aerosam
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| posted on 26/5/08 at 06:07 PM |
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Do you really need power steering?
I've been stripping some of the last few things off my donor and I've found that the power steering pump is also the hydraulic assistance
on the brakes.
I wasn't planning on using the power steering box as it sits behind the engine but I want to keep the big brakes on the beemer so I may be stuck
with it.
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JoelP
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| posted on 26/5/08 at 06:12 PM |
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id say you dont want power assist on a kitcar, but then id also say ditch the servo for the brakes. Assuming you're building a heavy and
powerful car, you could well want to keep both.
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theconrodkid
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| posted on 26/5/08 at 06:12 PM |
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you could just join the in and out unions on the pump to let the fluid circulate ,on the beemers i have worked on the brakes use an electric motor to
pressurize an accumulator (green sphere) to provide assistance
who cares who wins
pass the pork pies
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Danozeman
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| posted on 26/5/08 at 06:19 PM |
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Id junk it and put a different vac pump on it if u need one. Ps is only good for parking.
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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smart51
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| posted on 26/5/08 at 06:26 PM |
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There's no real need for power steering on a seven, unless your car will be very heavy. Nor servoed brakes.
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Guinness
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| posted on 26/5/08 at 06:30 PM |
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I could be wrong but I think Aerosam is using a BMW 5 series as a donor, complete with the V8.
Having had a 540i as a daily driver, I'd say keep the power steering! Assuming you won't be using little 13" wheels on it.
When you are finished you can try it without it, but to retro fit it may be a right pita.
Mike
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mr henderson
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| posted on 26/5/08 at 06:38 PM |
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Good quality power sterring is very pleasant, and I don't think it would be detrimental to a kit car, especially one with a large engine close
to the front wheels
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JoaoCaldeira
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| posted on 26/5/08 at 06:44 PM |
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In my BEC the steering (non powered) is perfectly usable. no need for any more assistance.
Can't comment on a CEC, though.
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Chippy
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| posted on 26/5/08 at 10:09 PM |
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I considered fitting the power stearing on my car, but as it wouldnt fit didn't bother. Would be nice at low speed 10 to 15 mph or less, but
above that not needed. One thing I would say DON'T fit a quick rack, it makes the stearing far too heavy. Cheers Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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aerosam
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| posted on 27/5/08 at 07:06 AM |
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Guniess is quite right, I'm using a BMW 530 V8 as my donor.
I'm hoping to keep the ABS, so I really want to use the brakes as a complete system. It does have an electric motor and an accumulator, but the
hydraulic assist is also plumbed into the power steering circuit. (perhaps this is just to run it through the oil cooler?) TBH I'm not very
familiar with the system.
I'm trying to use as much of the donor as possible, but the steering is just completely unsuitable. I think conrodkid might be on to something
with just plumbing the hydraulics through the brakes alone. Will take some serious thinking to work out how to do it though.
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RazMan
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| posted on 27/5/08 at 07:13 AM |
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I would have thought the Beemer rack is quite difficult to design into a Locost and the stock brakes will probably be ott with the servo on such a
relatively light car. Also you might find the steering will be too twitchy at speed, although a big V8 over the wheels might require some good biceps
when parking
[Edited on 27-5-08 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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mr henderson
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| posted on 27/5/08 at 07:44 AM |
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quote:
Originally posted by RazMan
Also you might find the steering will be too twitchy at speed,
[Edited on 27-5-08 by RazMan]
I think you might be hearing from the BMW lawyers soon!
Car makers design their power steering systems to avoid this problem, and BMW's will be one of the best out there.
John
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RazMan
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| posted on 27/5/08 at 08:54 AM |
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Yeah but ... no but ... yeah but on a car under half the design weight it will behave rather differrently 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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NS Dev
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| posted on 28/5/08 at 04:35 PM |
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A couple of things.
(I have a 740i which uses the same setup as far as I know)
1) the hydraulic system (filled with that bloody pentosin expensive fluid) provides the power steering assist AND the brake assist BUT it acts like a
servo on the brakes - there is a conventional abs brake system, then there is a hydraulic assist cylinder on the master cylinder, which is fed from
the main hydraulics.
The ecu that controls everything also monitors the pressures in this system.
2) Surely the bmw uses the same power steering BOX as mine (recirculating ball ZF system), not a rack at all............which will be fun fitting to a
locost!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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NS Dev
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| posted on 28/5/08 at 04:37 PM |
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ok, see you mention not using the steering box, and I agree, whatever you do don't!! it weighs nearly as much as a bike engine on its own!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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iank
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| posted on 28/5/08 at 05:12 PM |
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quote:
Originally posted by RazMan
Yeah but ... no but ... yeah but on a car under half the design weight it will behave rather differrently
Same with the ABS, I suspect they put a lot of work into tuning it to work properly on a BMW, doubt it will work nearly as well on a car half the
weight.
I've done some robotic control systems in the past and if you change the weight/weight distribution on a robot or pan/tilt head all the PID
loops (i.e. control algorithms) need to be re-tuned else you get horrible oscillations or really sluggish behaviour.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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mr henderson
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| posted on 28/5/08 at 05:20 PM |
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quote:
Originally posted by RazMan
Yeah but ... no but ... yeah but on a car under half the design weight it will behave rather differrently
But not to the point of becoming twitchy. In any case, all decent systems provide very little assistance near the straight-ahead position.
If it was my project I would definitely use the power steering. I think the chances of it being a problem are very low (not zero) but very low, and
certainly well worth the try.
John
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aerosam
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| posted on 28/5/08 at 05:47 PM |
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Chris Gibbs brother Mick has successfully transplanted the BMW ABS (from a 525) into his mega-wide roadster, I'll have to get in touch and see
how it performs.
Just a thought, would it bepossible to use the power steering rack from another car (probably E30 or E36 BMW) and plumb it into the PAS system I have,
or would that just completely not work?
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MikeRJ
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| posted on 29/5/08 at 07:39 AM |
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quote:
Originally posted by mr henderson
If it was my project I would definitely use the power steering. I think the chances of it being a problem are very low (not zero) but very low, and
certainly well worth the try.
John
If it was mine I wouldn't entertain the thought of using the original BMW PAS, and I don[t think you would either if you saw it! Something based
on a Corsa/Fiat/Rover power column would be a possible compromise.
ABS systems not only sense speed differential between wheels they also look at the rate of change of speed of the wheels, and activate if above a
certain threshold. I would hope a Locost with decent tyres could stop somewhat more quickly than nearly 2 tonnes of BMW, so the ABS may well cause
problems by activating too quickly.
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