At the risk of a thread drift, the jabaru style floats look like a possible "cure" to another Rotax Bing problem of the guide pins coming loose. This is a scary problem in early models as the bottom of the pin hole arn't blind! The latest incident here saw a plane returning to its hanger trailing fuel, a bit of a close go!
I have looked into using these but the price was a deal breaker. They are definatly heavier which I don't think would be an issue if they are set up using The Rotax procedure of a syringe through the choke area. The float lever can be successfully tweaked to get the level right. Peace of mind I guess, but I check mine within every 25 hrs and have had only a few replacement due to variances. If the drip trays arn't used,checking is a very simple procedure of weighing or checking against scribed witness marks inside the float bowl so well worth the effort.
If I were to start over I would use the 6 pucks. There is the chance of combined sag but a little preload will negate this. I had a local engineer cut mine in a lath after freezing them. The suggestion of machining an angle is a solid idea . It's great to see so much enthusiasm for this project .
I haven't drilled the pucks yet, this is my next job. The reasoning behind this is to give the material an additional path to displace to and maybe soften the rate. If you can add extra pucks to your build this step may be unnecessary,the current setup works fine but I feel just a little softer/more wheel travel may be an improvement. I was thinking 5 x 5mm holes worth an option to encrease up to 10 mm?
Yes I used 4 pucks,1 inch x 2inch 1.5 deep.if I were to start from scratch. I would use more pucks as you suggest.You will loose some material when parting off but you have plenty of spare. I am not sure on going to 2 inch deep pucks, it may work in your favour to effectively soften your rate which is possibly a good thing. The diameter to depth ratio I assume will change the characteristics of the setup. Regarding sag ,there is a small amount over the last 6 months which seems to have stabilised 10mm?(similar to the die Spring) If you need to preload you can make a simple Spring compressor. I can post a photo later today . I am interested to know how this works out for you cheers Dusty
Your Spring may be a little long so will get a a weird looking sag in the straight part under normal use. By putting a constant curve in it ,this isn't so apparent. I don't know your setup but Avid/Foxes are typically nose heavy( not so much 2 strokes) so weight on the tail is a good thing. Extra leaves are advantageous with the benefit of still being able to fly and not having to repair a beat up rudder when a spring breaks. I run two springs with three staggered /tapered overload springs.
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.