I've seen a few cars that have removed part of tube Q ( I think ) to allow the engine to be fitted further back in the chassis but resulting in the loss of legroom for the passenger. Stuff the passenger I hear you say and I would agree but, is there any proven advantage in doing this ( the tube not the passenger)or is it done because it looks like it should be better.
Cheers Col.

I wouldnt bother if I were you, a BEC Locost is generally rear biased weight wise anyway (mine was around 55% rear when weighed recently), so putting the engine further back is not going to help handling, and may hinder it. The only reason to put it back would be so it goes under the bonnet easier and makes the prop a bit shorter, but not worth the hassle IMHO

Chris

the main reason i moved mine back was to get the engine further over to the left and get a better "prop angle" infact, my prop is allmost straight,

Makes sense Jon, never thought of that as a plus for bringing it back further.

Macca, just in case you hadnt read about it before, prop angle is something to take some time over when installing the engine, try and get it as straight as possible in both planes, tho having said that, mine isnt, its a fair bit over towards the driver and i've never had any prop vibration problems at all. I think there's a fair degree of hit and miss TBH, some people that have spent ages getting it seemingly perfectly aligned and yet get vibration, and others that threw it in without a thought to the angles and have none

Chris

Chris, thanks for the info.The prop angle that you are talking about is this in relation to the first section of the prop, as I'm led to believe that I will need a two piece due to the length, or are we talking about from engine to diff as if the prop was a "one" piece unit?Hope that makes sense.
Cheers Col.

Hi Col
Basically the entire length of the two piece prop needs to be as straight as possible, so that there isnt too much angle on the centre bearing in either the vertical or horizontal plane.
You will need a 2 piece prop definitely, somebody worked it out on the Yahoo BEC list, and to make a single piece one strong enough it would need to be about 7" diameter!
Not sure if this is any help or not, looks a bit complicated to me, but may help
http://uk.groups.yahoo.com/group/bike-engined-cars/files/prop%20angles.xls

Chris

Strange - I was always told that a propshaft should always have a slight angle, with the axis of the gearbox and diff parallel.

I've seen several web pages written by professional propshaft builders, explaining how this arrangement saves wear on the UJs, and reduces vibration.

...or is this a BEC speciality?

David

David

I think you might be right in fact, there's lots of technical stuff involved in prop phasing which I don't really understand (lots been said on yahoo list in the past). I think if you run it totally straight then yes I think it will eventually knacker the roller bearings as they will sit in the same place all the time and not rotate. The fundamental bit to get right is the relative angle of the flanges. This is because prop UJs do not transmit the rotational speed in a linear fashion, in that at one angle the prop is turning slightly faster than it is at certain other angles, setting up a type of oscillation I suppose. If you get the other UJ to run totally out of phase with the front one, then all this will cancel out and you wont have any vibration in theory. I'll ask a mate with a Megablade who's far more up on this to maybe post something if he gets time.

cheers
Chris

Here is some stuff he sent me to mull over in your coffee break

http://www.baileymorris.co.uk/technical_info.htm

Have a look at the last two topics there.

Chris