The > compressions were better after Lycon worked on the cylinder, but not > perfect. > > I've removed a lot of cylinders and if there is scuffing (and there > usually is) it looks like uniform scratches from the rings to the end > of the piston > skirt. This scuffing is confined to a small area just > below the oil rings. > > Cliff Wrote: > Normally, if scuffing occurs it will be on the skirt at the 12 and 6 > o'clock > positions. This can be pretty severe on a new engine that has tight > clearances when takeoff power is applied without the engine being > warmed up > adequately. The aluminum piston expands faster than the steel cylinder > and > starts to scuff. > > Reply: I always wait until the oil temp is above 100 degrees before > adding power. New, used, or abused. > > Cliff wrote: > Since it sounds like you didn't change the piston with the new > cylinder, I'd > want to check the cylinder bore diameter vertically and horizontally > with a > dial bore gauge and compare that to the piston skirt diameter in both > directions. There might be a clearance issue. The scuffed area as you > described it sounds abnormal and might be due to incorrectly made > parts. > Maybe the cylinder is not round near the top and the rings can't > conform to > the bore, resulting in a loss of compression. Lycon should be able to > take > some measurements and tell you if there is a problem. > > Reply: > It may sound like that, but, as far as I'm concerned, the pistons and > cylinders are a unit. I never mix or match. A new cylinder 'assembly' > was installed. Ken (Lycon) is going to inspect the cylinder/piston > assembly just-in-case this shows up again on an > other cylinder. The new > assembly I received from Lycon had been torn down, inspected, and > measured before they sent it to me to install. > > Cliff wrote: > Lastly, what about a dynamic cranking compression test. Did you do > that on > this engine? I guess that wouldn't show up the problem if it only > occurs at > 20-15 BTDC and not at the very top of the stroke. > > Reply: Like I said in earlier posts, I am doing dynamic testing of > cranking pressures to build a database of new vs old, roller vs flat > tappet cams, low compression vs high compression, etc. For example: > Compressions on a Lycon overhauled O320 with high compression pistons > are in the 140-145 range. Compression on a roller cam are in the 125 > range. Cranking pressure on the subject cylinder was only a point > below the other cylinders. Had the engine felt smooth in flight, and > reached red line in straight and level flight like it did with the old > engine and a bad cam, I wouldn't have thought anything about it. The > engine just didn't feel right. > > If Lycon finds something I'll post it. If the new cylinder is better, > I'll post that too. yeah pretty good you have that kind of cylinder, thanks for the help _________________ aluminum plate (http://www.preciseplate.com) Read this topic online here: http://forums.matronics.com/viewtopic.php?p=239735#239735 ________________________________ Message 9 _____________________________________ Time: 12:46:02 PM PST US Subject: TeamGrumman-List: Re: Squeaking nose gear From: "grumpyparts" The torque tube can be of three different make-ups, as far as I know. They are primarily made up of five parts. Two end plates, two toque tubes and a centre yoke, which the nose leg attaches to. If you follow the link below to the forum site you will see a picture of the assembly. In the original Grumman/Gulfstream tubes the two torque tubes were solely bonded into the two end plates. If both failed nothing stopped the nose leg rotating up into the bottom of the engine cowl. Frank Johnson then came out with a STCed repaired option where the tubes were bonded and tapered pinned to the end plates. Fletchairs and AGACs torque tubes were similar but instead of the one pin in each end plate and yoke they used two bolts at 90 degrees to each other. Pictures of these three different types are shown in the link below also as well as a failed joint Diagram taken from parts book Original bonded end plate Frank Johnson end plate Fletchair/AGAC/Tiger end plate Failure mode of bonded joint on end plate Comparision between Johnson and Fletchair tubes. One on the right is a failed Johnson tube, notice angle difference of nose leg yoke exit. Sorry about the kitchen background. Regards Ian MatAir Read this topic online here: http://forums.matronics.com/viewtopic.php?p=239738#239738 ________________________________ Message 10 ____________________________________ Time: 12:50:28 PM PST US Subject: TeamGrumman-List: Re: Squeaking nose gear From: "SteveR" Wow. Absolutely great information Ian. It'll be fairly easy to diagnose now, the hard part is just crawling under the panel. Thanks for the great information and pictures everyone. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=239740#239740 ________________________________ Message 11 ____________________________________ Time: 01:45:14 PM PST US Subject: TeamGrumman-List: Re: Squeaking nose gear From: "grumpyparts" Pictures tell a thousands words. I only wish more would use the forum instead of the email listings. All those formatting emails finally made me give up on the email option. Use the forum and formatting is not an issue. 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