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Posted by Erik Olsen DK on January 13, 2008, 1:14 pm
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Dragon wrote:
>> Firstly, the tooth count will lead to the same teeth on the gears
>> engaging with eachother, this is not good practice and it would be
>> better to get away from 12/24 tothe ratio,
>
> How do you avoid this with a 1:2 ratio?
The overall two-stage gear ratio should be 1:4. This can be done for
instance with a 17 tooth gear driving a 28 tooth gear and that axle a 14
tooth gear driving a 34 tooth gear.
--
Best regards
Erik Olsen
http://www.modelbaneteknik.dk/
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Posted by Steve on January 13, 2008, 2:47 pm
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> Dragon wrote:
>>> Firstly, the tooth count will lead to the same teeth on the gears
>>> engaging with eachother, this is not good practice and it would be
>>> better to get away from 12/24 tothe ratio,
>>
>> How do you avoid this with a 1:2 ratio?
>
> The overall two-stage gear ratio should be 1:4. This can be done for
> instance with a 17 tooth gear driving a 28 tooth gear and that axle a 14
> tooth gear driving a 34 tooth gear.
>
> --
> Best regards
> Erik Olsen
> http://www.modelbaneteknik.dk/
>
Thanks Erik - I can stop banging my head on the wall now, I just couldn't
spot the trick and there it is!
Steve
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Posted by Dragon on January 13, 2008, 4:15 pm
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> Dragon wrote:
>>> Firstly, the tooth count will lead to the same teeth on the gears
>>> engaging with eachother, this is not good practice and it would be
>>> better to get away from 12/24 tothe ratio,
>>
>> How do you avoid this with a 1:2 ratio?
>
> The overall two-stage gear ratio should be 1:4. This can be done for
> instance with a 17 tooth gear driving a 28 tooth gear and that axle a 14
> tooth gear driving a 34 tooth gear.
Thanks Eric.
I missed the fact that Peter was probably considering the two stage
arrangement.
Henry
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Posted by on January 13, 2008, 3:17 pm
Please log in for more thread options > Having turned, milled, annealed and hardened and tempered, I now need to
> add cutting some spur gears to my CV.
>
> I have a mill and decent rotary table, so I'm assuming that I just need to
> buy the appropriate gear cutter and work out the "angle of dangle". This,
> like most of the things I do, will be fairly rare event. The design I'm
> currently working on suggests I need to make two 12 tooth and two 24 tooth
> module 1 gears cut with a 20deg pressure angle (that is to say bog standard
> stuff - but given my hobby is learning to make things, buying them misses
> point!).
>
> However, one question I'd like some help with is the material to use - the
> gear chain of events is a 12 tooth spur cut in EN8 and hardened will drive a
> 24 tooth gear on a countershaft. The countershaft also has a 12 tooth gear
> which then drives the final 24 tooth gear, to achieve a 4:1 reduction.
> This is being used to drive the valve timing cam in a 15 cc model engine
> (don't worry about 4:1 and four stroke -it's a trick I found on t'internet).
> Given I want minimum weight and to minimise gear noise what materials can I
> use in the gear chain after the driver spur (typically running at 5000rpm)?
>
> Steve
If you want lightweight, quiet gears how about tufnol?
Russell.
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Posted by newshound on January 13, 2008, 5:22 pm
Please log in for more thread options If you want lightweight, quiet gears how about tufnol?
> Russell
Excellent stuff, British motorbikes used to use it for magneto drive gears,
but it would need to be *big* to cope with spring operated valves. Maybe OK
for desmo?
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>> engaging with eachother, this is not good practice and it would be
>> better to get away from 12/24 tothe ratio,