Sprocket sizes

Started by Mike Farmer, 16 Jan, 2022, 17:54

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Mike Farmer

16 Jan, 2022, 17:54
 :) :) :) :)

Hi :) all and a good evening.

Can someone tell me what is the smallest gearbox drive sprocket available to fit A50/A65 Gearbox, I need one as small as possible to make and fit an idler/adjuster on my trike.

Or something small that will run in the std A50/65 rear chain.

Mike 8) 8) 8) 8)

Spaceman

#1
16 Jan, 2022, 19:41
One of the parts books lists a 16T sprocket (68-3074) for the A50 - how small do you want to go?

Mike Farmer

#2
17 Jan, 2022, 17:53
 :) :) :) :)

I cant really answer that, Suffice it to say as small as possible. If I could get down to about 12T I would be very pleased. The main consideration is the teeth spacing to run properly in the std chain.

Mike 8) 8) 8)

DAVE BRADY

#3
17 Jan, 2022, 18:31
Hi Mike,

Is this to support an extra long chain run on your trike?  Some competition bikes that run long chains use a slipper to support the chain mid run or over the swinging arm.  Perhaps something like the primary tensioner on an A65 might do the job.

Dave.

Mike Farmer

#4
18 Jan, 2022, 10:35
 :) :) :)

Hi Dave.

The answer to that is because of the way the differential is carried there is no chain adjustment.

Its perfectly OK but not MOT std. I have considered the slipper and I think it would prove difficult to fit on the return side of the chain. So the answer is a roller fitting of some sort. The smaller the sprocket the less room it will take etc. I could probably do it with an "in chain roller" but I've never felt comfortable with that idea. Fitting an idler sprocket on a spindle via the rear footrest mounting points seems the best option at the mo.
I shall let you know the outcome.

Any other suggestions very welcome. Anything is worth consideration.

Mike

idie

#5
18 Jan, 2022, 11:13
If you put sprocket onto Google, there are a number of companies who do sprockets. Perhaps one of them might be suitable.

Mike Farmer

#7
18 Jan, 2022, 20:25
 :) :) :)

Hi Dave.

Thanks for that, I don't fully understand their lingo so I'll have a chat with them tomo with luck. I've also been looking at bolton and they have some interesting items. I'll let you know.

Mike 8) 8) 8)

chaz

#8
18 Jan, 2022, 21:15
shame time has progressed so much, up to 25 years ago I could have made whatever sprocket you want or even gears in gearboxes, but our "engineering" company only has 10 machines now and not even an off hand grinding wheel, well there is one but has scotchbrite wheels on..
not sure (since the takeover) but Talon (in Yeovil) used to do custom sprockets and not sure, but our old Sykes gear cutters went to a firm in Bath

Mike Farmer

#9
19 Jan, 2022, 10:10
 :) :) :)

Thanks to all for your input.

I have found a chain tensioner on Ebay that says OK upto 500cc. If anyone has a spare mo perhaps you could take a look at
Item No 373648098348 and give me an opinion. To me it looks abit flimsy but it may be solid enough. On the basis that you get what you pay for I have my doubts.

Mike 8) 8) 8)

DAVE BRADY

#10
19 Jan, 2022, 11:08
Good morning Mike,

I think you are right, it does look a bit flimsy. With your trike the load on the chain when shutting off suddenly will put a lot of force in to the chain tensioner.  Have a look on  Simply Bearings. They have a 14T 5/8 pitch sprocket with bearing in the middle.  Perhaps the basis of a tensioner.  Also, it may be worth visiting a dealer that sells motor cross bikes.  They must have quite substantial tensioners fitted and they would understand what you are tying to achieve.
I found this image of a substantial looking one.

Dave.

Mike Farmer

#11
19 Jan, 2022, 15:22
 :) :) :) :)

Thanks again, I'll let you know.

Mike 8) 8) 8)

Mike Farmer

#12
19 Jan, 2022, 15:37
 :) :) :) :)

Hi Dave :) :) :)

Further to last-I have just ordered that sprocket--thanks again.

As there is no "swing arm action" the chain doesnt change tension as it would on a bike, which means there is no requirement for a sprung tensioner. A simple adjustable idler to take up any slack will suffice so perhaps we are on our way.

I must be losing it cos I looked on simply bearings last night and didnt see that item.

Mike  8) 8) 8)

Mike Farmer

#13
20 Jan, 2022, 16:03
 :) :) :)

My idler sprocket came today. It runs beautifully in the chain. now all I have to do is fit it. Let you know.

Mike 8) 8) 8)

idie

#14
20 Jan, 2022, 19:05
Well done, it's good when a plan comes together.
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