Page 1 of 1
Prop Shaft
Posted: Sun Apr 11, 2021 3:09 pm
by new to this
The centre mount brackets that are bolted to the floor,how is the centre bearing mount fitted to it,from above or below,what i mean is are the bolt heads pointing upwards or down wards
or does it not make any difference ?
Thanks Dave
Re: Prop Shaft
Posted: Sun Apr 11, 2021 4:48 pm
by Richard the old one
It depends on the model.
A. For Dolomite manual change gearbox and automatic gearbox models.
Both lugs on the prop shaft centre bearing housing are located on the upper face of their respective mounting brackets.
B Sprint manual gearboxes and automatic gearboxes.
LHS mounting bracket is secured as per A above but the RHS lug of the central bearing housing is fitted below the mounting bracket with one washer spacing it from the bracket.
I am now confused as the document that I am reading states Dolomite automatic gearbox model only and goes onto state this model uses a different mounting bracket which moves the prop shaft centre line 0.375 inches to the right compared to the centre line of other models. The LHS mounting arrangements stay the same as in A above but on the RHS washers are fitted between the bracket and the car body and the lug of the central bearing housing is fitted below the mounting bracket.
The document states the various installations are to avoid possible noise and vibration. I think I may have a play and see if changing my installation will reduce the vibration I get at approx 1800 rpms.
Re: Prop Shaft
Posted: Sun Apr 11, 2021 8:39 pm
by Bish
If I remember rightly Dave I bolted mine from above because that’s the only way I could get it to work. I looked at the manual, and as Richard suggests, there are different methods listed but I couldn’t get mine to fit either way. So just bolted it up with the bolts coming down and the plates level. Hope that makes sense?
I’ve had no vibration issues so far
Re: Prop Shaft
Posted: Mon Apr 12, 2021 12:43 pm
by SprintV8
Does this help.
http://www.dolomitesprint.com/prop.htm
I don’t have this problem.
Single piece custom Propshaft.
Re: Prop Shaft
Posted: Mon Apr 12, 2021 8:24 pm
by new to this
Thanks for the reply guys,when i took mine off it had one bolt pointing up and the other pointing down,i thought that was the previous owner,getting the bolts in from above was a pain,would be even harder now,ive run my fuel and brake lines under the tunnel 
Dave
Re: Prop Shaft
Posted: Mon Apr 12, 2021 11:24 pm
by new to this
Why did the Sprint have a two piece propshaft in the first place ?
Okay........
Posted: Wed Apr 14, 2021 8:35 pm
by sprint95m
new to this wrote: ↑Mon Apr 12, 2021 11:24 pm
Why did the Sprint have a two piece propshaft in the first place ?
That is a good question Dave.
I cannot explain the theory, it is way beyond me,
however I understand that if a single piece propshaft was employed it would have to be a much greater diameter
and therefore heavier.
(Triumph 2000s had single piece props and these caused vibration problems.
Many attempts were made to cure this but the problem persisted.)
Ian
Re: Prop Shaft
Posted: Wed Apr 14, 2021 10:21 pm
by xvivalve
The two piece propshaft is designed to avoid harmonic frequencies which occur in tubes and cause resonation. I forget the exact criteria from my O and A level physics, but length and diameter come into play.
Re: Okay........
Posted: Thu Apr 15, 2021 8:22 pm
by new to this
sprint95m wrote: ↑Wed Apr 14, 2021 8:35 pm
new to this wrote: ↑Mon Apr 12, 2021 11:24 pm
Why did the Sprint have a two piece propshaft in the first place ?
That is a good question Dave.
I cannot explain the theory, it is way beyond me,
however I understand that if a single piece propshaft was employed it would have to be a much greater diameter
and therefore heavier.
(Triumph 2000s had single piece props and these caused vibration problems.
Many attempts were made to cure this but the problem persisted.)
Ian
The Stag uses a single piece propshaft,but its a thicker diameter than the Dolomite one
Re: Prop Shaft
Posted: Wed Apr 21, 2021 12:15 am
by Carledo
I asked the guy at Proptech, who built the custom props for the Carledo and Dolomega, whether i'd be better off going for a one piece and he said no way! As others have mentioned, the longer it gets,the bigger diameter it needs to be and the heavier it gets the more chance of unwanted harmonics developing. You run into the law of diminishing returns. I've been totally happy with his advice, the Carledo's split prop has done many thousands of hard miles (and lots of linelock burnouts) with no bad vibes at all - EVER!
A Stag prop is considerably shorter than a Dolomite split prop, despite the longer wheelbase on the Stag, go figure! EDIT, probably down to the Stag/2000 diff nose carrier being about 18" long!
Steve
Re: Prop Shaft
Posted: Wed Apr 21, 2021 9:57 am
by SprintV8
The Carbon Fibre RX8 prop was actually longer than the Sprint.
So I went for a single piece prop, and from the advice from Dave Mac Prop-shafts.
3” diameter with 27mm UJs (As found on Stags and 2/2500) which are bigger than the Sprint.
Overkill more than likely but should take more horse power than I can throw at it.
You could always go thicker wall tube but keep the smaller diameter.
I’ve since learnt I could of had the Carbon Prop shortened with new diff joint/UJ
No mention at cost at this stage.
