A+ Gearset with an 18 Tooth First Motion Shaft

[ianh1968]

Is there any evidence that the following gearset exists?
It is alleged to be for "Some MPI" cars...

Code: Select all

First Motion Shaft 18
Laygear   30,26,21,15
1st 15/31 = 3.444
2nd 21/26 = 2.063
3rd 26/21 = 1.346

Apart from the First Motion Shaft, all tooth counts match the
"single groove" DAM4931 laygear set, as per the standard A+ box.

This is not to be confused with the 18/29 "SGT" set with the
large bearings and a pre-A+ tooth style.

Ian

[rich@minispares.com]

ive never seen one

just the two a plus types dam4930 - 17 tooth, or dam6242 - 16 tooth

I wonder if someone has got confused and got mixed up with the French drop gears when they have been working the ratios out as they would alter the count (cant be bothered to actually see if this happens though!)

[ianh1968]

Thanks, Rich...

I mangaged to find out where I got that little gem from:
http://www.minifinity.co.uk/forum/viewt ... =5&t=16082

The last couple of posts are the set that I detailed above.
The implication is that this set was a standard set geared up
by a fixed amount and this turns out to be true.

If you take the standard single groove A+ gearset and swap
the 17 tooth First Motion Shaft for an imaginary 18 tooth one,
you get the ratios in that post.

This info is said to come from "Calver", who I assume is Keith...
He used to work in a shop that I've bought quite a lot of stuff from!

I have removed the "4MPI" set from the "Ratios" spreadsheet due to
lack of credible evidence.

The link quoted is also quite interesting...
http://www.dummett.net/ime/website/ime/ ... drive.html
The speeds in the chart seem a bit high, though...

The author is quoting :-
165x70x10 with 3.444 at 60mph as 3637rpm = 16.5mph per 1000rpm
This uses a "Wheel Revs Per Mile" figure of 1056.

For Yokohama 165x70x10 the official WRPM figure is 1080, giving 16.1mph
Source: I emailed them and this was their reply.

The figure is the "Rolling Circumference"...

Some people "calculate" a WRPM figure based on the tyre dimensions
and the aspect ratio, i.e. using a mathematically worked out circumference.
What this does not take into consideration is the "flat" at the bottom of the
tyre where it sits on the ground. Using this method yields higher road
speeds which sound much better used as "pub-talk"...

Don't believe everything you read on "the internet", not even this.


Ian