Denford Software & Machines

Hi,

my TDS 1/1 G.B.L. is still in refurbishing process. I plan to make some big changes to head stock. Please tell me what you guys think about that my idea: change original motor to 2.2 kW (3 H.P.) / 2800 rpm@60Hz, remove intermediate pulley shaft assembly, remove ML100-137, ML100-138, ML100-139, ML100-140, ML100-141 and all the other back gear elements like gear shifter fork, lever...

Instead I plan two options:
1st: mount multi-V belt pulley using taper bush system directly on the spindle. Seconf multi-V pulley will be mounted on the motor shaft.

2nd: use intermediate shaft with two multi-V pulleys: one belt will connect intermediate shaft and spindle, second one will be on two stepped multi-v pulley on intermediate shaft and the stepped multi-v pulley on the motor shaft. This will allow for 'back gear' if somehow i need very high torque on the spindle.

Ads:
- much less elements that may failure
- wide multi-V reinforced neoprene belt will last forever
- lower vibration resulting in better finish (?)
- quiet operation (original desing can not be considered quiet!)
- no more lube in the head stock (i'm not talking about Timken bearing of course)
- no wear elements like oilite bushes,

Cons:
- the lathe will not be 'original' anymore. But you can always switch back to the original design because no original elements need to be modified
- ?
- ?

How about that?

Assuming you are using typical 4 step pulleys, with steps of 2",3",4" and 5" with a 2800 rpm motor, the lowest speed you will get is about 450 rpm, followed by 850, then 1500, and so on up to a theoretical maximum of 17500! I don't know what you intend to use the lathe for, but you'll only have about 3 useable speeds for metal turning, and all of them far too fast for a lot of work, including screwcutting.
Whats the problem with the existing standard set up, apart from noise?

Richard

I'm going to change pulleys ratio completely. First of all standard V-belt will be replaced by multi-v belt. Much better 'gripping force'. Assume option 1: direct drive form motor to spindle, assume pulley ratio 2:1 then max rpm on spindle will be 2800/2=1400rpm. Using VFD I can safely speed the motor up to 3600rpm resulting in 1800rpm on spindle. This will cover all my needs. I assume 2,2kW motor will have enough torque on low revs. If it turns out the torque is not sufficent then option 2 will do: install intermediate shaft and fix pulley ratio between this shaft and spindle and add 2 step pulley between intermediate shaft and motor. All pulley will by multi-V type.

What is wrong now? I don't like noise and too many friction elements that have to be lubricated.

Sounds better. You didn't mention the VFD first time. I still think you'll need Option 2 to get slow speed low enough though.

My mistake:)

Hello

I have implemented option 2 on my Viceroy but I retained the link belt drive to the spindle.
Link belts are very good at absorbing shock loads. It would also be difficult to modify the spindle end to take a poly-vee belt

You can see my efforts here: Youtube - Denford Viceroy VSD Conversion

Below rated speed (50/60Hz), torque is constant.
Above rated speed, torque decreases. Double the speed = half the torque.

You need to think carefully about pulley ratios. More speed is not necessarily a good thing.

Thank you Dazz for input. Would you be so kind and take detailed photos of your drivetrain? I have to consider link belt use between spindle and intermediate shaft. But tell me why would it be necessary to modify spindle nose to take poly-vee belt? I plan to remove all the gears and elements mounted on the spindle and mount taper bush pulley. The real problem will arise when the belt will have to be replaced - the whole spindle will have to be removed... And this is something I don't like in this idea the most.

What max revs should I consider on the spindle? 2000rpm?

Hi

I have retained the factory link belt between the headstock and the lower intermediate pulley shaft. The poly vee belt goes between the motor and the intermediate shaft. There are photos already posted in the Denford forums.

It would be a major job to run the poly-vee belt all the way to the headstock. It is not something I would recommend.

2000rpm is too high. You won't have enough torque at lower revs.
My lathe goes out to 1800rpm at 150% motor rpm. With the experience I now have, I would have set the pulley ratio to max at 1500rpm.