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Advice on materials to use for 1/4 or 1/3 scale undercarriage

General discussion on any topic which doesn't have a natural home on any of the other boards.
John Treble
Posts: 14
Joined: 13 Jan 2021, 11:08
Location: Lyme Regis

Advice on materials to use for 1/4 or 1/3 scale undercarriage

Post by John Treble »

I have started drawing up plans for a 1/4 or possibly 1/3 scale project, which sports a substantial undercarriage used to aid auto- or aerotowing. I have access to an original set of plans as they were sold to potential home builders which are (not surprisingly) very detailed. The full size undercarriage was built mostly from mild steel tube and sheet, cut, bent, drilled, welded and crimped as necessary. For instance, there are several struts made of tube, with crimped ends or U-section fittings welded to the end.
My question is this: Does anyone have any ideas as to how best to render this to scale? I would like to recreate the original structure as closely as possible, but I don’t think using the original material is an option. It needs to be functional of course and therefore robust enough to stand the stresses of landing. Weight is also a consideration, of course.
Since I am interested in your ideas, I won’t say what options have crossed my mind.
Jolly Roger
Posts: 573
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Advice on materials to use for 1/4 or 1/3 scale undercarriage

Post by Jolly Roger »

Hi John,

You could use carbon tube or rod with an inch or so of thin brass or aluminium tube sleeved over each end and crimped to simulate the full size?
If you go with tube, you may know there are different types. Pultruded is cheapest, fairly strong in bending but can split along its length under the kind of shock load an undercarriage gets. Roll-wrapped has fibres running circumferentially as well as lengthwise, so is more robust.

I used carbon tube to make a Piper Cub undercarriage. The tube was actually just a shell to give a nice finish. The strength came from the bundle of epoxy-soaked carbon tows that were dragged through the inside of the tubes. Here’s a link….

viewtopic.php?f=10&t=2725

Have fun!
Rog
John Treble
Posts: 14
Joined: 13 Jan 2021, 11:08
Location: Lyme Regis

Re: Advice on materials to use for 1/4 or 1/3 scale undercarriage

Post by John Treble »

Thanks for this, Roger. I knew someone would have tried something similar!
I was thinking of somehow combining brass or aluminium tube and carbon rods. The u/c I want to model consists entirely of straight pieces of tube pinned or bolted together. It also has rigging wires keeping it all in shape.
SP250

Re: Advice on materials to use for 1/4 or 1/3 scale undercarriage

Post by SP250 »

John

I have just come across some articles I saved in magazines on how to make Cub or Stampe style undercarriages and also have access to a Fi156 Storch one built by Unitracts when they were trading.
If the UC you want to make is similar, or can use the same techniques, I can scan the pages and take pics of the Storch gear for you to copy/study.

All depends on what type you are trying to emulate really.

John M
John Treble
Posts: 14
Joined: 13 Jan 2021, 11:08
Location: Lyme Regis

Re: Advice on materials to use for 1/4 or 1/3 scale undercarriage

Post by John Treble »

Yes, please, John! Interested in anything you can offer. The type is a BAC VII, a British glider from 1931. I attach photos of the two drawings of the undercarriage, and one of the parts to illustrate how the full size was made. I’m new to this game, and have little idea of the relative strengths of materials. The mild steel specified here was, I suppose, sufficient to take the stress of landings in the full-size. How this compares to brass tube with CF infill at quarter scale, I haven’t a clue. Then there’s the weight….

90BB7B49-01DC-4390-B278-FEB8D32E8F5F.jpeg
B39AE6C5-9077-4DA7-8019-F86DBBE09AAF.jpeg
2B29390C-57DA-4D79-8458-E799A909D1D4.jpeg
SP250

Re: Advice on materials to use for 1/4 or 1/3 scale undercarriage

Post by SP250 »

John, PM me your email address and I will scan and send over as soon as I can.

Cliff, my PM messages are not working - I couldnt send John a PM.

John M

All permissions are set as they should be. Check to see if your in / out boxes are full or not. I have sent you a pm to test.

Screenshot(2).png
John Treble
Posts: 14
Joined: 13 Jan 2021, 11:08
Location: Lyme Regis

Re: Advice on materials to use for 1/4 or 1/3 scale undercarriage

Post by John Treble »

My email is in the BMFA News very now and then, so it might as well be here!

J.g.treble@swansea.ac.uk

Looking forward to hearing from you, John.
SP250

Re: Advice on materials to use for 1/4 or 1/3 scale undercarriage

Post by SP250 »

John

Just sent all the scans over on your email.
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