making a prop

[cameronfurnival]

I want to have a go at making a prop, my idea is to get the bits from an exisitng prop, cut it and tack it then take it to an engineer to have it fully welded and balanced.
My question is really about the parts i need. My donor is sierra with MT75 g'box which has a big rubber donut on its output shaft (shock absorber), the prop bolts to this via a yoke arrangement. Should I keep this setup or do away with it in favour of a more direct coupling - and has anyone got any experience of doing it?

[andy4]

Re: making a prop

Not sure you will gain that much cost by doing the bits you propose yourself, apart from satisfaction of having done some of the job yourself. I would expect the welding and balancing to be most of the cost. I have used H J Chard in Bristol, who do a good job, but are often pretty busy. I might be paranoid but DIY propshafts can be a bit scary as if they let go you only have a bit of thin ally between it and you ...

[Mike]

Re: making a prop

cameron

I had a go at making a propshaft, and think you could have difficulty welding it whilst keeping it true.
I bought one in the end from Dave Mac in Coventry - cost £150
He advised not using the rubber doughnut as they do not like running offset - it will fail very quickly. he advocates using a splined shaft with a proper UJ at both ends. His quality is very good, and service very quick. Comes highly recommended from several sources.
Rgds
Mike

[Mike]

Re: making a prop

cameron

I had a go at making a propshaft, and think you could have difficulty welding it whilst keeping it true.
I bought one in the end from Dave Mac in Coventry - cost £150
He advised not using the rubber doughnut as they do not like running offset - it will fail very quickly. he advocates using a splined shaft with a proper UJ at both ends. His quality is very good, and service very quick. Comes highly recommended from several sources.
Rgds
Mike

[chris_cussen]

Re: making a prop

Best bet is to change the flange on the gearbox to a proper one from a transit which takes a ordinary UJ. I'll look the part number up tonight.

[chris_cussen]

Re: making a prop

The DOCH serria donor for the cabrio has an MT75 gearbox. To Quote from the Marlin Build Manual "The 5-speed "MT-75" transmission used with these engines employs a "G.A.F." rubber transmission coupling; this must be exchanged for a Ford drive shaft flange, Ford part number 6171398, so as to mate with the flange on the propeller shaft.

[cameronfurnival]

Re: making a prop

thanks for this really good information. I will find said flange Chris and contact Dave Mac. The only reason I even contemplated trying it myself was because of a quote of £250 from a local engineering firm.
Is the gearbox GAF coupling a push fit do you know? ie pull it out then push in the other one? Is a new tail-seal required too? sorry to ask simple questions!

[chris_cussen]

Re: making a prop

You need to take the rubber GAF donut apart and right in the centre is a large nut,which holds it onto the gearbox output shaft.
The nut may have 12 points and look like a star. You will need a deep socket (an hex socket will fit despite it looking like you might need a special tool) or do what I did which was to find a friendly bloke in an engineering workshop to get it undone. The remains of the donut then pulls off the splines and the transit part slips on, then do the nut up.

I didn't change the gearbox oil seal on the grounds that it wasn't leaking.

[cameronfurnival]

Re: making a prop

Thanks Chris - will have a go this weekend :-) Is there a good supply of the transit bits anywhere or is it a main dealer only do you know?

[cameronfurnival]

Re: making a prop

I contacted Dave MAc as suggested and this is their reply! Thought I would include it so that other members can get an idea of price and what's required too.

We can supply a new propshaft unit with a special flanged end designed to bolt directly to the 3 armed gearbox flange of the MT75. Just remove the existing rubber drive joint, the 3 studs, the outer flywheel (harmonic damper, if fitted) and attach our new 3 bolt propshaft unit. (new bolts supplied)

We will build the propshaft with a std. Landrover / Jaguar sliding spline section with 50mm telescopic movement.
Rear flange to suit the Sierra rear diff.

Priced @ £120 +vat
P&P @ £10 +vat.

Just measure the distance from the 3 armed gearbox flange (actual face where the rubber joint would fit) to the diff flange and give us a call.

Should be produced in 24hrs.


HOpe this helps others who are thining about making their own!

[chris_cussen]

Re: making a prop

Sorry i didn't reply earlier, went to the Lake District to run around the mountains.
I bought a new flange from my Ford main dealer. I seem to remember it cost about £40....

[cameronfurnival]

Re: making a prop

Thanks Chris, I think I will go with the DaveMac solution though - seems straightforward. Got teh Damper off last night - you need a splined socket to get the long dowels out and boy were they tight!
I also knocked up a battery tray from sheet last night and measured for the new prop - so who knows in 10 years it mght be on the road!!!

[cameronfurnival]

Re: making a prop

update:
Prop ordered from Dunning and Fairbank - very efficient service, they have the MT75 flange adaptor to mate the output shaft to the prop in stock too. They made it to my spec, took about a week, then they phoned me at 5pm one evening, I paid on the old plastic and the thing was with me before lunch the next day. Cost was £145+vat plus £10+vat postage.
Got it mated up last night, the flange adaptor attaches with three allen bolts (supplied by D&F) then the prop bolts to that. I got the thing 90 degs out and wondered where the diff flange holes had gone but that was easy to sort out with a quick twist of the wheel.
and you know what....the beast is alive! All the cogs meshed nicely, the wheels spun around no nasty noises anywhere and a grin on my face like a cheshire cat!

[chris_cussen]

Re: making a prop

Glad to hear you got the prop sorted. As they used to say there is more than one method for removing the epidermis from a feline.

BTW how are the noisy tappets?

[cameronfurnival]

Re: making a prop

HI Chris the tappets seem to be quietening down as I run the engine. I just have a few seconds of rattle now so hopefully once i get some new oil in she might improve further
Am very happy with the prop = would recommend D&F to anyone.