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Homemade jack pads

Bicyclops

Well Known Member
Howdy,

Inspired by the cool jackpads from Winter, I made my own out of 1" X 1 1/4" 6061 T6. I did the whole deed with out much more than a drill press, carbide burr, and a miter saw. The mounting holes are 15/16" OC and I used AN4-21A bolts. I had to make one spacer at about 17/64". The AN4-31A bolt only has about a half inch of threads so I reamed the hole halfway and tapped the rest. That way the shank of the bolt is in shear. I made a sleeve out of 3/8" OD 4130 reamed 1/4" ID to take advantage of more bending resistance and so I could torque the bolt into place for jacking. The pad weighs less than 2 oz. and fits under the wheel pant with the jack bolt removed. I bought an aluminum Porsche jack on Ebay which weighs less than 3 lb. I'm gonna throw that in a bag for the baggage compartment on cross countries. With a spare tube and a CO2 inflator, I'm ready for tire trouble.

Ed Holyoke

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Thanks for sharing this! It's a good idea and definitely feasible without a machine shop.

Nicely done.

Dave
RV-3B, still on the fuselage
 
Can you get the jack under the flat bottom of the mount without using that bolt?

Dave

Not happily. The base of the jack would be right up against the tire and I only have an inch of block to work with. I wanted to have full registration on the jack to reduce the chance of slipping off. The bolt through the slot seemed to me to be the best/easiest way to accomplish that. If I had made the block thick enough to put the jack on, the wheel pant wouldn't fit over it.

Hmmmm..... I could, I suppose, make a block that bolts on instead of the bolt sticking out with the bottom flush to the one on the axle. I do like the way the bolt in the slot of the jack keeps it from moving fore or aft, tho.

/Looks like that may easily break off? /

I hope not. I've got a lot of meat where the bolt is. With a half inch of shank in a snug fitting (reamed) socket, I'm trying to prevent the bolt from bending at the end of the threads. I think that also reduces the stress on the bottom of the threaded area. If the bolt were to pivot on the fulcrum of the edge of the hole, it would try and blow out the bottom of the threads.

I jacked the tire right off the ground using this setup and nothing bent. We'll see how it holds up to continued usage, but so far I think it works as intended.

Ed
 
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If you are really worried about the strength of the bolt, widen the slot in the jack, and up size the bolt.

The reamed hole bearing on the shank is a good idea, puts the stress where it belongs, not on the threaded area.

I may have to steal this idea............
 
Are the 2 bolts (heads flush with the aluminum bracket) replacing the lower 2 bolts holding the axle to the gear? If so, it looks like much longer bolts with the head on the opposite side than before the mod. On my RV9A, all 4 bolt heads are on the outboard side. Are there any issues with clamping force (axle to gear) being reduced due to softness of aluminum? I.e., aluminum yielding over time?
 
Are the 2 bolts (heads flush with the aluminum bracket) replacing the lower 2 bolts holding the axle to the gear? If so, it looks like much longer bolts with the head on the opposite side than before the mod. On my RV9A, all 4 bolt heads are on the outboard side. Are there any issues with clamping force (axle to gear) being reduced due to softness of aluminum? I.e., aluminum yielding over time?

Yeah, I used the two lower bolts on the axle to brake stay. They have been increased in length to account for the 1" thick jack pad. I turned the bolts around so I could get the jack closer to the axle. One of the bolts required a longer spacer to get it out flush with the wheel pant bracket. I was a bit concerned about the nut and washer being on the wheel side of the brake stay, but it clears everything just fine. I don't think I'll be able to significantly crush the 1" thick block of aluminum, and I will inspect for tightness every time I remove the wheel pant. The nut side of the bolt is on the steel brake stay, so no problem there.

Hmmmm..... Flush with the jack pad. 'Nother idea. I could counterbore the jack pad for the bolt heads and install shorter bolts. That would allow me to get the jack that much closer to the action and I could use a shorter bolt and spacer for the jack. I don't have a piloted counterbore to make a nice flat bottom hole, so I probably won't bother.

Ed
 
I see no problem with the design using a good quality bolt.
I have never weighed an aircraft main but I don't think I could bend that bolt.
 
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Somebody interested in crowdsourcing this?

I like this idea a lot, C/S the bolts makes it even better. I?d buy a set. It hits on my biggest C/C concern.
 
When jacking does the gear leg move outwards? I have the Avery type jacking arrangement and as it rises the gear leg moves outwards.
 
When jacking does the gear leg move outwards? I have the Avery type jacking arrangement and as it rises the gear leg moves outwards.

I didn't notice it move significantly, though you might expect it to have done some. With the Avery style pad you are sticking a tube into the end of the hollow axle and putting a jack, what, about 10" or so outboard of that. That's what I used to get it off the ground while I was installing the jack pad and I did notice the flex to which you refer. You are basically levering it up and it's no real surprise that it bends as if it were in the process of a hard landing. Where the jack pad is mounted is putting the lifting force right into the gear leg instead of out at the end of the axle.

I was wondering if my new setup would wind up putting the auto jack up on an edge. That's the main reason I wanted the jack bolt to be the full width of the jack. I was hoping that the head of the bolt would prevent it falling off if it came to that. It didn't move on the bolt at all and, as you can see in the picture, there is still space before the jack hits the bolt head. Though it isn't obvious in the picture, the tire was well off the pavement. I'll have to jack it up again and see if I can get a measurement of any outboard movement, but I didn't notice any the first time. My impression is that it went straight up.

Ed
 
Using 1/2" Bolt and 29k psi as point the bolt starts to bend, shows it would be around 5,800 lbs. Hopefully nobody built an RV that heavy.


A 1/2" bolt will shear @ around 10,000 lbs


I suspect bolt size is not a problem.
 
Using 1/2" Bolt and 29k psi as point the bolt starts to bend, shows it would be around 5,800 lbs. Hopefully nobody built an RV that heavy.


A 1/2" bolt will shear @ around 10,000 lbs


I suspect bolt size is not a problem.

I'm using a 1/4" bolt with a sleeve of 4130 around it, bringing it to 3/8" OD. I think that the ultimate strength of the bolt isn't the issue, anyway. I wouldn't worry about shear. Bending would be the potential problem and I don't think it will.

The hole in the jack pad is probably the vulnerable part. It could oval at some point. We'll see. I wanted to reduce the stress on the tapped threads by carrying the load in shear as much as possible. I could have set a heli-coil, I suppose. If the threads start getting loose, I will. It's not like it's going to get used very often, anyway. At annual to rotate the tire and grease the bearings and maybe once more if I manage to wear out a tire in between annuals. If it holds up through one flat tire repair away from home, it'll have been well worth the effort.

Ed
 
I was wondering if my new setup would wind up putting the auto jack up on an edge. That's the main reason I wanted the jack bolt to be the full width of the jack.

Brilliant job!

The first time I had to jury rig a solution to a flat tire I used the smallest (lowest!!) scissor jack I could find and put it under the small bolt that holds the wheel pant to the axle nut. Clearly not a robust solution but it served the purpose. But YES, it does tip the jack. It worked but I wouldn't try it again unless under the worst circumstances.

I learned 2 things. First, you need a small or large amount of extension away from the wheel or you cannot get the jack close enough to sit under the jack point. Two, you probably need some amount of height added to the jack point as well, or the jack will likely be too tall to fit under the jack point.

Thanks for the ideas. I am going to take a look at the problem again using you solution. I like the fact that I can build something using hand tools!!

Incidentally, when I saw your mount, I presumed it was temporary. So in my mind, I could fabricate something that wouldn't fit under my wheel pant because I could carry it in my flight bag and attach it as needed with an open-end wrench.

Thanks for sharing!!
 
What about using the holes where the tie down rings screw in? I bought a couple of Category8 bolts at Tractor Supply, screw them in and put the jack under that and it lifts the entire wing. I got the idea here https://antisplataero.com/products/quality-jack-points

A lot of people like that scenario. Probably responsible for a surge in tall bottle jacks at one point. I don't feel comfortable with that idea. There have been some slips.
 
What about using the holes where the tie down rings screw in? I bought a couple of Category8 bolts at Tractor Supply, screw them in and put the jack under that and it lifts the entire wing. I got the idea here https://antisplataero.com/products/quality-jack-points

Better than nothing while in the shop. Useless on the road unless you can find somebody with a tall bottle jack. We used to jack using tie down rings screwed into the bottom of the wing until the day we broke one. I don't recommend that! Got lucky and didn't punch a hole in the wing.

My jack pad solution allows me to use a floor jack in the hangar and the scissor jack when on a cross country. I probably won't bother to load it for short jaunts but I'll definitely have it with me when I go long distances.

Ed Holyoke
 
Sounds like I'll leave mine for shop use then. We have tall jacks that are used for some Bonanzas my IA services.

I'll look into the other type for the rest of the time. Thanks.
 
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