[modeleng] Re: sprockets

Hi TEL,

If there is a paying customer, I'd order the sprockets from a power
transmission supplier like Browning. Hell of a lot of work to make them from
scratch from stock plate.

Good luck, Jeff Dayman Waterloo Ontario Canada



----- Original Message -----
From: "Terry Lane" <tel@xxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Monday, August 30, 2004 4:07 PM
Subject: [modeleng] Re: sprockets


> Thanks Richard - yes, the diameter is a bit flexible & that would be big
> enough. To make the problem a little clearer (?) this wheel is wanted for
> the drive system under a HO scale canal. One big sprocket at one end under
> the turning pool, two smaller ones at the other - ditto, & a couple of
idler
> wheels to hold everything in shape (coming down the narrow central canal
> section) The chain carries a series of rare earth magnets that pull the
> barges along thru' the water.
>
> We did have the whole system operating on cable drive with MDF pulleys (on
> spring arms for tensioning) but the customer wants to revert to his
original
> concept of chain drive.
>
> Once we get all this sorted it's back to getting the working lock to do
just
> that (work). And they wonder why men drink????
>
>
> > Hi Terry,
> >
> >     In imperial figures, 240 holes on 19.105" pcd will be exactly .250"
> > apart. This is only a 486.41 mm pcd, but you did say approx 500 and 240
> > holes at 1.500 degrees sounds a lot easier to me, not that I fancy
having
> to
> > drill them.
> >
> > ----- Original Message -----
> > From: "Terry Lane" <tel@xxxxxxxxxxx>
> > To: <modeleng@xxxxxxxxxxxxx>
> > Sent: Monday, August 30, 2004 11:45 AM
> > Subject: [modeleng] Re: sprockets
> >
> >
> > > Thanks Rich - now where did I put that 247 tooth gear wheel to index
it
> > > with?
> > >
> > >
> > > > Hi there Terry,
> > > >
> > > > I'd suggest the following (hoping my maths is correct):-
> > > >
> > > > Guess the number of holes - a good estimate would be to say that the
> > > > circumference of your 500mm sprocket is about pi*500mm, which is
> 1571mm,
> > > > and your pitch is 1/4"=6.35mm, which goes into the circumference
about
> > 247
> > > > times.
> > > >
> > > > Divide 360 degrees with that number - leaving 1.4575 degrees.
> > > >
> > > > Now draw out a right angled triangle in front of you, with one angle
> > very
> > > > small.
> > > >
> > > > Assume that this small angle is half of the 1.4575 degrees (0.7287
> > > > degrees), and that the side opposite this angle is half of your
pitch
> > > > (1/8"=3.175mm).
> > > >
> > > > The hypotenuse of the triangle should not be the RADIUS that you
> should
> > > > form the holes on for your sprocket for 495 teeth:-
> > > >
> > > > hole radius= 3.175mm/ sin 0.7287degrees = 249.633mm
> > > >
> > > > giving a diameter for your holes to lie on of 499.267mm.
> > > >
> > > > This doesn't allow for any clearance between the chain rollers and
the
> > > > sprocket though.
> > > >
> > > > Hope this is of some use.
> > > >
> > > >
> > > > Yours,
> > > >
> > > >
> > > > Rich.
> > > > PS 247 HOLES!!! OUCH!
> > > >
> > > > On Mon, 30 Aug 2004, Terry Lane wrote:
> > > >
> > > > > I'm sure the info is somewhere but - have any of you got a quick
way
> > of
> > > > > calculating sprocket cutting. I got a job here that calls for a
> > sprocket
> > > > > aprox 500mm diameter to drive 1/4" pitch chain. Now OK - the teeth
> > gotta
> > > be
> > > > > one pitch apart, & the holes gotta be pin dia.+?, but how do I
> arrive
> > at
> > > a
> > > > > pitch circle for the ring of holes?
> > > > >
> > > > >
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