belt down mod for hitorque lathe.

[MCRIPPPer]

hi guys. a few months back i was thinking about making a speed reducer for my mini lathe. some guys recommended using poly-v/ micro-v belts, so i ordered some up and got them a while ago. i also bought some material and have made a part once in a while and have finally got something going. pictures are worth a thousand words, so here you go.


some of the parts



all the pulleys





here is the cutting tool i made for the job.


























mocked up















minimum speed in low range is 27rpm, max is 825rpm , with significant torque. will be good for threading and tapping. ratio from chuck to motor is about 7:1 (original belt is 2:1). to measure the speed i used a home made worm wheel and screw. timed how long it took to advance 310 teeth (the gear had some weird number and i just counted the tens to make it easy). it took over 11 minutes at low speed!


i still need to make proper tensioners for the belt. even with incorrect tension on the belts it has more usable power than before!

 

[David Kirtley]

How do you tension the belt between the motor an jack shaft?

 

[MCRIPPPer]

with a tensioner. i still need to make it. it is just thrown together into working order right now. not quite done.

 

[6sigmaford]

Excellent mod, very clean. Multi-groove belts are very tough and last.

 

[Rbeckett]

I like it!!!! 27 RPM is a nice slow speed for tapping and thread cutting. Did all the change gear and threading positions stay the same or do you have to recalculate everything based on the new gear ratios too? 7:1 should preserve a lot of available torque at low speeds and keep motor heating to a minimum too. Thanks for the pics!!

Bob

 

[MCRIPPPer]

thanks guys. hopefully i can get back to work on it soon. its been raining here and i have been working on making my workshop weatherproof.

I like it!!!! 27 RPM is a nice slow speed for tapping and thread cutting. Did all the change gear and threading positions stay the same or do you have to recalculate everything based on the new gear ratios too? 7:1 should preserve a lot of available torque at low speeds and keep motor heating to a minimum too. Thanks for the pics!!

Bob

yes slow speed is nice for things like that.

im not sure what you are really asking but threading ratios will stay the same because they are still driven off of the spindle, but i need to make a new mounting plate for the tumblers because of the large pulley not allowing the stock piece to fit.

 

[12bolts]

Nice job! Thats some substantial stock there that you made the pulleys from. Are they cut out of thick plate or.......?

Cheers Phil

 

[MCRIPPPer]

made from 3" diameter aluminum 6061 round.

it was a real pain to hack saw the parts out! i think i paid about $35 U.S. for a 12" long piece. the smaller ones were machined from 1.5". had to use my 4 jaw to machine the big pulleys because my 3 jaw won't hold that size material.

 

[LEEQ]

I look forward to seeing your tensioner. Very nice looking project!

 

[MCRIPPPer]

built the first tensioner today.

first get out the 4 jaw.





then i put it into the 3 jaw to face the other side.



i used my lathe as a "rotary shaper"



then i milled it a little





machining the idler pulley





i drilled the holes 5/16 so that an 8mm shaft is a tight press fit. the longer shaft took a few tons to press.
thankfully i have a 20t press from harbor freight!

i cross drilled and taped the smaller shaft so that im sure it wont come out.