Drilling gear leg flanges for brake caliper mounting 4 bolts versus 6

[DBeaulieu]

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Mainly finished one wing and wanted to try something different so went about installing calipers to gear legs. Got one done and learned a couple of things...

Using the ABI 199-62 setup I clocked the caliper forward and as up high as possible (being limited by the gear leg and caliper interference). I used the brake anchor plate as a template for drilling with a 3/8" threaded drill bit on an 8" extension. This allowed me to clear the axle which also serves as a good visual reference for drilling "plumb" I drilled six holes following the layout on the brake anchor plate. One or two of the holes will be hard to fit nuts on to the thru bolts (even if going to AN5 bolts and bushings) because of the gear structure. I called Alaskan Bushwheels and they stated that 4 bolts will be fine on the Patrol. I may still try to finangle the other two bolts in. Anyone have some comments or thoughts on 4 versus 6 bolts?

[Mark Goldberg]

They call the wheels/brakes you got "three bolt" system. So four would certainly be plenty. And bushing down to 5/16" will not hurt anything either. Mark

[DBeaulieu]

Thanks Mark, will plan on drilling only 4 holes in the next gear leg...

[Nev]

From memory I had to grind one of the nuts to get clearance for it to fit. After about 1000 landings the right caliper had some movement and the bolts required tightening. I wondered if in hindsight it would be possible to weld the nuts into place for a future mod.

[alaskabearhawk]

I have a 4 place with Cleveland 199-62s and just used three bolts. AN5s have a shear strength of 76,000psi which is plenty. The yellow gear is mine, the white gear is Rob Taylor's BH. He has almost 700hrs and no issues so far. We used MS21042 nuts for clearance with no issues, sometimes called jet or missile nuts around here.

Edit: Besides, there are only three bolts holding the disc onto the wheels and the wheel halves together. Four is more than enough.

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[DBeaulieu]

Thanks to all who replied and posted. Drilled out second gear leg and had room for AN6 bolts and standard elastic locknuts. Ended up with 4 bolts in each gear leg. Got the axles drilled and cottered and the wheelsets (ABI 199-62) assembled. All ready to bolt up to the fuselage.

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