Clarke CL300

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Clarke CL300

This topic has 52 replies, 8 voices, and was last updated 5 December 2013 at 10:26 by David Heath 1.

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5 October 2011 at 09:42 #75846
Kiaran Walker
Participant
@kiaranwalker64939
Hello to all. I have the Clarke CL300 mini lathe for four years and is in regular use.
It was still ok to use when the variable speed switch broke as I was using the forward/reverse switch to power off and the potentiometer was still ok, the idle speed is zero with no power to the motor until about an eighth of a turn. After a while on the odd occasion when the switch kicked in the motor would surge as if to run full speed for just a second. Now after finding the impressive amount of CL300 info. on this site I have fitted a new maplins potentiometer, new irfp450 mosfets and a new C14 capacitor, C4 on my board. Now it runs as well as ever apart from the surge to the motor when the power is turned by the variable switch but only for the first time then is ok to on/off until the power is offed then it surges again on the first power on. Using the emergency switch to cut power and restart also causes the surge. So not really a huge problem as it can worked around but something is miss somewhere. I wired the control box up to my mini mill with the same result to rule out the motor and I don’t think the new mosfets or C14 made any difference. Something simple I hope.
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5 October 2011 at 09:42 #38077
Kiaran Walker
Participant
@kiaranwalker64939
Surge
5 October 2011 at 12:20 #75857
john swift 1
Participant
@johnswift1
Hi Kiaran

the capacitor C4 (or C14 for SMT board ) is only needed if the relays buzz

the change in contact resistance ,using the potentiometer from maplin

could affect the minimum speed setting and a small DC error cause the

burst of high speed when starting from cold

have a look at the “speed control for Clarke CL300 lathepost –   page 2 3rd post

    http://www.model-engineer.co.uk/forums/postings.asp?th=38809&p=2

with the switch in forward direction

set the ” speed” preset R15 on the PCB for the required minimum speed

and R15 for minimum buzz

if you can , avoid the “torque” preset   R37

unless you know its been incorrectly adjusted

John

Edited By john swift 1 on 05/10/2011 12:43:20
5 October 2011 at 15:30 #75861
Kiaran Walker
Participant
@kiaranwalker64939
John, thanks for the quick response, extremely impressed with your know-how. I did read all the other posts and have fiddled around with speed preset with no change, hopefully it’s back where it started. The R12 quietened things down pretty well. The zero speed at switching on is how it’s been from new and I’m pretty sure the surge developed before fitting the maplin potentiometer, if I short out the potentiometer switch will that rule it out?. Don’t have a tester or much idea of what to do with one.

Cheers, Kiaran

Edited By Kiaran Walker on 05/10/2011 15:31:37
5 October 2011 at 16:00 #75862
Gone Away
Participant
@goneaway
Interesting Kiaran.

I have a generic asian 7x minilathe (not Clarke) and I have a similar situation. The first time I switch on with the speed control switch everything works normally. Every (or most) subsequent times I get the speed surge. This goes on until I cut power at the main on-off switch.

I think this is actually opposite to yours by the sound of it.

As far as I recall, it’s always done this from new – so much so that I’ve assumed it’s normal operation. It’s not really a problem so I’ve never bothered with it.
5 October 2011 at 16:28 #75863
john swift 1
Participant
@johnswift1
Hi Kiaran ,

thats great that its working OK now

if you can start the motor at minimum speed and it dosen’t start at a higher speed

the switch is working correctly

while the control looks like the switch and volume control used in radios and tv’s etc

the switch works the other way round

when you would expect it to be off its on , and vise versa

the switch on the back of speed control potentiometer is only used to start the motor at minimum speed , provided the motor direction switch is in forward or reverse ( but not stop)

one of the relays wired across the switch maintains the supply when the switch opens as you increase the speed

the other relay switches the DC power to the motor

this makes you start at minimum speed to protect the motor and speed control

and provide the no volt release so if the mains goes off, it doesn’t restart by its self

when the mains supply is restored

depending on the type of preset used on your version of the board

the setting of the preset could of moved

or the effects of heat generated by the high wattage resistors has cause the alignment of the board to drift

John
5 October 2011 at 16:42 #75864
Kiaran Walker
Participant
@kiaranwalker64939
John,

A bit confused now, the minimum speed starting as normal is still zero rpm as it has always been but the surge at power on remains, I was going to short the switch as a check to remove it from the equation.

Kiaran.
5 October 2011 at 16:44 #75865
Kiaran Walker
Participant
@kiaranwalker64939
Hi Sid,

This problem is definaitly new to mine after four years, it makes me jump every time now.
Because my idle speed is zero I can just leave it not running without using the switch
as I had been doing with the old damaged one. Does changing direction and going through
the off position count as powering off and so allow you a normal start in reverse?.

Cheers, Kiaran.
5 October 2011 at 19:01 #75870
john swift 1
Participant
@johnswift1
Hi Kiaran

Hmmm It looks like I miss read your last post

the boards I’ve seen had a minimum speed of 30 to 50 RPM

if its set to zero speed

there is still a voltage across the motor and quickly switching direction could shorten the life of the switch

provided the speed control is at minimum when you switch the mains on

you can test the board with the switch bypassed

which version of the board do you have? the one with the square blue multiturn ones?

John
5 October 2011 at 19:47 #75871
Kiaran Walker
Participant
@kiaranwalker64939
John

Sorry for any confusion it’s a bit difficult to get into words sometimes.

When I say minimum speed I mean the speed it runs at when the power is switched on which is zero rpm, after about an eighth of a turn the power kicks in and the idle speed is as you say 30 rpm (got a wilkos cycle speedo rigged up).

I’ve by-passed the switch and there is still a surge at power on.

The board has small blue oblong multiturn adjusters.

Kiaran
5 October 2011 at 20:29 #75872
Kiaran Walker
Participant
@kiaranwalker64939
With the switch by-passed I swapped back the old potentiometer, hey presto I think the term is, all normal and no surge, the original pot. says B4.7K, maplin gave me 47KA, could this be it.

Kiaran.
5 October 2011 at 21:05 #75874
john swift 1
Participant
@johnswift1
Hi Kiaran

yes thats it , the original control is linear

“volume” controls are logrithmic !!!!!

I thought I’d made a note of it in the speed control post

you need one from Machine Mart , Arc Euro Trade or Chester machine tools,etc that sell the lathes

I’m slightly distracted at the moment

since the last upgrade of my antivirus software ,I not been able post on this forum

till now

so far it apears the forums IT dept has not replied to my email to Diane

so I’ve installed windows and some another antivirus package on another drive !!

at the moment ,windows is having another go at its 50+ updates !!!!!

John

Edited By john swift 1 on 05/10/2011 21:36:01
5 October 2011 at 22:14 #75878
Gone Away
Participant
@goneaway
Posted by Kiaran Walker on 05/10/2011 16:44:11:

Does changing direction and going through

the off position count as powering off and so allow you a normal start in reverse?.

Er … offhand I dunno. Can’t ever remember actually using reverse.

I’ll try it when/if I can but it may be a little while. I’m interdicted on using that machine at the moment…… something’s putting noise on my ICD-pacemaker leads (not a happy situation), likely something in the shop. That lathe is one of the suspects so I’m staying off it for a while.
6 October 2011 at 09:03 #75881
Kiaran Walker
Participant
@kiaranwalker64939
Hello again John,

nearly there with this now, it looks like Maplins pots are available in linear and logarithmic, I have store a few miles away and took the old one in and asked for a replacement and took what was given, so if I go back and ask for a linear one might that be ok?, also is it a 47k I need, the original says 4.7k, they have a 4k7 just to confuse more.

Nearly done, thanks a lot,

Kiaran.
6 October 2011 at 10:34 #75884
Steambuff
Participant
@steambuff
Hi

4.7k is 4k7

Also did someone say the switch was reversed. (Closed when Off … and not open when off) – You won’t get one of these at Maplin … I’ll check my spare switch/pot I got from ArcEuro for my Sieg Mill.

Dave

Edited By Steambuff on 06/10/2011 10:36:29
6 October 2011 at 13:28 #75902
Kiaran Walker
Participant
@kiaranwalker64939
Done and done,

Cheers Dave, been to maplins, got and fitted a 4k7 and all is perfect, was given a 47k the first time so it obviously makes a difference. Will be back for a couple of spares for two quid each.

Thanks to all, much appreciated.

Kiaran.
6 October 2011 at 22:11 #75918
john swift 1
Participant
@johnswift1
Hi kiaran

glad to see its working

just double checking whats the catalogue number ?

does the switch work the correct way ?

PS 4.7k = 4K7 , putting the K in place of the decimal point avoids any confusion

with low resolution copies of circuits & parts lists

Hi Steambuff

the switch should be closed when the speed control is fully anticlockwise

this powers the coils in the relays to start , just as the green start button does on a direct on line starter

the switch opens as you turn the control clockwise to set the required speed

one of the relay contacts maintains the power to the relay coils and the

speed control circuit until you hit the stop button or switch the direction switch to off

this gives you the “no volt release” function

and ensures you have to turn the speed to minimum to start

protects the motor and speed control provided you don’t switch direction

too quickly with the motor running

John

Edited By john swift 1 on 06/10/2011 22:14:41
6 October 2011 at 22:29 #75919
Kiaran Walker
Participant
@kiaranwalker64939
Hi John,

cat. number is FW41U, all functions working as normal so far.

Cheers,

Kiaran.
7 October 2011 at 21:11 #75961
Sub Mandrel
Participant
@submandrel
Just to clarify John’s point about logarithmic pots:

“the original pot. says B4.7K, maplin gave me 47KA, ”

“A” means a logarithmic pot and “B” means a linaer one.

On a ‘B” pot the resitance changes evenly by the same amount, while for an “A” pot the resistance increases slowly at first, faster as you continue to turn it (clockwise, usually).

If the mini lathe is set up for a ‘B’ pot with an ‘A’ pot the speed conrol will not work quite as expected, it will be insensitive at the low end and too sensitive at the top end..

Neil
7 October 2011 at 22:06 #75972
Kiaran Walker
Participant
@kiaranwalker64939
Curious one, all maplins switched pots. are listed as linear yet both supplied to me are marked A, the last one has 4k7A stamped on the side but is listed FW41U Sw Pot Lin 4k7, got to be linear.

Kiaran.
8 October 2011 at 11:40 #75988
john swift 1
Participant
@johnswift1
it looks like there is two standards to indicate if the potentiometer is log or linear

old system , linear = A , new system linear = B !!!!

may be it was the same bright spark that thought its a good idea to use blue as the new neutral colour when it has been use to ident one of the three phases for years —

http://sound.westhost.com/pots.htm

the switch on the maplin part works the wrong way

while the lathe will work you will lose the no volt release function

you may be able to find a potentiometer with a double throw switch ( change over switch)

Omeg ltd for instance will make them to order in a small quantity

(but its a bit expensive if you only need one !!!)

John
8 October 2011 at 13:23 #75997
Kiaran Walker
Participant
@kiaranwalker64939
Hi John,

The only difference for me I can tell is that the emergency cutout acts like an on/off with the motor restarting itself when it’s released, think I had to reset before to resume power.

Will the maplin switch do any damage or cause any other problems later on or should I just get a proper one from machine mart, what would you do?

Am waiting a responce from maplins re the A suffix on their pots.

Kiaran
8 October 2011 at 14:20 #76000
john swift 1
Participant
@johnswift1
Hi Kiaran

the old version of the control FC250J you will do damage with an instant start at a high speed

but with the new FC250 SMD version , there is an extra RC network added that gives you a controlled increase of speed that should protect the control board and motor

one danger ,with the maplin part ,is the loss of the No Volt Release function

if you lost the mains to the workshop and you forgot to switch off the lathe

it would restart when the mains is restored

with the original part

the emergency stop switch only needs to open long enough for the relay to open

to stop the lathe

with the maplin part the stop switch has to latch down to stay switched off

John
8 October 2011 at 14:52 #76001
Kiaran Walker
Participant
@kiaranwalker64939
Thanks John,

I can live with the no volt thing and I never really use the emergency stop.

My board says FC250JSMD so should have the extra RC thing.

Kiaran.
8 October 2011 at 18:45 #76013
Sub Mandrel
Participant
@submandrel
Kiaran, you never use teh emergency stop … until the day you need it!

Also, when I had the ‘wrong’ pot fitted I had to take huge care to make sure the machine was switched off , because there was always the danger of it leaping into motion.

I needed one of these N/C switched pots for my Mill (same PCB, essentially).

> Omeg ltd for instance will make them to order in a small quantity

> (but its a bit expensive if you only need one !!!)

I rang them up to ask about singles and they very kindly sent me a free sample!

I don’t suppose they will do they every day if you all ring up at once, but if one person does…

Or perhaps Arc Euro or similar could buy in a few dozen as stock?

Neil

Edited By Stub Mandrel on 08/10/2011 18:47:47
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