Materials for sprung struts
 

Hi,

I was considering making a set of sprung struts for a DH mosquito but i was wondering what type of material to use. I've seen Aluminium, brass and copper tube available but which is the best to use.

Cheers

Hi :ws: Unless you have a Machine Shop, its cheaper and easier to buy them already made.

http://www.altecare.com/struts.htm

Aluminium tube is obviously the lightest but "aly on aly" makes a horrible combination that wears very fast.
Steel on aluminium is a bit better but brass on steel is very good, particularly if it is modestly lubricated.
Do you have a design in mind?

No design in mind at the moment. I have future plans to build a DH Mosquito which is my favourite warbird. I'm at the bottom of a very steep learning curve for both flying and building so i don't expect to build it for a year or so. I was just thinking out loud really.

Well, since the Mosquito is your dream, you will no doubt have noticed that the full size had very thick legs. This was because it used rubber sandwiched between flat plates, so you could be REALLY scale and do it that way without getting into different metals.
All the Mosquitos (including my own) that I have ever seen use oleos that are far too thin to look scale... so that's laid down a challenge for you!

Yes the springing was done with rubber & flat plates as shown here.
Attachment 162597
However it still required a close fitting sliding tube at the bottom of the leg to take the side loads.
Attachment 162598
The appropriate material selection would still be critical in this location but as you point out at least there is plenty of room in the scale legs.

I would suggest doughnut shaped rubber blocks and plates (washers) with a small diameter music wire running through to centre them and slide in a small diameter tube at the top of the leg and the thicker bottom of the leg made out with brass tubes (K&S do a range of incremental sizes) to run in a larger diameter ring at the bottom of the leg. That way you have two sliding positions with the springing between them.
(Of course you could do the same arrangement with conventional springs!)

If you want good information on various metals and what they can be used for, this web site works well. They also sell their stuff at decent prices. you can buy anything from tool steel in 1/16 inch or 2 mm and larger, to a piece of aluminum bar stock 16 inches in diameter. (For that 16 inch diameter stuff, bring your credit card!)

A few years ago I bought two pieces of tubing from there, 4 by 8 inches in size, 24 inches long with a 3/8 inch wall thickness. Converted a Sherline Lathe to a vertical milling machine with it. Yeah, it is heavy.

And, more recently, picked up some aluminum 3/8 inch thick flat stock, and used it to build up that 60 Amp 12 volt DC supply. (The original alternator failed by going to 18 Volts DC output. So now its an 78 Amp DC supply.) Ref http://www.wattflyer.com/forums/showthread.php?t=66066

http://www.speedymetals.com/

After some experimenting, I'm using aluminum outers and stainless steel thin wall tubing for the inners. Al on Al works, but does wear fast and the inners look bad quickly. You've really got to be careful of weight, especially the smaller you go, so tubing is your friend. After many, many hours I just finished gear and retracts for the He-111 in 1/13 scale (I do have a machine shop). The gear took about 3x as long as it would take to just scratch build the rest of the plane, but they are scale in look and exact scale in function.... Do you have any good scale drawings and reference pictures? I can probably provide some guidance.

Wow, that is incredible machining work!

I recently completed 3 sets of retracts for BT 81 Mosquito's. Check out the builds on Rc Groups under "Mosquitos in formation".
Here's a pic of the LG,made from HobbyKing oleos, some aluminum and steel arms. They have been tested but not used yet. They will have a 12kg servo each for operation. Weight is approx 12.5ozs each with the 5" wheel. flying-barely:D

That looks like a good way to do it.. Have any good pics/drawings of mossie gear? Might be fun to model up...

(Thanks for comment DennyV)

Hi spinnetti There are no plans, I took what measurements I could from the 81" Brian Taylor Mosquito plans. I made a jig from those dimensions.
Whether they will work has to be determined this spring. They certainly seem strong enough. I used 130mm oleo struts, and 5" aluminum hub wheels from HK. Lift is provided by a 170oz HD Power servo for each, pushing thru a 3/16" steel rod connected by 4mm ball links.
You can see all the pics on RC Groups, under Giant Scale, the thread is called "Mosquito's in formation. flying-barely;)