landing gear

Discussion in 'Warbirds / Warbird Replicas' started by arcticserv, Aug 23, 2007.

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  1. Aug 23, 2007 #1

    arcticserv

    arcticserv

    arcticserv

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    Hi all, things have been moving slowly though the spar is now half completed.
    Have been doing a lot of experimenting with urathane disc's for the landing gear suspension, I got the idea from this forum and on investigating found that the Chipmunk and the Mosquito used this method of supension.
    I have tested many different types of urathane made here in Australia, but with not much success.
    Some had suggested fibroflex in one of the threads I had read here, so
    I pursued this company which I found in Germany, the have very comprehensive data on their products which turned out would have saved me a lot of time and expense if I had went to them first.
    Any how we have successfully designed and tested a leg (as attached j-peg)
    to give 135mm of travel under 1250kgs per leg.
    This is sufficient for a 950 kg aircraft to have up to a 3.5 g landing, (including tyre crush).
    If your looking for urathane rubbers you cant go past Fibroflex
    http://www.fibro.com/xdesk_neu/ximages/265/1145_b2hkgb2006.pdf
    Have also put a picture of setting up the outer wing spar jig just for interest.

    Shane
     

    Attached Files:

  2. Aug 23, 2007 #2

    PTAirco

    PTAirco

    PTAirco

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    Rubber discs in compression were very common in British aircraft of the 30's and 40's. In compression it tends to be more effective as a shock absorber than ibn tension such as bungees. I believe even aircraft as large as the Mosquito used them. It was recomennded not to to stress the rubber much over 200lbs/sq.in though to get a good service life out of it. Urethane sounds good, but can you get it as soft as typical neoprene rubber?
     
  3. Aug 24, 2007 #3

    Dana

    Dana

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    Polyurethane is available in a wide range of hardnesses, from around 10 Shore A (very soft) up to 85 Shore D (like hard plastic):
    [​IMG]
    Of course those earlier aircraft probably used natural rubber or neoprene as I don't think polyurethane existed then.

    -Dana

    You do not need a parachute to skydive. You only need a parachute to skydive twice.
     
  4. Aug 24, 2007 #4

    Falco Rob

    Falco Rob

    Falco Rob

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    Shane,

    Can I ask what model no. discs you used and if these guys have an Australian distributor?

    I played with making replacements for the gas struts on my Falco using urethane do-nuts but the ones I eventually bought were super hard.

    I finally bit the bullet and had hydraulic struts fabricated as per the plans, but they do have a reputation of leaking oil and deflating, so having an alternate would always be a good thing.

    Rob
     
  5. Aug 24, 2007 #5

    arcticserv

    arcticserv

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    Rob, I purchased the fibroflex spring through Bruderer Australia,
    Model No 246.6.040.040 which is a 90 shore A 40mm dia and 40mm long,
    I used 13 of these per leg with .5mm stainless disc's and a 3mm disc in the centre to aliviate the tendency to bow.
    Speak with Rudi on 0419400995.
    I pre compressed to 494 mm in length which gives a pre-loading of 220 kgs.
    Iam not sure if will suit your needs because to get the results I have the total leg length not counting the wheel or the fork ended up at 770mm which suited the p51 scale I am using.
    If you look at the site I listed at around page 50 through to 65 you will be able to design of these figure as they are quiet accurate.

    Shane
     
  6. Aug 29, 2007 #6

    Falco Rob

    Falco Rob

    Falco Rob

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    Shane,

    Ok, many thanks for the detailed info - I'll check them out.
    Good luck with the Mustang.

    Cheers

    Rob
     

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