torque
The friction wheel is on a spring loaded arm keeping it pressed against the fly wheel. The simplest way to disconnect the small friction wheel from the fly wheel would be to remove the fly wheel completely. Not the end of the world modification wise, but I find myself reluctant to do that, not sure why. Probly because I have this habit of losing parts that aren’t attached…
And yes, the rest of the moving parts don’t weigh much at all, the fly wheel is the big thing.
off grid
I definetly want the option of being able to run without plugging in. I suppose it could be as simple as buying a battery pack to plug into, but I’d prefer to have a battery wired in.
3D Printed
A custom printed part could save a lot of trouble.
What does it take to make an STL file for the printshop for this?
Remove spring?
Remove the spring and tie it back?
spring
The springs are part of the hinges. I was just debating just tucking a wedge in to keep it away from the fly wheel. I think I’d rather go with the edge drive setup, but it gives me another option…
velocity
"Velocity is “2 * pi * radius * RPM”."
RPM I want the motor to run at or the RPM I want the fly wheel to run at? I’m assuming the fly wheel RPM…
Batteries
NiMH (nickle metal hydrate) I think.
A lot less trouble than the alternatives. You can either buy an RC battery as a single ~12V unit, or buy AA batteries. Panasonic Eneloop are a good choice.
After you pick a motor we can figure out how big a battery you need.
Edge driven
If you edge drive, take the diameter of the flywheel and divide it by the diameter of the drive wheel. That gives you the “gear” ratio.
Multiply that by the treadle RPM you prefer and that will get you the required regulated speed.
I should add for the same size new drive wheel. If the new drive wheel is twice as big the motor would have to be half the speed.
math
Ok, now to do a bunch of math…
Edge Drive Updated
I rewrote this post to make it a little easier to understand:
If you edge drive, take the diameter of the flywheel and divide it by the diameter of the drive wheel. That gives you the “gear” ratio.
Multiply that by the treadle RPM you prefer and that will get you the spinner speed.
If the new drive wheel is the same size then that is the regulated speed you need. If the new drive wheel is twice as large, divide the spinner speed by 2.
The motor you choose will need to be much faster as it will be regulated down.
RPM
Speed of the component you are trying to calculate the torque on. Could be just the bobbin if that is of interest. To be super nit picky we could compute them all and add or we could do the heaviest and fudge.
Math
EDITED
Ok. Fly wheel is 14.25" in diameter (or radius 7.125"). Rubber drive wheel (thats currently on the wheel, there are options, but going with whats infront of me) is 2" in diameter. This gives me a ratio of 7:1 which is what the manufactuor says it should be, so thats good.
ggallant’s guesstimate of 120RPM might be high, after talking with some other spinners. I’ve never tried to calculate the RPM I treadle at, but between 60 and 100 seems to be more normal. So 75 * 7 = 525RPM though obviously the wheel that goes on the motor for the edge drive would affect that.
ok, so velocity would be 2 * 3.14 * 7.125 * 75 = 3355.875" or 279.66’?
math
so plugging those numbers into the linked to calculator I get THIS.
Does that look reasonable? If I do an accel of more than 6ft/s^2 the calculator doesn’t like it, though I could probly still work with its results.
Looks good
I will repeat the calculations Some place there should be a torque. Did you look at the next section?
Error in calculations
They wanted feet per second. You entered feet per minute.
Possible motor
The following is a very powerful motor. Just for example. Assuming a belt drive system with a 5:1 reduction, this solution would deliver approx 24Kg/m torque to the wheel. My calculations (iffy at best) using the RFM calculator are that this is about 16 times what you would need. It is about $30.00US on ebay. 480g-cm == 4.80kg-m. The 5:1 will multiply this to 24kg-m.
Buehler 12V 500 RPM - Heavy Duty Gearhead DC Motor - Very High Torque Output - Low Current Demand
Another
My feeling is that a little faster is better:
$17.50 free shipping…
Quite useable
The whole drive mechanism needs to be geared down such that the flywheel rotates somewhere around 75 RPM. Might be nice to have the range go higher, ie 120, if the 75 assumption proves false.
I hope ruthcatrin doesn’t send me to internet purgatory for calculating torques and then proposing motors that wildly exceed the requirements. Unless of course I erred and am off by a factor of 100. In which case the wheel just eats motor driver boards.
hah
I’d rather have a more powerfull motor that I don’t use the full capacity of, than in a few months discover I didn’t get one powerfull enough!
Just got home from work so I haven’t had a chance to look at the links you both posted yet.
error
"They wanted feet per second. You entered feet per minute."
K, what number should I have entered and how do I get it from what I had?
