Have you talked to any machine shops? You might find it's not that expensive compared to the various homebrew methods, and you're more likely to have a smooth running system. A tiny bit of misalignment can inject some real annoying vibrations into the system. Can you open the gearbox and pull the shaft out? It would be a simple lathe job then. Just turn off the splines and mill a keyway, or skip the keyway and use a clamp type coupler.
Jim McMillan
--- In electricboats@
>
>
> If you used the spider type connector from M-C yu could drill a hole through the coupler and the shaft and insert a roll pin or bolt. That would give you a metal connection instead of relying on the epoxy. I guess I am just leery of the epoxy connection.
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>
> -----Original Message-----
> From: David Goldsmith <suntreader@
> To: electricboats@
> Sent: Wed, Dec 16, 2009 5:34 pm
> Subject: Re: [Electric Boats] MARS motor shaft to spline coupling?
>
>
>
>
>
> McMaster was my first stop on this problem. No luck on the spline coupler, they have some but none that will fit. They had couplers that would fit the motor end. The solution they had for splined shafts was using two couplers with a spider in between. I liked that solution, they just don't have one that will fit my input shaft.
>
> I had thought of machining an 'as close as possible' coupler to fit the splined, the problem is how to make it in such a way that it will take the load of the motor. I thought of filling it with epoxy and letting that mate it up, that might work, or a clamp type coupler bearing down on the splined shaft. Or set screws mating with the spline grooves. I just don't know enough about the forces and wear involved in such a setup to know what would work.
>
> I'll probably try a thickened epoxy mating the input shaft to a 1 1/8" hub and a 7/8 keyed hub on the motor mating up with a spider. This is all on page 1157 of McMaster. Looks like it'll run about $35 before shipping (plus the epoxy.)
>
> David
>
>
> On Wed, Dec 16, 2009 at 4:35 PM, Myles Twete <matwete@...
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> Not likely…sure, they’ll have the keywaycoupler, but the spline is the bugaboo.
> You won’t likely find the wholething off the shelf and you cannot beat the $15 plus epoxy that my firstsolution required. That solution applied in this case of a larger, but coarserspline requires a different approach and brings the cost up to a likely $50.
> Shipping alone can eat up part ofthat budget if online purchase with McMaster---a good local bearing shop willhave the keyway coupler for under $15.
> -mt
>
>
> From: electricboats@
> Sent: Wednesday, December 16, 2009 12:19 PM
> To: electricboats@
> Subject: Re: [Electric Boats] MARS motor shaft to spline coupling?
>
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> A few minutes at McMasterCarr.
>
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>
> -----Original Message-----
> From: Myles Twete <matwete@...
> To: electricboats@
> Sent: Wed, Dec 16, 2009 3:00 pm
> Subject: RE: [Electric Boats] MARS motor shaft to spline coupling?
>
>
>
>
>
> Options that I know of:
>
> · Cheapest(~$50)
>
> o Buy a 7/8†keyed shaft coupler
>
> o Buy or make a short tube that slips over the OD ofthe coupler
>
> o Weld or JBWeld the tube to the coupler
>
> o Make a a 1 1/8†spline fitting out of the insidepart of the tube by “casting†a spline using JBWeld or titanium putty or otherstrong epoxy
>
> § Fillthe spline part with wax
>
> § Lubeyour spline with WD40 or other lube to act as mold release
>
> § Mixappropriate amount of epoxy and pour into tube end
>
> § Smooshthe spline into the epoxy, keeping the spline shaft and the coupler coaxial(biggest problem)
>
> § Aftercured, use gear puller to remove the new coupler from the spline
>
> § Voila…couplermade for under $50
>
> · Cheap(~200):
>
> o Buy a 7/8†keyed shaft coupler
>
> o Buy a 1 1/8†spline coupler (if available) or splinegear/pinion
>
> o Bore one end of the spline coupler out to the outerdiameter of key shaft coupler
>
> o Connect, align and bond (JBWeld) or weld the 2couplers together.
>
> o Cost: $200 or less I’d guess (mine cost $100total---
>
> · Expensive,but Best ($500+): Have a machinist make a coupler for you, boring for 7/8â€w/keyway on one end and broaching 10-point spline at 1 1/8†on the other.
>
>
>
> I used the first approach for my outboard motor (ETEK 7/8†keywayto 14-pt nom. ½†diameter spline coupler) conversion for about a year. Inmy case, the splines were too narrow and would only last for perhaps 20-hoursbefore self-disintegrating and having to be replaced. After going thruabout 3 coupler recasts, I made one out of titanium putty and used it until Idiscovered the 2nd method above. That new coupler cost me $100total and has now lasted 5 years or so---I used a lower unit pinion gear forthe spline fitting and the pinion gear teeth on the OD were never ground offsince they don’t interfere in my use as a coupler.
>
>
>
> -Myles Twete, Portland, Or.
>
> “The REACH OF TIDE†electric barge cruiser: www.evalbum.
>
>
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>
>
>
> From: electricboats@
> Sent: Tuesday, December 15, 2009 8:40 PM
> To: electricboats@
> Subject: [Electric Boats] MARS motor shaft to spline coupling?
>
>
>
>
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>
>
> I've been working on getting my gear box ready to mate up to aMARS
> brushless motor set-up. The gear box and flywheel housing will make
> mounting the motor through a 1/4" al plate easy enough. The problem
> I'm running into is how to mate up the motor to the gearbox input. The
> MARS motor has a 7/8 keyed shaft. The gearbox has a 1 1/8" spline
> shaft (10 splines.) I've done some searching and can't find a coupling
> that will accommodate that spline shaft. Is this something I'll have
> to have made custom or what? Any ideas out there?
>
> Thanks,
> David
>
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