Subject: Sprocket cutting
From: (Claude P)
Date: 17/07/03 00:03 GMT Daylight Time
Message-id:

Hi guys, could anyone tell me what would be the best way to cut a 5
teeth sprocket for a 3/8 pitch chain.

Yes, don't. That's not enough teeth for a sprocket to work properly.


Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
"How's life Norm?"
"Not for the squeamish, Coach" (Cheers, 1982)

On 16 Jul 2003 16:03:21 -0700, (Claude P) wrote:

Hi guys, could anyone tell me what would be the best way to cut a 5
teeth sprocket for a 3/8 pitch chain.
Thank you in advance.

I made a six tooth for my snowblower, this small a sprocket will only
work at very low speed. Anyway, here was my steps.

1. measure diameter of roller. Use a drill 1/64 over this size to
drill the base of all the sprocket teeth.

2. Do a layout of holes around a circle with the distance between
holes the chain distance. In your case, you're drawing a pentagon, 5
holes on a circle with the distance between holes 3/8 of an inch. You
need to find the diameter of the circle that solves this. In my case,
I used autocad.

3. Using a rotary table, drill the center hole and sprocket holes in
your disk.

4. I faked in the tooth ends with a bandsaw and finished with a die
grinder. If you're into perfection, the sprocket side is defined by an
arc centered at the center of your drill hole with a radius equal to
the distance from the center of one roller to the inside edge of the
next roller.


Hope this helps.

I now have access to master cam. It will draw up the sprocket in just
seconds. Then run it on a CNC mill. My son has made several perfect
sprockets this way for his four wheeler.



Karl

Not enough teeth for it to work properly, don';t waste your time.


On 16 Jul 2003 16:03:21 -0700, (Claude P) wrote:

x-Hi guys, could anyone tell me what would be the best way to cut a 5
x-teeth sprocket for a 3/8 pitch chain.
x-Thank you in advance.
x-
x-Claude.

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That sprocket is only .6380 pitch diameter. On most chains, by the time
you get the depth for the bottom diameter you would have no room at all
for a bore.

The worst part, however, is the chordal speed variation. Because the
chain travels around the sprocket as a series of chords rather than a
smooth level, there is a speed variation imparted either to the sprocket
(as an idler) or to the chain (if the sprocket is driving) with each
tooth engagement. In this case that speed variation is 19.1%. In some
cases this speed variation is enough to essentially beat the system
apart. (picture beating the system with a dead blow hammer at 19% of the
load with each tooth that engages)

Another side affect of this speed variation is harmonics. If you hit
the right speeds with it, it will send some nasty harmonic vibrations
down the chain and cause a high degree of whipping. Most people get
beyond this by increasing tension...the end result of this is generally
to wear things out in short order.

Koz

Claude P wrote:

Hi guys, could anyone tell me what would be the best way to cut a 5
teeth sprocket for a 3/8 pitch chain.
Thank you in advance.

Claude.

Thanks for your responses.
As it turns out I found another sprocket and now have to make an eight
teeth sprocket. The maximum rpm for this sprocket will be 7000 rpm.
can this still be done with an eight teeth sprocket or should I
consider gearing down some other way? What about a torque converter?
Is there one for small engines? Can I build one?
Claude.

Koz wrote in message ...
That sprocket is only .6380 pitch diameter. On most chains, by the time
you get the depth for the bottom diameter you would have no room at all
for a bore.

The worst part, however, is the chordal speed variation. Because the
chain travels around the sprocket as a series of chords rather than a
smooth level, there is a speed variation imparted either to the sprocket
(as an idler) or to the chain (if the sprocket is driving) with each
tooth engagement. In this case that speed variation is 19.1%. In some
cases this speed variation is enough to essentially beat the system
apart. (picture beating the system with a dead blow hammer at 19% of the
load with each tooth that engages)

Another side affect of this speed variation is harmonics. If you hit
the right speeds with it, it will send some nasty harmonic vibrations
down the chain and cause a high degree of whipping. Most people get
beyond this by increasing tension...the end result of this is generally
to wear things out in short order.

Koz

Claude P wrote:

Hi guys, could anyone tell me what would be the best way to cut a 5
teeth sprocket for a 3/8 pitch chain.
Thank you in advance.

Claude.

In article bfcb5f69.0307171701.3dd633d2
@posting.google.com, says...
Thanks for your responses.
As it turns out I found another sprocket and now have to make an eight
teeth sprocket. The maximum rpm for this sprocket will be 7000 rpm.
can this still be done with an eight teeth sprocket or should I
consider gearing down some other way? What about a torque converter?
Is there one for small engines? Can I build one?

Even though (much to my surprise) the Dodge book shows #35
9T sprocket running at 7000RPM in the HP chart, I'd be
looking for another reducer. I'd expect noise and vibration
to be pretty awful, and lubrication is going to be a
problem--enclosed oil bath is recommended at those speeds.

Any chance of using a timing belt, at least for a first
stage?

Ned Simmons

On 17 Jul 2003 18:01:57 -0700, (Claude P) wrote:

Thanks for your responses.
As it turns out I found another sprocket and now have to make an eight
teeth sprocket. The maximum rpm for this sprocket will be 7000 rpm.
can this still be done with an eight teeth sprocket or should I
consider gearing down some other way? What about a torque converter?
Is there one for small engines? Can I build one?
Claude.

Koz wrote in message ...
That sprocket is only .6380 pitch diameter. On most chains, by the time
you get the depth for the bottom diameter you would have no room at all
for a bore.

The worst part, however, is the chordal speed variation. Because the
chain travels around the sprocket as a series of chords rather than a
smooth level, there is a speed variation imparted either to the sprocket
(as an idler) or to the chain (if the sprocket is driving) with each
tooth engagement. In this case that speed variation is 19.1%. In some
cases this speed variation is enough to essentially beat the system
apart. (picture beating the system with a dead blow hammer at 19% of the
load with each tooth that engages)

Another side affect of this speed variation is harmonics. If you hit
the right speeds with it, it will send some nasty harmonic vibrations
down the chain and cause a high degree of whipping. Most people get
beyond this by increasing tension...the end result of this is generally
to wear things out in short order.

Koz

Claude P wrote:

Hi guys, could anyone tell me what would be the best way to cut a 5
teeth sprocket for a 3/8 pitch chain.
Thank you in advance.

Claude.


It would probably help to know what you are building.... 7K is pretty
fast, even for a belt. You may want some kind of a gearbox.
Ken.