26 replies to this topic

[havlicek]

I'm looking at doing a full-sidewinder and one of the problems here is coming up with gears large enough at an over 4:1 ratio to cover the distance between a modern C-can shaft and the rear axle. Of course, the spur gear diameter will also affect the size of the rear tires. So:

1) What's the deal with so-called "drag spurs"? Are these simply larger spur gears that are as durable as any other by the same manufacturer? I see tooth counts that go way up there on these.

2) Is there a resource online somewhere that gives approximate diameters of spur gears so I can figure out what size rear tire would be necessary to keep the spur gear clearance? Having to go to a huge rear tire is also going to mean even higher gear ratios.

Thanks in advance.

[Don Weaver]

John,

I have a bunch of the old Weldon (?) sidewinder gears with taper-locks from the '60s... if you can put me in the ballpark on ratio and diameter I'll see what I have.

Don Weaver

[Prof. Fate]

Hi,

John, no reason for a full sidewinder in the first place.

In the second place, you can do the sums yourself.

48 pitch gears mean 48 teeth on a 1" gear. 64 means 64 teeth, 72...

You get the idea.

Fate

[JohnnySlotcar]

I have a bunch of Fass and Sonic 41-44 tooth 64 pitch gears that should work.

Email me at bigpedo@aol.com if interested.

[havlicek]

Thanks, Don and John. I may just take you guys up on your generous offers!

John, no reason for a full sidewinder in the first place.

Hi Rocky,

But I don't get your answer!? Of course there's a "reason" to do a sidewinder. Aside from the mechanical advantage, it's an "old form" that's not often done anymore. There's no "reason" to do jail-door inlines either... or for that matter floppy-pan inlines

In the second place, you can do the sums yourself.

48 pitch gears mean 48 teeth on a 1" gear. 64 means 64 teeth, 72...

Ah... I thought those designations were the number of teeth per inch on a straight line (so a 48 pitch gear would have teeth 1/48 of an inch) and didn't realize they meant the number of teeth on a 1" diameter gear!

[Jairus]

I didn't either... that is a good piece of trivia to know!

[havlicek]

Weird, I have a 39 tooth 64 pitch gear that measures .625". If a 64 pitch gear with 64 teeth = 1" diameter, then 39/64 of an inch should be .609".

Oh well... I guess it's close enough for rock and roll!?

[Cheater]

John,

Google on "pitch diameter" and see what you find.

IIRC the pitch diameter and the overall diameter differ.

[Noose]

Here ya go:

Explanation Of Gear Pitch

[Tex]

Mongo no read. Teeth-per-inch good enough for Mongo. Mongo sleep now.

[team burrito]

Go here instead:

PIC Design

In general, 46t is .750" OD, 48t is .781" OD, and 50t is .813" OD. It doesn't show a 52t gear, so your guess is as good as mine. Hope this helps.

[idare2bdul]

Companies that make gears often make more then one tooth count gear on the same size blank. There is an optimum size and then there is the "how many teeth can we get on this little sucker" size. Mostly this is done for clearance reasons but it also cuts down on inventory for blanks.

Drag gears are often aluminum and don't like too much horsepower for applications other than drag racing. An FK or stock 16D is usually OK. Above that level gear life can be short.

[Foamy]

Hi,

John, no reason for a full sidewinder in the first place.

In the second place, you can do the sums yourself.

48 pitch gears mean 48 teeth on a 1" gear. 64 means 64 teeth, 72...

You get the idea.

Fate

Ummmm, no. Not so much. In 64 pitch, a 1"diameter is going to be 62 teeth.
Quickie formula to find teeth/diameter is. . .
1 divided by tooth pitch, multiply by number of teeth plus 2.

46 example. . .1divided by 64=0.015625". Multiply by 48=.750".

Mike is correct about compressing/expanding teeth to fit a specific diameter. Functions ok a couple teeth on either side of optimum.

Drag gears are good on low HP motors as they are only .040"-ish wide aliminum. For Vintage style big HP rewinds I would try to find Welduns or else use Cox gears.

[havlicek]

Thanks for all the replies!

Foamy, that makes sense and I'll look into those. Noose's link explained the difference I saw as they measure the pitch diameter about half-way out the length of the tooth.

-john

[Horsepower]

Hey John! If you need sidewinder gears I have 'em up to the keister so feel free to ask!

[Horsepower]

Mongo no read. Teeth-per-inch good enough for Mongo. Mongo sleep now.

I think I'm gonna shoot him!

[rdmac]

Hi John
In a nutshell, Outside Diameter = (Number of teeth +2) / Pitch

Example: Find the OD for a 37 tooth 48 pitch gear...
(37+2) / 48 = 39/48 = .8125

Example: Find the OD for a 69 tooth 64 pitch gear...
(69+2) / 64 = 71/64 = 1.109375

Example: Find the OD for a 52 tooth 72 pitch gear...
(52+2) / 72 = 54/72 = .750

More Info Here... Spur Gear Terms & Calculations


Stock Drive Products
On the above link click > Gears > Spur Gears > Metal
2024 Aluminum
48, 64, 72, 80 Pitch
With Hub / Set Screw
Face Width = .125
Bore Size = .125

At approx $13 each they are a little pricey, but available.

Also Here... W.M. Berg

[Tex]

That's why Mongo no read.

Mongo look at clouds.

Better.

[Bill from NH]

Also Here... W.M. Berg

Bob, would this be Walter Berg, the long-time International 15 racer?

[Horsepower]

That's why Mongo no read.

Mongo look at clouds.

Better.

Wouldn't want to shoot Mongo. It would just make him mad...

['Slots of Fun']

Revran!

V/R,

Don

[havlicek]

In a nutshell, Outside Diameter = (Number of teeth +2) / Pitch

Thanks again, everyone, for all the information. The above is a nice simple formula (me mongo, too) I can easily use. Thanks, Bob

[stevefzr]

Hi John
In a nutshell, Outside Diameter = (Number of teeth +2) / Pitch

.....

So, can I use this to sort out my 48 pitch and 50 pitch (metric) pinions? It's easy to pick the metric crown and spur gears as they have a 3mm axle hole instead of 1/8", but the pinions are all designed for the same armature shafts. I could never see what the teeth on a pinion all had to be the same length, so I didn't think I could just measure the diameter to sort the metric from the imperial.

Anyway, if your formula still holds for pinions, then a 10t 48 pinion would have an outside diameter of:

(10+2)/48 = 1/4" = .25"

and the metric (approx 50p) would be (10+2)/50 = .24"

I was just last night thinking I needed an 11t metric pinion for a Tamiya. Can I use this formula to find one?

Regards,

Steve C

[rdmac]

WARNING - WARNING - WARNING

Mongo + Metric = Cranium Cavity Explosion ( Head Go Boom-Boom )

Mongo Watch Whirlie Thingie, Mongo Go Sleep...

Mongo Watch Whirlie Thingie, Mongo Go Sleep...

Mongo See More Whirlie Thingie Here...

Bathsheba Sculpture

Do Not Pass Go, Do Not Collect $200

WARNING --- Mongo No Read Next Post --- WARNING

[rdmac]

...Anyway, if your formula still holds for pinions, then a 10t 48 pinion would have an outside diameter of:

(10+2)/48 = 1/4" = .25"

and the metric (approx 50p) would be (10+2)/50 = .24"

Hi Steve
Quick Answer... Yes the same formula will work.

I am assuming that the "approx 50 pitch" gears are actually a 0.5 millimeter "module" gear. (see attached picture for description of metric "module")
A 0.5 millimeter "module" gear would have an equivalent "pitch" of 50.8 teeth per inch ( 25.4 / 0.5 = 50.8 )

Therefore using your example for a 10 tooth pinion: (10+2) / 50.8 = 12 / 50.8 = .2362 inches



If you know the gears module you can use the formula in the pic marked in Red.
D = (N+2) x M
D = (10+2) X 0.5
D = 12 X 0.5
D = 6 mm = 6 / 25.4 = .2362 inches

Hope this helps...