phelpsa
|
| posted on 27/8/08 at 07:19 PM |
|
|
Engine Positioning
After a couple of years off doing other projects, I've finally come back to my Locost. I've started by re-positioning the engine and
re-doing the engine mounting system as I wasn't happy with it, but I need some other opinions before I go ahead and crack out the welder.
Here's the main problem when it comes to positioning:
I know that ideally I want the two prop faces parallel but that isn't going to work. Its only a few degrees out and i'm not overly
bothered about UJ wear, its not going to be doing any huge distances or speeds.
Any other thoughts?
Adam
|
|
|
|
|
Mark G
|
| posted on 27/8/08 at 07:24 PM |
|
|
The UJ actually runs better at a slight angle, they don't like being in a straight line.
You my be lucky if you take off your oil filter and take it to your local parts store they may be able to find one that would fit which is smaller.
also, you may have some trouble welding that wood as it tends to be difficult to work with...
|
|
|
phelpsa
|
| posted on 27/8/08 at 07:28 PM |
|
|
quote:
Originally posted by Mark G
The UJ actually runs better at a slight angle, they don't like being in a straight line.
You my be lucky if you take off your oil filter and take it to your local parts store they may be able to find one that would fit which is smaller.
also, you may have some trouble welding that wood as it tends to be difficult to work with...
The filter isn't actually the problem, it sits above the rails, its the connections for the oil cooler that cause the problem. I think that as
long as I keep it in that position it should be fine 
I have a magic welder that welds wood. Dead handy around the house.
|
|
|
matt_claydon
|
| posted on 27/8/08 at 07:36 PM |
|
|
UJs do like a slight angle, but the gearbox and diff flanges must be absolutely parallel to cancel out the cyclic speed changes you get from an angled
UJ. i.e the angles of the joints at each end must be equal and opposite.
|
|
|
phelpsa
|
| posted on 27/8/08 at 07:38 PM |
|
|
quote:
Originally posted by matt_claydon
UJs do like a slight angle, but the gearbox and diff flanges must be absolutely parallel to cancel out the cyclic speed changes you get from an angled
UJ. i.e the angles of the joints at each end must be equal and opposite.
How quickly is not having them parallel likely to wear the UJs?
|
|
|
matt_claydon
|
| posted on 27/8/08 at 07:47 PM |
|
|
It's not really the UJs that are the problem, it's the vibration through the whole drivetrain due to the vehicle/engine speed fluctuating
with each revolution of the propshaft.
I expect a very slight misalignment is allowable, although I couldn't say what a safe limit would be, but really you want to aim for the
flange to face straight backwards.
There's a video here that kind of explains the issue. It's an interesting watch for an engineer anyway but spin on to 3:15 if you
don't want to see the rest. http://uk.youtube.com/watch?v=xgQgm3GwaFs
|
|
|
phelpsa
|
| posted on 27/8/08 at 07:54 PM |
|
|
I can see the problem.
Hmmm.
Do you have to use UJs in the propshaft? Would it be possible to say use CV joints in the front section and UJs in the rear section?
[Edited on 27-8-08 by phelpsa]
|
|
|
meany
|
| posted on 27/8/08 at 08:01 PM |
|
|
interesting video, made me a little paranoid now.....lol.
i.ll have to go and check mine out.
|
|
|
clairetoo
|
| posted on 27/8/08 at 08:06 PM |
|
|
quote:
Originally posted by matt_claydon
There's a video here that kind of explains the issue. It's an interesting watch for an engineer anyway but spin on to 3:15 if you
don't want to see the rest. http://uk.youtube.com/watch?v=xgQgm3GwaFs
That is a very interesting vidio - where can I get some of those `thomson couplings` for my propshaft 
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
phelpsa
|
| posted on 27/8/08 at 08:10 PM |
|
|
http://www.dp-graphics.nl/seven/engine-4.jpg
I've seen many installations where the prop faces aren't parallel, like the photo /\. Has anyone actually had any trouble?
|
|
|
matt_claydon
|
| posted on 27/8/08 at 08:48 PM |
|
|
It's also OK if the angles on the joints are equal and in the same direction. In bike engine layouts it's possible to have the front half of
the prop with equal angles and the rear half equal/opposite. In this diagram:
 
Prop angles
The top two cases are OK and will give constant velocity, the bottom is bad. If the front half of the prop is like the middle diagram and the rear
half like the top (or straight) then you should be OK.
|
|
|
phelpsa
|
| posted on 27/8/08 at 08:55 PM |
|
|
quote:
Originally posted by matt_claydon
It's also OK if the angles on the joints are equal and in the same direction. In bike engine layouts it's possible to have the front half of
the prop with equal angles and the rear half equal/opposite. In this diagram:
Prop angles
The top two cases are OK and will give constant velocity, the bottom is bad. If the front half of the prop is like the middle diagram and the rear
half like the top (or straight) then you should be OK.
Ahaaaa that's great. I should be able to manage as close to that as makes no difference.
|
|
|
blakep82
|
| posted on 27/8/08 at 09:25 PM |
|
|
quote:
Originally posted by phelpsa
Has anyone actually had any trouble?
i think just about every lorry has a prop shaft angled down from gearbox to axle. especially them 13ton rigid body ones. or the 7.5 ton rigid body
ones. they take more force and torque than any of our cars ever will
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
|
|
|
Liam
|
| posted on 27/8/08 at 10:32 PM |
|
|
quote:
Originally posted by blakep82
i think just about every lorry has a prop shaft angled down from gearbox to axle.
Yeah but still with parallel flanges  . Seriously though i've been in cars where it's been impossible to phase uj's to totally
cancel out non-uniform velocity (dax rush quadra to name one) and haven't noticed any undue vibration. It'll all come out in the soft
floppy tyres.
Liam
|
|
|
blakep82
|
| posted on 27/8/08 at 10:34 PM |
|
|
^ yeah, parallel, but at different heights
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
|
|
|
Liam
|
| posted on 27/8/08 at 11:30 PM |
|
|
quote:
Originally posted by blakep82
^ yeah, parallel, but at different heights
Which is ideal for a prop shaft - non uniform velocity can be cancelled out and the uj's are running with some angle on them to keep the
bearings moving. So not an example of a theoretically bad setup actually giving no problems in practice.
Liam
|
|
|
blakep82
|
| posted on 28/8/08 at 07:18 AM |
|
|
ahhh, cunning 
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
|
|
|
motorcycle_mayhem
|
| posted on 28/8/08 at 01:45 PM |
|
|
Perhaps I'm missing the point here, but why not simply move the offending chassis rail...
|
|
|
phelpsa
|
| posted on 28/8/08 at 05:06 PM |
|
|
quote:
Originally posted by motorcycle_mayhem
Perhaps I'm missing the point here, but why not simply move the offending chassis rail...
Because I don't need to if I can keep it in that position. It only becomes a problem if I need to straighten it out.
|
|
|
