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+--- Thread: App. center of mass on Ulster Rep (/showthread.php?tid=1958)
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App. center of mass on Ulster Rep - Erich - 02-11-2018
I don't like the balance of my trailer with the car in it and would like to reconfigure it. Alas, my engine is out so I can't determine the center of mass on my SWB Ulster Rep. Can anyone get me close? I know the tail weighs next to nothing and the engine, G/B, tank and rad add a fair amount of weight at the front, so the center of mass must be much further forward of the rear axle. Can anyone give me an approximate location?
Erich in Seattle
RE: App. center of mass on Ulster Rep - AustinWood - 02-11-2018
I weighed my car using bathroom scales. I'd never owned any before and it's the first thing I did with them.
Simply jacked up the car and put the scales under a wheel with a board the same thickness at the opposite side.
did the same for all 4 wheels and added up the numbers. Tells you the front-back distribution too.
My 1929 fabric saloon came out at 10cwt including all the stuff I carry about.
RE: App. center of mass on Ulster Rep - Chris KC - 02-11-2018
(02-11-2018, 09:56 AM)AustinWood Wrote: I weighed my car using bathroom scales. I'd never owned any before and it's the first thing I did with them.I think it's the front - rear distribution Erich is after Jim; do you still have the numbers?
Simply jacked up the car and put the scales under a wheel with a board the same thickness at the opposite side.
did the same for all 4 wheels and added up the numbers. Tells you the front-back distribution too.
My 1929 fabric saloon came out at 10cwt including all the stuff I carry about.
RE: App. center of mass on Ulster Rep - Alan - 02-11-2018
Well my SWB Ulster, admittedly with no lights mudguards or other extraneous matter weighs 350lbs at the front end and 440 at the rear.
RE: App. center of mass on Ulster Rep - AustinWood - 02-11-2018
It'd very easy to weigh using this method.
I don't still have the numbers but would be very different for an Ulster rep with no engine.
RE: App. center of mass on Ulster Rep - Howard Wright - 02-11-2018
If it's any help?
I did this exercise for my long wheel base special some time ago (fuel tank at the back). The overall mass of the car with fuel and water was 417kg. 212kg at the front wheels and 205 at the rear. Making the centre of mass 1008mm from the front axle (wheelbase 2058)
For my trailer I assumed that the centre of mass was pretty much mid way between the wheels. The short wheelbase shouldn't make much difference???? but the tank may shift the centre of mass further back? For trailering I would have thought the assumption of the centre of mass being mid way between the wheels would be OK (as long as you have a bit of leeway to move the car forwards and backwards to get the nose weight correct?
Cheers
Howard
RE: App. center of mass on Ulster Rep - AllAlloyCup - 02-11-2018
I think my aluminium Gordon England Cup
Will weigh less than 400kg and am thinking
Of changing my car . I’m looking at a Panda 4x4
They can tow 900kg braked.
What does a typical small A7 trailer weigh?
I’d have thought the cg of an Ulster would have been
at the end of the gearbox at most?
Regards
Bill G
RE: App. center of mass on Ulster Rep - John Mason - 02-11-2018
This may be a stupid question but putting the car on the trailer so it is facing backwards would alter the CG and take the weight of the front as the heaviest part is engine and gearbox.
John Mason
RE: App. center of mass on Ulster Rep - Alan - 02-11-2018
You’d be surprised. The engine isn’t all that heavy. It’s counteracted by the weight of the body and the rear axle and the rear suspension. Mine’s heavier at the back end like I’ve said.
RE: App. center of mass on Ulster Rep - Erich - 02-11-2018
Thank you all for the responses. Yes, Chris, I am looking for the center of mass as opposed to front and rear weight distribution. The engine is not as heavy as one might expect. My crated engine weighs 145 pounds and includes carb, dizzy, manifolds and and dynamo. That's quite light. It is, of course, without oil. If anyone has the center of mass, or at least close, that would be very helpful. The trailer I have is a 14 foot enclosed aluminum trailer. I put motorcycle chocks at the front to catch the front tyres and a winch and deep cycle battery at the front to pull the car in. The trailer itself weighs about 1000 pounds, but its axles is only about five feet from the rear. With the car loaded, the trailer is quite front heavy.
Erich in Seattle