odd pitch on Tower Hobbies Nitro ST-15? Help!

[Buzz]

I want to know the pitch of the spur gear on my Tower Hobbies Nitro
ST-15. So I learned how to figure it out. I measure the diameter
including the tooth on one side but not the other. Then take the
number of teeth and divide by the diameter. I have a few pinion gears
around from my electric motors, so I tested my math with these:
pinion #1: 10 teeth, 5/16" diam. 10/0.3125 = 32 pitch!
pinion #2: 14 teeth, 7/16" diam. 14/0.4375 = 32 pitch!

ST-15 spur gear: 45 teeth, 1 3/4" diam. 45/1.75 = 25.71 pitch?
ST-15 "top gear" in gear box: 10 teeth, 3/8" diam. 10/0.375 = 26.7
pitch?

Tower's write-up says it has a "48-pitch tranny". Wouldn't that mean
the "top gear" in the gear box would be 48 pitch? I took the top gear
out and rolled it around the spur gear and they are the same pitch. I
realize there is no reason the spur gear needs to be the same pitch as
the gears in the gear box, but it is... and so I ran it though the
calculations as another test point. I understand my measurements
aren't perfect but I thought it would be obvious what the pitch for
these are.

Do I need to measure these in metric or something? What's the deal?
Thanks for any insight.
Buzz

[Jonathan Hodgson]

On 7 Jul 2004 05:58:20 -0700, Buzz wrote:

> I want to know the pitch of the spur gear on my Tower Hobbies Nitro
> ST-15. So I learned how to figure it out. I measure the diameter
> including the tooth on one side but not the other. Then take the
> number of teeth and divide by the diameter. I have a few pinion gears

Sounds like a good method to me :-)

> ST-15 spur gear: 45 teeth, 1 3/4" diam. 45/1.75 = 25.71 pitch?
> ST-15 "top gear" in gear box: 10 teeth, 3/8" diam. 10/0.375 = 26.7
> pitch?

> Do I need to measure these in metric or something? What's the deal?

1.75" = 44.45 mm... 44.45 / 45T = 0.98777 module
similarly, the 10T would be about 0.95 module...

How close to exact are those values of 3/4" and 3/8"? They sound like
they could be 1 module (diameters of 45 and 10 mm).

HTH,
Jonny

[buzzweetman]

Sweet. I measured in mm this time, and I get 45mm for the 45 tooth spur, and 10mm for the 10 tooth top gear. I measured my clutch bell and I get 15mm, and guess how many teeth it has... 15!
So it looks like you are right. 1.0 module.

Thanks for your help!
Buzz

[buzzweetman]

OK. So I've determined it is a module 1.0 pitch. But why does it say it is "A 48-pitch tranny".
Here is the link that says it:
http://www.towerhobbies.com/products/towc0055.html

The gears in the gearbox obviously mesh together, and I just figured the top gear in the gear box is 1.0 module. I have a few 32 pitch pinions that clearly have finer teeth... so 48 pitch would be even finer. Right?

Ok... this chart agrees with me:
http://www.engineersedge.com/gear_pitch_chart.htm

Must be a mistake by Tower, right?
Buzz

[Dean]

On Thu, 8 Jul 2004 18:36:53 -0500, buzzweetman
<buzzweetman.193r0b@rcgroups.com> wrote:

>"A 48-pitch tranny".

From what I know, the "48 pitch" in r/c is a standard that only
applies to r/c, and is based on some arcane measurement of pitch that
isn't normally used. All pinions and spurs in nearly all 1/10 buggy
or truck are this "48 pitch"

-Dean
---
Proud owner of:
Associated RC10GT <the other basher>
Team Losi XX "CR" <the basher>
Team Losi XXX KE <the racer>
http://ripperd.com
email: dean (at) the above domain

[Justin]

RC cars use Diametrical Pitch, which is fairly standard and easily looked up
on the web. Diametrical Pitch can be found by dividing the number of teeth
on the gear by the diameter of the gear in decimal inches.

Thus, a 48 pitch gear which is one inch wide would have exactly 48 cogs or
teeth.


"Dean" <look@sig> wrote in message
news:2iste0hp6s2pga47rlo9hd04co430dmujn@4ax.com...
> On Thu, 8 Jul 2004 18:36:53 -0500, buzzweetman
> <buzzweetman.193r0b@rcgroups.com> wrote:
>
> >"A 48-pitch tranny".
>
> From what I know, the "48 pitch" in r/c is a standard that only
> applies to r/c, and is based on some arcane measurement of pitch that
> isn't normally used. All pinions and spurs in nearly all 1/10 buggy
> or truck are this "48 pitch"
>
> -Dean
> ---
> Proud owner of:
> Associated RC10GT <the other basher>
> Team Losi XX "CR" <the basher>
> Team Losi XXX KE <the racer>
> http://ripperd.com
> email: dean (at) the above domain

[Dean]

So maybe not quite so arcane...

On Fri, 9 Jul 2004 14:45:39 -0500, "Justin"
<gabril@panties.tcainternet.com> wrote:

>RC cars use Diametrical Pitch, which is fairly standard and easily looked up
>on the web. Diametrical Pitch can be found by dividing the number of teeth
>on the gear by the diameter of the gear in decimal inches.
>
>Thus, a 48 pitch gear which is one inch wide would have exactly 48 cogs or
>teeth.
>
>
>"Dean" <look@sig> wrote in message
>news:2iste0hp6s2pga47rlo9hd04co430dmujn@4ax.com...
>> On Thu, 8 Jul 2004 18:36:53 -0500, buzzweetman
>> <buzzweetman.193r0b@rcgroups.com> wrote:
>>
>> >"A 48-pitch tranny".
>>
>> From what I know, the "48 pitch" in r/c is a standard that only
>> applies to r/c, and is based on some arcane measurement of pitch that
>> isn't normally used. All pinions and spurs in nearly all 1/10 buggy
>> or truck are this "48 pitch"
>>
>> -Dean
>> ---
>> Proud owner of:
>> Associated RC10GT <the other basher>
>> Team Losi XX "CR" <the basher>
>> Team Losi XXX KE <the racer>
>> http://ripperd.com
>> email: dean (at) the above domain
>

---
Proud owner of:
Associated RC10GT <the other basher>
Team Losi XX "CR" <the basher>
Team Losi XXX KE <the racer>
http://ripperd.com
email: dean (at) the above domain

[Justin]

Trust me, no standard that man can dream up is too arcane for another man
(as in human) to understand.


"Dean" <look@sig> wrote in message
news:9j1ue0pc3v77u1tfe8hfq6sm4prapuru2a@4ax.com...
> So maybe not quite so arcane...
>
> On Fri, 9 Jul 2004 14:45:39 -0500, "Justin"
> <gabril@panties.tcainternet.com> wrote:
>
> >RC cars use Diametrical Pitch, which is fairly standard and easily looked
up
> >on the web. Diametrical Pitch can be found by dividing the number of
teeth
> >on the gear by the diameter of the gear in decimal inches.
> >
> >Thus, a 48 pitch gear which is one inch wide would have exactly 48 cogs
or
> >teeth.
> >
> >
> >"Dean" <look@sig> wrote in message
> >news:2iste0hp6s2pga47rlo9hd04co430dmujn@4ax.com...
> >> On Thu, 8 Jul 2004 18:36:53 -0500, buzzweetman
> >> <buzzweetman.193r0b@rcgroups.com> wrote:
> >>
> >> >"A 48-pitch tranny".
> >>
> >> From what I know, the "48 pitch" in r/c is a standard that only
> >> applies to r/c, and is based on some arcane measurement of pitch that
> >> isn't normally used. All pinions and spurs in nearly all 1/10 buggy
> >> or truck are this "48 pitch"
> >>
> >> -Dean
> >> ---
> >> Proud owner of:
> >> Associated RC10GT <the other basher>
> >> Team Losi XX "CR" <the basher>
> >> Team Losi XXX KE <the racer>
> >> http://ripperd.com
> >> email: dean (at) the above domain
> >
>
> ---
> Proud owner of:
> Associated RC10GT <the other basher>
> Team Losi XX "CR" <the basher>
> Team Losi XXX KE <the racer>
> http://ripperd.com
> email: dean (at) the above domain

[buzzweetman]

Right... so my 45 tooth gear with 1.75 inch diameter would be:
45/1.75 = 25.71 pitch
Not the 48 pitch that tower says... even if I am off by a 1/16 or two in my diameter.
But 45/45cm = a metric pitch of 1.0, or 1.0 module.
I'll have to ask Tower what's up.

Buzz

[QUOTE=Justin]RC cars use Diametrical Pitch, which is fairly standard and easily looked up
on the web. Diametrical Pitch can be found by dividing the number of teeth
on the gear by the diameter of the gear in decimal inches.

Thus, a 48 pitch gear which is one inch wide would have exactly 48 cogs or
teeth.

[Justin]

You're probably right, but I really think you mean 45mm. ;-)

"buzzweetman" <buzzweetman.195loa@rcgroups.com> wrote in message
news:buzzweetman.195loa@rcgroups.com...
>
> Right... so my 45 tooth gear with 1.75 inch diameter would be:
> 45/1.75 = 25.71 pitch
> Not the 48 pitch that tower says... even if I am off by a 1/16 or two
> in my diameter.
> But 45/45cm = a metric pitch of 1.0, or 1.0 module.
> I'll have to ask Tower what's up.
>
> Buzz
>
> Justin Wrote:
> > RC cars use Diametrical Pitch, which is fairly standard and easily
> > looked up
> > on the web. Diametrical Pitch can be found by dividing the number of
> > teeth
> > on the gear by the diameter of the gear in decimal inches.
> >
> > Thus, a 48 pitch gear which is one inch wide would have exactly 48 cogs
> > or
> > teeth.
>
>
> --
> buzzweetman
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