Mini Lathe Speed Reduction.......

Gallery, Projects and General > How do I??

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Stilldrillin:
Managed an hour or so in the workshop, this aft! :thumbup:
It's been a long time, but I've been a good boy, and finished all the upstairs spring cleaning....... :ddb: :ddb:

Realised, I should check the belt tension. Someone said, should be able to comfortably turn the belt to 90*, mid longest run. All was ok.

While I was in there, I stuck some reflector tape on the pulley.........

I got some interesting results.

Running free. Forward, 4940rpm. Reverse, 3585rpm.

Belt attached.
Low gear. Forward, 5085rpm. Reverse, 3760rpm.
High gear. Forward, 5190pm. Reverse, 3860rpm.

Machine spindle. High gear, 1850rpm. Low, 790rpm.

So...... The motor runs around 100rpm faster, when driving the spindle. And 100rpm faster still, in High gear! :scratch:

It's all a mystery to me........

David D

loply:
David,

It's the motor speed controller, it supplies more power to the motor when it thinks it's needed.

Not sure exactly how it knows when the motor is bogging down but when it does it cranks up the juice.

Unfortunately the mechanism is evidently a touch crude - aside from what you've noticed it also creates an anomaly if you bog the motor down somehow (say by taking a deep cut) then it suddenly cuts more freely, the motor will over-rev before settling back down to the original speed.

Particularly noteable if you turn the variable speed right down, because it essentially turns it back up when it feels the need :clap: Generally works well though.

Stilldrillin:
Loply.
That speed controller is a clever piece of kit, if it knows the belt is fitted, or not!

I have noticed the momentary over revving, after heavy cutting.

Another puzzle, to me....... Motor spinning free, takes some seconds to come to a standstill, at switch off.
Belt connected. Despite the inertia of the chuck etc. It brakes quickly to a standstill......

These things are a bit more sophisticated than we take them for!

Anyroad! No more flashin' and poppin'. Working well, with much more torque available than before.

Thanks for posting your down gearing instructions.... :thumbup:

David D

HS93:
That information will help me greatly in the conversion of my mill , it uses the same motor and I am going to remove the gears as I don't need low speed and just have a belt drive that should get rid of the noise. Ill use just under 2 to 1 so will get about 3,000 plus max rpm.
thanks again

Peter

loply:

--- Quote from: Stilldrillin on March 19, 2012, 06:54:38 PM ---Loply.
That speed controller is a clever piece of kit, if it knows the belt is fitted, or not!

--- End quote ---

Hi David,

Yeah it is quite clever.

I'm not sure if it senses the amount of current being drawn or if it uses feedback from the digital tacho, or both, but I did once observe that my motor behaved odd when I disconnected the tacho. Perhaps it was just a coincidence though as I would suspect the current monitoring option is more likely.

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