Winston Todge
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| posted on 25/9/05 at 11:38 AM |
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Torque Resilient Tubing - Propshafts...
Just wondering about peoples opinions on TRT in a propshaft made for a BEC?
Just in case anyone is curious, a TRT is a section of the propshaft that has one outer tube connected to the differential end and another tube running
inside the outer which is connected to the engine end of the prop. These two tubes are connected to one another via rubber therefore producing a join
with a small amount of flexibility within it.
My main question is how much power can this bonded rubber connection take?
I'm starting with an R1 motor at around 150bhp but am going to fit a 40 shot wet N20 kit to it for track use. Would this TRT take that kind of
power?
Thanks for any advice,
Chris.
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NS Dev
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| posted on 25/9/05 at 11:45 AM |
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don't know, but didn't volvo 340/360's and porsche 944's use this setup?
If the 944 turbo did then they should be fine!
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OX
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| posted on 25/9/05 at 12:08 PM |
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i cant realy remember but im sure the trt is over 2 feet long with a thin layer of hard rubber,i asked if they could shorten it but they said it only
comes in one size,im sure the tube will take your nos,,im changing the diff in mine soon for the second time so i'll give the prop a once over
to see if theres and signs of the trt coming apart 
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Winston Todge
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| posted on 25/9/05 at 12:26 PM |
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Fantastic! Ta Dev and Ox. Just the sort of replies I wanted to hear.
Much appreciated.
Chris.
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chrisf
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| posted on 25/9/05 at 03:22 PM |
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Is the TRT on the front section or rear? Or is it both?
--Thanks, Chris
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Winston Todge
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| posted on 25/9/05 at 03:27 PM |
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On the BECs it is usually on the rear as the front section of a two piece prop isusually very short... As shown in this thread...
http://www.locostbuilders.co.uk/viewthread.php?tid=31716
The TRT is the thicker tubing at the rear of the prop.
 
Description
^^ Sorry to steal your picture Pat! ^^
Just for illustration purposes... 
Chris.
[Edited on 25-9-05 by Winston Todge]
[Edited on 25-9-05 by Winston Todge]
[Edited on 25-9-05 by Winston Todge]
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chrisf
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| posted on 25/9/05 at 03:39 PM |
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Good, because space is at a premium in the front section--as I'm sure it is with others.
--Chris
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JoelP
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| posted on 25/9/05 at 09:48 PM |
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as with all things like this, your prop supplier will be well versed in the specs of their different products, what with making them all day every
day, and could undoubtedly tell you a whole host of facts about it, be it max torque, max rpm, ideal temperature range, if the item is lifed etc. It
is their job to know these things in detail! If they dont know them, id buy it from somewhere else!
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Winston Todge
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| posted on 25/9/05 at 10:18 PM |
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Very good point Joel... I may have to drop them a line at www.propshafts.co.uk
Ta, Chris.
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Avoneer
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| posted on 25/9/05 at 11:19 PM |
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Tell em Pat sent you who bought one a couple of weeks ago.
Won't make any difference though!
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
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JB
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| posted on 27/9/05 at 08:28 PM |
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Propshafts.
The TRT shafts definitly have a power limit, but I think you will be Ok with your application.
Dunning and Fairbank (www.propshafts.co.uk) definitly know what they are on about (I worked there for years) and will be able to advise.
We replaced many TRT shafts with plain tube on high powered cars. We also often saw TRT shafts twisted (the rubber would come unbonded)
If given the choice I would not run a TRT shaft for a number of reasons.
1) It is power limited
2) It is heavier
3) It is generally a larger diameter
4) It is more difficult to balance
You can shorten them, the rubber only runs part of the way.
John B.
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Winston Todge
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| posted on 3/3/06 at 01:03 PM |
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Sorry to drag up an old thread, but I hadn't realised that John B had posted!
Very interesting you mention that a TRT is power limited. Obviously a bonding of rubber is less strong than a straight through connection and weight
is also an issue for my build.
I'm just curious whether a TRT's advantages out weigh the disadvantages mentioned above?
Any comments from peeps with a TRT that have used a straight through connection also?
Ta, Chris.
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Bob C
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| posted on 3/3/06 at 01:13 PM |
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I would expect the propshaft torque to be very effectively limited by the grip of the rear wheels. Big powerful cars could possibly increase this by a
few 10s of % due to weight transfer on acceleration. But basically you have a 1/2 weight car so the prop will see 1/2 the torque it does on a normal
car. I can't really see why a power limit should apply here . ? ?
Bob C
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JoelP
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| posted on 3/3/06 at 01:28 PM |
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the prop and drivetrain does in some situations see the full power and torque. Namely, whenever you are flat out with no wheelspin, more so when not
accelerating (ie top speed, toe to floor)
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Bob C
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| posted on 4/3/06 at 08:39 PM |
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Nah - don't see it Joel; flat out you won't see such high torque (it would be a mad car that could spin its wheels in top!). I agree you
see max revs then (obviously) but can't really see why revs should worry a TRT (unless it's out of balance).
I reckon the worst torque stress on drivetrains could be when 'bump starting' in a low gear: and even here wheelslip will limit the
torque, but larger instantaneous torques might be seen due to resonant 'overshoots' due to the step load applied. Certainly the belt
driven bikes are (I believe) supplied with a warning not to bump- start them.
cheers
Bob
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Bob C
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| posted on 4/3/06 at 08:42 PM |
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Just had another look at what you said & I think I understand your point now - yes in high gear the prop will see full motor torque, but remember
that in a low gear, with no wheelslip, it could see about 3 times this because of the gearbox ratio. I still say the torque experienced by the prop is
limited by wheelslip. .. .
cheers
Bob
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blueshift
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| posted on 5/3/06 at 03:51 AM |
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I think this has come up before and I thought: there's significant inertia in the diff, driveshafts and mostly, wheels. if you are mechanically
unsympathetic and drop the clutch at power the prop could see a lot of torque.
I think that is when it would see peak instantaneous torque, more a product of the inertia in the driveline after the prop, and the inertia and speed
the engine was running at when you dumped the clutch (and strength of the clutch)
if you drove sympathetically then you'd have drivetrain inertia and tyre grip adding to the torque the propshaft saw.. but the reduction in
torque produced by the engine due to it revving up rather than running at constant revs would be in your favour..
I dunno, I'm rambling.
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JoelP
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| posted on 5/3/06 at 10:06 AM |
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quite right bob, i didnt include the gearing in my thinking!
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