ned
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| posted on 30/1/06 at 01:15 PM |
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propshaft diameter?
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.
beware, I've got yellow skin
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DarrenW
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| posted on 30/1/06 at 01:35 PM |
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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.
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NS Dev
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| posted on 30/1/06 at 01:45 PM |
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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
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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James
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| posted on 30/1/06 at 02:36 PM |
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Ned,
Think I went with these guys who you've probably tried:
http://www.autoprop.co.uk/
Was around £100.
Cheers,
James
------------------------------------------------------------------------------------------------------------
"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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stevebubs
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| posted on 30/1/06 at 03:04 PM |
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quote:
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...
That's the price you pay for living in Surrey 
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ned
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| posted on 30/1/06 at 03:54 PM |
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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
beware, I've got yellow skin
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James
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| posted on 30/1/06 at 04:01 PM |
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quote:
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
Blimey, wonder why they've gone up so much!
Cheers,
James
------------------------------------------------------------------------------------------------------------
"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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Liam
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| posted on 30/1/06 at 04:55 PM |
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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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ned
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| posted on 30/1/06 at 05:03 PM |
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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]
beware, I've got yellow skin
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JB
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| posted on 30/1/06 at 07:39 PM |
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Propshafts
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
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Liam
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| posted on 30/1/06 at 09:40 PM |
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Wonder if Hicost would disclose his propshaft tube and joint size? Would be interesting to know...
Liam
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ned
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| posted on 30/1/06 at 10:09 PM |
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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]
beware, I've got yellow skin
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Peteff
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| posted on 30/1/06 at 11:34 PM |
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If 2" will propel a Transit fully loaded I don't think it will have any problem with a Locost
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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Fozzie
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| posted on 31/1/06 at 12:00 AM |
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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
'Racing is Life!...anything before or after is just waiting'....Steve McQueen
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NS Dev
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| posted on 31/1/06 at 12:12 AM |
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quote:
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
Hmmmmm!
As I am sure JB will also chime in a moment, that is completely and utterly wrong!!!
The strength is in the material furthest from the neutral axis, which is the middle of a shaft in pure torsion.
This is why we use a tube and not solid bar to start with!
The strongest prop will be one of a huge diameter, with weight then reduced by using a very thin wall, but practicalities of manufacture and damage
resistance then come into play.
My old rally car prop was 3" but very thin wall (1.2mm I think iirc) so was not very heavy but was extremely strong.
As I pointed out and JB also emphasised, just fit the biggest OD prop that you can.
I am using a 2" one as I have the joints already attached to a caterham prop, and the UJ's on the 3" prop I have foul the gearshift
extension. If I could fit the 3" one I would.
PS though I don't think he's mentioned it. JB used to work for a prop manufacturer so he has some idea!!
[Edited on 31/1/06 by NS Dev]
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Fozzie
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| posted on 31/1/06 at 12:23 AM |
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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
'Racing is Life!...anything before or after is just waiting'....Steve McQueen
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NS Dev
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| posted on 31/1/06 at 12:25 AM |
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quote:
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
The power (actually torque, power has little to do with it) that the joints will transmit is indeed very large, but you have to remember that the
torque loads on a car prop are not just what the engine can produce. They are multiplied by the gearing for a start, and then shock loads can be
MASSIVE!
a 2" prop will be fine in a locost but don't think that it isn't a highly stressed component because it is!
2" failed shaft, with 200hp n/a cossie engine, ok it's a driveshaft not prop so the torque is over 3 times higher but
still!!...............
[Edited on 31/1/06 by NS Dev]
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Liam
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| posted on 31/1/06 at 01:29 AM |
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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]
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NS Dev
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| posted on 31/1/06 at 09:00 AM |
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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....................
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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britishtrident
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| posted on 31/1/06 at 09:21 AM |
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quote:
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
Hard engineering science rather than a different view --- for torsional stiffness (and to a lesser extent beam stiffness) an increase diameter wins
over thickness every time by a very large margin.
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britishtrident
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| posted on 31/1/06 at 09:33 AM |
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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]
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ned
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| posted on 31/1/06 at 09:34 AM |
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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.
beware, I've got yellow skin
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Fozzie
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| posted on 31/1/06 at 09:34 AM |
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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
'Racing is Life!...anything before or after is just waiting'....Steve McQueen
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NS Dev
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| posted on 31/1/06 at 09:37 AM |
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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]
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Fozzie
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| posted on 31/1/06 at 09:47 AM |
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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
'Racing is Life!...anything before or after is just waiting'....Steve McQueen
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