Club 80-90 Forums

I weighed a Mefro with an MT on it ages ago and I think it was 37 kgs which was about 12 kgs heavier than the Ronals and Contis I run.

That sounds a bit heavy to me, I have just weighed a Vito 15" fitted with a part-worn Grabber AT2 at 23.5kg

If possible we need to start with a Syncro 14" plonker and work up from there.
anyone?
I doubt if the Syncro 16" wheels & tyres were partic. heavy

axeman wrote:When we get home, I will weigh a 14" wheel and tyre and comparr it to a metro and 215 75 15 BFF m/t .

Neil

And the answer from the Belmont correspondent's bathroom scales is...?

just been out to the garage forgot that the mefro is bolted to the back of the van and i cant be arsed to take it off and weigh it.
but on the bath room scales

14inch X 5.5inch wheel and tyre (inflated) weighed it 21kg
14inch X6.0inch wheel no tyre, valve or weights, was 11.4kg

i will weigh the mefro with a BFG M/T tomorrow

neil

axeman wrote:but on the bath room scalesl

Are these calibrated, or the 'one at a time please' type from the funfair?

sally is convinced that they are no very accurate but i am not so sure.

neil

silverbullet wrote:That sounds a bit heavy to me, I have just weighed a Vito 15" fitted with a part-worn Grabber AT2 at 23.5kg

It was a long time ago .....

Mefro 15" and BFG MT KM2 26.5KG on my workshop bathroom scales, doesn't include nuts or centre cap

Pepperpot 14" Alloy with 205R14C Marshall road tyre 20.5kg with centre cap

That's a straight +30% for starters... we'd need the suspension's contribution to unsprung mass to get a true comparison, I suspect we could estimate it at approx 1/2 ~ 2/3 of that difference though, so 15 ~ 20%.

Now, apart from that, who's going to workout the radius of gyration so we can compare the effect on acceleration

Sounds like we're getting into angular momentum and K.E. calculations there Clive...it's been a while

All strengthening the debate for adjustable dampers due to wildly varying wheel and Tyre choice. No one damper could cover all these.

I have some 15" BFG AT on Ronal R8 plus a loose tyre, I'll weigh each to give an idea of where the mass is concentrated. I bet the tyre is responsible for most of the increase, not the wheel.

Ian

The best way I can envisage is this:

Pivot the whole wheel & tyre as high as possible on a horizontal shaft on good low friction bearings or trunnion blocks...

Wrap a string or rope around the tyre a few turns attaching a known weight to the free end, say a few kgs.

Let the weight drop to the floor from its resting position just below the edge of the tyre by letting go of the wheel so it rotates.

With a stopwatch time the fall to the floor.


Need to know:

Weight (mass) of wheel/tyre combination;
Radius to outer edge of tyre (rope lever arm).;
Distance of fall of weight;
Time of fall from letting go of wheel.

The latter will be the largest margin of error so keep at it until a consistent average can be established (the fun bit if of an experimental mindset)

I think I can then calculate the Radius of Gyration and as you say, the MoI from that, just two ways of expressing the same thing.

Not feasible to calculate MoI from geometry without sectioning each wheel & tyre, and knowing their density so accelerating the wheel is best.

PS. The shaft & wheel clamp flange will be almost insignificant, but could be accounted for...