TimC
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| posted on 23/10/10 at 10:10 PM |
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Intuitively, what do people think about this prop angle?
Evening All,
I've had a nagging doubt about the ability of the Gemini chassis to swallow a 5VY R1 engine. Another forum member (thanks again Mate!) has very
kindly lent me his spare to have a dry fit.
Some photos are below. I think it's very border-line. What's the general opinion from folk here? You'll notice that the engine is
forward (85mm) of the bulkhead. This is an attempt to:
a. Make the prop angle slightly better.
b. Make some room for an electric reverse at the engine-end (live axle.)
I'm not terribly concerned about the weight distribution as I'm no flyweight, the major criticism I have of BECs is a lack of steering
feel due to the light front-end and the anti-dive built into the chassis should aid things a bit anyway. I am concerned about the prop angle. What
do you think?
Bare, empty chassis:
Top-down:
From cockpit:
Down the tunnel:
Ta
TC
[Edited on 23/10/10 by TimC]
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ReMan
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| posted on 23/10/10 at 10:26 PM |
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Apart from the engine being canted, it does'nt look like its going to even clear the tunnel uprights in that pic
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blakep82
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| posted on 23/10/10 at 10:34 PM |
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no. just no.
angle's too sharp i think, UJ's will be knackered pretty quick i reckon
________________________
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matt_gsxr
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| posted on 23/10/10 at 10:36 PM |
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Are you planning to have the middle UJ around the point of your horizontal cross-member. If so that looks a lot like what I have.
Here is a picture of my set-up. I don't know whether mine is perfect, but it seems to work and I've done a couple of thousand miles and a
couple of trackdays and its intact.
link
Final bracket was not made of wood!
These UJ's don't mind a bit of angle on them, it always looks worst when viewed from the diff, as the lengths are shortened.
Matt
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matt_gsxr
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| posted on 23/10/10 at 10:38 PM |
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It sounds like you are going to get some variation in the answers to this one.
;-)
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ReMan
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| posted on 23/10/10 at 10:54 PM |
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From the last photo it looks impossible let alone too sharp.
Why cant you pull the engine further over so the output is closer to the centre of the tunnel?
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fesycresy
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| posted on 23/10/10 at 11:07 PM |
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There's no angle because that footwell looks immense !!
Cut out the upright and move it over?
-----------------------------------------------------------------------------------------------------
The sooner you fall behind, the more time you'll have to catch up.
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daviep
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| posted on 24/10/10 at 05:53 AM |
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Looks pretty exterme in the last photo but I think it's a bit of an optical illusion. Photo's 3+4 look as if it will run parallel with the
top rail of the tunnel, presuming that the engine will be square in the chassis then measuring the angle of the transmission tunnel will give a good
indication of prop angle, you can then telephone your chosen prop supplier and confirm that it will be ok.
If it was me I would mock up a prop for a better idea of angles but it looks like it will probably be ok to me.
I'd be tempted to rotate the engine slightly more upright to improve the angle if it didn't mess up the exhaust route.
“A truly great library contains something in it to offend everyone.”
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TimC
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| posted on 24/10/10 at 08:10 AM |
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quote:
Originally posted by ReMan
it does'nt look like its going to even clear the tunnel uprights in that pic
quote:
Originally posted by ReMan
From the last photo it looks impossible let alone too sharp.
Why cant you pull the engine further over so the output is closer to the centre of the tunnel?
Its certainly not impossible. I agree that the picture down the tunnel makes it look as though it might be but the output shaft is about 250mm from
the narrow tunnel upright. The engine can't move further to the pax side as the head is almost touching the chassis as it is (see first
pic.)
quote:
Originally posted by matt_gsxr
Here is a picture of my set-up. I don't know whether mine is perfect, but it seems to work and I've done a couple of thousand miles and a
couple of trackdays and its intact.
That's quite encouraging Matt. It doesn't look terribly different from yours.
quote:
Originally posted by fesycresy
There's no angle because that footwell looks immense !!
Cut out the upright and move it over?
I know - I did tell you didn't I? I only have size 8s too - was already thinking about doing something like this:
The extra tube at the bottom of the tunnel was always going in anyway.
quote:
Originally posted by daviep
I'd be tempted to rotate the engine slightly more upright to improve the angle if it didn't mess up the exhaust route.
The factory Fisher Fury installs do have the engine running more upright, however a conversation with a guy who really understands the 5VY has
confirmed to me that it should be as in the pic. In any case, as you suggest, the alternative does make a sensible exhaust run near impossible.
Thanks for all the comments. On the plus side, I think it'll fit under the bonnet and not effect my planned ride height by protruding below the
floor.
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matt_gsxr
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| posted on 24/10/10 at 10:23 AM |
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regarding rotating the engine I would be surprised if a little rotation would make much difference. I say this because the acceleration forces in
your application are pretty large (i.e. 1g lateral) which corresponds to rotating the engine by 45deg.
I'd be interested to understand better why vertical is the only option, just keen to learn, not doubting your expert.
Matt
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adithorp
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| posted on 24/10/10 at 11:05 AM |
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Looks OK to me, Tim. The view of the chassis from the front gives a better idea of the angle than the rear view up the tunnel. Can you ask thge
prop' manufacturers what themax' allowable angle is? Racing will put high strain on it but for nothing like the amount of time you'd
be running it on the road.
Edit... The overhead view makes the anlgle look fine.
The angle you have the engine is the standard orientation in the bike with the sump base horizontal (not as in my pictures). Makes a flat floor easier
to achieve. You need to consider the position of the throttle bodies (and therefore airbox) before you decide on the angle of the sump. They stand
very high. Bare in in mind the forces on the engine and the effect on the oil when in the bike under acceleration and you see it is designed to cope
with the oil at that angle. You do need the breather mod though.
adrian
[Edited on 24/10/10 by adithorp]
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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TimC
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| posted on 24/10/10 at 11:52 AM |
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Thanks Matt & Adi.
The reason for having the sump flat is:
1. The pick-up is half way along the flat portion rather than in the deep-end as it were.
2. Having spent a lot of £££ getting the pick-ups analysed and moved if the sump is lower than 75mm, the pick-ups will be imperfect, which would be
bad!
The good thing about the Gemini is that it has a seperate bonnet which makes a relatively small GRP part to modify if it needs a bonnet bulge (I
wouldn't need to cut the whole front clam apart.)
I think it makes sense to move the upright member anyway as it may mean that I can get the whole install including reverse a smidge further back.
That said, I can put the pedal box right back (I'm only 30.5" inside leg) to bring me back in the car.
Phew - happier again.
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bitsilly
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| posted on 24/10/10 at 12:08 PM |
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When I was talking to AB the other day about ground clearance, he said he was looking at making an improved shallower R1 5VY billet sump.
It may be an idea to talk to him.
Also as said, ask prop manufacturers about max angles, I am sure they prefer an angle to absolutely straight.
Last thing, would putting an MNR reverse box in the chain help? Could it give two extra UJs to mitigate things?
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mark chandler
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| posted on 24/10/10 at 04:04 PM |
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Are you making an exhaust to suit or looking to buy a pre-made one?
If the latter I would purchase and fit to the engine then see where it fits in the chassis.
For myself as the car is mostly driven only 1 up, my choice was to lump the engine over to the passenger side to balance the driver.
Regards Mark
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richard thomas
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| posted on 24/10/10 at 06:40 PM |
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Looks similar to mine Tim...should be ok.
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Gergely
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| posted on 24/10/10 at 10:40 PM |
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Hi,
We have a LHD car with the same 5VY engine, and it is pushed to the right hand side to help with weight distribution. The setup is a front propshaft
at about 20 degrees, a reverse box and a longer cush propshaft straight to the diff.
What I have experienced is that there is a lot more noise coming from the driveline when off the power than in any RHD car I have sat in. I thought it
was the reverse, so had that changed, the noise remained. I thought then, it must be the propshafts, so took them out and had them looked at. All
crosses had to be changed and the propshafts re-balanced (after about 1000 road miles). But the propshaft operated within its technical limits (the
angle we run is within the tolerance of the joints). The noise remained though...
The problem is that the car is now on its 5th reverse box, as all of the boxes went pop after driving about 100 miles on the road...
I'm pretty frustrated since we have done everything we can now, but for some reason, the drivetrain is an issue. The car is also on its second
engine, the noise the same, so not an engine issue either. I can only think now that the front propshaft angle creates vibrations and load on the
reverse box and the drivetrain that kills the box. So if I were you, Tim, I would move the engine so that the engine is dead straight with your diff.
It would also help your car's weight distribution.
But can someone more clever than me in physics confirm if an angle of about 20 degrees creates more load on the reverse box than a 0 degree angle,
supposing that the propshafts are perfectly balanced in both cases?
Gergely
Our build pictures
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TimC
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| posted on 25/10/10 at 07:34 AM |
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Gergely,
I think 20 degrees is a hell of a lot. I'm not sure I'd have even bothered posting the question if I was looking at an angle like that...
do you have any pics? I've checked your album and can't see the engine install terribly clearly.
Back to mine, I have knocked up a sketch and reckon I'm looking at about 10 degrees at present but think I might get that down to something
closer to 7degrees by carefully positioning the centre bearing.
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Gergely
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| posted on 25/10/10 at 12:14 PM |
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Hi Tim,
I will try to get a good shot and try to calculate the angle more carefully, but looking at the angle with an angle gauge held on top, it came to
about 20 degrees... so not good...
Can you not position your engine further to the left? Or is the chassis rail in the way?
Gergely
Our build pictures
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TimC
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| posted on 25/10/10 at 12:46 PM |
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quote:
Originally posted by Gergely
Can you not position your engine further to the left? Or is the chassis rail in the way?
Gergely
No, that's as far as it goes. The Gemini stays the same width as the seat-back right up to the end of the footwells and then tapers quite
suddenly to form a rectangular engine compartment.
I'm a bit happier now - I think the only sacrifice I will need to make is to have the engine shunted forward of where it otherwise would have
been. That said, I'm not too worried - some extra steering feel would be nice and I can shove myself backwards to compensate.
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Johneturbo
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| posted on 25/10/10 at 01:21 PM |
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Interesting stuff
i think it's the one thing negative about bec's the trying to get the propshaft happy
i'm just in the process of setting my engine in the right place for making the mounts
Tim, if i stick up a piccy would you do me a angle gauge please so i can get an idea of what i have.
Matt ,when you talk about phasing do you mean having the same angle up as you would have across? if that makes any sense
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TimC
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| posted on 25/10/10 at 01:28 PM |
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quote:
Originally posted by Johneturbo
Tim, if i stick up a piccy would you do me a angle gauge please so i can get an idea of what i have.
Sure thing - in the absence of better tech, Paint and I have become good friends. Just try to get the picture as square as you can - I can only put
the protractor through 90deg rotations! 
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Breaker
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| posted on 25/10/10 at 02:05 PM |
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quote:
Originally posted by Gergely
I'm pretty frustrated since we have done everything we can now, but for some reason, the drivetrain is an issue. The car is also on its second
engine, the noise the same, so not an engine issue either. I can only think now that the front propshaft angle creates vibrations and load on the
reverse box and the drivetrain that kills the box. So if I were you, Tim, I would move the engine so that the engine is dead straight with your diff.
It would also help your car's weight distribution.
But can someone more clever than me in physics confirm if an angle of about 20 degrees creates more load on the reverse box than a 0 degree angle,
supposing that the propshafts are perfectly balanced in both cases?
Gergely
I think you're almost right. The engine and diff don't have to be perfectly inline as long as the flanges (gearbox - diff - reversebox)
are parallel.
I think TimC's situation is OK as the gearbox flange is parallel to the diff. As long as you also mount the reversebox or central bearing
parallel you should be OK.
The "problem" wit UJ is when the flanges are not parallel; constant RPM at one side of the UJ, will result in (small) oscillating RPM at
the other side of the UJ, causing vibration and stress to reversebox-gearbox.
Read more here:
http://en.wikipedia.org/wiki/Universal_joint
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Johneturbo
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| posted on 25/10/10 at 03:02 PM |
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Tim, don't know if you can do anything with this pic
 
Description
So is it ok to have this angle, as long as the sprocket face and diff face are parallel
 
Description
[Edited on 25/10/10 by Johneturbo]
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TimC
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| posted on 25/10/10 at 03:21 PM |
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quote:
Originally posted by Johneturbo
Tim, don't know if you can do anything with this pic
You won't believe this: my X-ray vision and extra perception module have just both failed. Sorry, I shouldn't be so flippant.
You've not given me much to work with there. What might be best is to measure the distance from the centre of the first UJ to the centre
bearing and then measure how far laterally the centre the prop centre bearing mount is from the centre of the output shaft on the motor. This will
then give you one side of a triangle and the hypotenuse and geometry will do the rest.
Sorry that doesn't read terribly well, but its not an easy thing to explain.
What is evident is that the face of the prop adapter is not parallel to the chassis tube at the top-front of the footwell and tunnel and is therefore
not parallel to the face of the input shaft on the diff. This is a no-no as per the comments above.
[Edited on 25/10/10 by TimC]
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TimC
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| posted on 25/10/10 at 03:28 PM |
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quote:
Originally posted by Johneturbo
So is it ok to have this angle, as long as the sprocket face and diff face are parallel
[Edited on 25/10/10 by Johneturbo]
The angle looks ok. What I'm not clear on is whether its better to reduce the angle on the front half of the prop by misaligning the centre
bearing or if it is alway better to have the centre bearing parallel to both the prop adapter and the face of the diff input shaft. Anyone?
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