Gearing confusion

[Richard]

Hi

I am very confused about the gearing on my trike.
As far as I know the engine and gearbox are standard, modified original prop-shaft feeding a Ford Sierra differential. After I took the wheels and brakes off I turned the prop shaft by hand and counted the revolutions needed to turn the wheels once = 3.6 ish, looking at this site it looks like its a 3.62
http://www.super7thheaven.co.uk/Sierra_Rear_Differential
The back tyres are 225/40 18

So looking at this site
http://www.gearingcommander.com/
the 1400 GTR is already in the drop down and feeding in the tyre size and diff ratio in place of the final drive we get the RPM / speed ratings in each gear, notice 6th @ 4000 RPM = 49.3 MPH

This is great, apart from the fact that at 4000 RPM in 6th I am doing 75 MPH   

I have checked the information Gearing Commander uses for the GTR, and apart from a slight difference in the 4th gear ratio it matches the spec here
http://www.kawasaki.co.uk/Product/Specifications/340E096ACCE

This has left me confused, I know my speedo is bang on having fitted the speedo-healer
http://www.bikersdiscountstore.co.uk/speedo-healer/healtech-electronics/speedo-healer-v4-pd-18.php
and set it using TomTom

Am I missing something, being daft  or is it possible the builder changed the primary reduction in the gearbox 

Do the RPM / speeds on Gearing Commander for the stock machine look right?

Richard

I have just fed all the data from my handbook into another site
http://woodsware.aciwebs.com/gears/
and got the same results 

[Debs]

I could think 'what makes this computer work?' 

I really don't give a  as long as it does what I want it to do 

Just ride it Richard and don't worry about it... 

[Richard]

I could think 'what makes this computer work?' 

I really don't give a  as long as it does what I want it to do 

Just ride it Richard and don't worry about it... 

I hear what you are saying, and I will ride and enjoy, but I need to know 

[O.C.]

Its all a bit of a 'Dark Art' to me Richard, I can understand that you would want to know especially as you've now started to investigate the whole final drive ratio thing.

I can also see debs point and  I do agree with her, if you like it the way it is then ride it and enjoy it.

If you curiosity is now driving you crackers  then maybe you could contact the builder and ask them what changes have been made within the bike and its drive train 

[Burchy]

Just a thought.

When you were turning the propshaft into the Sierra diff, did you have one wheel/driveshaft stationary, or were both rotating?.  There is obviously a gearing reduction in the diff, but if one wheel is stationary the other will go at about twice the speed.

[Richard]

Just a thought.

When you were turning the propshaft into the Sierra diff, did you have one wheel/driveshaft stationary, or were both rotating?.  There is obviously a gearing reduction in the diff, but if one wheel is stationary the other will go at about twice the speed.

Hi

Yes I marked both wheel hubs and made sure they both turned the same amount.

Richard

[Martin#30]

http://www.gearingcommander.com/

Do the RPM / speeds on Gearing Commander for the stock machine look right?

Yep, 4000rpm in 6th is 85.6mph according to that site. That tallies with my 2010 bike.

Your trike builder must have done something with the diff or primary ratio though. A sierra red-line is ~6,000, our bikes over twice that.

Martin

[Boomer]

The only conclusion is that the diff is not 3.6 ratio.
Changing the primary is damned near impossible, changing the gearbox ratios is difficult, changing the front bevel ratio difficult, but the car diff ratio is usually pretty easy to change.
The GTR rev limiter is 11,000rpm so I would imagine that they halved the ratio from 3.6 to 1.8 or there abouts.
In fact in the gearing calculator if you put 1.9 as the ratio you get exactly 75.2Mph.

Another possibility is that there is a step-up gear partway along the linkage between the motor and the diff.

[BigAlan]

My bike is geared wrong as well, just last night in the damp air i seemed to be going in excess of 100mph when i am sure i was only doing 70mph,  something weird but i was smiling all the way.

Alan

[Richard]

Yep, 4000rpm in 6th is 85.6mph according to that site. That tallies with my 2010 bike.

Your trike builder must have done something with the diff or primary ratio though. A sierra red-line is ~6,000, our bikes over twice that.

Martin

Hi Martin

Thanks for that, so given the sites are right the only option left is there has been a change in the primary or output gearing in the gearbox.
I can not see why they would have done this, must have been very involved and expensive compared to getting a diff at the right ratio, I have seen BMW 3 series diffs used, loads of ratios to choose from all the way down to 2.4:1 ish.

[Richard]

The only conclusion is that the diff is not 3.6 ratio.
Changing the primary is damned near impossible, changing the gearbox ratios is difficult, changing the front bevel ratio difficult, but the car diff ratio is usually pretty easy to change.
The GTR rev limiter is 11,000rpm so I would imagine that they halved the ratio from 3.6 to 1.8 or there abouts.
In fact in the gearing calculator if you put 1.9 as the ratio you get exactly 75.2Mph.

Another possibility is that there is a step-up gear partway along the linkage between the motor and the diff.

Hi

I will re-re-recheck the diff ratio tonight, but have already done this 3 times when it didn't make sense 

There is nothing between the gearbox output and the diff, just the modified original drive shaft, which having spent some time turning it by hand has a wobble in it      

"Changing the primary is damned near impossible, changing the gearbox ratios is difficult, changing the front bevel ratio difficult, but the car diff ratio is usually pretty easy to change." - agreed.

[Richard]

My bike is geared wrong as well, just last night in the damp air i seemed to be going in excess of 100mph when i am sure i was only doing 70mph,  something weird but i was smiling all the way.

Alan

  on a private road I trust 

[Richard]

     think I can see where I have gone wrong, at work now so will check on the gearing site lunch time to confirm

[Boomer]

  Waiting with bated breath! 

[Richard]

 

OK I now understand 

The final drive ratio (2.036:1) shown on the Kawasaki site spec, and used by the Gearing Commander site it the result of 2 sets of bevel gears, one each end of the prop shaft
One set in the back of the gear box driving the prop shaft
http://www.kawasakioriginalparts.com/kawasaki_motorcycle_parts/kawasaki_motorcycle_parts_large_image_M50.php?block_01=E3131.gif&block_02=99912-1648&block_03=mc
and one set in the original hub unit from the prop shaft to the wheel
http://www.kawasakioriginalparts.com/kawasaki_motorcycle_parts/kawasaki_motorcycle_parts_large_image_M50.php?block_01=E3132.gif&block_02=99912-1648&block_03=mc

Now on my trike I have still got the set of bevel gears driving the prop shaft, but the back set have been replaced with the diff.
The mistake was putting 3.62 into the gear calc in place of 2.036
As you can see the bevel gears in gear box are gearing up so this was missing from the calc.

From the owners manual the final drive is given as 2.036 (14/22 x 32/10), so looking at the pictures and the size of the gears the 14/22 is in the gearbox, gearing up 0.6363':1, and the 32/10 is in the hub gearing down 3.2:1
So I have 0.6363 (driving prop shaft) x 3.62 (diff in place of original hub) = 2.303

If you put 2.303 into gearing commander with my tyre size etc you get 77.6MPH in 6th at 4000RPM

going to get on with what I should be doing now instead of worrying about this stuff   

Richard