Since I am now many miles away from my KR2, I keep myself busy by making some parts that do not require many measurements. I started with redoing the throttle quadrant. Of course, you don't need a throttle quadrant if you are happy with a push-pull, vernier type throttle, but if, like me, you like to fly "HOTAS" (Hands on Throttle and Stick, another militaruy acronym), fighter style, a quadrant is not only nice to have but also fairly easy to make. Today, ZS-WEC (that's my KR2) just has a boat type aluminum handle that is simply bolted through a hole to a plate along the side wall, and tightened with a locknut. It has worked fine for eight years, but it lacks two things: adequate protection, and adjustable friction.
My new throttle is now finished. I am very happy with the result. In fact, it is the best looking part I have ever made. Pictures available, as well as Power Point templates to cut the parts, if you want to replicate it. It is a bit overdesigned, but as Tony Bingelis puts it, it's the single most used control, so, maybe it's worth a few extra grams and added effort. Here are a few advices that will save you some trial and error. - The most difficult part to find is the knob. Ideally, what you need is a screw, anything between 6mm and 12mm, at least 30mm in length, with a knob attached. I found one at a hardware shop, but I have no clue for what it is normally used. If you can't find anything, a butterfly (wing) screw will do. - The easiest way to make the throttle lever, and more important, the throttle friction knob work, is to avoid any friction between the knob and the lever. Otherwise, the action of the lever will loosen the knob. So, make the knob so as its axle goes freely through the handle, and design your work so as if you tighten the knob, it squashes the lever and its friction washers between two plates. - The best washers for friction seem to be Nylon washers. - You will save a lot in working time and design complexity by using Rivnuts (these are sorts of large rivets, threaded on the inside, that you can rivet to a plate pretty much like a Pop rivet). Here is what I did: - The throttle is basically made of one plate (the handle) squashed between two other plates (the base plate and the cover plate), with everything adequately spaced. - I cut the support plate out of a 2mm aluminium sheet, hard grade (2024T3), and the cover plate out of a 1mm sheet. I think 1mm everywhere would work just as fine. - I then rivetted one 8mm thread Rivnut to the plate, at the position of theknob axle. This is the thread where the friction knob will screw in. - I riveted four 5mm Rivnuts at the corners, facing up (these hold the two plates together) - I cut 4 spacers out of an aluminum tube. These go at the 4 corners, and are held by 5mm screws that thread in the Rivnuts. I now had two plates, spaced together. - I made a small bush to go through the handle, to avoid friction with the knob thread (frankly, an overkill). - I put Nylon washers on either side of the handle. - I then made a spacer to fill the space between the top washer and the cover plate. The spacer consists of three large washers piled up and glued together with Epoxy. - And that's it! The knob goes through the cover plate, then the spacer, then top washer, then handle plate, then bottom washer, then Rivnut; when you tighten it, the cover plate bends slightly, and squashes the handle between the two Nylon washers. The friction remains even, even after 100 push-pull actions (Yes, I tried). - The rest is details: giving the hande a double bend to make it S-shaped, making wood stocks, fitting holes, and of course, the throttle cable mounting hole and screw. Oh, by the way, when you make your spacers, check how much thickness you will need for your cable attachment, and allow for some extra clearance. That throttle is very simple, yet, it's still 45 parts altogether! Unbelievable how fast the parts count goes up! Here is the datasheet. Throttle data Mass: 188 g Travel: 7.9mm Overall dimensions with handle at centre position: Height 151mm Length 98mm Width 50mm Overall dimensions with travel: Height 151mm Length 200mm Width 50mm Parts list 1. Base plate, aluminium, 2024T3, 2mm thick 1 2. Rivnut, 8mm 1 3. Rivnut, 5mm 4 4. Spacers, aluminium, 12.7mm OD, 10mm ID, L18mm 4 5. Capscrew, 5mm x 20mm 4 6. Washer, 5mm 4 7. Self tapering screw, SS, 3.5mm x 16mm 6 8. Face plate, aluminium, 2024T3, 1mm thick 1 9. Throttle handle, aluminium, 2024T3, 3mm thick 1 10. Wood stocks, seligna wood 2 11. Screw, 3mm x 21 2 12. Washer, 3mm 2 13. Locknut, 3mm 2 14. Friction adjustment screw, 8mm x 30mm 1 15. Washer, 8mm 1 16. Spacer, 8mm ID x 25mm OD x 9mm thickness 1 17. Washer, Nylon, 9mm 1 18. Bush, 8mm ID x 9mm OD x 4.2mm 1 19. Washer, Nylon, 8mm 1 20. Button head screw, 4mm x 16mm 1 21. Washer, 4mm 2 22. Locknut, 4mm 1 23. Throttle cable mounting bracket, alumiinum, 2mm thick 1 1 Tools list for mounting 1. Screwdriver, flat 2. Allen key, 2.5mm 3. Spanner, 7mm 4. Allen key, 4mm Serge Vidal KR2 ZS-WEC Tunis, Tunisia
