jliltd
Well Known Member
My RV-8 came with an API tailwheel. As API tailwheel owners know, API is out of business. The tailwheel has served me well especially when I bought a replacement tailwheel steering horn from Flyboys Accessories about 3 years ago to solve a too sensitive steering kickout problem. I have always had great support from Flyboys. During my recent condition inspection I noticed uneven wear on the original tailwheel tire assembly. And it is kind of heavy and the bearings are not easy to press out and re-pack. It looks to be an industrial unit with upgraded bearings. API stuff was good stuff and it's too bad they are gone now.
Original tailwheel tire assembly:
The API wheel casting shows it to be a 6 x 2.25 unit made by R&K. I checked industrial sources and decided I needed something more aviation specific. JD Air looks to have some good products but not anything that would work with the API fork and 1/2" diameter axle. I noticed that the Flyboys Deluxe Tailwheel can accommodate either a 3/8" or the 1/2" diameter axle like on the API fork. The Deluxe ships with an adapter bushing for the 3/8" standard Vans axle. I didn't need the adapter bushing so I would leave it in the spare parts bin. The Deluxe wheel assembly is also 2.25" wide which matched the API tire assy. And the Deluxe was lighter than the API. I was sold. So I ordered one up from Blake. Like many things in aviation there can be wide tolerances in manufacturing and when I got the new tailwheel tire it wouldn't quite fit inside the API fork. So out came the digital calipers and sure enough the API fork was about 24 thousandths narrower than the Deluxe tailwheel tire. The Deluxe was dead nuts on at 2.25" wide at its bearing shoulders. Those shoulders are basically the inner bearing races that stick out farther than the rest of the bearing to provide a proper clamp up without having any induced load on the bearings. The Deluxe is a better design than the API wheel where I had to watch the axle bolt tightening because of bearing bind.
Here is the measurement of the API fork:
It made more long-term sense for me to modify the API fork to get the spacing up to 2.25" rather than try to modify the Deluxe. How would I do it properly? Hand files and angle grinders were considered but I wanted to make sure the grinding was done perfectly flat on the inner surfaces and perpendicular to the axle. After some thinking and dinking around with different ideas I settled on running a grinding stone on the inside face of the fork clevis using a die grinder while pulling outward with the stone's shaft centered in the axle hole. So side loading the stone and axially loading the die grinder. I happened to see a variable-speed die grinder at the HF Chinese store and it was on discount for Advantage members for $19. I had to find the right grinding stone and the local Northern Tool had a proper one with a slightly longer shaft than typically found on other stones. The stone was also thicker than most which would be an advantage when side loading. So I did a little grinding on each side to keep things even as I applied pulling pressure outboard. I used the spare Flyboys axle bushing the gauge the progress since it matched the tailwheel thickness. I ran the grinder twice on each side between using the bushing to check the spacing. It was important to start the grinder slowly before increasing speed while watching to make sure the shaft of the stone was centered in the axle hole straight.
Here is the weird and non-OSHA approved farm boy method I employed to grind from the inside out:
The results speak for themselves and I now have a new Deluxe tailwheel tire. It spins really nice and the bearings are smooth. I look forward to trying it out after my engine cylinder delayed CI. More importantly my tailwheel tire/wheel is no longer orphaned by API like the original unit. I now have support and source of replacements from Flyboys Accessories.
Original tailwheel tire assembly:
The API wheel casting shows it to be a 6 x 2.25 unit made by R&K. I checked industrial sources and decided I needed something more aviation specific. JD Air looks to have some good products but not anything that would work with the API fork and 1/2" diameter axle. I noticed that the Flyboys Deluxe Tailwheel can accommodate either a 3/8" or the 1/2" diameter axle like on the API fork. The Deluxe ships with an adapter bushing for the 3/8" standard Vans axle. I didn't need the adapter bushing so I would leave it in the spare parts bin. The Deluxe wheel assembly is also 2.25" wide which matched the API tire assy. And the Deluxe was lighter than the API. I was sold. So I ordered one up from Blake. Like many things in aviation there can be wide tolerances in manufacturing and when I got the new tailwheel tire it wouldn't quite fit inside the API fork. So out came the digital calipers and sure enough the API fork was about 24 thousandths narrower than the Deluxe tailwheel tire. The Deluxe was dead nuts on at 2.25" wide at its bearing shoulders. Those shoulders are basically the inner bearing races that stick out farther than the rest of the bearing to provide a proper clamp up without having any induced load on the bearings. The Deluxe is a better design than the API wheel where I had to watch the axle bolt tightening because of bearing bind.
Here is the measurement of the API fork:
It made more long-term sense for me to modify the API fork to get the spacing up to 2.25" rather than try to modify the Deluxe. How would I do it properly? Hand files and angle grinders were considered but I wanted to make sure the grinding was done perfectly flat on the inner surfaces and perpendicular to the axle. After some thinking and dinking around with different ideas I settled on running a grinding stone on the inside face of the fork clevis using a die grinder while pulling outward with the stone's shaft centered in the axle hole. So side loading the stone and axially loading the die grinder. I happened to see a variable-speed die grinder at the HF Chinese store and it was on discount for Advantage members for $19. I had to find the right grinding stone and the local Northern Tool had a proper one with a slightly longer shaft than typically found on other stones. The stone was also thicker than most which would be an advantage when side loading. So I did a little grinding on each side to keep things even as I applied pulling pressure outboard. I used the spare Flyboys axle bushing the gauge the progress since it matched the tailwheel thickness. I ran the grinder twice on each side between using the bushing to check the spacing. It was important to start the grinder slowly before increasing speed while watching to make sure the shaft of the stone was centered in the axle hole straight.
Here is the weird and non-OSHA approved farm boy method I employed to grind from the inside out:
The results speak for themselves and I now have a new Deluxe tailwheel tire. It spins really nice and the bearings are smooth. I look forward to trying it out after my engine cylinder delayed CI. More importantly my tailwheel tire/wheel is no longer orphaned by API like the original unit. I now have support and source of replacements from Flyboys Accessories.
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