Mid engine Karmann Ghia

[vwbloodline]

Of course if I won the lottery I would just buy one of these and put a ghia body on it. http://www.sterlingsportscars.com/in...id-engine.html

[evilC]

Originally Posted by volkdent

Don't mean to hijack, but this is a related question for EvilC.

Given the mid-engine layout that VWBloodline is proposing, where do you think the battery should end up?

And then, given my engine location 900lbs front/1300lbs rear with me in it (260lbs ) where do you think would be the best place for mine? My engine layout is identical to a Lotus Elise and the battery is currently where the windscreen washer bottle would be behind the spare, and I've recently moved it to the floor of the spare tire well as an optional location.

If VWBloodlines proposal works out, his weight should be distributed more forward of what I have and I think that may get it close to 50/50.

Jason

Hi Jason,

The ideal layout is to contain all the mass or a good proportion of it within the wheelbase of the vehicle and as close to the centre of gravity as possible. Also, a 50/50 weight distribution is desireable so as to equally load the tyres for maximum benefit. The geometry of all the mass locations is governed to a large extent by the physical limitations of the bodywork but I personally look to locate all the masses close to the centre of gravity in preferance to equalising the weight distribution. Keeping the mass close to the CofG means the vehicle reacts quicker to external forces eg. driver but makes the car less stable. In a bug the standard battery location is nearly ideal being about the line of CofG and therefore its moment of inertia is small (Mass x radius of gyration around the CofG). Moving the battery forward to say infront of the scuttle means that although the mass is relatively small say 15-20lbs the radius of gyration is 6ft(?) then the moment is 90-120lbft whereas previously it was in the region of 30-40lbft.
If you move the battery to the front wheel well all of the mass is on the front axle but the moment of inertia has significantly increased. With the battery placed just behind the axle line most of the mass is still on the front axle but the moment of inertia is somewhat reduced (typically 30-40%)
Just to add even more variables into the thinking - rally cars benefit from having the majority of the mass over the front wheels so that the rear end can swing with least resistance to aid turn in where the surface or the bend shape is uncertain. In fact a rally car set up is probably more appropriate to our increasingly uneven (UK)roads than a track set up that is favoured by the supercar builders.

Originally Posted by vwbloodline

Of course if I won the lottery I would just buy one of these and put a ghia body on it. http://www.sterlingsportscars.com/in...id-engine.html

This sports car looks remarkably like the Novas being produced in the UK in the late '70s and early '80s that were fixed to standard bug chassis' The tube chassis looks particularly unsophisticated and I would question it torsional rigidity that would affect its handling. I would at least bond sheet metal to the frame structure if not redesign it a bit. the spine looks particularly weak.

evilC

[volkdent]

Makes sense, I'll probably move the battery to under the passenger seat then, as it will both tend to equalize my significant mass and help the weight distribution forward at the same time.

Jason