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Ray Phillips
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Location: Vestal, NY
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Posted Monday, July 21, 2014 @ 05:32 PM  

Does anyone know the sizes of the bearings at the folding wing section linkage for an RF-5B? One side has far more play than the other in our RF-5B.

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Ray Phillips TCSS

Mike-RM
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Posted Thursday, October 2, 2014 @ 09:53 AM  

Hi Ray

Are you talking about the small self aligning bearings in the two aileron linkage bellcranks at the wing fold, or the main wing fold hinge pins and locking pins?

I don't know what size the self aligning bearings are. There has been some discussion about these bearing on the forum and I think they are hard to get. However, if there is play in the linkage at the bell crank, make sure that the bell crank lever central bearing is properly mounted. The centre of the bearing should be firmly clamped to the mounting brackets by the bolt. Otherwise the bell crank bolt will turn on the mounting brackets rather than the bell crank turning on the bearing. I found this problem and there was quite a lot of play. The cause was that two small spacer washers were missing - these fit on the bolt between the bearing centre and the mounting plates. If they are not there you cannot tighten the bolt or the whole bell crank locks up. So someone had loosened the bolt enough for the bell crank to turn, but the bolt was turning in it's mounting, so inevitably, wear was caused and the whole linkage became sloppy. Introducing two small 5mm washers to pack it out so the bolt could be properly clamped up solved this problem.

If you are talking about the main hinge pins and locking pins, these are nominal 12.00mm diameter as standard. However, oversize pins in 0.20mm oversizes can be fitted up to a maximum of 12.80mm. I confirmed this with Manfred Schliva, the designer of the RF5B, last year. Oversize pins can still be obtained from Alfred Krewinkel through a curious arrangement which is still being described as through E.I.S but you deal direct with Alfred. The prices are about 35 euro for hinge pins and 50 euro for locking pins. It' not really worth trying to source the correct grade LN steel and precision cylindrical grinding these your self. However, while the original parts I received from Alfred were extremely precisely machined - 12.595mm within about 0.002mm for a 12.60mm nominal oversize, it appears that he had 12.80mm pins made recently and these were not so precise, although they were parallel within acceptable limits. I bought a precision ground reamer to the exact size to ream out the fittings, it's not as difficult as it sounds. Alternatively an expanding reamer cound be used, but I prefer to use a fixed hand reamer in the chuck of a battery powered electric drill with an extension shaft and plenty of cutting fluid. If you buy a special fixed reamer, get the actual bolts first and get the reamer ground to fit the bolt.

Hope this helps.

Mike

[Edit by Mike-RM on Saturday, October 4, 2014 @ 03:33 AM]

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