HELP "flex shaft assembly" - Page 2 - RC Groups
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Aug 23, 2010, 01:39 AM
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Bradles's Avatar
ok here is what ive got. when its assembled in second pic the gap im guessing 0.5mm or so by eye. couldn't find my digital calipers.

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Aug 23, 2010, 07:21 AM
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wparsons's Avatar
You'll want a thrust bearing / washers between the drive dog and the strut and the strut, but you don't need a gap since the flex cable can shrink without pulling the stub in tighter. You won't need a thrust bearing at the motor 'cause the stub will be carrying the load, not the whole shaft.
Aug 23, 2010, 07:28 AM
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Bradles's Avatar
so a small washer where the gap is will be fine then? should it have a little play, so it doesn't bind??
Aug 23, 2010, 07:31 AM
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wparsons's Avatar
Not a regular washer, something like this:

It will fill spin smoother under load. Looking closer at it with the prop on it, I'm not sure you can fit one though, unless you can move the drive dog back towards the threads more?
Aug 23, 2010, 07:43 AM
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Bradles's Avatar
nope a thrust bearing wont fit, the nylon nut is already flush with the shaft. cant shift any further forward. a shim will have to do i guess,

it should work ok with just shim, as i know a few people that have replaced the thrust bearing in a nitro 3d clutch with a brass washer and the engine still ran perfectly fine, couldn't tell the difference. and didn't have to worry about greasing it.

thanks wparsons
Aug 23, 2010, 09:41 AM
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wparsons's Avatar
I wouldn't shim it, that'll probably create more drag.
Aug 23, 2010, 10:05 AM
RELAX. You'll live longer
785boats's Avatar
That shaft set up is completely different to the one in the first pic you posted. So that link I posted about the glueing of the flex into the stub doesn't apply.
these square drive set ups usualy have a teflon washer detween the dog drive & the strut like the ones at the bottom of the attatched page.

Here's a similar set up on my old cat.
Aug 23, 2010, 10:24 AM
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You know what, disregard the washers and leave about 2 1/2 mm spacing at the strut. When you first run it, check the spacing when brought in and see how it looks to you. Do this every so often and see where you are at. The thicker the cable, less chance of it winding much tighter but always check , just for your piece of mind. Thrust bearing at motor end does no good as the bl motors shaft don't move like the BRUSHED MOTORS shaft does. I bought a Arpro 1 and it came with a bent shaft and coupler and they wanted certified pictures and the like and hee haa stuff. I told them forget that. So i tore out drive system and put in .130 flex and shaft and bent doublewalled brass tubing and am leaving about 2 1/2mm spacing between dog drive and stuffing tube. The .130 flex will wind up more than your thicker flex cable. I bench tried and is smooth as flass. I also sanded the cable and used liner so water will not come up the shaft. The motor is a Turnigy 36 40 05 3900 on twin lipos at 7.4 which gives me a good 30,000 rpm for a 650mm lenght boat. The reason i went on with mine was to explain why and what i did and to help you out.------Paul's nylon washers can be used but leave some space. I couldn't find the correct width but dremeled it down. Next i sanded nylon washer on 600 wetdry sandpaper to smooth both sides to rid of burrs and smooth the edges. Lowes is the only place i found those washers.
Last edited by Mikedown; Aug 23, 2010 at 10:35 AM.
Aug 23, 2010, 10:29 AM
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wparsons's Avatar
^^ The spacing only applies if the flex and stub are fused together... This setup has the flex shaft with a square end fitting into a square hole on the front of the stub. The flex can wind up and shorten without pulling on the stub.
Aug 23, 2010, 06:56 PM
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siberianhusky's Avatar
exactly the prop load is transfered directly to the strut and the square end cable floats in the stub shaft, Thought it was a glue/solder one in the first picture. sorry bout that. Looked like a pre assembled octura to me! Don't tell me I need another pair of glasses!
Just cut a shaft for the rigger, need to make it about 1/8 shorter. Easier to cut more off than try to add it back on! Just missed dripping silver solder on my foot! And of course I was wearing sandals! Stupid!
Two winter ago got some mean burns on my right hand. Welding a plow harness back together in the middle of the night about 20 below! Wearing nylon winter gloves. The slag caught the right one on fire, melted nylon all over my hand!
Aug 23, 2010, 09:09 PM
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Bradles's Avatar
thanks everyone, will take all of you suggestions and see what i end up with when i do the final install.

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