Why not just take your 7/8 coupling and have somebody with a lathe bore one end to a shrink fit for the spline, get it hot and slip it on. What happened to the original drive plate for the gearbox. Roy
--- On Wed, 12/16/09, David Goldsmith <suntreader@gmail.com> wrote:
From: David Goldsmith <suntreader@gmail.com>
Subject: Re: [Electric Boats] MARS motor shaft to spline coupling?
To: electricboats@yahoogroups.com
Date: Wednesday, December 16, 2009, 11:10 PM
That was one idea but I'd rather not disassemble the gearbox to get the shaft out. The epoxy connection seems dodgy to me too but I've been amazed by the stuff before. The hub will have a key slot in it and the splined shaft sure has plenty of 'tooth' to it so I'm thinking the epoxy would work. I may give the epoxy a try and if there's a problem pull the shaft and do the machine work. David On Wed, Dec 16, 2009 at 9:42 PM, <postal6@juno. com> wrote: One could always take the shaft from the gearbox, machine it on a lathe, which would permit the adaption of a coupler. Don Swanson 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.
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
Not likely…sure, they'll have the keyway coupler, but the spline is the bugaboo. You won't likely find the whole thing off the shelf and you cannot beat the $15 plus epoxy that my first solution required. That solution applied in this case of a larger, but coarser spline requires a different approach and brings the cost up to a likely $50. Shipping alone can eat up part of that budget if online purchase with McMaster---a good local bearing shop will have the keyway coupler for under $15. -mt A few minutes at McMasterCarr. com will probably come up with a cheaper off the shelf solution. The spline part will be hardest. Do you have access to a marine salvage yard that may have broken parts? o Buy a 7/8" keyed shaft coupler o Buy or make a short tube that slips over the OD of the coupler o Weld or JBWeld the tube to the coupler o Make a a 1 1/8" spline fitting out of the inside part of the tube by "casting" a spline using JBWeld or titanium putty or other strong epoxy § Fill the spline part with wax § Lube your spline with WD40 or other lube to act as mold release § Mix appropriate amount of epoxy and pour into tube end § Smoosh the spline into the epoxy, keeping the spline shaft and the coupler coaxial (biggest problem) § After cured, use gear puller to remove the new coupler from the spline § Voila…coupler made for under $50 o Buy a 7/8" keyed shaft coupler o Buy a 1 1/8" spline coupler (if available) or spline gear/pinion o Bore one end of the spline coupler out to the outer diameter of key shaft coupler o Connect, align and bond (JBWeld) or weld the 2 couplers together. o Cost: $200 or less I'd guess (mine cost $100 total---(1) 7/8" keyway coupler ($15), (1) used pinion gear w/14-pt spline ($35), plus $50 to grind one end of pinion down to 7/8" to fit in the end of the keyway coupler. · Expensive, but Best ($500+): Have a machinist make a coupler for you, boring for 7/8" 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" keyway to 14-pt nom. ½" diameter spline coupler) conversion for about a year. In my case, the splines were too narrow and would only last for perhaps 20-hours before self-disintegrating and having to be replaced. After going thru about 3 coupler recasts, I made one out of titanium putty and used it until I discovered the 2nd method above. That new coupler cost me $100 total and has now lasted 5 years or so---I used a lower unit pinion gear for the spline fitting and the pinion gear teeth on the OD were never ground off since they don't interfere in my use as a coupler. -Myles Twete, Portland, Or. I've been working on getting my gear box ready to mate up to a MARS
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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