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 Amos g/box mod.

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mjpowell

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Number of posts : 1074
Localisation : Lincoln England
Registration date : 2006-12-09

PostSubject: Amos g/box mod.   Thu Dec 15, 2011 8:39 am

Hi Trevor

Have you done a layshaft bearings mod too or just the sleeve gear?

I assume the advantage of the sleeve gear mod is it doesn't gear/become sloppy?

Are you prepared to share how you converted your sleeve gear? and ? mainsaft?

Mike

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Trevor Amos



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Registration date : 2010-08-13

PostSubject: Re: Amos g/box mod.   Thu Dec 15, 2011 10:17 am

Hi Mike ,
Will do , i`ll take some photos and explain it all to you , and a bit more besides !

Cheers for now , trevor
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Edward Pickering

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PostSubject: Re: Amos g/box mod.   Fri Dec 16, 2011 12:38 am

Courtesy & Property of Trevor Amos







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Trevor Amos



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PostSubject: Re: Amos g/box mod.   Fri Dec 16, 2011 1:28 am

Hi all ,
Firstly , many thanks to Ed for posting the photos , what a great guy he is and if he gets on the track he surely would deserve "rookie of the year" !
Scrutiny of my notes tells its own story, excessive bush wear , with a lot of friction in first and second gear and the end of the mainshaft deflecting
making gear slection even more of a problem !
This is the sleeve gear that Mark ran with at the last Cadwell meeting , so the conversion is durable and reliable . I was initially worried about
lubrication but everything seems fine .
One word of caution , don`t bore the gear through from just one end ! Go in from each end and leave a full radius at the newly created shoulder
and make the depth no more than the bearing width . It will be a fiddle to set up for each end , but you only have to do it once , and use the
existing , ground diameter as the set up datum , that way the new bearings will be co-axial and concentric and will run like a dream !

As a final thought , how many of you dynamically balance your clutch ? It does make a difference !

Catch you all later Trevor .
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Trevor Amos



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PostSubject: Re: Amos g/box mod.   Fri Dec 16, 2011 1:47 am

Sorry Mike .
Missed out the lay shaft . Yes , this was done first and was part of the original design brief , to eliminate as many areas of parasitic power
loss as possible, i just did`nt have enough time to include the sleeve gear as Steve was clamouring for the new engine . So this had to wait
for the following 98 season , i must say that the bronze bush wear rate was staggering , dread to think what might have happened if it was
left any longer .

Fire away if there are any more queries , Regards Trevor
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john bass

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PostSubject: Brilliant!   Fri Dec 16, 2011 2:18 am

Brilliant engineering Master Amos (master as in engineer not as the teenager!) and using Imperial BRITISH inch units -- Brilliant!!...
Well done son!

Sorts of backs my theory that the 175 has an enormous amount more friction Losses -- hence needing a bigger flywheel -- than the 125....

Cheers!
JayBee.
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mjpowell

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PostSubject: Re: Amos g/box mod.   Sat Dec 17, 2011 10:22 am

Many thanks Trevor ... I think you are the only person to date to do this modification?
Have you 're-bushed' sleeve gears previously?

Regards Mike
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alan
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Registration date : 2006-12-01

PostSubject: Re: Amos g/box mod.   Sat Dec 17, 2011 10:26 pm

Hi All,
I have been using this mod since 2004, I did have some issues with the bearings but is was mainly the acuracy of my machining, I sorted this out and then no trouble there after!
The moral of the story is.... Take your time and do a good job!
Cheers,
Alan
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mjpowell

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PostSubject: Re: Amos g/box mod.   Sun Dec 18, 2011 3:45 am

Alan do you use the same bearings as Trevor?
And do either of you have problems with oil being throw
out the open end of the sleeve gear?
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alan
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PostSubject: Re: Amos g/box mod.   Sun Dec 18, 2011 9:58 pm

Hi Mike,
I use the HK1212 (I will check if this is the correct number!) which is a metric bearing, then I grind the mainshaft end to 12.00 mm dead for the bearing internal size, it gives no trouble if you do a good acurate job.
I also pin the layshaft over to the clutch side with a central screw and washer so that there is no float on the layshaft, but this is typical of most race gearboxes and I beleive the BTW style gearbox is done the same way.
I have not changed the Sleeve bearings for a few seasons, but I should do this every second or third season just for safety as the bearings are cheap so there is no reason to take a risk.
Cheers,
Alan
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john bass

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PostSubject: Transmission efficiency...   Sun Dec 18, 2011 10:49 pm

In the book, "Theory Of Machines" by Thomas Bevan, there is an example requiring the calculation of acceleration and speed of a motorcycle under given conditions whilst being driven in second gear and the example gives the efficiency of transmission as 88% ...
Which means 12% of power is lost because of transmission inefficiency

If the chain drive of the system was say 98% for each of the chains -- giving 98% x 98% = 96% -- we then have 12% - 4% = 8% inefficiency for the gearbox????? Which 8% means as much as 1.6 -1.92horsepower could be lost to gearbox inefficiency. Thatīs about 1.3 to 1,4 kilowatts of heat ---

Where does all the heat go? Do gearboxes get really hot -- the oil must be boiling?

Gearboxes on racing Bantams are much more efficient but I still ask -- where does over a kilowatt of heat go....?
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