Tim K Posted February 21, 2023 Share Posted February 21, 2023 Hi, can anyone tell me the outer diameter of the 19 tooth speedo drive pinion, for a Triumph 3HW please? I’m talking about the spur gear that drives the speedo drive, not the larger gear that’s fitted to the hub. cheers, Tim. Quote Link to comment Share on other sites More sharing options...
welbike Posted February 22, 2023 Share Posted February 22, 2023 Following! Lex Quote Link to comment Share on other sites More sharing options...
Ron Posted February 22, 2023 Share Posted February 22, 2023 I've been thinking about this Tim. If you cut out a cardboard copy of the large gear and lay it on the inside of the brake plate, dead center. You should be able to measure the distance between it and the speedo drive spindle. (By screwing the drive in only a few threads) Some careful calculating will give you the diam of the small gear. Unless someone has one that doesn't involve dismantling a bike. Ron Quote Link to comment Share on other sites More sharing options...
Tim K Posted February 26, 2023 Author Share Posted February 26, 2023 Hi Ron, I’ve worked out the dimension, but measuring the hole centres and the od of the hub drive gear, less the depth of its teeth. I’ve also sourced what should be a suitable gear to make the drive pinion from. I’ve kind of had to make a guess as to the depth of mesh of the two gears. If someone knew the od of the pinion drive gear, I would know if my guess is correct or not. The object of the exercise is to drive the speedo, so achieving that is my main aim, but it would be nicer to know that I’ve made an accurate copy, if that makes sense? Quote Link to comment Share on other sites More sharing options...
Ron Posted February 26, 2023 Share Posted February 26, 2023 (edited) The mesh is quite sloppy actually. Triumph also used 20" wheels on some bikes and they just fitted an 18T or 19T pinion and ran it on the same 58T driving gear. I wouldn't have thought that would work....but it does. Ron Edited February 26, 2023 by Ron Quote Link to comment Share on other sites More sharing options...
Tim K Posted February 26, 2023 Author Share Posted February 26, 2023 Hi, thanks for that info Ron, I had no idea about that. If it works, it works, I guess….. Quote Link to comment Share on other sites More sharing options...
rewdco Posted February 28, 2023 Share Posted February 28, 2023 (edited) On 2/26/2023 at 8:53 AM, Tim K said: I’ve worked out the dimension, but measuring the hole centres and the od of the hub drive gear, less the depth of its teeth. I’ve also sourced what should be a suitable gear to make the drive pinion from. I’ve kind of had to make a guess as to the depth of mesh of the two gears. If someone knew the od of the pinion drive gear, I would know if my guess is correct or not. I guess you will be using a new industrial gear that you will modify to fit your bike? Be careful, as nowadays these industrial gears always have a metric module. The WD bikes usually have gears with imperial modules. Only metric module 1 will fit the appropriate imperial gear system (difference is negligible), all other sizes won't fit. No idea about the module of a Triumph gear set... Edited February 28, 2023 by rewdco Quote Link to comment Share on other sites More sharing options...
Ron Posted February 28, 2023 Share Posted February 28, 2023 Tim I guess you know that Cornucopia has 18T and 19T in stock? Ron Quote Link to comment Share on other sites More sharing options...
Tim K Posted February 28, 2023 Author Share Posted February 28, 2023 Thanks for that information REWDCO, I’ve sourced what seems to be a suitable imperial gear, they are both only spur gears not rolling contact ones, as far as I can tell?. I’ve machined up a suitable hub and it drives the speedo drive round. It was a bit notchy, which I put down the burrs on the hub drive gear. I ran out of time to dress them up and re-try. I will know for deffo next time I’m off work and can attack the hub gear with a file. I do know about the Cornucopia ones Ron, thanks. He seems to have a similar sales technique to Bantam John!! So I’m exploring other avenues first. Quote Link to comment Share on other sites More sharing options...
Ron Posted February 28, 2023 Share Posted February 28, 2023 Peter Long and his mate Trevor, rude to customers!!!??? How dare you Tim😁 Ron Quote Link to comment Share on other sites More sharing options...
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