How easy is it to make a chain sprocket?

I ask because I've never had to make one. I have cut gears and am assuming that the process is similar with just a different form.

I need to make a pair of sprockets to suit 1/4" pitch chain and looking at various sites, I can buy the chain but not the sprockets.

(Almost) any advice welcome.

Brian

Edited By Brian H on 30/05/2020 18:22:01

Have a look here Brian....

Chains & Sprockets

Regards

IanT

HPC Gears list that size of sprocket - available from 8 to 72 teeth

There is a wide range of sprockets used on motorcycles - some for the transmission, some to drive the camshaft. Cakll in at your local motorcycle shop with an example of the sort of size you need and there may be something off-the-shelf. And there is a man in Mid Wales who will make you any size you like in sxteel or light alloy.

The shape is basically a ring of circles exactly the chain-pitch apart, blended to a radius generated by the arriving or departing roller.

Cheers, Tim

THIS program wa suggested by the late JS in a thread on sprockets.

The thread is HERE .

I expect cutters are available from China, but some I just looked at from the UK(?) were eye-wateringly expensive!

sdp-si sell roller-chain sprockets if you can find something suitable.

The reason for the interest in chains and sprockets is that I want to build a 1/4 scale model of Henry Ford's Quadricycle, the first car he made himself in 1896.

Below is part of a drawing made by a Ford employee with details taken from the actual car at the Ford works.It is supposed to have 7 teeth but it looks as though every other tooth is missing!

Were old chains different to modern ones?

Brian

On a much larger scale, the sprockets for the duplex chain drive on the Rolls-Royce Sentinel Diesel Hydraulic Shunting locomotives were machined with a form cutter. In the same way that we cut gears, by plunging a form cutter through the workpiece in one pass, with a slow feed. The machine was most probably the one used to produce the sprockets on the chain driven Sentinel steam Waggons, fairly simple but effective in cutting 14" or more diameter. sprockets.

So for smaller pitch chain, and smaller diameter sprockets, a cutter of suitable form would be needed..

From memory, the teeth were straight sided, with just a small radius at the outer end, so maybe one cutter might suffice for a wider range of tooth counts than an involute gear cutter.

Howard

Cant see the pic. But it was common for early sprockets to have every second tooth missing. Still used a standard chain. You see it on old bicycles from circa1900. No idea why. Cost saving?

Were old chains different to modern ones?

The modern roller chain was invented in 1880, so it is possible that Ford was using the older type of chain which had pins with no loose rollers on them. A lot of early chain driven bicycles had alternate 'missing' teeth on their sprockets, and I think the reason was something to do with the properties of this type of chain. From my limited experience of riding a bicycle so equipped, they are clunky and noisy, and feel very inefficient!

I managed to find on the internet, an article about old bike sprockets and chains and it describes this arrangement as 'skip tooth'

I'm not sure how this affects calculations. the drg shows a 7 tooth sprocket at 1" pitch, I worked this out at 1/4 scale to be 1/4" pitch but should it be worked out as a 14 tooth sprocket at 1/8" pitch?? or just a 14 tooth sprocket at 1/4" pitch??

My 1940 edition of Machinerys Handbook has tables for 'block chain' but with little explanation.

It's too hot for mental arithmetic.

Any help gratefully received.

Brian

Older agricultural machinery did not use Roller Chain, but a series of flat links, so the sprocket teeth would not necessarily be the same form.

I assume that you are thinking in terms of Roller Chain, which is what Scammel, and Sentinel used on the final drive to their waggons, and shunters. (The solid rubber tyred Hundred Ton Scammel, used to haul the propellers for the Queen Mary used chain for the final drive. )

Howard

A pure guess. In the evolution of the chain, for me it would make sense to have made a chain with a solid links that are joined using side plates. This would explain why sprockets had every other tooth missing as the chain only had a hole between the solid links. When the roller chain came along, if the pitch was the same it could run on the old sprockets. So maybe either the sprocket design took a while to catch up with roller chain, or the original chains were replaced with roller chain.

Adrian

Ahha, it is called block chain. Looks like 1 inch block chain is still used too. This bike site has some pictures of it **LINK**

On this site **LINK** they still sell it, interestingly it looks like they make it from standard chain components. They just stack up the center plates to replace the rollers. So If you wanted to make a 1/4" version you could dismantle a 1/4" chain and reassemble it without the rollers.

Adrian

Brian, Technobots do nice chain and sprockets, the online shop is pretty good too.

John.

**LINK**

If it helps, here's a picture of the original Q plus a close-up of the large sprocket area (which clearly shows the skip-tooth profile):

Edited By Bandersnatch on 31/05/2020 18:27:23

Try Tracy Tools,they stock gear cutters and they may have aquired some sprocket cutters,I have a sprocket cutter for 1/2 inch pitch I found that in a job lot of gear cutters I bought at auction. sprockets are quite thin so may vibrate during cutting,suggest make the blank thicker ,cut the teeth and then face to required thickness,

Do you really need a sprocket cutter? I have seen descriptions of making sprockets with a drill, hacksaw and a file. I would think they would be quite simple to make using an end mill and rotary table.

Adrian

I found this, it is a picture from above and clearly shows a block chain **LINK**

Many thanks for the replies and especially to AdrianR for the very clear picture of block chain. My thoughts were to use standard commercial items but ran into a snag because the small sprocket has 7 teeth and that is not commercially available but then, if we are talking about a gear with every other tooth missing, that would make it a 14 tooth gear which IS commercially available and every other tooth could easily be machined off and still work with standard chain.

The problem is that the calculations for standard sprockets do not give the correct O/D or PCD.

It is not a great problem as it will be a long time until I need the sprockets and chain and, as a last resort, sizes could be worked out from the existing centres.

Brian