Let's talk gear geometry

41 posts in this topic

Posted (edited)

JF - and I think I could pronounce your name, but you would laugh at my attempt to write the spoken words in American! Half of my ancestors were from Quebec and Arcadia...

4130 is the strongest for the weight, weldable, most cost effective, steel that we can get for our planes.

Some guns are made from 4130, or the 400 series and other Stainless equivalents.

Do you have any alternative suggestions?

Some of us on here have a background in metallurgy and welding.

EDMO

Our planes could be made stronger and heavier, but they might not get off of the ground - Like the African tank! :lol:

EdMO

BTW: I saw some Hydrosorb parts on ebay today...

Edited by Ed In Missouri
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Posted

4130 is a very pliant metal, yes. That is what makes it perfect for aircraft. It will bend rather than break. It is also very light, due to its strength, compared to other alloys.

A rubber bump-stop would be a great idea.

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Posted

4140 sound good for that job...and i take some info on net for reinforcement on fuselage around the gear attach section ..i want to make it before covering..

Jf

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Posted

What is hydrosorb???

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Posted (edited)

What is hydrosorb???

Maybe some others can explain it better than I can:  Some Pipers and other planes had a gear that used something like the shock absorbers used on cars instead of the bungee cords.  It was supposed to be a better system.  I don't know if it is only shocks or contains springs with the shocks.    EDMO

Edited by EDMO

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Posted

What is hydrosorb???

Maybe some others can explain it better than I can:  Some Pipers and other planes had a gear that used something like the shock absorbers used on cars instead of the bungee cords.  It was supposed to be a better system.  I don't know if it is only shocks or contains springs with the shocks.    EDMO

The hydrosorbs were used in conjunction with the bungees on the pipers.  Its just basically an inline shock.

:BC:

 

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Posted

I finally got to do a little playing with the gear. I made a mock-up and ran some tests, and here is what I found, or think I found anyhow. I documented what I did, and since the file is long, instead of posting it here and taking up space, I have attached it as a .doc file. If you are interested, you can read it, if not, ignore it. I figure if you guys find anything wrong, you'll soon let me know.


Bob Landing Gear Geometry.doc

Landing Gear Geometry.doc

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Posted (edited)

I finally got to do a little playing with the gear. I made a mock-up and ran some tests, and here is what I found, or think I found anyhow. I documented what I did, and since the file is long, instead of posting it here and taking up space, I have attached it as a .doc file. If you are interested, you can read it, if not, ignore it. I figure if you guys find anything wrong, you'll soon let me know.


Bob Landing Gear Geometry.doc

Landing Gear Geometry.doc

This sounds like a good one to get Leni and his CAD mechanical engineers working on?  I think he had already figured that the cabane had to be lowered?   EDMO

Edited by EDMO
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Posted

I am going to try to build a set of gear to the dimensions and angles used on the Piper Cub. Has anybody built gear where the front leg comes straight down from the fuselage instead of leaning forward 3 7/8 inch. This would put the mains a bit farther back. It would make the gear leg and the cabane easier to build.\

It would make the tailwheel come up faster but what other effects might it have?

 

Bob

 

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Posted

That is the way I had my new tall gear built with no defects and would do so again.

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Posted

 

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Posted just now · Report post

Update on the gear. One possible fix for existing gear. I had two yokes made similar to the yoke on a universal joint. They were made out of 1 1/4 cold rolled square stock. I threaded them 3/4-16 inside, and turned that end round to give 3/8 inch wall thickness. The fork end I milled out 7/8 inch wide to provide +1/8  wall thickness, and drilled that 1/4 inch.

I then made new longer axles, but threaded the inboard end to give a tight fit on the thread. The fork was threaded on, then drilled and pinned. I had to make new lower spring strut rods since they are shorter than original. The only issue I had was that the axle end of the spring rod has to be canted a bit to fit to the existing cabane. That and the 3/4 inch tubing AirSpruce provided won't accept a 3/4 inch wheel bearing without polishing it first.

The top (spring) end of the inner rod should be doubled internally to avoid the hole tearing out. I saw that happen on a Super Cub clone.

I put the gear back on the plane, but have not tried it yet.

The other possible fix is to weld tabs to the existing axle tubes. I will try that next.

MVC-011S.JPG

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MVC-008S.JPG

MVC-009S.JPG

MVC-010S.JPG

 
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Posted

Arent those the red springs that everyone decided that they would not allow enough travel?   Leni replaced those with some SnoGo black springs that didn't bottom out so quick, and he made longer slots to allow more travel.   EDMO

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Posted just now · Report post

Update on the gear. One possible fix for existing gear. I had two yokes made similar to the yoke on a universal joint. They were made out of 1 1/4 cold rolled square stock. I threaded them 3/4-16 inside, and turned that end round to give 3/8 inch wall thickness. The fork end I milled out 7/8 inch wide to provide +1/8  wall thickness, and drilled that 1/4 inch.

I then made new longer axles, but threaded the inboard end to give a tight fit on the thread. The fork was threaded on, then drilled and pinned. I had to make new lower spring strut rods since they are shorter than original. The only issue I had was that the axle end of the spring rod has to be canted a bit to fit to the existing cabane. That and the 3/4 inch tubing AirSpruce provided won't accept a 3/4 inch wheel bearing without polishing it first.

The top (spring) end of the inner rod should be doubled internally to avoid the hole tearing out. I saw that happen on a Super Cub clone.

I put the gear back on the plane, but have not tried it yet.

The other possible fix is to weld tabs to the existing axle tubes. I will try that next.

MVC-011S.JPG

MVC-006S.JPG

MVC-008S.JPG

MVC-009S.JPG

MVC-010S.JPG

 
  •  

 

84c1e40ea0e759e3f1505eb1788ddf3c_default
 
 
 

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Posted

Ed;

Yes, Thanks.

Actually they are die springs from McMaster Carr. 9584K98. They are six inches long, and will compress to 3 inches. McMaster also lists an eight inch spring. I have the numbers for the Ski-Doo springs. 503190854.  They are readily available for about $50 each. I also kept the dimensions for the spring struts, and can make a replacement set without taking the gear back off the plane. I only need to make the spring carriers. Two bolts on each side changes them.

Incidentally, the Super Cub only has 3 1/2 inches of travel. Measured it myself.

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Posted

Just thought I would put in my 2 bits. I built a Bush gear for my Mod 1 Kitfox. I used die springs in a housing similar to the bearhawk gear. Designed it to take 3 G's before spring would go solid. I did a very poor landing. The gear held up fine but the fuselage failed. I don't believe the springs went solid because the safety cable cable ties were unbroken. I have considered building new tension members with bungees. I believe an Aluminum Spring Gear or bungees are the more forgiving as they provide the most flex (not including the new Highlander gas strut gear). Here is a link to the drop test video I did on my gear; http://www.youtube.com/watch?v=fvQtKQ5gHVY

Dave  

I know this is an old thread, but what was the spring you specified, that was used in your video (drop test)?

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Posted

A skidoo 503190854 seems to work well.

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Posted

Rather than repeat my last reply on bush gear failure thread,I add a comment on Spring replacement.it may be of some help?

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