Mini Lathe Speed Reduction.......

[John Swift]

 Hi Dave,

It may be a bit of a frankenstein machine ,but it looks good to me 

your picture answers a question of mine , how they fit the tacho into the control box
its easy , make  the box is bigger !

  John

[Stilldrillin]

Hi John.
Thanks for that! 


The readout gubbinses are fitted in the bottom of the box. (Right hand end, here)......




Just below where the leadscrew passes through!

I've fitted an angled piece of plastic under the screw, to keep it from rubbing the wiring........



Incidentally, the new belt arrangement is blummin noisy! Would a shot of WD40 do any harm? 

David D

[Bluechip]

Used to use Lubriplate # summat, can't remember, on timing belts.

Instinct says not wildly excited about hydrocarbon solvents on ( probably) rubber.

So,

Margarine, Hand cream, pork dripping etc. etc. should not do much harm.

Dunno really, helpful eh??

BC

PS Low cholesterol marge of course   

[lordedmond]

talc powder will quieten it down a bit

[PekkaNF]

Used to use Lubriplate # summat, can't remember, on timing belts.

Instinct says not wildly excited about hydrocarbon solvents on ( probably) rubber.

So,

Margarine, Hand cream, pork dripping etc. etc. should not do much harm.

Dunno really, helpful eh??

BC

PS Low cholesterol marge of course   

Agree, I would not use antything that is not intended to this use. Some belts have rubber and some polyurethane, they hate different lubricants. Some handcreams render some plastics spongy and frail. Tooth belts will cause noice, specially at high speeds. Also wrong belt tension can cause all sort of problems.

PekkaNF

[Stilldrillin]

Hmmm...... Thanks Chaps! 

I think I might have it set a little tight. Will ease it off a bit.......

David D

[PekkaNF]

I hope I don't sound here like I pretend to know something about this, because - quite frankly - I don't. However this is what I know:
* too loose and the belt will whip, too tight and it will whine
* I have broken pretty good size journal, because I was tightening the belt drive by ear. There was really little difference between "pretty good" and "even better". This even better worked for three years and then shaft bore next to cogged wheel.....
* One company recommeds hand thightening it and then further tightening of 0.4% of wheelbase. I.e 4mm per every metre of the centre of the shafts. This is on pretty high spec linear drive....rotary ones we use Trummeter.

I found this one, where is some info on pages 22 on, but if you don't have this info then it is only mildly interesting.....
http://www.mulco.net/content/en/download/res/34298-1.pdf

PekkaNF

[HS93]

out of interest did you ecer check the RPM of the motor free running ?

Peter

[Stilldrillin]

out of interest did you ecer check the RPM of the motor free running ?

Peter

No, Peter.

There's only a pifflin' little shaft on it. Very little room to stick a reflector........ 

David D

[HS93]

OK thanks

Peter

[Stilldrillin]

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


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! 

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  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.... 

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]

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

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.

[Stilldrillin]

Loply.
My tacho has no means of sensing the spindle revs, as the original machine does not have that feature. The read out stays at 0, whenever the machine is live........

I guess it must be current monitoring.........

David D

[John Rudd]

David,

I Dont know what happened to my orignal reply that should have appeared some posts further back.......

Anyhoo....Current monitoring is done by the big white resistor shown in post 26 of yours...The controller looks very much like one from KB controls..maybe the KBIC240? and no the tacho plays no part at all in the speed control of the motor...Shame you cant make use of the readout...although nothing is impossible..You could buy the sensor from one of the suppliers and add it as a retro fit...

[Stilldrillin]

Thanks John!

Don't need a readout.
Like when driving my car. (Apart from restricted zones). If it feels ok, then it is ok........ 

David D