sgraber
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 posted on 8/12/04 at 07:51 PM |
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Whats Wrong with this Twin BEC idea? Discuss.
I belong to the Open Source Car group on Yahoo. Actually an interested observer since I actually "tried" to contribute several times, but my
ideas were dismissed. *and then I see they are building a car almost like mine... hmmm. Oh well. But I Digress. Someone posted a bunch of renders with
twin engine BEC idea. I didn't have the heart to say the the front output of the rear differential would be driven on the coast side of the
pinion and would therefore be very noisy and not last too long. But then again, might it work? You tell me. 
[img][/img]
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Cita
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| posted on 8/12/04 at 08:13 PM |
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Would it be of any help to turn the right hand side engine 90° and let it power the propshaft or flange so that only half of the power can do damage
to the crown/pinion wheels?
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kb58
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| posted on 8/12/04 at 08:38 PM |
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I'd turn both 90deg (cranks parallel to the driveshaft) and run chains to two sprockets bolted to the input flange of the diff. You could still
have the driveshaft go to the front. The only issue would be the side load on the pinion bearing.
Is 4WD really that important in a road-racing track environment? Does the added weight, complexity, and cost result in a faster lap time?
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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Aloupol
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| posted on 8/12/04 at 08:41 PM |
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If I understand the drawing each engine drives one rear wheel, there's no central diff and actually there's no rear diff eighter?
If the left engine fades, you turn left.
If they dare to show this, then they shouldn't dare to criticize you...µ
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andylancaster3000
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| posted on 8/12/04 at 08:47 PM |
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I think it would be very hard to balance the two engines to give exactly the same power in the same places on the rev range, therefore I would imagine
that under power it would steer the car. It would also get rather 'interesting' if one engine cut or seized for any reason!
This part may be a load of rubbish but I don't know whether the crown wheel and pinion in the diff are designed to drive pinion to crown wheel,
rather than crown wheel to pinion as they do in that design. This is due to the direction the helical gears are cut.
Other than that, it is nice to see people trying some innovative ideas!!!
Andy
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kb58
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| posted on 8/12/04 at 08:48 PM |
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No they're normal diffs. The idea is the engines drive the back tires *and* backdrive through the diff gears to the front of the car. Probably
assumes Quaife type LSDs.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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drmike54
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| posted on 8/12/04 at 08:48 PM |
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I agree with Aloupol. Unless there is a spool in the rearend this thing would have unequal torque right to left. What happens if one transmission
shifts and the other doesn't?
[Edited on 8/12/04 by drmike54]
Started Welding the chassis!!!!
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Sven
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| posted on 9/12/04 at 09:02 AM |
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To circumvent driving the coast side of the diff, you could extend the jackshaft from the leftmost engine and connect both engines to it and then run
a chain from the jackshaft to the crownside sprocket.
This might also ease problems (if it is a problem) with one engine giving less power that the other and causing torque steer (or whatever it's
called in this application).
I haven't a clue if sending power from the crown into the pinion and along a driveshaft won't actually destroy something.
-Steve
[Edited on 12/9/2004 by Sven]
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derf
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| posted on 9/12/04 at 02:16 PM |
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Not a bad idea, but if both engines and 1/2 shafts are connected, independantly of the rear diff, won't the rear diff act like a solid diff?
This would work as far as sending power to the front (even if using an open diff), but it would kill any type of performane that the car might have,
except for straight line acceleration.
For some reason I think that they'd be better off driving the center drive shaft, with one of those fance straigt diffs (for front to back, then
have a diff in the front for the front 2 wheeels, and same in the rear.
On another note, are they sharing their SW models?
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sgraber
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| posted on 9/12/04 at 03:02 PM |
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quote:
Originally posted by derf
On another note, are they sharing their SW models?
What part of the File are you looking to have? I can always ask...
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Volvorsport
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| posted on 9/12/04 at 04:53 PM |
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i think it would work if bothe engines were turned 90 degrees and turned the prop . the way thats engineered , both reaer wheels are driven by
seperate engines , and theyre hoping , that the diff in the middle will drive the front wheels .
i think that diff would fail early since the gears have the helical part the wrong way to the drive . Not only that , but the centre prop is gonna
turn at some hellish speed , unless of course i just spoke without thinking about gearing .
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derf
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| posted on 9/12/04 at 08:58 PM |
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Axles, engines, and chains, tried to figure out how to do chains, and I just kept replicating individual links, took a long time to keep moving the
same part, and mating the pieces to form a chain, plus my chain looked kinda childish.
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Rorty
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| posted on 10/12/04 at 06:14 AM |
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That exact set-up has been done before. With a spool in the rear diff (understeer won't be the problem with front wheels driving too). One of
the engines could be in the wrong gear or even drop a cylinder and it won't matter.
The front diff IS a front diff, and is therefore driving the correct way.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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RallyHarry
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| posted on 10/12/04 at 09:53 AM |
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... or you could go with hydraulics, I've checked it out and I really can't se the downside to it .
weight is low, cost is low, efficiency is high
www.parker.com
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Rorty
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| posted on 10/12/04 at 12:16 PM |
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quote:
Originally posted by RallyHarry
... or you could go with hydraulics, I've checked it out and I really can't se the downside to it .
weight is low, cost is low, efficiency is high
www.parker.com
Jeez, that's a nice looking wee motor! How far have you got with the remainder of the system; pump, filters, reservoir etc?
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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malcolmstoddart
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| posted on 10/12/04 at 05:50 PM |
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could think about using "Gates Megadyne".. very strong timing style belt approx 50mm wide, able to put huge amounts of power through (we put
200 hp one direction and then change direction, at work) through similar widths and haven't had any problems. my pics show two input shafts
common'ed off onto one output shaft..could make the side plates out of aluminium..surely someone will dispute this now..!!
email me for cad versions of same pics if you want..
[Edited on 10/12/04 by malcolmstoddart]
 
Rescued attachment 2-3SHAFTS.JPG
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malcolmstoddart
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| posted on 10/12/04 at 06:13 PM |
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and heres another one..
 
Rescued attachment MEGADYNE.JPG
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sgraber
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| posted on 10/12/04 at 07:52 PM |
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Whoah Malcom, there sure is a lot of white space around those drawings.... Just giving you a hard time.
The idea is sound IMHO, and I like it a lot. Both engines have their sprockets facing rearwards. Simple really. Not the most attractive method for
mounting the engines, since there is no symmetry, but the output reversal is solved nicely and one can use an off-the-shelf car differential for the
final drive. Rorty mentioned in one of his other posts (referencing chain and sprockets) about changing ratios to better suit automotive
differentials. This holds true for your drive system as well. One can use any ratio differential and achieve the desired final ratio by choosing
different size pulleys. Is it really this simple?
I have heard horror stories of belts not being able to handle the high torque loads of a clutch dump (for instance) and stripping out, but the latest
belts by Goodyear appear to be much better in this regard.
Please read the following PDF for some neat info regarding the Goodyear belts.
http://www.goodyearindustrialproducts.com/powertransmission/products/pdf/eagle_pd_belt.pdf
Does anyone know how expensive these belts and drive pulleys are? 150Hp range...
I forgot to say that adding an electric reverse to this setup would be incredibly simple too. What about an electric motor/alternator combo belt
driven off the final drive?
Now I'm going off the deep end, but with a n electric motor/generator a controller and a few batteries you could easily implement a hybrid
electric system, complete with regenerative braking, giving you reverse, the ability to boost low end torque from start AND you could cruise in a
parking lot with the BEC engines turned off... Plus with dual engines you could turn one off while cruising to conserve fuel! Now all I need is
another job to pay for this all.
[Edited on 12/10/04 by sgraber]
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Aloupol
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| posted on 10/12/04 at 08:49 PM |
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quote:
Originally posted by RallyHarry
... or you could go with hydraulics, I've checked it out and I really can't se the downside to it .
weight is low, cost is low, efficiency is high
www.parker.com
And what about the efficiency?
The mechanical efficiency of a whole gearbox is more than 90% (loss of power less than 10%) if my remembering is good, but I think it would be a far
lower figure with all that oil runing in pipes at high speed and pressure around the car..
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kb58
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| posted on 10/12/04 at 09:16 PM |
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As I posted above, this would work well for two sportbike engines, oriented north/south, feeding a standard IRS diff. The only problem I see with the
above is keeping the belts tight. Why not dispense with the housing altogether and just put those cogged wheels on the output shafts of the sportbike
tranny?
This could work really well for making a twin mid-engine sportbike-powered car, with it very easy to add a drive to the front tires...
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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RallyHarry
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| posted on 10/12/04 at 09:50 PM |
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quote:
Originally posted by Aloupol
quote:
Originally posted by RallyHarry
... or you could go with hydraulics, I've checked it out and I really can't se the downside to it .
weight is low, cost is low, efficiency is high
www.parker.com
And what about the efficiency?
The mechanical efficiency of a whole gearbox is more than 90% (loss of power less than 10%) if my remembering is good, but I think it would be a far
lower figure with all that oil runing in pipes at high speed and pressure around the car..
Efficiency is over 90%, starts at 98% at slower RPM (1K RPM) and decreases to 92-91% at > 6000RPM
That's OK in my world ...
Cheers
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RallyHarry
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| posted on 10/12/04 at 09:57 PM |
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quote:
Originally posted by Rorty
quote:
Originally posted by RallyHarry
... or you could go with hydraulics, I've checked it out and I really can't se the downside to it .
weight is low, cost is low, efficiency is high
www.parker.com
Jeez, that's a nice looking wee motor! How far have you got with the remainder of the system; pump, filters, reservoir etc?
Not very far, work seems to take to much time from my interest :-)
Also I was kind of hoping you could give me some hints since you have been down this alley before ...
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Rorty
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| posted on 10/12/04 at 11:44 PM |
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quote:
Originally posted by RallyHarry
Not very far, work seems to take to much time from my interest
Also I was kind of hoping you could give me some hints since you have been down this alley before ...
I have indeed, but as I mentioned in the other thread, it was a few years ago, and there was nothing (affordable) like that little Parker motor
around. I am still convinced hydraulics would make the most flexible and efficient 4WD system if the whole thing could be contained and restrained to
a practical weight limit. There are all sorts of hydraulic/viscous drives these days that don't seem to require large filtring or oil storage
facilities, but I'm not a hydraulic engineer, nor do I currently have my finger on the associated pulse anymore.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Aloupol
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| posted on 11/12/04 at 01:41 AM |
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quote:
Originally posted by RallyHarry
Efficiency is over 90%, starts at 98% at slower RPM (1K RPM) and decreases to 92-91% at > 6000RPM
Looks good.. Do you have info about the layout that gets this numbers?
I guess it's the whole system efficiency, so taking into acount the pipe diameter and lenght, and the efficiency of the pump and motors..
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kb58
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| posted on 11/12/04 at 05:04 AM |
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98% is pretty good... but 90%... I don't know. If you have 200hp going through it, that leaves 10% as heat, or 20hp. 20hp * 750watts/hp =
15,000Watts of heat. That's a lot to get rid of.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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