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Propshaft alignment
xico_ze54 - 21/3/07 at 04:43 PM

Hi,

please see this pic attached and tell me if we can put a bike engine maximum far right, to use in a LHD car, and put some angle in those U-joints?

is there some danger in broke propshafts or U-joints at high rpm?

thks
Amadeu Rescued attachment new-2.jpg
Rescued attachment new-2.jpg


BenB - 21/3/07 at 04:45 PM

IIRC props work best with a slight angle on the joints and cant go wrong if you run it absolutely straight. Not sure where I remember that from!!!!


Hellfire - 21/3/07 at 04:49 PM

A UJ is designed to run with an angle so no fear of problems here. They are made to run with a (IIRC) 5 degree minimum.

Your engine has no effect on the speed of rotation of the propshaft, it's dictated by the speed of the wheel/differential ratio. You won't break a properly designed propshaft on a slightly modified seven (read - PROPERLY). The se7en weight is almost half it was originally designed for.

Steve


worX - 21/3/07 at 04:50 PM

I'm not sure about having the angle between the engine/prop adaptor to the prop - I would of thought that it would be a lot better if those mating faces were at 90degrees to each other?
I am only going from what I think, not from proven fact so maybe someone else on here can confirm/deny.

the mid bend in the prop is more than fine, it can be angled a lot further than that, as mine is already!

hth
cheers,
Steve.

[Edited on 21/3/07 by worX]


Bluemoon - 21/3/07 at 05:18 PM

Allways wondered how the BEC get way with it. The yokes should be phased at 90 degrees (in theory) and outputs shafts at each end should be in parall, but offset to allow the UJ's to work otherwise you wear flats in the bearings..

Would like to hear what others think about this..

Cheers

Dan

[Edited on 21/3/07 by Bluemoon]


jcduroc - 21/3/07 at 05:30 PM

quote:
Originally posted by xico_ze54
Hi,

please see this pic attached and tell me if we can put a bike engine maximum far right, to use in a LHD car, and put some angle in those U-joints?

is there some danger in broke propshafts or U-joints at high rpm?

thks
Amadeu

Amadeu

I would place the engine on the RHS and make a reverse box from the pinion to the CL of the car.


02GF74 - 21/3/07 at 05:32 PM

hmmm .... I always thought the important bit was to have the drive flange (on engine) parallel to the driven flange (axle) and the angle does not matter too much providing it is not more than the UJ can take.

if you angled your engine so the drive flange was in vertical plane, then I would have no problems but like you have it, not sure.

read all about propshaft angles here


Bluemoon - 21/3/07 at 05:55 PM

02GF74, yep that's what I was trying to get at...

Dan


xico_ze54 - 21/3/07 at 06:13 PM

so... what´s the best solution? bearing in mind the driver will sit on left and the problems of much weight on left side. plus the steering column have to have room to pass though, gives no other chance than put that engine some distance to the right side.

can anyone sketch over my sketch an ideal solution to this problem? Rescued attachment new-3.jpg
Rescued attachment new-3.jpg


Peteff - 21/3/07 at 06:14 PM

You'll need a sliding joint in the front section where it connects to the engine or it will shake the joint to bits. Prop suppliers have these.


ChrisGamlin - 21/3/07 at 06:29 PM

As others have said, the two flanges should ideally be parallel, and as I mentioned in another thread recently, don't forget to consider VERTICAL angles as well as the horizontal ones you're looking at here, i.e. if the output shaft is vertically higher / lower than the diff flange, you have an angle there as well.

Im not sure about it shaking the joint to bits without a slider though Pete, all live axle BECs have to have the slider in the rear half for obvious reasons and Ive never heard of any trouble at all with the front UJ.

In fact, I would actually suggest the slider on the rear with a fixed length at the engine end, because if your prop flange on the engine ever comes loose (and they do - mine did), with a slider on the front the prop is able to disengage from the engine and potentially cause serious injury, with the slider on the rear half it will simply cause some extra vibration but won't be able to escape off the output splines.

cheers
Chris

[Edited on 21/3/07 by ChrisGamlin]


xico_ze54 - 21/3/07 at 07:03 PM

Chris,

just finished to see one of the pics you show in your archive (named: R1 Prop angle) and it's like I have talked first.

in that photo your sprocket isn't in the centerline of the car, making an some angle with the first shaft, the same with centre bearing.

do you want to coment that?


JoelP - 21/3/07 at 07:27 PM

the two prop mating faces need to be parallel because a u/j isnt a constant velocity joint, if they arent square you get a pulsing of motion rather than constant at both ends. The worse the angle the more the drivetrain gets abused. I have no idea how badly this will affect it, but thats the theory. However, the engine can happily be off the centreline.

If i was building a LHD bec, i would leave the feet areas out until the engine was being positioned, and balance them around each other. You can take a chunk out of the passanger (right hand side) footwell to allow the engine further over.


ChrisGamlin - 21/3/07 at 08:24 PM

quote:
Originally posted by xico_ze54
Chris,

just finished to see one of the pics you show in your archive (named: R1 Prop angle) and it's like I have talked first.

in that photo your sprocket isn't in the centerline of the car, making an some angle with the first shaft, the same with centre bearing.

do you want to coment that?


Hi Amadeu

I assume you mean this one, which Ive modified to show the differences...

Prop Angles
Prop Angles


As you can see, my prop angles are different to your picture because my engine is mounted inline with the chassis centreline, not at an angle across the chassis like in your drawing. This means my output and diff flanges (blue lines) are parallel with each other and the angles of the prop cancel themselves out along its length.

cheers

Chris

[Edited on 21/3/07 by ChrisGamlin]


xico_ze54 - 22/3/07 at 10:52 AM

Chris,

thanks for the modified pic to observe the explanation.
so the 'receipt' to a good job is to put diff & sprocket flanges paralel. I see.


matt_gsxr - 22/3/07 at 11:59 AM

3 simple options:

1) find an engine which has the prop coming out of the other end. That is a bike with a sprocket on the left.
2) move to England and build it RHD.
3) chop your legs off.


No no no, there is no need to thank me.

Matt


grb - 22/3/07 at 12:04 PM

quote:
Originally posted by matt_gsxr

1) find an engine which has the prop coming out of the other end. That is a bike with a sprocket on the left.




my KTM LC4 is... (and would be rubbish in a car!) ...but I wonder if the LC8 V-twin is too?


grb.


robertwa - 22/3/07 at 03:32 PM

Take a look at this LHD BEC to see what he has done:

Left hand drive R1 BEC


Peteff - 22/3/07 at 04:26 PM

I don't think the Isonblade has, I'm sure his is in the front. The centre bearing mount has enough flex to cover live axle movement, same setup,Transits, Marinas and plastic pigs with 2 piece prop didn't have a sliding joint in the rear only the slider at the gearbox end.

if your prop flange on the engine ever comes loose (and they do - mine did)
Ever thought why this happened?



[Edited on 22/3/07 by Peteff]


ChrisGamlin - 22/3/07 at 09:28 PM

Hi Pete

I guess there probably would be enough flex in the centre bearing to cope with a live axle moving at the rear, but if thats the case there's certainly enough to accomodate any movement on the engine end.

FWIW my bolt loosened itself a bit despite being correctly torqued / threadlocked. I caught it in time after I noticed the vibration, but the flange couldnt come off anyway because of the fixed prop length, had it been a slider its possible it could have sheared the bolt head off even if it hadnt come fully undone, which is what appeared to happen to a car on the Yahoo list a while back (I forget who).

Hopefully not such a problem on the R1 though as they have tabbed washers to hold the nut as well as copious amounts of threadlock, but I can't see a lot of point in tempting fate by putting the slider at the front if you have the choice.

cheers

Chris


Peteff - 23/3/07 at 12:11 AM

If it had been a slider it wouldn't have happened. A slider would be engaged by at least 50mm so if it disengages your engine has fallen out. Guess all you like about the centre bearing, Ford have been doing it like that for years and they don't guess.


ChrisGamlin - 23/3/07 at 08:37 PM

Pete, I used the word "guess" as a figure of speech which I'm sure most people picked up on without too much bother, I could have just as easily used "can see", or "accept". You obviously failed to recognise that though judging by the slightly patronising tone to your reply.

quote:

If it had been a slider it wouldn't have happened.



Errr, prop sliders have bolt tightening tendancies ?

quote:

A slider would be engaged by at least 50mm so if it disengages your engine has fallen out.



You've clearly got the wrong end of the stick Pete! Im not talking about the slider itself extending to the point that it disengages from the rest of the prop, Im talking about the slider allowing the prop to shorten and so allow the prop flange to drop off the output shaft. Some output shafts are only ~15-20mm deep, so you only need that amount of travel in the slider for the flange to disengage.

[Edited on 23/3/07 by ChrisGamlin]


Peteff - 23/3/07 at 11:40 PM

No that was sarcasm Chris, I knew it wouldn't be long before you replied.
My point was that if there'd been a slider on there would have been no stress on the nut and it wouldn't have come loose in the first place.
Your go, I've done now.


ChrisGamlin - 25/3/07 at 08:22 PM

Pete

You're still making statements as fact without actually saying why, if you're going to argue against it then why not explain why you believe a fixed length prop puts stress on the engine UJ / flange?

As you've said yourself, the centre bearing has enough movement in it to allow a live axle to move at the rear, so how does this suddenly become non applicable when discussing the comparatively fixed span of engine to centre bearing?

If your engine is moving fore/aft more than your live axle, you have some serious problems that a prop slider isn't going to fix!

Chris



BTW, I really don't want to turn this into a slanging match but you're seemingly writing in a condescending manner without realising! Sarcasm by definition has an element of humour / wittyness / irony about it, saying "Guess all you like..." in reply to something I said is a plain attempt at a put down, suggesting you believe you're knowledge is superior. This makes the comment patronising, not sarcastic.

[Edited on 25/3/07 by ChrisGamlin]


Peteff - 26/3/07 at 04:24 PM

Unlike your prop, the angles on his will not cancel each other out. The rear is straight and the front is angled so the prop will pulse or phase as the prop turns as Joel said. As it is the front which is at an angle and the rear is straight he will need the slider in the front as I will with mine and Jon does in his. I have consulted with a manufacturer and his suggestion was a slider in the front and a torque tube in the rear for my application which is like xico's but angled to the other side. As he says, the ideal would be to mount the engine with the joints parallel but it's not always practical.
I'm sorry that I couldn't let it go but why should I not take my position in this and only see yours, you mentioned my name in your post prompting me to retaliate Chris. Why is it only condescending or patronising when I say it?
Im not sure about it shaking the joint to bits without a slider though Pete, all live axle BECs have to have the slider in the rear half for obvious reasons and Ive never heard of any trouble at all with the front UJ.
Does this sound a touch condescending as well, it does to me. I can't see the reason for a slider in the rear however obvious it is to you and you have made no effort to explain to me just told me I am wrong and put me in a negative frame of mind. I would not resort to name calling and insults on a forum any more than anywhere else,
"In fact, I would actually suggest the slider on the rear" sounded to me that you were calling my suggestion wrong implying that I do not know what I am talking about and causing me to take umbrage.


[Edited on 26/3/07 by Peteff]


Bob C - 26/3/07 at 08:25 PM

If you have 2 UJs on a propshaft, with parallel end flanges, then the non-linear transfer angles can cancel out. But on a BEC split prop you have 3 so it won't. It can only possibly cancel if one of the joints is straight (which will wear it out quickly due to 'brinelling'
I'd say use a doughnut for the straightest of the joints - cheaper than a TRT (but a bit tricky to fit in a locost tunnel), soaks up minor length variations and every sierra prop comes with one built in!
cheers
Bob


JoelP - 26/3/07 at 09:25 PM

are you sure you're right there bob, as far as i can see if the ends are parallel then it doesnt matter what happens in the middle. Shame i dont have lego any more to test it!

How fast would brinneling realistically were the joint out? Is it a real problem in anticipated kit car mileage?


ChrisGamlin - 26/3/07 at 10:06 PM

Hi Pete

If the fact that the flanges are not parallel really is your reasoning, why did you not at any point simply say "you'll need it in the front if your prop flanges aren't parallel", and why argue that its the reason my bolt came loose when you know my flanges ARE parallel?

I apologise if you think my initial comment was patronising, it certainly wasnt intentional which I hoped was obvious given my second reply to you which was plainly written in a non confrontational way, despite what I thought was a fairly abrupt reply from you.


quote:

I can't see the reason for a slider in the rear however obvious it is to you and you have made no effort to explain to me just told me I am wrong and put me in a negative frame of mind



Not true, I clearly gave you my reasoning why I think its a bad idea to have it in the front (which are completely unlrelated to your reasonings for having it there), and given that I accepted your explaination that the rear of the prop has enough movement for a live axle without slider, Im clearly no longer saying its NECESSARY in the rear of the prop. What we hadn't cleared up until now is why you feel its paramount to fit it in the front given the amount of flex in the centre bearing, up until now haven't explained anything other than to say the UJ will be destroyed without it, so it would appear that you're the one expecting me and everyone else to accept your view as gospel without any reasoning behind it, not me.

Back onto the technical side of things, I would think (and anyone please correct me if its wrong) virtually all the vibration induced by prop phasing will generally end up in ocillating vibrations making the prop "whirl" like a skipping rope, not fore-aft vibrations - so if this is the case I don't see how the slider would help damp these? In addition the sliding joints Ive seen appear to have far too much stiction / damping to damp high frequency vibrations like that even if they were fore-aft.

I guess it boils down to the fact that I am still of the opinion that the slider's primary role is simply being there to accomodate tolerences in manufacture and movement of the engine / gearbox due to rubber mounting, not to dampen an out of balance / out of phase prop.

Chris

[Edited on 26/3/07 by ChrisGamlin]


Bob C - 26/3/07 at 11:02 PM

With 2 UJs you have to line up the yokes on the middle section. Which bits would you line up with 3??? 'cos if you line up both middle sections the end ones would end up at 90degrees, which would be totally wrong if the middle joint were straight & the other 2 at an angle - it just don't work with 3 UJs!!
I think the "wearing straight" thing is not too important - at worst you end up with a tiny bit of backlash, nothing compared to the diff & CVs on the driveshafts! I've seen it on an aincient prop (off a spit I think) - the joint seemed to 'click into position' in the straight ahead state.
ATB
Bob


Peteff - 27/3/07 at 12:02 AM

Because that was the obvious point of his question as illustrated by his diagram. I didn't therefore think it necessary.

I could have just as easily used "can see", or "accept". which would have worked better. The only reason you gave for putting it in the rear was because it might let go at the front which just illustrates a lack of confidence in the prop.
The link in 02G2s post illustrates prop principle and the reason the sliding joint is needed in the front is to allow the prop some movement when the knuckle of the centre uj is on the inside of the centre angle pushing the front of the prop towards the engine and pulling it on the outside. I think Bob is using the same logic as me in saying that the centre angle cannot be cancelled out on a two piece prop, the joint is phasing. The slider is a bodge to allow this movement to go somewhere other than back into the engine end of the prop.
According to the vibrate website
On vehicles with two piece propshafts there is an odd joint. The working angle of the odd joint should be kept below 1/2 degree and above zero degrees. This is because there is not a companion U-joint. Think of the front piece of a two piece propshaft as being an extension of the transmission output shaft.
1/2° is not practical in my application so now I may have to rethink the engine position


Peteff - 27/3/07 at 09:28 AM

The designer will have specified a material rigid enough to stop the prop from whirling like a skipping rope which is why it is made in two pieces to keep the thickness down, not to get round a corner like we use it on a Locost, so the movement will be translated into fore and aft and be operating at an angle to the centre bearing. Rescued attachment propphase.jpg
Rescued attachment propphase.jpg


xico_ze54 - 27/3/07 at 10:05 AM

I forgot to tell you I'll use a Sierra 3.15 fixed diff.

the discussion is very nice indeed, great theories but no unanimous conclusions at all.

so what kind of way must I follow?

cheers
Amadeu


Bob C - 27/3/07 at 10:10 AM

Pete - there is no axial movement as a UJ rotates, the vibration is purely rotational. (provided the 2 rotational axes of the spider intersect, which they always do in a prop, sometimes don't in a socket set!).
cheers
Bob


ChrisGamlin - 27/3/07 at 10:49 AM

quote:
Originally posted by Peteff
Because that was the obvious point of his question as illustrated by his diagram. I didn't therefore think it necessary.

I could have just as easily used "can see", or "accept". which would have worked better. The only reason you gave for putting it in the rear was because it might let go at the front which just illustrates a lack of confidence in the prop.


To be fair the chap originally asked the question if he could do it this way, and by the time we'd got into a discussion about it, we'd already covered various different options including having them parallel, so I don't think it was particularly obvious your ongoing stance was only related to the original drawing. It also doesn't explain why you thought that the lack of slider in the front was the culprit for my bolt loosening given mine is different to that, but anyway Im happy to let that drop.

Your second sentence above was the part you seemed to misunderstand because I didnt suggest putting it in the rear due to a lack of confidence in the slider failing in the front, its a lack of confidence in the prop flange retaining mechanism on the engine which was only ever designed to hold a sprocket, not a heavy flange plus a prop hanging off it. My reasoning had nothing to do with the prop itself, it simply uses the lack of slider as a safety net if the flange bolt were to undo.

Anyway, thanks for putting in the effort with the diagrams etc, I do understand what you're saying but I still think that UJ angle changes affect the speed the prop rotates, not its length (hence it not being a CV - Constant Velocity joint), which seems to be backed up by what Bob has said, and in this technical article by Bailey Morris which doesn't mention length change, just angular velocity change. Even if there were axial movements though, I can't see how the heavily damped / high stiction slider would be able to damp movements at 100Hz+ which is what would be experienced with a prop rotating at 6-7000rpm, or why simple 2 UJ props also have sliders in them but again Im happy to agree to disagree.

cheers

Chris


ChrisGamlin - 27/3/07 at 11:07 AM

Amadeu

As you can probably guess, its quite a complicated subject if you want to get everything "textbook". In reality most installs are a compromise of some sort but what's been discussed about balancing two of the UJ angles and keeping one almost straight is a good starting point, so either like mine (with the rear UJ almost straight) or with the front UJ almost straight with the rear two cancelling each other out should give acceptable results. If you want to look further into the technical stuff, have a look here.

As for the slider, you've seen the arguments for and against positioning it at the front so I'll leave that one for you to decide on.

cheers

Chris


G.Man - 28/3/07 at 06:37 AM

so, I have to ask this.. why not use a cv joint instead of a universal?


ChrisGamlin - 28/3/07 at 09:40 AM

From what I understand, its very hard to make / find a CV joint thats capable of rotating at ~7k rpm, obviously as a driveshaft they are rotating at 1/3 to 1/4 that speed.


Bob C - 28/3/07 at 12:28 PM

Quite a few cars do use a CV in the prop, I know rover SDI did for example. Also the later front engined single seaters used CVs because of the extreme prop joint angles needed to negotiate the driver's arse (the rzeppa joints from mini driveshafts)
I'd recommend a sierra donut for the straightish joint - then you won't need a TRT. Why has no-one else done this, it works a treat!
Bob
Bob


G.Man - 28/3/07 at 01:05 PM

quote:
Originally posted by Bob C
TRT. Why has no-one else done this, it works a treat!
Bob
Bob


I have been saying that for ages


ChrisGamlin - 28/3/07 at 01:14 PM

Is it not too big to fit in some transmission tunnels?


G.Man - 28/3/07 at 01:37 PM

To be fair, looking at the top pic, I think it would be a lot easier to route the steering column differently than the propshaft?

Many have router the column around a V8 so dont see a Bike engine could be harder?


xico_ze54 - 29/3/07 at 10:36 AM

quote:
Originally posted by G.Man
To be fair, looking at the top pic, I think it would be a lot easier to route the steering column differently than the propshaft?

Many have router the column around a V8 so dont see a Bike engine could be harder?

its not impossible, but very difficult because the great concentation of elements on the left of the chassis.

I made (almost done) a Locost with an old Toyota 1200cc with much mechanical elements on the left side and I tell you it is was an hard job to pass the steering column through that site, plus I had to rotate slightly the engine to the right side.

(see http://www.viseudesign.com/Sevenesque-04.htm)