Originally posted by theoldALFER
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im going to do the Robart 3.5 inch wheel mod, too. :Confused:What “issues” are you dealing with?
Thanks for the heads up!
toA
:Cool:[/QUOTE]
Update on the Robart wheel modification, although TiredironGRB had a great post back on December 20th at 10:59AM (not sure the post number) where he described the set up with Robart 3.5" and 3.75". I install Robarts on every plane I can, including my 4 Extreme Flight birds. Have the 4" on my 1700mm P-51 and Robarts on all my warbirds, love them. The stock foam wheels get fairly ragged after about 10 flights on our asphalt runway, so the Robarts are the way to go for me. I can put at least 50 flights on them and still they look and perform well, no bounce and smooth running. If you do nothing else, you definitely need to put these shoes on your plane!
For the Corsair I opted for the 3.5", would have loved to go with the 3.75" but I was running out of patience to get this done and didn't want to rework the gear door servo linkage and cut out foam to accommodate the larger wheel (see Tirediron's post-he's my hero). For the 3.5" here is what is needed: (I should also say that you will need to heat up the set screw to get the axel out as they used lock tight to keep it in, otherwise you will strip the allen head in the set screw-I used a small butane torch-or use a lighter)
1) The axel will need to be shortened by about 5-7mm (measure how much by putting all the parts and washers needed for unobstructed running) and the flat spot will need to be ground in (mark that through the empty set screw hole)
2) Using the existing metal collar/spacer it comes stock with, you will also need to add another couple (or 1) #10 washers (both on the inside of the axel near the strut) so the wheel does not hit the strut and maintains the same spacing as stock. Instead of metal washers, I used 1 Dubro 10-32 nylon flat washer number DUB 638 and it fit perfectly.
3) Now that the easy part is done, on to what for me was the pain in the a... So if anyone has a better method, please let us know. The Robarts come with a variety of wheel hubs/bushings, however, none of them are big enough for the stock axel. So I took the largest, the 3/16 and drilled it out to accommodate the axel (thank god I have a drill press). Unfortunately, it's easy to mangle the little plastic hub when holding it or drilling it so I started with a 13/64 drill (which now makes the axel fit, but too tight). Then I continued to slowly "ream" it out to make it work. Couldn't use a 7/32 drill, cause that ended up mangling the bushing beyond use because the bushing walls are now getting too thin. Had to finish making it larger with a round file and some elbow grease. Now the bushing ID is good but it is expanded slightly on its OD and doesn't fit well back in the wheel, so I used the round file on the wheel to enlarge that slightly to get the bushing in. Now the bushing fits tight in the wheel and the axel spins freely. :Whew: I guess you could put the wheel on without the bushings (1/4" hole), but for me, that resulted in too much wheel wobble as the axel is something like 7/32 (but I'm sure it's a metric size so if any of you out there have the metric size, please post it and you can use a metric washer instead of the 10-32's I used, but they did fit perfectly).
I'm waiting for the paint to dry on the spokes, so I haven't put it back together yet, otherwise I'd post a photo, though not that much to see. I'm sure you'll get them on just fine. Any questions or run into any difficulties, just let us know.
I will say that the way FL set up the wheels and axels and where the set screw is, for me, the absolute best way to do it to allow changing wheels simple. For other models, you need a mechanical engineering degree (I barely got out of kindergarten) and the Robarts are a labor of love trying to install, especially if you want to keep the wheel covers and spoke covers.:Angry:
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