Johneturbo
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| posted on 26/8/10 at 10:53 PM |
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Mine is parallel on the horizontal plane but not in a vertical plane
i take it the busa has to be mounted like that to compensate for fitment?
so how would they modify the propshaft for you, is that something DF can do
[Edited on 26/8/10 by Johneturbo]
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cosworthspeed10
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| posted on 27/8/10 at 05:24 AM |
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I think they offset the universal joints on the splines, the angle will depend on how much.
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40inches
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| posted on 27/8/10 at 10:41 AM |
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quote:
Originally posted by cosworthspeed10
quote:
Originally posted by Mal
You may have a problem caused by the flanges that the ends of the shaft connect to not being parallel to each other.
Looks like you may have hit the nail on the head there!
When I spoke with Dunning & Fairbank today they asked if the prop flanges were parallel to each other. The flanges ideally need to be parallel
(Horizontally and Vertically) for the Universal Joints to work well together, in the Horizontal plane because the engine is rotated 10 degrees in the
chassis the prop flanges are not parallel to each other but they are in the vertical plane. I think you can have flanges that are not parallel to
each other but this need to be specified when selecting the prop as the Universal Joints need to be angled differently from one end of the prop to the
other to allow for this. My prop is designed for parallel flanges (as may all the MNR BEC props) and MNR may not have taken into consideration the
unparallel flanges.
Does this make sense?
I can't grasp this because:
Your second drawing describes many BEC installations (my MK is the same)
Wouldn't the centre bearing compensate for the discrepancy in angle?
If the joint is offset on the splines, how is it calculated? There are 2 more joints on the centre bearing, surely they would also have to be
adjusted?
Perhaps I am thicker than I thought, and am talking borrocks
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Johneturbo
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| posted on 27/8/10 at 11:22 AM |
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This is a good site to understand angles
i find it all rather confussing to be honest!
http://www.vibratesoftware.com/html_help/html/Diagnosis/Propshaft/Propshaft_Angles.htm
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cosworthspeed10
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| posted on 27/8/10 at 05:19 PM |
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I can't grasp this because:
Your second drawing describes many BEC installations (my MK is the same)
Wouldn't the centre bearing compensate for the discrepancy in angle?
If the joint is offset on the splines, how is it calculated? There are 2 more joints on the centre bearing, surely they would also have to be
adjusted?
Perhaps I am thicker than I thought, and am talking borrocks
I think the link Johneturbo posted is very useful but also very Mathematical. They talk about the phase of the UJ's being in line when the
flanges are parallel. MK may have taken into consideration the flanges being angled and had their props make with a phase offset on the UJ's,
this is not the case for MNR. Don't know how to calculate that but D&F do. The standard props with UJ's in phase will take some
misalignment but not as much as 10 degrees. The UJ's are currently fighting each other and this may have caused the failure.
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JoelP
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| posted on 27/8/10 at 07:30 PM |
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the easiest way to understand the phase issue is to take it to the extreme - if you had a lego U/J which bends to 90 degrees, then you would have to
rotate one shaft 180 degrees, then the other, and they could not drive each other. So with a small angle in one uj, assuming the input side is a
constant rpm, the output side is going slightly slower for 180 degrees then slightly faster for 180 degs. This vibration would be ruinous eventually.
By having the two or 3 u/js lined up, with parallel ends, the vibration cancels out.
If i build a 7 style bec, id have the engine pulled backwards into the passanger footwell and use a shorter one piece prop, and make a much
stronger/lighter front frame for the suspension to mount to. It could be done much better if there wasnt the need to leave a huge hole for the engine.
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silky16v
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 posted on 29/8/10 at 08:06 PM |
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1 thing to point out which i found out on my MK Indy R1 BEC is alot of people overlook greasing the UJ's the needle rollers go dry and then
wearout and break thus causing the UJ to fail
7 out of 9 4x4 Cosworths i owned i had to replace the front propshaft UJ's because of this
I remember taking 1 off and it had no needles roller left and i'd been doing some top speeds the nite before
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coyoteboy
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| posted on 25/2/13 at 12:36 PM |
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quote:
Spoken with conviction but still a load of rubbish apart from the bit about clutches which is irrelevant.
Sorry, but you're wrong. Sure you can work back to torque if you know your BHP and shaft RPM, but it's still a torque rating on the prop.
Shafts should not be specified in BHP, they should be specified with a torque limit and an RPM limit (max bearing speed, might be important depending
on shaft angle). Anyone specifying them in BHP is ignoring details that matter and are making massive assumptions. I'd rather not work with
people who make such assumptions, or buy from them. Sometimes you're forced to, but it doesn't make it right.
Anyone specifying a power limit on a shaft is opening themselves up to failure. If you present the torque limits and RPM limits the customer must
identify their shaft speeds and torques and match them to suit. If you spec a power the customer will brainlessly match flywheel output to shaft
rating and there's a distinct possibility that'll go pear shaped - you can't possibly claim that the RPM ranges for automotive
shafts are similar. Nor can you assume that engine output torque is the only torque-based cause of shaft failure - if I have sticky tyres and a 20Kg
flywheel spinning at 10K RPM on the end of a V8 and I sidestep the clutch it'll have much more effect on the shaft than if I do the same with a
bike engine, even if the cars weigh the same and are restricted to the same output power, due to the vastly higher inertia of the powertrain.
Since you think I'm wrong, please explain why.
[Edited on 25/2/13 by coyoteboy]
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Charlie_Zetec
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| posted on 25/2/13 at 05:03 PM |
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This is something I think has been significantly overlooked in the whole topic here! As silky16v says, you need to remember to grease the UJ's
to keep them in good working order. All good quality UJ's will have a grease nipple in them, doesn't take 2 seconds to top them up and
check from time to time.
I know this from personal experience, not with 7's, but with Land Rovers - where you can all imagine they take a beating on and off road. I
think this alone adds to the question of how to choose a suitable prop shaft.... Defenders have not got great power, but plenty of torque!
But in terms of spec'ing up propshafts, I think you can't rely of BHP or torque alone when ordering. It's like ordering a steak -
you can have it very rare through to well done. But there's also the choice of t-bone, rump, fillet, etc. Unless you know all the details,
you're never going to get the right one. Speak to any professional, and they'll ask these details before supplying anything.
quote:
Originally posted by silky16v
1 thing to point out which i found out on my MK Indy R1 BEC is alot of people overlook greasing the UJ's the needle rollers go dry and then
wearout and break thus causing the UJ to fail
7 out of 9 4x4 Cosworths i owned i had to replace the front propshaft UJ's because of this
I remember taking 1 off and it had no needles roller left and i'd been doing some top speeds the nite before
Artificial intelligence is no match for natural stupidity!
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flak monkey
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| posted on 25/2/13 at 07:21 PM |
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FWIW when I rebuilt mine with the Duratec Bailey Morris gave me the same advice and recommended I went for the heavy duty prop. It was considerably
bigger diameter and much heavier than the standard duty one. Can't remember what it was rated to for power and torque, but it was
'adequate' 
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