Clarke CL500M – Belt Sizes?

[MWParticipant @mw27036]

Posted by Howard Lewis on 04/10/2016 18:43:36:

Is there a reason why the idler cannot be fitted the other way round?

The tumbler reverse adaptation sounds interesting. Has anyone any details, please?

Howard

1. I dont think you can turn it around, as the motor pulley has a much small step on the back for this mode, and the idler is a simple smaller to larger graduation, so it would be more like Motor small, idler small, spindle large, idler large.

Theres a but and a big one, theres nothing to stop you making another idler that gives you a much slower speed, would be an interesting modification and please post it on here if you did. You'll need to figure out the ratios, and a traditional dial RPM gauge would be needed to test the theory, i found one but you could probably pick one up on ebay quite cheaply. Provided theres no drastic change in size you could get away with using the same belts too, they'd be cheap enough even if you did have to change them. 

I have no need for this mod as i went down the VFD route, purely because of the super fast screw cutting problem.

The VFD is obviously quite an expensive mod and not for the faint of heart, but i'd reckon the skill to make another pulley from a foundry cast bar would make it quite the cheaper alternative! You wouldn't need to cover all the steps, simply one to the motor and another to the spindle should be sufficient.

If you wanted to go down the VFD route, go for a motor thats 1/4-1/2 HP greater than a single phase to account for the loss in torque on lower speed settings. Not official advice there but probably worth telling. 

2.The tumbler reverse mod is a mod i haven't done, but intend to, from what i know it's simply a case of adding an additional gear to the train to change the direction, so long as it's a simple train it should cast no bearing on the final resulting ratio. An additional swing banjo plate is probably the easiest way to go about this.

Michael Walters

Edited By Michael Walters on 04/10/2016 19:50:28

[Howard LewisParticipant @howardlewis46836]

Thanks Michael,

I 'll bear what you've said in mind, once we get it up and running, and if the owner wants to go down those routes.

Howard

[Cedric NormanParticipant @cedricnorman47847]

Howard.

Michael's comments are correct. It will be helpful to know that the mod you both are talking about have already been outlined in the Model Engineering Workshop. The slow speed adaptation is in Issue 118 and in Issue 119 there is a reverse threading gear. A tumbler gear with a lever would be easier to use than a fixed gear and there are ample examples on the internet to use as a base. The issue with the screw-cutting on this lathe is that the leadscrew engages on a hex bolt head, so if you disengage the leadscrew there is no easy way to ensure you pick-up the correct point. This would negate the use of the tumbler when screw cutting as you can not ensure the gears re-mesh in the exact same place. The solution I developed uses a single dog clutch and constantly meshed gears so that the drive can be interupted and re-engaged without concern. Presumably, if you do not interupt the gear train (ie. use a tumbler), you could set the chuck in a given orentation, with the saddle in a specified position and the clutch should re-engage in the correct place. This concept might be OK if you are turning the chuck by hand to cut the thread.

Cedric

[Author]

Posts