I have been on the phone to 3 different prop suppliers this morning.

I have been specifying type9 to sierra dif for a 7 type kitcar. Engine currently producing 220bhp but want the prop rated for 280-300bhp.

I am getting different responses - some say that 2" tube will be fine upto 300 others say you should really be using 3" tube over 230-250.

I am yet to measure the tunnel for the length of said prop and to check diameter tubes that would fit but what do other people have?

ps prices vary from £95 +vat&post to £139 +vat&post !! worthing ringing around and the closest aren't necessarily the cheapest either...

thanks,

Ned.

Ned,

What diameter did the 2wd Cosworths use? Id suspect they were meaty enough for a few more horses than they were put out by the factory.

Just use the biggest dia you can get in the tunnel ned, and also beware that a 3" prop UJ may not clear the gearshift bellcrank if you are using a gearshift extension on a type 9.


2" prop on mine

Ned,

Think I went with these guys who you've probably tried:
http://www.autoprop.co.uk/

Was around £100.

Cheers,
James

quote:

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Originally posted by ned
ps prices vary from £95 +vat&post to £139 +vat&post !! worthing ringing around and the closest aren't necessarily the cheapest either...

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James, Autoprop were wanting £120 + vat+ delivery

up north was the cheapest, just gotta have a measure up in a minute

quote:

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Originally posted by ned
James, Autoprop were wanting £120 + vat+ delivery

up north was the cheapest, just gotta have a measure up in a minute

---

3" prop Making a lorry?

I've got a bit of cossie shaft that's 2". I remember when i was talking to Bailey Morris about my prop needs, telling him what bits i was planning to use (27mm cap diameter/71mm span ujs on 2" tube from my volvo and cossie shafts) and saying well I might have up to... 300bhp! (sounding impressive), will they be up to it? He politely chuckled and told me that size of joint is used on stuff like transit vans and land rovers.

Cant imagine what sort of application would call for 3" tube and the correspondingly enormous ujs! Like I said - maybe a lorry.

Liam

Liam - thanks for that -I think bailey morris were infact one of the people that said 2 inch would be fine.

James - no idea, I even tried to do a deal for cash and collection but they weren't interested..

Ned.

[Edited on 30/1/06 by ned]

Basically you want the largest diameter you can fit in.

The length of the prop is also an issue. The shorter it is the less critical the tube dia.

If you had come to me asking for a prop as you describe I would have recommended at least 2 1/2" tube and preferably 3", with the 1300 series UJ`s.

John

Wonder if Hicost would disclose his propshaft tube and joint size? Would be interesting to know...

Liam

Right,

I've been a measuring and it looks like a 3" tube will fit it in the space assuming I can get it in. I haven't riveted the passenger side panel on yet and the engine gearbox thats in there will be coming out before the proper engine goes in.

Next silly question - I measured as directed from the gearbox oil seal to the dif flange face. I measured at the top and bottom to be sure - it appears that my dif is in at a slight angle as the dimension for length were 624mm bottom and 632mm top! Presumably I should go with the shorter of the two to ensure it fits, just wondered what the tolerances were like and how much slack the uj's can give/lose.

Ned.

tranny tunnel

[Edited on 30/1/06 by ned]

If 2" will propel a Transit fully loaded I don't think it will have any problem with a Locost

I would have thought that instead of worrying about 2" or 3", you should be asking what wall thickness the prop is! Thats where the strength is.

HTH Fozzie

quote:

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Originally posted by Fozzie
I would have thought that instead of worrying about 2" or 3", you should be asking what wall thickness the prop is! Thats where the strength is.

HTH Fozzie

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Yes I do appreciate what you are saying, but, just also giving the benefit of very many years of restoration/race prep!....We all have different views!....
Fozzie

quote:

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Originally posted by Liam
3" prop Making a lorry?

I've got a bit of cossie shaft that's 2". I remember when i was talking to Bailey Morris about my prop needs, telling him what bits i was planning to use (27mm cap diameter/71mm span ujs on 2" tube from my volvo and cossie shafts) and saying well I might have up to... 300bhp! (sounding impressive), will they be up to it? He politely chuckled and told me that size of joint is used on stuff like transit vans and land rovers.

Cant imagine what sort of application would call for 3" tube and the correspondingly enormous ujs! Like I said - maybe a lorry.

Liam

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Pic doesn't work for me, Dev. Would be interested though - nothing makes me think of piling weight onto my car like nice failure pictures . I'm probably more paranoid about most when it comes to props (maybe it's cos I have two) - in fact i've even considered prop retaining rings, something i've never even seen mentioned here! So I dont underestimate the stress on a prop for a second. Still, you only need so much safety factor...

Yes I agree it's the most efficient use of material to go for the largest diameter you can on the tubing, but isn't this offset by the inefficiency of using grossly overated enormous ujs? Sure it would be great if I could fit a 5" 22swg prop tube in my tunnel, but the necessary HGV ujs at each end would hurt my wallet, my acceleration, and my sense of engineering elegance . With such short shafts as a locost uses, with most of the weight in the ujs/yokes, wouldn't you be looking to size the joints sensibly and accept marginally heavier, smaller diameter tube?

Liam

[Edited on 31/1/06 by Liam]

Certainly an interesting subject........

On short props (presumably like your front prop will be) the subject gets more complex.

Shock loads are more concentrated on a short prop, and therefore the UJ's need to be bigger still to cope, as the prop tube has very little "spring" in it to cushion the loads.

The alternative, if the length is short enough to prevent whip, is to use a small diamater solid or gundrilled driveshaft, made of a very high specification material, which behaves elastically and provides the cushioning effect, which then would allow the use of smaller UJ's.

Obviously all this is purely qualitative, I have no idea on calculations etc.

Totally off thread now but an interesting point..................

From grasstrack racing I can call on quite a bit of "destructive testing" evidence of broken driveshafts (not props)!!!!!! Most of the welded axleshafts I have seen have broken at some point, as have a large number of std sierra lobro type shafts when used with a locked diff on grass.

The solution has always proved to be either small diameter flexible shafts (which 90% use now) or MASSIVELY overspecced UJ's and sliding spline props (i.e. ones from a light truck).

As an interesting aside, which recalls the transit and landrover comments earlier, a friend buillt a car with a 160hp pug 16v engine, in a special weighing 450kg, and used landrover sliding spline props as driveshafts.

They both smashed to pieces in the second race, the UJ's (new ones!) just shattered with the shock loading....................

quote:

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Originally posted by Fozzie
Yes I do appreciate what you are saying, but, just also giving the benefit of very many years of restoration/race prep!....We all have different views!....
Fozzie

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Sliding spline joints lock solid under load --- obviously this causes major problems-- this is a bigger problem on drive shafts than prophafts because of the torque multilpication effect of the final drive ratio..

With in reason a bigger than standard diameter propshaft isn't required for torque transmission with a more powrrful engine --- however diameter required depends on the length of the shaft. To prevent whipping of the shaft longer shaft at higher rotational speeds greater beam stiffness is required -- this is why rwd Escort base models fitted with a one piece propshat use a larger diameter shaft than the upmarket models with a 2 piece shaft and centre bearing.



[Edited on 31/1/06 by britishtrident]

What a nice healthy discussion

for info I believe the tube specified / suggested by the prop manufacturers I spoke to was 2mm wall.

I agree with both fozzie and NS Dev in some respects, imho there are two ways of looking at it: you could keep the prop diameter smaller and make the tube thicker or larger diameter tube with thinner wall - question is which would be lighter? A 3" tube (the same diameter as my fuel swirl pot!!) is quite large and worries me about being very heavy - obviously I don't want to compromise safety for a bit of weight saving though.

My other thought/solution in relation to the shock loadings NS Dev mentions (and hence allowing use of a smaller tube) is that I know you can get these rubber bonded tube in tube type props to absorb some of the shock loading, same idea as a rubber donut but not such a large od - are they any good/an option in this context?

cheers,

Ned.

A very interesting subject indeed!..
I agree with Liam and you NS. You have to, IMO, take each vehicle as an individual, as to what is going to work best for that vehicle.

I think that was our Neds original question/queirey, some Propshaft manufacturers say 2" and some say 3".

My Locost prop is very short, (book chassis) and I don't even have a type 9 gear box!..LOL

I remember us having an E-Type in quite a few years ago that was (rolling roaded) 500bhp, that had a 5" (IIRC) prop in it, but then look at the difference of the length of the prop, plus the weight to speed difference from a locost!

For my own locost which is built for road and race, I had my prop made to measure by the firm and also had it balanced, which, IMO, is the crucial part!

For Locosts, I stick with my original opinion of saying 2" of a good quality, balanced prop is sufficient.

To conclude,a very interesting subject indeed!

ATB Fozzie

Certainly hope 2" will be ok, as that's what I am using, despite my ramblings!!

5" prop on the Jag...cripes!!!

in fact, just read it again, 500hp e type..............now that is something I would like to drive and hear driven!!!!

love the sound of a proper jag v12!

[Edited on 31/1/06 by NS Dev]

Definately awesome......
Breathed fire (needed its own petrol tanker behind it though!).........We have many Jags of that era in and loads of E-types, but none as awesome as that beast was........memories.....aaaah!

Fozzie

Nice

so, what size prop should i get then guys


[Edited on 31/1/06 by ned]

If it were not rotating, the biggest diameter wins the argument.

BUT...rotating inertial mass has to be taken into account. (You lighten a flywheel at the periphery, not the centre, for greatest effect.)

So, the smallest diameter is preferable. BUT... then you get into whirling and whipping frequencies. The design compromises are many.

With the short length of a Locost prop, I'd go for the smallest diameter I could get away with, and maybe a slightly heavier wall. But that's just me.

Then again, I know a man who makes these things out of carbon fibre.

Syd.

heh heh!

If a 3" will fit, use that, if not use a 2". As I said, a 3" prop won't really fit if you have a gearshift extension (similar to the westfield one)

Caterham-Vauxhall HPC used a 2" one, which is what I am using.

quote:

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Originally posted by ned
Nice

so, what size prop should i get then guys

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So to recap:
prop should be rated for 280-300bhp / 200lb/ft
prop length 25" (approx 624mm)
suggested diameters 2" or 3" (one manufacturer mentioned 2.5" )
suggested wall thickness 2mm
1300 series uj's

[Edited on 31/1/06 by ned]

PS Ned, cut that seamless tube for your steering column, just got to find a way to attach an address so the postie can read it!!

ta muchly Nat.

When i ordered my prop from autoprop they recommended a 3" item for my 270-300bhp indy. By the time you added vat and carriage it was nearly £150.... but it is very well made. A little over engineering on something that spins that close next to your legs is not a bad thing!!!

A friend bought a carbon fibre prop for his 300zx from a company in the states who also make them for the indy cars. It cost him £1400

Sorry for being a bit late on this one.

I used to work for one of the Uk`s leading propshaft firms and have made 100`s of shafts for kit cars, rally cars and racers.

Tube thickness. Tube thickness will have a bearing on the strength of the prop. But parts to build props come in standard sizes. For 2" tube you are looking at 0.064" or 0.095" wall thickness. Any thing else will require non standard tube yokes and tube.

For a prop you describe I would not fit a 2" x 0.095" tube prop to my vehicle. It may be OK but I would fit 2 1/2" tube.

The other thing you could specify is DOM tubing instead of welded. Most prop tube for cars is actually seamed ERW. Do not use CDS as the wall thickness is not consistent enough.

One other point I found out from experience. If the prop is well made it should hardly have any balance weights on it. One about the size of a 2 pence piece maximum.

John

Hi all,

I'm not yet a the stage of needing a propshaft, but I had thought about the price.... Dax quote £125 ex VAT for a standard Ford to Ford one (which sounds roughtly right ish) but want a whopping £287 !!!! for one to connect an omega box to the standard sierra diff.... Has anyone ANY idea about the price differential at all - seems a lot - and can anyone suggest some people to ask for quotes.

Thanks

Chris

http://www.propshaft.co.uk
http://www.propshafts.co.uk
http://www.autopropuk.co.uk/
http://www.baileymorris.co.uk/

Cool..

Thanks Ned

Does the Omega box have a rubber guibo (donut) on the it? If so then this is the reason for the big cash as you will probably require a special adapter.

John

PS I used to make all the props for Dax.

Yes it does - that'll be the reason then

Anyone you'd recommend then??

Chris