Advice on making a propshaft
Mr Whippy - 24/12/25 at 09:35 AM
Hi,
Right first thing this is not for a car and has been a problem not resolved for about 2 years now (other projects got in the way). In fact this is for
a model ship. The issue is the shear length of the shafts (2 off) their 117cm long! much much longer than anything commercially available. I've
tried various things nothing worked at all. Basically I just need two steel shafts with a M5 thread on the end and four sintered bronze bearings per
shaft that are a good sliding fit over the whole shaft length. Sounds simple?
However, I cannot find anyone who can supply these and I don't possess any equipment capable of doing this myself. Below is a screenshot of this
section, the orange shafts shown. There's a lot of talented machinists on here I'm hoping would be able to suggest a way forward. Thanks
Yeah on the real ship they were crazy long too.
[Edited on 24/12/25 by Mr Whippy]
adithorp - 24/12/25 at 02:52 PM
What have you tried?
Quick goggle found 5mm round stainless round bar from metals4u is £7 for 2m length. Cut to length and tread the ends.
Mr Whippy - 24/12/25 at 05:20 PM
quote:
Originally posted by adithorp
What have you tried?
Quick goggle found 5mm round stainless round bar from metals4u is £7 for 2m length. Cut to length and tread the ends.
How did you specify the thread cutting, I don't see any option on their site for that or have come across a supplier that did offer it?
I ordered some Silver Steel but found the diameter varied along the length so much so the bearings I had rattled or jammed (ball bearings), I also
tried a carbon rod but it also was not consistent diameter, it also had a bend in it. Got in touch with a guy who made model propshafts but he wanted
£170 per shaft!
I have found websites that sell the sintered bearings, that's easy and I don't need the normal brass tube as most do due to there being a
sealed "chamber" around the shaft for oil. The bit I was struggling with was the bearings tbh and getting a good fit along the whole length
(but not too tight as to get hot).
Thanks.
[Edited on 24/12/25 by Mr Whippy]
adithorp - 25/12/25 at 11:33 PM
I assumed someone on a car building forum was capable of using a tap+die set.
Schrodinger - 26/12/25 at 08:58 AM
is there any reason not to have a two part shaft?
PAULD - 26/12/25 at 09:52 AM
I've just picked this up. I'll u2u my phone number, if you still need help call me.
gremlin1234 - 26/12/25 at 11:42 AM
will some of the threaded parts need to be 'left hand thread' ?
edit:
the propellers in the diagram suggest so...
[Edited on 26/12/25 by gremlin1234]
Mr Whippy - 26/12/25 at 10:36 PM
quote:
Originally posted by adithorp
I assumed someone on a car building forum was capable of using a tap+die set.
Yeah I have threaded one for another ship but without using a lathe its actually quite hard to get it dead straight by hand so the prop doesn't
wobble, you should try it.
Mr Whippy - 26/12/25 at 10:38 PM
quote:
Originally posted by gremlin1234
will some of the threaded parts need to be 'left hand thread' ?
edit:
the propellers in the diagram suggest so...
[Edited on 26/12/25 by gremlin1234]
Fortunately the threads for left and right hand model props are all right hand, but it's a very sensible question as on real ships they probably
are different.
Mr Whippy - 26/12/25 at 10:39 PM
quote:
Originally posted by Schrodinger
is there any reason not to have a two part shaft?
No not at all and I did look into that but even then I could not find off the shelf props long enough...good shout though.
MikeR - 27/12/25 at 11:20 AM
Don't you have a 3d printer - isn't this a 'simple' case of printing a split block to hold the shaft with 'something' on
the end to align the tap and die?
Bits in quotes as I often spend literal days of time drawing up umpteen versions of something simple.
edited to add - been googling and found this to inspire you -> https://www.youtube.com/watch?v=Q_pKrAjZ3b0
https://cults3d.com/en/3d-model/tool/tap-guide-tool-perfectly-aligned-thread-tapping-every-time
[Edited on 27/12/25 by MikeR]
[Edited on 27/12/25 by MikeR]
coyoteboy - 28/12/25 at 01:42 PM
Have you checked in with https://www.prestwich.ndirect.co.uk/ on the phone?
Sarah - 28/12/25 at 09:20 PM
https://www.maxitrak.com/ might be able to help.
For material, I'd suggest piano wire
MikeR - 29/12/25 at 12:43 AM
Looking at the website suggested by coyoteboy - not as per the original design, but couldn't you take 3 lengths of 40cm prop shaft and add
couplings into it to make the length required?
coyoteboy - 29/12/25 at 02:01 PM
Personally I think you need to reduce the length from a design perspective anyway, at 1m long it will whip and resonate inside the shaft tube. Whether
you move the motors back or just have multiple shaft supports, it seems better than the original. My boat has a 450 mm shaft, there's plain
bearings at either end of the tube but the centre is all over the shop like a wet noodle.
nick205 - 29/12/25 at 02:14 PM
Have you looked at RC car prop shafts?
Particularly AWD RC cars that have longer prop shafts from front to rear. Some will surely withstand high torque and be available with a variety of
end fittings. Many RC car enthusiasts favour "Hop Ups" (upgrades) to their cars, including higher power batteries and motors so shafts must
be available as well.
Theshed - 30/12/25 at 02:19 PM
How about a three piece shaft?
Three bits of precision ground bar - https://www.ebay.co.uk/itm/280655222160 and
A couple of flexible shaft couplings - https://www.abssac.co.uk/p/Budgetbeam+Couplers/BBS075+189mm+Diameter+Set+Screw+Type+Coupling/277/
The ground bar should sort out your bearing clearance issues but a flex coupling in a couple of places means that the alignment would not need to be
quite so spot on anyhow.
Would it offend you if the couplings were visible?
Is there no paper/register or some such on the propellers - if the prop is not registering on threads who cares if the thread is a bit wonky.