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"A" model nose gear question

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WildThing

Well Known Member
Hi All,

I bought my 2003 RV-8A in FEB and am getting ready to do the (somewhat overdue) nose gear SB and install the new style fork. Here's the $64K question: Has anyone done or looked at just moving the top collar down 1" instead of cutting and re-threading the bottom of the gear leg? I called Van's and they said that they hadn't looked at it. My TLAR engineering degree (That Looks About Right) says that the extra hole is probably not an issue (?). The 1" of extra "down" leg on the gear tube below the bend would be subjected to more input from forward loads, but I'm having a hard time seeing that it would be failure prone. Any and all input appreciated - especially from actual load/stress analysis comparisons. Or some more TLAR engineering :rolleyes:

THANKS!
 
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Interesting idea - it would lower the tail a bit, might look a bit better sitting on the ramp. A little less margin for landing on the nose wheel, but nothing like the 6A I wouldn't think.
 
The fit of the nose leg fairing will change... probably require a custom fairing.
The bending moment on the leg at the sharp fwd bend will increase (I would guess about 20%)
The tail will be 3.5 to 4 inches lower (my guess) when sitting on the ground.
 
I'd suggest modifying the WD-631 swivel stop with a 1" longer tube extension, rather than drilling a second hole in the lower gear leg. Also I'd use the next thicker tube thickness for the mod as I've replaced two WD-631s on aircraft that had been damaged by unknowing rampies aggressively pushing back on the plane & you know what happens...
 
Thank you!

Thanks guys. That's pretty much what I came up with. I expected to need to "extend" the gear leg fairing. It needs cosmetic work anyway.

Ralph - great idea! I hadn't considered a reinforcing tube/extension. I'll see if I can locate a piece of tube and weld it together as a modified WD-631.
 
I didn't point it out in my other post, but it is entirely possible that the increase in bending moment this mod would cause to portions of the gear leg would 100% negate any benefit gained by doing the mod.
I.E. after all of the effort, you are no beter off than if you just left it as is,amd in a resale value consideration (assuming it might some day be one), you now have an airplane that has a one-off unproven mod done to it.

Have you investigated having the leg mod'ed as described in the S.B.?
I think the cost is quite reasonable (by aircraft dollars standards) and they turn them around relatively quickly.
 
I'd suggest modifying the WD-631 swivel stop with a 1" longer tube extension, rather than drilling a second hole in the lower gear leg. Also I'd use the next thicker tube thickness for the mod as I've replaced two WD-631s on aircraft that had been damaged by unknowing rampies aggressively pushing back on the plane & you know what happens...

This type of damage is far more often caused when builders installed the WD-631 180 deg out of proper position. This is very common. The proper clocking of the part is with the stop tang facing Forward.

Improper clocking does two things. It reduces the pivot angle to less than what is needed when a pivot turn on one wheel is executed (puts a high load on the part every time a sharp turn is done), and it makes it very vulnerable in any nose wheel shimmy event (that is what usually destroys them).
 
Thanks guys. That's pretty much what I came up with. I expected to need to "extend" the gear leg fairing. It needs cosmetic work anyway.

Ralph - great idea! I hadn't considered a reinforcing tube/extension. I'll see if I can locate a piece of tube and weld it together as a modified WD-631.

You are considering fitting a reinforcement and welding instead of just modifying the gear leg per the SB? We bought a die from McMaster for about $54 and did the mod ourselves, first adding the threads and the pin cutting of the extra with the die still on so it would clean the threads from cutting as it came off. Super easy job. I may be able to still put my hands on that die if someone wanted to borrow it.
 
This type of damage is far more often caused when builders installed the WD-631 180 deg out of proper position. This is very common. The proper clocking of the part is with the stop tang facing Forward.

Improper clocking does two things. It reduces the pivot angle to less than what is needed when a pivot turn on one wheel is executed (puts a high load on the part every time a sharp turn is done), and it makes it very vulnerable in any nose wheel shimmy event (that is what usually destroys them).

I agree the preferable mod would be to do the SB method, just made the suggestion of modifying the WD631 to avoid the idea of drilling a second hole in the leg.

Also WD631 damage to the two aircraft mentioned was probably caused by repeated push backs without using a tow bar & letting the nose wheel forcefully jam sideways. in both cases the weldment orientation was correct. Damage in both cases were discovered during Annuals.
 
You are considering fitting a reinforcement and welding instead of just modifying the gear leg per the SB? We bought a die from McMaster for about $54 and did the mod ourselves, first adding the threads and the pin cutting of the extra with the die still on so it would clean the threads from cutting as it came off. Super easy job. I may be able to still put my hands on that die if someone wanted to borrow it.

Jesse, yours must be soft steel if it was super easy. Pete Howell and I did two of them, and they were a real bugger. Clearly in the "we'd never do that again" category. We had a tool room quality die set, and I've done plenty of machining, but wow, that was a real bugger. There is a thread (fun pun) on these forums about our trials.
 
Jesse, yours must be soft steel if it was super easy. Pete Howell and I did two of them, and they were a real bugger. Clearly in the "we'd never do that again" category. We had a tool room quality die set, and I've done plenty of machining, but wow, that was a real bugger. There is a thread (fun pun) on these forums about our trials.

I agree with Alex. The leg is very hard and it is not an easy thing to do.
I strongly recommend using Langair for the work.
 
I did mine after talking to a friend that owns a local machine shop and getting a quality die from him (about $60 I think). I actually did mine still on the plane (braced it some how, but can't remember exactly what I did) Used plenty of cutting oil and about a 2 ft pipe on the end of the die handle. I was very apprehensive about doing it after reading the thread explaining how difficult it was, but found it to be a non issue. In fact, I thought I must have done something wrong as it was no where near as difficult as the thread made it sound. Perhaps,I just got lucky... Maybe it's a die quality thing? Not advocating one way of the other, but my experience was quite different then those that posted on that thread. As a matter of fact, I found cutting the excess threaded length more difficult then threading it. I also left the die threaded on the leg and then cut the excess off in so that the die would clean the threads after the cut.
 
I did mine after talking to a friend that owns a local machine shop and getting a quality die from him (about $60 I think). I actually did mine still on the plane (braced it some how, but can't remember exactly what I did) Used plenty of cutting oil and about a 2 ft pipe on the end of the die handle. I was very apprehensive about doing it after reading the thread explaining how difficult it was, but found it to be a non issue. In fact, I thought I must have done something wrong as it was no where near as difficult as the thread made it sound. Perhaps,I just got lucky... Maybe it's a die quality thing? Not advocating one way of the other, but my experience was quite different then those that posted on that thread. As a matter of fact, I found cutting the excess threaded length more difficult then threading it. I also left the die threaded on the leg and then cut the excess off in so that the die would clean the threads after the cut.

Might want to get a hardness test done on that leg. Your experience is so different from the norm on this.
 
Hmmm... Hardness test? This concerned me so I reread some of the old treads. Looks like several others have completed the mod themselves, bad batch of legs? Actually could not find one post of someone who started it but could not complete it. People had varying levels of difficulty when completing it, but that is relative, right... Some people would never dream of building an airplane! Again, it was a while ago, so maybe it was harder than I remember. I did see the price to have it done was only $75 (plus shipping). I paid that for the die with shipping. If the time to have it done (several weeks) was not an issue I would have sent mine off as well.
 
Roger....

Thanks guys - great input! I was hoping to find a viable way to install the new gear fork without the time delay of sending the leg out. Currently, I'm going to try and come up with a local shop, but wanted to see if anyone else had come up with a better mousetrap. I'll let you's know how I end up doing it.
 
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