MadModder
Gallery, Projects and General => How to's => Topic started by: GrahamN on May 19, 2011, 02:31:08 PM
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Hi
I have recently started collecting the materials together for my first attempt at a 'Cracker' loco. However, I am having problems locating a UK supplier of the gears. Hobbys tell me that they no longer have any stock, and are not hopeful of ever getting these back as a stock item, and the nearest I've found is from a US supplier at about 4 or 5 times the price I was expecting to pay.
Any ideas?
I'll buy from the US if I have to, but it will mean saving for quite a while to cover the extra cost, and I would much prefer to find a UK supplier if there is one.
As a possible alternative, I may be able to use some plastic gears, but they will need gluing onto the shafts and I'm concerned about them slipping or being damaged by the heat.
Any help or ideas would be appreciated.
Thanks
Graham
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Whats the DP and number of teeth?
HPC has most spurgears or GMB Associates are agents for Boston Gears in the UK, I've used both.
http://www.hpcgears.com/
http://www.gmbassociates.co.uk/
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If you can live with steel gears, Technobots (in the UK) do some in Mod 0.6, 0.6 and 0.8: http://www.technobotsonline.com/gears.html
Andy
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Have you considered machining your own? Only a thought - I`ve done a few now and it is a great skill to learn. Granted, it is easier buying for the effort invested perhaps, but like I say, its a really great feeling of accomplishment when done!
What DP or module are they?
Chris
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Thanks for the replies.
The sizes I need are 20mm dia x 40Teeth and 5mm dia x 10Teeth.
I will take a proper look at those links later, though the prices still seem very high compared to what Hobbys were charging - though I must admit I have no idea what mod 0.6 (or mod anything!) means, so hopefully the sizes are there also!
This is my first proper engineering project, so I think actually cutting gears myself is still some way down the road!
Graham
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I reckon the diameters you quote are the Pitch Circle Diameter ("PCD") of each gear, Graham, rather than their overall (tooth-tip to tooth-tip) diameters. If the gears are Mod 0.5, their PCDs would be 20mm and 5mm. Their ODs would be 21mm and 6mm, because the PCDs lie part-way up the teeth.
If you mesh together two Mod 0.5 gears, one 40T and the other 10T and hence with PCDs of of 20mm and 5mm, their centres will be (20 + 5) divided by 2 = 12.5mm apart. Does that accord with your drawings?
Andy
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Seems like you have a mismatch or typo there
0.5MOD x 40T does have a 20mm PCD but 0.5Mod x 10T has a PCD of 5.5mm (6.5mm OD)so they won't mesh.
The smaller teeth numbers have to be fiddled a bit so the usual formula does not quite work. see the corrected formula here (http://www.hpcgears.com/newpdf/technical_gearing.pdf)
Jason
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You're quite right, Jason; thanks. I'd forgotten the smallest toothcounts were a bit different. Figures should have been ODs of 21 and 6.5mm, PCDs of 20mm and 5.5mm, centres (20 + 5.5) divided by 2 = 12.75mm apart.
Andy