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same ratio dfferent gears

6256 Views 64 Replies 19 Participants Last post by  stoner
hy would some one like to explain the different combo,s, and why. take a 3-1 ratio, the standard is 9-27. going to extremes, what about 7-21 or 11-33 there must be a difference and i,d like to know. a euro sport runs 6-1 6-36 why. john
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Stoner opened the thread by asking questions about two very different sorts of slot car.

1 The sort of car for which 3:1 is about the right ratio

2 Euro sport where 6:1 is about the right ratio

As the motor power and gear ratio of these two sorts of slot car is very different, nobody should be surprised that the gears normally used are different.

The 5.5 and 6.5mm pinion diameter standard from companies such as Slot it are widely used in cars where 3:1 is about the right ratio, and completely unsuitable for Euro sport
Hi Stoner
You are asking about gears that are the correct diameter for the size of teeth rather than these standard diameter pinions with different numbers of teeth?

Two different possibilities
1 The tooth size is changed so the diameter remains the same (for example 9:27 in 48 pitch and 12:36 in 64 pitch are approximately the same size and both the same ratio)

2 The tooth size is constant so more teeth means bigger diameter.

Taking those in turn
1 Doesn't make much differance. I have some practical experience of this - it doesn't make any noticeable differance. (Although some makes mesh better than others)

2 Bigger diameter gears are inevitably heavier. Theoretically that'll reduce acceleration and braking.
Bigger diameter gears that are delivering the same torque put less side load on the bearings Theoretically that'll reduce friction.
Both effects are probably so small so they don't matter much
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