holbrook c13

hi all i recently brought a holbrook c13 lathe im wanting to change the orginal 3 speed motor to a single speed and have 3 different setting on the vfd to replicate the 3 motor speeds i know somebody on here had done this on a holbrook c10 i wonder if anybody has any further information on this iv used vfd inverters in the past to wire my old lathe with start stop fwd revs etc just not played with using different frequency settings to the vfd to replicate the speed 1 2 3 of the holbrooks controls

thanks in advance

Wow! That's a long sentence. I wonder why you want to replicate the three fixed speeds of the original lathe? One of the great advantages of using a vfd, to my mind, is that by wiring in a 50p potentiometer, you can have infinitely variable speeds between near zero to the highest available.

John

Edited By John Hinkley on 22/08/2022 11:30:30

An advantage of replicating the three speeds of the lathe _motor_ is that when the gearbox upstream of the motor is in a particular gear, the speed shown on the manufacturer's data plate for that gear is still correct.

Otherwise, either a tachometer or considerable mental gymnastics is required: I have the motor set at 33Hz and in gear A3 (for example). So I am running at 33/25 of the plated lowest motor speed or 33/50 of the medium speed or 33/100 of the high speed.

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Some ideas for the OP:

http://www.metalworkingfun.com/showthread.php?tid=2524&page=3

https://www.madmodder.net/index.php?topic=12182.0

https://www.hobby-machinist.com/threads/vfd-conversion-for-smart-and-brown-1024.94645/

dc31k thats exactly what i want and then it replicates the machine as standard

thanks for the links il take a look

Thanks, gents. That answers my question. I'm fortunate that the electronic lead screw conversion I did for my lathe has a tachometer built in, so I get the best of both worlds I guess and the ability to tune out some chatter, should it arise. Horses for courses.

John

Sean

Best to join the Holbrook group on groups.io and ask for advice as to the best way to go about this.

**LINK** https://groups.io/g/holbrook/topics should work.

Fitting VFD drives is a reasonably regular topic and there is a fair bit of experience as to what works well, what doesn't do so well and what is a metric boatload of effort for little return!

My impression is that there is rather more to it than a simple swop. Doing it the right way is said to be fairly straightforward but there is a fair amount to do. Going about it wrong can leave you with a monster motor and gear box sitting the base of the machine from which it appears that only a serious crane (or semtex) can extract it. "Lift lathe from motor and gearbox assembly" sort of thing.The motor and gearbox unit is built along standard Holbrook lines as in "design twice as much cast iron in as everyone else uses". Then double it!

There are also potential alignment issues.

Consensus seems to be best not to disturb things unless you have to. If all is working well leave well alone as the standard speed range is sufficiently comprehensive that the infinite variability of a VFD doesn't bring that much to the party. If all is in good order and to tools sharp chatter isn't an issue with a Holbrook. All that cast iron stays where its put pretty effectively.

If you've not got a manual best to get hold of one from Tony at www.lathes.co.uk so you have a decent wiring diagram to work from. Holbrook wiring and control gear tends to be both splendiferously Steam Punk in appearance and somewhat complex in layout with lots of exposed 220 and 440 volt connectors. Mr Holbrook seemed to think that hiding things behind panels weighing significant fractions of a hundredweight was ample protection against unskilled fingerpoken with no need for namby pamby insulation and non conductive boxes.

A weightlifters belt is advisable!

Clive

Edited By Clive Foster on 22/08/2022 13:25:50

If you use a single phase 230V domestic power source for the VFD, then its best to keep to a maximum of 3hp for the motor. Three phase motors come in several guises according to how many poles they have.

2 pole- 3000rpm, 4 pole- 1500rpm, 6 pole- 1000rpm, 8 pole 750rpm, approximately at 50Hz.

Modern motors can usually run faster than standard, I bought a 6 pole motor and run it from 25-75 Hz, between 500 and 1500rpm.

You need to make a note of the rpm of your motor and choose accordingly.

Here is a link to Inverter Drive Supermarket, their "quick start guides" are excellent for making the wiring and VFD programming easy.

**LINK**