close ratio gears

DavidSage
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close ratio gears

Postby DavidSage » Fri Feb 09, 2018 2:34 pm

I been gathering the remanding parts of the build for the sprint/race/parade bike and would like to very much build this with both a standard gearbox and then a close ratio one.

I have been in touch with Ellis Moore at moore engineering Ellis has suggested one of two options:

Option One - four new gears:

1st 2.652:1
2nd 1.696:1
3rd 1.961:1
4th 1.000:1

Option two with six gears:

1st 2.021:1
2nd 1.418:1
3rd 1.191:1
4th 1.000:1


he states that standard ratios are as follows:

1st 3.197:1
2nd 1.860:1
3rd 1.311:1
4th 1.000:1


I would very much welcome any feedback or advice on the information provided by Ellis

best regards.

David Sage

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AndyEames
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Re: close ratio gears

Postby AndyEames » Fri Feb 09, 2018 5:43 pm

I know that Roger (Jess) has had Ellis do a gearbox for him. Not sure if he's used it yet. No doubt he will give you his thoughts. We have made our own using existing Burman components somewhat altered. The pinions we have used going from 1st are 20/26, 22/24, 24/22 , and a final reduction of layshaft 20 to sleeve gear 26. A very high 1st gear, but we are only looking at a top speed of 80mph for hillclimbs so the final drive will be considerably lower than standard as we hope to be pulling 2,000rpm more than a stock machine. Time will tell. I have heard that Ellis does a good job. Keep us posted.
Andy

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Re: close ratio gears

Postby DavidSage » Sat Feb 10, 2018 10:30 am

Andy,

Thanks for the feedback. I have a question, in the burman gear box are the main shaft and lay shaft of a similar size to the arrow / leader gearbox?

Regards,

David

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AndyEames
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Re: close ratio gears

Postby AndyEames » Sat Feb 10, 2018 3:31 pm

We have some pinions from the 'normal ' Burman GB boxes that we have machined, and the spline sizes (or at least some of them ) are the same as the 2 strokes as are the tooth forms. The 4 stroke GB sleeve gear for instance can be made to fit but it is considerably wider across the teeth. The other GB gears are also wider as you might expect. The magic number is 46 . So for instance a 26 on the mainshaft would mate with a 20 on the layshaft. We have not altered the Arrow mainshaft, but have turned the ends of the layshaft down to fit 15mm needle bearings instead of the iron bushes fitted originally. You then have to make up some form of thrust washer to take the end float. We made brass ones with a short 15mm spigot to fit into the modified housings (21mm) and grooves to allow oil into the needle bearing. Using an open ended bearing in the detatchable housing and a closed end one in the main case back of the sprocket. Be careful NOT to get bearings with seals in them as they will be starved of oil.

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AndyEames
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Re: close ratio gears

Postby AndyEames » Sat Feb 10, 2018 3:49 pm

Ellis' option 2 1st gear uses 18-28. This may well be what we will end with. 2nd and 3rd are the same as ours, probably using 2 x 3rd gear sliding dogs.

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Re: close ratio gears

Postby DavidSage » Sun Feb 11, 2018 12:09 pm

Andy,

Many thanks once again, real helpful information. I dropped Roger a note a year or so ago looking to purchase two alloy cylinders and mentioned to him that I was or just had retired and that I was trying to build a workshop, so that I may do some of the machining myself. I have a fairly good quality lathe and I am looking for a small milling machine. I spent many years in project management, sales and service business's but my background and original training was as a scientific instrument maker, serving as an apprentice at the Imperial college in London. The down side however, is this was a long time ago, so I will have to bring my self back up to speed with not just the machine but also the fabrication of the exhaust systems. Really interest to know how you get on as Ellis is quoting figures of around £400 + for four gears and £600+ for six gears.

On one of the documents that I have printed off from this forum is indicates the use of a needle roller HK1516 is this what you are using on both ends of the layshaft.

At the moment I have the 8inch front wheel hub in the lathe so that I may clean it, unfortunately I cannot gripped it on the outside and have just managed to hold it on the brake plate side.

regards,

David.

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AndyEames
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Re: close ratio gears

Postby AndyEames » Sun Feb 11, 2018 3:45 pm

Hi David. The skills will come flooding back, I'm sure. And once you start, who knows where it will end. I have the ideas but limited skills. A Chester (chinese) lathe for me is about as far as it goes. Mind you I did surprise myself a few years ago when I made some fork parts for our Scott ! My nephew Harvey has abundant skills when it comes to machining. So I just feed him an idea and stand back ... Ellis' costs are reasonable in our view, as Harvey says if he was doing some general engineering , he would be charging £450 a day. Now he knows what he is doing he says it would take a day to do the gear conversion. Yes, 1516 needles are the ones, 1 closed end, 1 open ends. Good luck and keep us informed of your progress.

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Re: close ratio gears

Postby bh.sprint » Sun Feb 11, 2018 9:25 pm

I found these gear ratio's in my information file, I assume they are from the Nova gear box.

I've not used a close ratio box bike but on the road the 4 speed box is reasonable except when going up a long hill and then another gear between 3 rd and 4 th would be nice to have to keep the speed up.

Brian H.
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john.whiting
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Re: close ratio gears

Postby john.whiting » Mon Feb 12, 2018 2:30 am

Before even considering a close ratio 4 speed box for the road,I suggest you try riding a bike with one.......or simpler,try riding your bike without using first gear,at all....Even Gold Stars are just about unridable in traffic with the close ratio box........what you need is a six or seven speed box,with close ratios,which is what the Japs did 50 years ago.

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Re: close ratio gears

Postby john.whiting » Mon Feb 12, 2018 2:38 am

Now there is a project.....see if you can fit a 6sp Jap box into a Ariel.....all crossover indirect,with sprocket on opposite side to clutch.....with a 2/s you can reverse the engine rotation easily........I know that I have fitted jap boxes into machine tools......just choose a 2/s one ,it will be closed off from the crankcase.....all the gears and bits are free,just needs a bit of ingenuity.....years ago guys here made Bantam gearboxes into 8 speeds for racing.


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