The inside and outside diameter is stock,we are metric here but I suspect they were supplied in imperial which is fairly close. The internal diameter felt a little tight so I wrapped a bit of tube in sandpaper and clearances it, I don't think this is really necessary as friction is an advantage. I used grease more for corrosion control. 4 pucks fitted the high tech ( looks about right) philosophy . The distance between washers however is an area worth experimenting with(3x50mm v's 4x38mm?As is extra length of the puck assembly(your 8-10' sounds good).I used Standard washers however they could be fibreglass or CF . I am keen to see others experimenting with this setup as at the moment rebuilding a fox 4-1200 for my brother is taking most of my non flying spare time cheers Dusty
The pucks are definitely firmer than the springs., which I believe is a good thing as my spring setup had been bottoming out.
This is the top of the rod that goes out to the wheel. The bolt was partial chopped through from the hammering. I fly off field a lot and on some pretty rough hillsides. I have tried different urethane shore hardness. Currently the red (90) is the best. I tried a 75, which was too soft and sagged.
The next step is to machine the pucks to have grooves around them, or vertically drill them. Like a pistol magazine. Urethane can't be though of as a spring as it doesn't compress. Think more like water where it just displaces and absorbs energy in the process.
The piece of wire is my high tech device for measuring suspension travel. This is from a normal landing, so there is plenty of travel, but I would like more.
If rebuilding a suspension I would use 5 or 6 pucks to effectively change the rate. My weight saving calculation was out a little, approximately 1.4kg weight saving. We get the urethane here from an industrial supplier as a one piece tube. We freeze it,and part it off in a lathe. This is extremely cheap so not a huge cost for experimenting. I have a wee way to go, but even at this stage I see a huge improvement over the die spring. I will post updates as I go, but am pretty busy with work at the moment, and rebuilding another kitfox.
Regarding springs,my choice would be acme aero springs but my budget (read wife) says no way. I am experimenting with eurethane pucks with some success. 2 kg weight saving,no chance of bottoming out and a degree of rebound damping.some more hard testing is required but results are favourable.
I've posted most of the results of how a kitfox compares to other aircraft. The 701s are all flown by previous competition winners. The airfield is 100ft above sea level. Due to a miscalculation I still had 60 litres of fuel on board.
Does anyone have a NGK or Bosch reference number for the 582 mod 17 plugs .Rotax p/n 297656. These are like the 912 type with small thread and double electrodes. These plugs are like trying to find a one ended stick!!
Here is my first attempt at a stol competition. I've now got the bug. Kitfox JFA starts about 1.40 This class was the tightest and I still got 4th among the 701's It's interesting to see how all the different aircraft perform and people were surprised how an 80hp heavy kitfox can perform I can post the results in metres if anyone is interested
Mine was originally riveted with washers on the capstrips. I epoxied a spruce strip to the back of the capstrip for a good bite for stainless screws. The screen replacement will be easier next time. Don't be tempted to try 1.5 mm lexan as the flexing above 90 kts is a bit disconcerting!