spring rating

Posts : 69 Join date : 2018-06-16

my moped motor (lavalette aml 50/2 ) has clutch weights that have 2 tiny springs and the manual says they are rated at 700grams and the other is 3kg.what does this exactly mean so I can check it and find suitable replacements as mine are missing.

I would have thought you needed grams per centimeter or metre or summat
but the manual clearly says just 700 grams. its dated 1960

Admin Posts : 472 Join date : 2017-10-17 Age : 116

Hi arfur

The rating expressed as a weight, is indeed the weight that is required to extend the said spring by a set length, I presume under the influence of gravity.

In Imperial, it's the weight required to extend the spring by an inch but I'm struggling to see the sense in it being just a Millimeter in Metric.. Surely a Centimeter would have been more sensible?

This is slightly different, expressed as a force.

https://www.thespringstore.com/spring-rate-calculator.html

Posts : 69 Join date : 2018-06-16

yeah ive looked at all the online spring calculators
here's the manual bumf look at section marked IMPORTANT

Posts : 69 Join date : 2018-06-16

I BOUGHT A CHEAPO SPRING SELECTION BOX OFF EBAY BUT NOT KNOWING ANYTHING ABOUT SPRINGS I DIDNT REALISE THAT ITS MAINLY DOWN TO WIRE THICKNESS oops caps lock on

all the springs were 0.5mm wire and the larger diameter springs are slacker than smaller diameter springs with the same wire. opposite of what you'd think
ive bout some springs off ebay at 0.4mm and 0.2mm wire and will see if I can just blag it as opposed to fitting the exact 700grs and 3kgs springs
that's even if I knew what that meant
is grs the same as grams?

Admin Posts : 472 Join date : 2017-10-17 Age : 116

I'd done the Google thing too, but your article there looks like it might have suffered a bit in translation from whatever language it started in..

It's not clear at all.. Yeh, I'd go for the closest you can if you can't get an exact item.

I think I get the the drift too.. the 700g spring starts the clutch to bite for setting off then the 3Kg spring locks it solid at higher revs.

Posts : 69 Join date : 2018-06-16

it hasn't been translated its written in pretty good English by some eloquent old french fooker.

ive just got to post the intro, took me back to quainter less complicated times...

Admin Posts : 390 Join date : 2017-10-17 Age : 61

The two springs have a rating differential of 4.28... i.e. one of them is 4.28 times stronger than the other. So i guess if you can find two springs of similar differential they will do the job...the actual strength probably doesn’t matter as long as the difference berween them is correct.. if that makes sense? Shocked

Admin Posts : 472 Join date : 2017-10-17 Age : 116

I see it differently Rob, since they will be holding the weights against the centrifugal force flinging them outwards, I'd have thought closest to those figures would be the way to go..

Maybe I'm missing something?

Posts : 69 Join date : 2018-06-16

the springs have got to be summat like
the 700 grams spring is apparently really weak and can easily be deforemed just by stretching with your fingers
the stronger the starting (weaker) spring the faster you have to go to build up enough centrifugal force to overcome the spring and mate or lock up with the clutch surface - a bit like a drum brake.

too stong a spring and you would have to push the moped at 70mph to get it started

too weak and it would come on at slow walking pace. which is not really a problem
ive tried springs made out of 0.5mm wire and they are too stiff for the 700grs so ive ordered some at 0.4mm and some at 0.2mm wire.
if I knew what the 700grs meant I could save time by testing and modifying before fitting
but its a 1 minute job to remove the clutch to fit the springs. it really is a simple motor.