"DoN. Nichols" wrote in message
...
[...]
I cannot imagine that a lot of torque was required of Singer sewing
machines. What hapens to torque at the lowest speeds?
Enough to handle sewing through leather to make thumbstraps for
English system concertinas. (Granted, you are part of the feedback,
adjusting the pressure as needed to maintain the speed which you can
work with.
That cleared that up...:-)
[ ... ]
I got one of them drills, too. But again, what happens to the torque at
the
low speed if using a rheostat? On mine there is a slow start feature
which I
take to be nothing more than a rheostat. I can stop the chuck by hand at
the
low speed.
At absolutely the lowest speed, yes it is easy to stall. If you
have a foot pedal, you are adjusting the pressure to maintain the speed
you want, so it is no problem.
It is standing on one leg while turning I am a bit concerned about :-)
And remember that you are also *first* using the maximum *belt*
speed reduction to keep the motor's speed up a bit.
The whole thing (Singer, foot pedal etc.) has a certain attraction to it. A
sort of Kalashnikov feedback. When the time comes I shall explore this
concept.
I got a 13.6V 20A power supply - that's 1/3HP.
Just 13.6V or variable voltage all the way down to zero? If the
latter, you can use it with a 12V drill motor to get variable speed.
It is fixed but making a solid state voltage controller is no problem.
Others have put me off doing that because of the feedback issues discussed
earlier.
[...]
O.K. Looking in McMaster Carr's web site, I find 1/2" wide belt
pulleys with a 0.200" pitch (MXL series). Let's see the largest
which will fit within 5" diameter.
The range for this size is 60 teeth max and 10 teeth minimum, or
6:1 ratio.
OD Teeth Bore Cat No Price
0.87" 10 3/16" 57105K11 $7.40
1.13" 14 1/4" 57105K14 $7.51
3.80" 60 5/16" 57105K33 $17.15
So -- if you need to fit it on a 1/4" shaft, you will need at leat 14
teeth (60:14 ratio, or about 128 RPM for 550 RPM in.
If you can turn the end of the shaft down to 3/16", you get a full 6:1
ratio, or 91 RPM.
These (and others) are on McMaster Carr's catalog page 1044 via
the web. (You'll also need to select a belt to fit including the
proper spacing between pulleys.) The pulleys which I have listed are
acetal plastic, and I would suggest that you go for the steel ones
listed a bit later in the page for stronger gears. And you'll
probably need to pin
the hubs instead of just use setscrews to get enough strength with the
small diameter shafts.
This would mean turning the spindle shaft down to at least 3/8". I do not
think this is possible. AFAIK the spindle is 5/8" with a 5/16" ID. Some
of
the plain bore pulleys have large enough bores but maximum of 24 teeth
or
so.
Look at the hub diameter in the pulley data. You should be able
to bore it out to fit the existing spindle. I would *never* consider
turning down the spindle to fit the pulley -- always modify the least
expensive and easiest to replace part.
I somehow asumed that it was not a done thing to bore out the *finished*
pulleys as they make the plain pulleys that *are* meant to be bored to
specs.
Looking at the 57105K3 the hub is 7/8" which after boring to 5/8" ID would
leave walls 1/8" thick. You think that is all right? The 6495K733 is steel
and has a 1.5" hub.
The other issue I thought was that using the exisiting Taig step pulley on
the countershaft together with, say, 6495K713, would lead to an ID
mismatch which could not be corrected by boring alone (this one has a hub of
only 1/2"). Some sort of bushing for the Taig pulley perhaps?
And you won't want to be stepping up speed to the spindle, so
the larger pulley will be on the spindle, thus with the largest hub
diameter too.
Or -- go for the taper-lock type hubs where you can change hubs
to fit the shaft once you have the right pulley.
Presumably you are referring to something like this: 6495K222. The cost is
getting up there.
It is beginning to feel like trying to make a silk purse out of a sow's
ear.
Some limitations will have to be accepted I think.
:-)
12" swing,
Increased rigidity,
The Holy Grail...
How about 18" swing or larger? :-) It all depends on what you
want to make. In this case, how large a dial do you want for your
sundials? You *could* use a gap-bed lathe for that -- but there can be
problems getting the gap insert back in precisely enough so it does not
affect accuracy of turning close to the headstock.
I do know that I occasionally find projects which would go
better with a larger lathe -- but I don't really have room for one.
Oh, about 12 feet I guess:
http://www.milesfaster.co.uk/gallery...k/sun-dial.htm
But one has to walk before one can run. Also one must consider the size of
the etching bath, how many gallon bottles of Ferric Chloride one would need,
etc...
--
Michael Koblic
Campbell River, BC