Model 19 landing gear repair

[CaptainJon]

There appears to be a lot of rust (pitting) under the epoxy primer on one gear leg of my model 19 project. My neighbor, an A&P and career welder for the phone company, says he can make a jig and repair the gear. We assume it is all 4130 steel, being a 1951 model, so I need to order up some tubing. Instead of opening the gear legs up and measuring, can someone tell me the wall thickness of the two tubes that go down to the axle (straight in this case). Is it the same on BC12-D's and the F19, or did they change the size when they went to the 1500 pound gross planes..........

Jon

[3Dreaming]

The safest bet is to drill a hole and measure the wall thickness.

[CaptainJon]

Thanks, you are right. I was just trying to avoid doing that before my friend starts on it. Still new at this restoration stuff, I hate to destroy airplane parts (even knowing it's junk unless we fix it). Somebody probably has the specs............

Jon

[3Dreaming]

Drilling a small hole will not degrade the part in any manner regarding the repair. If you have a Cherry rivet depth gage you can get by with a hole as small as 1/8". Even a small wire will work.

[CaptainJon]

OK, progress being made on the right gear repair............. but, before my neighbor starts the repair he wants to ensure that the gear actually fits the airplane, as we know that MANY tubes were replaced back in 2013 by the previous owner........

Well, it does fit..... kind of........... I was able to get it aligned and the bolts in, but there seems to be an issue where the cross bar at the top hits the adjacent welding reinforcing strap,

keeping the gear leg from going to the fully "sucked up" position by a smidge. This shows the difference in space between the gear legs and the bumper pads......... note how the left one sits higher off the pad.........



Now is that smidge enough to be a problem or not..........

I put in the "bumpers" and the gear leg stops (hits that strap") just about when it hits the bumper..........

Not satisfied, I put Terri on her back and added the left gear leg to see if it had the same problem............ well, not quite, it contacts the strap just a little later............ So, the question of the day is how far should the gear get "sucked up" if the bungees were on? Should they be able to come up further (higher) than where they would contact the bumpers? Shouldn't the bumpers stop the gear legs, and not a binding back at the attachment fitting? I don't want the gear leg to be under added stress in the normal "sucked up" position............ Should the gear leg tube be parallel with the fuselage bottom tube when sitting against the bumpers? This shows them slightly above "parallel"......... Do I need to adjust the bumpers ?



There's just something wrong with this picture.............. hate to see her on her back.............



Cheers,

[Dick Smith]

The picture that shows the rubber bumpers...It looks like they may have been made using "ax handle protectors"...the one on the right side in the picture appears to be thicker than the one on the left. If you swapped the bumpers, the extra thick one might interface with the higher tube and capture it before the concern with the "metal to metal" contact point on the other end comes into play. Then you might have to fabricate a custom, "thicker" bumper to even things out on the side from which you borrowed. The best bet might be to cut the weld out on the end where the problem is and raise the joint a fraction to eliminate the offending contact point.

[CaptainJon]

Dick,

Good points. I am still not sure where the gear leg tubes should sit when fully pulled up by the bungees, but I have a feeling that they need to be parallel to the fuselage tube. The bumpers were roughly trimmed to fit and may need to be cut further. Still, I don't like the metal to metal contact back at the hinges........... The mechanic doing the welding may have been a little heavy on the reinforcing strap and his welding............ I probably should lift Tami T-Craft up and check where her gear legs go to...........

[Scott]

Your sense is right, there should be no metal to metal contact.

From the photo it looks like the top forward tube of the gear leg has been field welded as well. I'd check the location of that tube on the trunnion is correct.

Perhaps try another gear leg if you can get your hands on one.

[Dick Smith]

This picture seems to favor a parallel orientation, with the bumpers installed.

[Guest]

In addition to Scott's comments it also appears that the longeron has been repaired and perhaps the landing gear attachment lug has been twisted or bent into the wrong location and it is causing the pinch.

There appears to be a splice in the longeron just an inch or two forward of the attach lug.

Are the black marks on the paint from rubber mallet driving the bolt in?

The bolts should slide right in, if not that is an indication that the landing gear hinge line thru the mounting lugs or the hinge line thru the landing gear holes is not straight.

Take the gear off and put a 5/16 threaded rod thru the both lugs on the longeron and see what you can learn. Then put it thru both holes on the landing gear and see what you learn.

Then repeat on the other side, you will figure it out.

Dave R

[CaptainJon]

Thanks Dave,

I think you have hit on it! This plane has had major welding repairs by the previous owner while starting a rebuild that he didn't finish. Now I have to find out what I have here. My neighbor who is going to rebuild the gear leg said the same thing, "Start with a 5/16" rod and see if everything is aligned. Yes, the marks are from a rubber mallet.......

Then the question remains, if everything is not aligned, where do we go from here?

Then there is the contact issue......... I think grinding into the reinforcement strap just enough to stop the metal to metal contact might fix the situation, but how much will that operation degrade the strength of the strap? If we actually grind through the strap, then it would need to be welded again I assume..............?

When we repair the gear, we are starting with the Landing Gear Bearing Assemblies, AA53, which will be aligned by a 3/8" rod between the two. Of course, the bushing bringing the hole back to 5/16" , A520, is on backorder and I can't find a suitable replacement..... I need to call Wag Aero and see if they anticipate ever having them back in stock......

Cheers,

[3Dreaming]

For the A520 you can use 2ea. 5/16 ID x 3/8 OD x 5/8 long. They can be picked up from McMaster Carr.

[Guest]

Thanks Dave,

I think you have hit on it! This plane has had major welding repairs by the previous owner while starting a rebuild that he didn't finish. Now I have to find out what I have here. My neighbor who is going to rebuild the gear leg said the same thing, "Start with a 5/16" rod and see if everything is aligned. Yes, the marks are from a rubber mallet.......

Then the question remains, if everything is not aligned, where do we go from here?

Then there is the contact issue......... I think grinding into the reinforcement strap just enough to stop the metal to metal contact might fix the situation, but how much will that operation degrade the strength of the strap? If we actually grind through the strap, then it would need to be welded again I assume..............?

When we repair the gear, we are starting with the Landing Gear Bearing Assemblies, AA53, which will be aligned by a 3/8" rod between the two. Of course, the bushing bringing the hole back to 5/16" , A520, is on backorder and I can't find a suitable replacement..... I need to call Wag Aero and see if they anticipate ever having them back in stock......

Cheers,

If it was mine I would look on the inside of the attachment fitting where the reinforcement strap is that interferes. I would look to see if the bolt hole on the inside is round or oblong. If oblong I would consider removing the welded on washer would allow the oblong-less of the hole to resolve the interference. Then re-install the washer.

If that did not help I would cut of the weld shown in your first picture at post #5 l at the end of the tube (that has the black arrow pointer) that interferes and move it away from longeron and then reweld. Also check to see if that tube is the same size tube as the other side. It may have been replaced with a larger one than original.

Regrading the A520 bushings and things like that I just get 4130, 1015 or 10xx steel tubing from Wicks Aircraft that has the same o.d. and an i.d. that can be reamed to what I want. You can buy 1 foot and make many bushings.

Dave R

p.s. OOPS! I was thinking of steel bushing I bet you are working with bronze. I get those here => https://asbbearings.com/

[3Dreaming]

p.s. OOPS! I was thinking of steel bushing I bet you are working with bronze. I get those here => https://asbbearings.com/

I looked, and didn't see any that were 1.25 long. The length seems to be the problem. Also remember that when you install the new bushing(s) to remember to drill a hole for lubrication.

[Guest]

I looked, and didn't see any that were 1.25 long. The length seems to be the problem. Also remember that when you install the new bushing(s) to remember to drill a hole for lubrication.

Perhaps use two of these 3/4" long ones?

http://asbbearingsonline.com/index.php?main_page=product_info&cPath=87_89&products_id=4016

I think that is what I have done a few times, use two shorter ones to make up the length.

Dave R