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+--- Thread: App. center of mass on Ulster Rep (/showthread.php?tid=1958)
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RE: App. center of mass on Ulster Rep - AustinWood - 02-11-2018
I don't know how you'd measure the centre of mass in three dimensions. Finding the height of the centre of mass isn't obvious. It'll vary between body styles. Quite low for an Ulster rep with no engine.
For towing I would have thought position of the centre of mass fore and aft would be the important dimension. That is given by the ratio of the weights on front and rear axles.
RE: App. center of mass on Ulster Rep - Reckless Rat - 02-11-2018
Better front heavy than the other way round, Erich. You could measure it with a set of bathroom scales and a block of wood between them and the tow hitch. Most tow balls in the UK advise no more than 100kg nose weight, some less than that. I don't know if US specs are any different. A twin axle trailer is generally more stable than a single axle one, but even so it can get out of shape if the weight distribution is wrong. Be guided by the recommended nose weight for your particular tow hitch and the trailer manufacturer's guidelines.
RE: App. center of mass on Ulster Rep - Colin Morgan - 02-11-2018
From the weight measurements given above for Alan's SWB car, 350lb front, 440lb rear, the C of G for his car is 42" back from the centre of the front wheels. (Wheel centres are 6'3" apart = 75".)
Colin
RE: App. center of mass on Ulster Rep - Viteran - 02-11-2018
I would agree with Reckless Rat, nose heavy is best, I used to tow a caravan extensively and preferred to be on about the manufactures limit or possibly slightly over it ( the limit is conservative and usually allows for two adults in the back seat as well) but now only have a car trailer and l light trailer.
Everyone needs a car with a tow bar!
RE: App. center of mass on Ulster Rep - Erich - 02-11-2018
That's very helpful Colin. Thank you. Yes, tongue weight in the trailer is crucial. Too light and it wanders all over the road. Too heavy and it forces the tail of the tow vehicle down. The latter is what I have. The trailer is a v nose 14 foot and the axles was mounted by the builder for a longer, heavier load. So that, even with the winch and battery and no car, the tongue weight is 200 pounds. Add the car and the tongue weight went up to 500 pounds. So I had to add a type of hitch that offsets that weight and it is a PITA. I could move the car backwards, but all the mounts are in, and it would move the rather delicate tail, much closer to the rear door. So, my idea is to center the trailer axle under the center of mass of the car, and it will trailer easily both empty and loaded.
Erich in Seattle
RE: App. center of mass on Ulster Rep - Howard Wright - 02-11-2018
(02-11-2018, 12:55 PM)AllAlloyCup Wrote: 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
Hi Bill
I've towed with the "twinair" Panda which is quoted as 800kg. Unfortunately my braked trailer (built for a Smart car) is nearly 300kg and my special about 450kg (see post above). This was getting close to the 800kg and with a couple of passengers it really felt it on the hills. I now have an Audi A1 1.2 TFSI with a tow capacity of 1200kg. It sails up hills!
Cheers
Howard