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Is the height of c of g relative in mass transfer?

Is this a trick question ?



In my personal opinion , yes , I'd say it was .

I'm sure a lower bike flops from side to side a whole lot easier than a high bike ...

Just my own opinion .

Having only raced bikes in the 70s and 80s when they were generally smaller than todays bikes .

Not a trick question.

The full story is that at the weekend, during one of the wsbk races Jamie witham said that one of the riders softened off the front suspension to get more weight transfered onto the front tyre. I was just trying to think through how that would work. That's all.

The front forks compressing would move the c of g a bit closer to the front, but surely the c of g would also go lower in height? Unless it is the fact the the rear suspension extends as well and maybe this kind of keeps the height of c of g the same? All this assuming that mass transfer is affected by height of c of g, which it surely must be?

Mass and weight are 2 different things. Make sure of your facts before posting.

tanneman wrote:Mass and weight are 2 different things. Make sure of your facts before posting.

Mass is a more "primary" label, would it be fair to say? So if the weight moves (or even just the effective position) how can it move without saying that the primary thing from which it is derived also moves?

At the end of the day we are dealing with accelerations and therefore forces, aren't we? So why is it wrong to say that the force involved acts upon the mass? Is that wrong? I suppose mass only gets "morphed" into weight once a force acts upon it, so maybe this is where I'm using the wrong term? My lack of education is exposed. Otherwise I'd be able to converse with more authority and less question marks!

Once we've settled this point can you help me with my puzzle? If I'm factually wrong in using the term "mass" in this context then I apologise and stand corrected.

Ps. If you are proving me wrong, then I'm grateful. It's just that you have a rather abrupt (harsh, even) way of letting me know.

Load transfer seems to be the preferred term. Makes sense. Go with that then.

Is it right to use the word or term gravity? Once we are moving (along the track/road) other forces are involved. Should I have said "centre of mass"?

Crikey, there's a lot to clear up before we even get to the point of the op.

I accept that I've used the wrong terminology in my title. I should be thinking in terms of "weight transfer" or better still "load transfer". I'm grateful that tanneman pointed this out.

So.....

Motorcycle design and technology by gaetano cocco. A great book, just let down because of the translation into English sometimes leaves you wondering. But that's my problem for being English rather than his problem for being Italian!

Anyway, page 88. Section on "how to determine attitude of the motorcycle during braking"

This tells me that I'm right, in that the c of g goes downward a lot more than it goes forwards, but it suggests that the nett movement of c of g is still downwards in spite of the rear suspension extending.

It confirms to me that the weight transfer is affected by the height of the c of g. Higher c of g leading to more forwards biased weight transfer. All fine so far.

But then the bit that confuses me and I'm going to need a racer to explain this. A softer front end definitely lowers the c of g and this definitely lessens the forwards weight (load) transfer but he says categorically :-

"with the sinking of the motorcycle, the height of the centre of gravity from the ground will also diminish, helping to create a greater braking capacity, because the tumble effect is reduced (remember that weight transfer depends on the height of the centre of gravity)."

I think what he means is that we are lessening the tendency of the bike to rotate about its front wheel. So, in spite of the fact that there is less weight on the tyre, we can still use more braking force because the bike isnt trying to flip over as badly.

It's suggesting that vehicle dynamics are the limiting factor, not tyre grip. I was making the assumption that we'd be looking to increase weight on the front tyre at all costs, but this doesn't seem the case.

Is that my answer?

(We are considering bikes with telescopic forks)