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MG Midget and Sprite Technical - Centre of Gravity?

Evening all

Anyone know where the CoG is on a spridget?

I can work it out, but I'll need to buy some scales etc so wondered if anyone knew where it was, or how high off the ground it is?

thanks :)

Rob Armstrong

Rob,
as you've not got a standard Spridget yours will be slightly different, are you also thinking fully loaded with petrol and driver

(spare starter, rotor arm, etc. in boot too :) )
Nigel Atkins

I did the calculation along time ago...but you have to remember its going to be differant for every car unless your bone factory stock

On mine it was (x, y axis) around the door handle and about top of the sill high....

But with all the mods ive done, im sure my CG has completly new home

Prop
Prop and the Blackhole Midget

When I did my electric conversion I had access to 4 scales. Below is what I measured on my Stock '74 (1275) car. Hope this helps. This is posted on my site under basic car statistics. www.electricmgmidget.com

Frank

Weight:

I was able to obtain the use of 4 scales, one for each wheel when I started this project. This allowed me to weigh my stock 1974 gas midget, and my 1977 electric midget as I built it. Below are the weights (units are in lbs)



’74 Gas midget

LF 427, RF 436, LR 414, RR 403 Total = 1680, weight distribution 51.37% (slightly front heavy)



’77 electric midget with the Warp 9 Impulse motor installed

LF 413, RF 370, LR 344, RR 376 Total = 1497



’77 electric midget, 20 batteries in the trunk, 18 batteries in the engine compartment, ready to run

LF 488 RF 489, LR 550, RR 533 Total = 2060, weight distribution 47.4% (Slightly rear heavy)
FWB Frank Bernett

Hey frank....

You dont happen to recall how high you raised the rear end do you

I read some time back that on short wheel base cars it couldnt be more the 20 some inches

I remember raising my rear end with the engine lift hooked to the rear bumper... but I jacked mine way up there ...probably well above 30 inches im sure

But I didnt lock out the front shocks ither as I learned that needed to be done just a few months ago

That said I also learned at the same time you can do a simplier less accurate method using a truck scale and just measure the front and rear from a pre defind mark inside the wheel base and uses the center line of the camshaft as the hieth CG



Ill have to look up the website its not on my phone...so it will be a few hours before I can get back with you.
Prop and the Blackhole Midget

Thanks frank, that's helpful :)


I've come across that link as well prop, which is the reason for asking the question, as locking out the shocks is annoying...
Rob Armstrong

Prop,
I'm not sure what you mean by raising the rear end. The scales I had were designed to measure race cars. I had to shim them to get them level, then place the car on them. The scales themselves were only 2 inches high. Is that what you meant?

Frank
FWB Frank Bernett

prop - frank's done the wheel weights without the extra step for CoG height calculation.

frank - prop's talking about a method of finding the CoG height by jacking the rear up a bit then re weighing the front to find the change in weight and therefore the height of CoG.

do you reckon it'll work with normal bathroom scales? Might be a bit heavy.
Rob Armstrong

Ok I got it. No I was lucky to have a friend who races, and this measurement was done using his 4 electronic scales simultaneously measuring. He insisted that I make sure the scales were level because that can change the measurements. I leveled them using a laser level he gave me with the scales. Obviously I was lucky to know someone like that. I never realized that midgets where that close to 50/50 distribution. My '74 was probably a little light in the front because I didn't have the smog pump on at the time. Maybe I shouldn't have described my car as stock. It had a header and Weber 45 DCOE carbs, and I had the smog pump off. The interior and body were stock.
FWB Frank Bernett

I've just known that as corner weights for setting up suspension
Nigel Atkins

Thanks rob,

Because I sure cant remember the details of what i did,.. it was a case of unexpected opportunity came a knocking on a sunday afternoon... and I took advantage of the moment at hand....otherwise I probably never would have done it

Prop
Prop and the Blackhole Midget

I got to agree... bath scales to light

The guy that helped me was someone I was painting for that was a farmer, rancher, fabricator, machinist and built dirt track racers ...just a great guy all around.

Prop
Prop and the Blackhole Midget

This thread was discussed between 08/02/2014 and 10/02/2014

MG Midget and Sprite Technical index

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