coronet major lathe

[WoodySteve]

Hi WoodySteve, which motor do you have on your coronet hobby lathe? I have a Major with a Brook Crompton 2850rpm 1hp motor, think it's rated at 6Amps. Someone told me a while ago that some electronic speed reducers can make the motor buzz and get hot and lose some power/torque. Sounds like a great solution for speed reduction but would hate to ruin a good motor and have the hassle of trying to source another or have it fixed. If yours is the same motor I might give one of those gizmo's a whirl if you say yours works fine.
Cheers
Jaypee

Hi Jaypee, I will have a look tomorrow and let you know as im not 100% sure as i have never looked at the motor, ive not had the coronet hobby lathe long, but i brought the lathe speed controller from ebay 3 weeks ago and never had any buzzing from the motor, i plugged the lathe lead in the socket and the plug in the main socket and away it went no more swapping the belt.

http://www.ebay.co.uk/itm/121195468533?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

cheers
steve

 

[Phil Pascoe]

It specifies that it will not control induction motors - I can't say I've come across a lathe with a brush motor.

 

[joethedrummer]

Hi Joe the drummer
Just found your pic of the speed reduction set up.
I have a Major mk3 and want to reduce the speeds to enable screw thread making for a repair I have been asked to do.
I can see from your pic that in essence the pulley goes between the drive and driven pullys on the lathe but cannot see the pattern or size of the pulley. I wondered if you could let me have pics showing the pulley looking from the side together with any measurments of actual pulley diameters.

I would like to have a go at turning the pulley, in wood, as I already have a bearing block that I could use to mount it.
Alternativly was 'RDG' the model making supplier in Yorkshire?

Hoping you can help
Thanx
Nigel

Hello Woodspinners,,
Nigel,,yes RDG from Yorkshire supplied a twin pulley which was for a Myford super 7,,it is 4 3/8 and 1 3/4 inch diameters so gives a 2.5 to 1.0 reduction,,,I could not find a twin pulley giving a greater reduction with the bore size I needed,,,I suspect you will need an even slower speed than I acheived, for thread chasing ,,,so making a wooden twin pulley will give you the oppotunity reduce more.
There is a pic; earlier in the thread of the back of the pulley I used.
I have turned some bowls up to about 13 inches dia: with my set up,, but now of course want to try something bigger,,so I"m toying with having an ali: pulley turned up to give a greater reduction,, tho" there will come a point when the lathe is just not man enough !!.
Steve has found a neat solution for £25 on ebay giving infinite variation,,but like Jaypee, who has the same motor as me, I am a bit wary of damage to the motors,, "cos when I spoke to a buddy who rewinds/repairs electric motors he did a lot of "sucking thro" his teeth " when I spoke about refurbing mine if it gave up the ghost,,
Hope that helps,, maybe I should just take up knitting,, it"s got to be easier !!!
,,,,,,,,,,,,,joe,,,,

 

[WoodySteve]

Hi WoodySteve, which motor do you have on your coronet hobby lathe? I have a Major with a Brook Crompton 2850rpm 1hp motor, think it's rated at 6Amps. Someone told me a while ago that some electronic speed reducers can make the motor buzz and get hot and lose some power/torque. Sounds like a great solution for speed reduction but would hate to ruin a good motor and have the hassle of trying to source another or have it fixed. If yours is the same motor I might give one of those gizmo's a whirl if you say yours works fine.
Cheers
Jaypee

same as your motor Brook Crompton 2850rpm 1hp motor.

 

[WoodySteve]

It specifies that it will not control induction motors - I can't say I've come across a lathe with a brush motor.

thats what it says on ebay description, it works on my Brook Crompton 2850rpm 1hp motor,
alot of mini lathes have brush motors, not sure on the bigger lathes,

 

[CHJ]

The device is for the control of Universal Motors, those with commutators and brushes such as electric hand drills.

They work by using an SCR or Thyristor to clip the AC waveform to limit the power available, main problem with the simpler circuits is the loss of torque at lower speeds/power settings, those with more advanced circuitry use the EMF feedback from the motor to adjust the waveform output to compensate somewhat for this limitation.

Using one with a single phase Induction motor will not slow it down as it is frequency dependant not power dependant, If an induction motor is showing a speed change it can only be that it is loosing rotor sync and slipping with loss of torque.
Under these conditions there is serious risk of the induction motor overheating as it is not producing any feedback to control the current input and is relying on source limiting.

An induction motor can take up to 10 times its running current when starting until it is up to speed, anything that stalls its rotor and brings it back into its starting configuration will be bringing it back into this high current consumption mode.

 

[vindyboy]

Ta ever so for that Joe
Sounds like it's not a good/safe idea to use a speed reduction gizmo so back to the chiselling.
Nigel

 

[Jaypee]

Thanks CHJ for your detailed description of the electronic speed reduction gizmo, far more eloquent than my mates evaluation, he described it as a ' nasty wave chopper that will eventually b****r your motor!' So I will give it a wide berth, I reckon trying to find replacement twin shaft Gryphon motor would mean a trip to the 'Hens teeth and Rocking horse poo shop!' I have the updated/later 5 speed multi rib pulley set up fitted and this gets me down to 750ish rpm so on the rare occasions I need to spin a large bowl I sharpen the tools and go steady, not had any issues to date.

 

[CHJ]

The ultimate speed control system is to fit a 3 phase motor and an inverter, not a cheap option unfortunately.
The only consolation being that with the existing pulley ratio selection to give you the torque you can get away with a reasonably small HP motor and inverter.

 

[WoodySteve]

The device is for the control of Universal Motors, those with commutators and brushes such as electric hand drills.

They work by using an SCR or Thyristor to clip the AC waveform to limit the power available, main problem with the simpler circuits is the loss of torque at lower speeds/power settings, those with more advanced circuitry use the EMF feedback from the motor to adjust the waveform output to compensate somewhat for this limitation.

Using one with a single phase Induction motor will not slow it down as it is frequency dependant not power dependant, If an induction motor is showing a speed change it can only be that it is loosing rotor sync and slipping with loss of torque.
Under these conditions there is serious risk of the induction motor overheating as it is not producing any feedback to control the current input and is relying on source limiting.

An induction motor can take up to 10 times its running current when starting until it is up to speed, anything that stalls its rotor and brings it back into its starting configuration will be bringing it back into this high current consumption mode.

Thanks for the advice. Today i was out doing some turning and i thought the motor was getting hotter than normal, so ive disconnected that lathe speed controller. im just hoping ive not damaged the motor,

 

[EnErY]

and i'd put some steel mesh on those windows in case a lump of wood decides to leave the lathe??

Certainly worth it also thought :lol: :lol: :lol: :lol: :lol: :lol:
Regards
Bill

 

[joethedrummer]

and i'd put some steel mesh on those windows in case a lump of wood decides to leave the lathe??

Certainly worth it also thought :lol: :lol: :lol: :lol: :lol: :lol:
Regards
Bill

HI EnErY,,,,I did put some guarding over the windows and the pulley arrangement,,,see previous piccy,, and tho" i"ve turned a few bits up to about 13 inch diameter nothings come adrift so far,,,,but only time will tell,,,it may happen,,,have I got a choice between grapes or a wreath,,,,tee hee,,,
,,,,,,joe,,,

 

[vindyboy]

Hi all
Can anyone confirm whether or not all Coronet models are based on the same diameter bed size ie 2 inches
? so that say bed platform fittings from a minor would also fit a mojor??
vindyboy

 

[Jaypee]

Hi vindyboy, I think the only difference between Major and Minor beds is the Major has a machined slot at the rear to self align the saddles and the Minor is plain round bar. Got some Coronet paperwork somewhere, will dig it out and see if there's anything on there to confirm.