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Hi Everyone

 

I want to replace the shock absorbers and springs on my Xair's main wheels. They look a bit like motorcycle gear. Anyone got any ideas re what they are or had experience buying/replacing them? Thanks

 

Bill

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They are motorcycle shocks made by Amstrong in India. I helped fit a set only a few weeks ago at our airfield.

 

That's the trouble when you wander around aimlessly on a Saturday morning at the airfield, you get put to work!

 

I remember having a good look at the box that they came in when I was putting it in the bin for the owner, it had the name Armstrong and made in India written on the box. They are way, way more stiffer than any mountain bike shock absorber.

 

I pushed my 100 kg body on top of them and they wouldn't even budge, I guess the aircraft is around 300 kg and when they are mounted they didn't compress at all with the weight of the aircraft, they only compressed with the pilot seated in the aircraft and then only a few millimetres I'm guessing. They must be for a pretty heavy motorbike because they are heavy, I'm guessing a couple of kilograms each.

 

They were replacing a set of fournales (I think that is the spelling) they were a nitrogen filled shock absorber but instead of having a spring on the outsidethey just worked with oil and gas. The chrome on the main shaft which I am guessing is about 30 mil diameter had started to peel off after about 15 years and it allowed the gas to escape because it damaged the seals. They looked like a very short motorcycle fork if that helps but the owner replaced them with conventional shocks because he said the other ones were no longer made. The gas shock absorbers would be lucky to weigh 500 g each so they were very light in comparison to what was put back on. To replace the shock absorbers on both sides only took around 25 minutes total time, the engine didn't even cooldown and the owner headed back to Boonah.

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Fournales still produce a lot of shock absorbers - was it just that particular model of Fournales that is no longer available? The Fournales can be rebuilt, couldn't he get any rebuild components?

 

http://www.mawsolutions.com/html/fournales_shock_absorbers.html

 

Heavy landings will produce a very substantial increase in loading on suspensions, due to the shock component.

 

If you operate a loaded crane, and drop the load just 50mm, then stop it again, the loading on the crane and components increases by 100%.

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Forces on the compression stroke will affect transmitted forces on the structure. Control of rebound is important with aircraft. You may also require rubber limit stops and a progressive spring. IF it coil binds or reaches a stop that doesn't have a bit of "give" it may damage the structure.. Nev

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The schock that were fitted had a progressive spring, more coils at the bottom and less at the top and it had a tappered rubber stopper at the top as well, from memory, say 15mm thick. I will be at the airport next Saturday and will ask if anyone is interested

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This is what my mate has done, woks well, If you put the mouse pointer on my name Waraton click start conversation and flick me a phone number so the owner of the aircraft can call you. I gave him a heads up and he is happy to share his experience which he described as "basically simple". This machine never sees bitumen and operates of some rough dirt strips.

 

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Hi Bill PM received and has been forwarded, he will point you in the right direction. Happy to help, I regularly seek advice from the collective knowledge of this group. Lucky to have it!

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