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Developments of the ITOM 4 Speed Racing Gearbox. A Members Enquiry
The History Page sometimes receives requests for information from members and so far they have been directed to the facebook page.  We are now going to create a new section in the History Page that will bring these enquiries to the members and draw on their experience in finding the right answers to the questions.
This first page is from Pio Herrero a 50cc enthusiast from Sweden. These are his words and pictures and my only changes are to to flowof the text.
"I've just received some ITOM gearbox parts that I've bought on ebay.uk. After quite some thought, measuring and comparing with my 3 and 4 speed gear clusters that I have I think I know what they are, a very well done 4 speed close ratio gear cluster".
"The curious thing is that it's done on 3-speed axles (a normal 4 speed cluster is slightly wider ). Perhaps this is an early 4-speed attempt before the arrival of the 4 speed box or an economic way of creating a close ratio 4 speeder? Ingenious, any how".
"A couple of the gear wheels are marked "macey", the name of the fabricator perhaps? There are other gear wheels and parts that eventually points towards a construction of a 5 speed box, but it's incomplete. I'm going to contact the seller to see if I can get into contact with the man he bought his ITOM racer from. He is an elderly gentleman".
"I'm contacting you to see if by chance the "macey" marking could shed some light on the story behind this box. Or if you know anything about this"practice" of constructing a 4 speed racing box by modifying 3 speed parts. It' quite ingenuously done. It seems like it's unused. If you think it is of interest I can take some pictures. Best regards from Stockholm", Pio Herrero
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Diagrams provided by Jeep, Editor, for build information.
There were 10 mainshaft gearwheels in total, and when I "solved the puzzle" (I hope so at least, haha) there is one main shaft gearwheel missing (none of the other 7 fits the bill). I suspect that It may be the 3:rd gear gearwheel of the standard Itom gearbox. But this will be easier to understand when I send you the pictures. I only had a couple 4-speed clusters to compare with at home, as I thought it was some kind of normal width 4 speed. So I need to go to my workshop for the Itom 3-speed parts.
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3-speed original axle (same widths and length)
After examination I saw that the whole axle and the gears of course, are fabricated new. Pressed on axle and with woodruff key. The gear is marked 4B. Second attempt?
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Pic. 3. Original layshaft with gearwheels and. 4-speed with the three most probable set of gearwheels (these three have sturdier inner cogs that lock the gears, more similar to the original/wider).
Pic.4. Modified 3-speed layshaft axle (bottom). Machined where the white strip of paper is, making that "heel" thinner and in so doing creating bigger width to accommodate gearwheels. Original 3- speed (top).
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Pic.5. "Macey" marking on 2 of 7 gearwheels that are set of wheels different from the three in picture 3. There were 10 in total. The "Macey" ones (7) have thinner inner cogs - too thin/frail I would say - and their overall width is smaller than that of the in pic. 3.
Pic. 6. Layshaft axle with with the 3 slightly wider and sturdier gearwheels from pic. 3. and one of the 7 "Macey" wheels. Not close and definitely no cigar...
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Pic. 7. This is how the gearwheels should line up on the layshaft axle (orig. 3-speed)
Pic. 8. with one "Macey" gearwheel as in pic 6. Not wide enough.
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Pic. 9. With the corresponding 42 cog gearwheel from the original ITOM 3-speed cluster. Slightly too wide. Either a gearwheel is missing or the original 42 cog wheel is the "missing link". Perhaps it made sense "economising" by using one original gearwheel? By machining it just approximately 1,5mm it could be made to fit. I have to check with a specialist if the different gearwheel cogs are cut so they are compatible.
Pic. 10. Layshaft with gearwheels, one the 42 cog one from the orig ITOM box as in pic 9.
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Pic. 11. The set of 7 slightly thinner wheels with thinner inner cogs. Some corrosion. The other set (the three in pic 9-10) are in better condition.
Pic 12. "Strange bird". This looks like a selector locking pawl (is that the correct term in english?,) selector in the ITOM spare parts catalogue). It is as the original ITOM ones but with 6 positions as for a 5-speed. It's a bit coarsely fabricated. (Itom 4-speed/5 positions 3-speed/4). An attempt to make a 5-speed? With the thinner wheels. Or just a try to get the pawls positions right?
If you have any comments to make on this problem, please address them to the Editor by clicking the tag.
Developments of the ITOM 4 Speed Racing Gearbox
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