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[howie55]

Hi everyone
this is typical of me, I have drilled the keel of my schooner to take a 6.5"long x .250" dia brass prop shaft with a m4 spindle, I will be attaching a 1.1/2"dia prop, which is not a problem, what is a problem is the other end, I have just 4" to house the motor and the universal joint, but now I am told I will also need plain/threaded couplings as well.
The motor I will be using is a  Mabuchi RS540 whilst it gives me the Dia of the motor and shaft dia it does not state the length, the same goes for the universal joint and the couplings
My question to anyone who has used this set up is ,will the motor, the joint and couplings fit in a 4" space between the bulkhead and the threaded end of the shaft ? 
And does the coupling slide into the universal joint to take up end float and if so how much do I allow for, I'm sorry if I sound dim, but I am reluctant to start buying without understanding what is involved
regards Geoff

[Martin (Admin)]

You should be able to squeeze it in.
Here's my springer, with a 540 motor and a double (cardan) coupling.
The standard Huco / Ripmax are shorter and do allow up to 2mmm end play....

[Martin (Admin)]

If that doesn't fit, you can always go for the Motor over Shaft arrangement, usually gear or belt drive.

Good page to read here:  http://matthewsmodelmarine.wordpress.com/writings/all-geared-up/

[howie55]

thanks martin
I understand that the joint takes out any errors in the alignment between motor and prop shaft, but what does the coupling do, is it like I thought to allow for end float,I can't see them in your photo.
Geoff

[Shipmate60]

MMB can produce a flexible coupling to fit your installation.
You can see them on his website: http://www.marksmodelbits.com

Bob

[howie55]

Hi Bob
thanks for your reply, the rubber coupling could be the answer I am looking for
Geoff

[Martin (Admin)]

The joint and the coupling are usually the same thing.
They join the motor to the prop shaft.
A normal single coupling (universal Joint - UJ ) with allow for a certain amount of misalignment in angles,
 whereas a double coupling will allow for a certain amount of angle AND shaft misalignment.

You don't want much end float in you system as that may allow water creep.
 Usually the prop is tightened onto the prop shaft with a lock nut, the inboard end can have a collet or lock nuts or the coupling as close as possible to take up the end float... 'slop'

thanks martin
I understand that the joint takes out any errors in the alignment between motor and prop shaft, but what does the coupling do, is it like I thought to allow for end float,I can't see them in your photo.
Geoff

[Islander1951]

I used the motor over shaft method on my tug, using 2:1 graupner nylon gears.
  This made a neat and compact arrangement, and having the motor slightly higher has not affected the stability.

[DickyD]

Hi Geoff check these out, they should solve your problem.

http://www.cornwallmodelboats.co.uk/acatalog/couplings-modular.html

If still stuck give them a ring, Malcolm is really helpful and efficient. Delivery is quick.

[howie55]

thanks guys
what would I do without this forum to turn to, I' ll be buying the parts this weekend.
thanks again for your help
Geoff