Herbert B drill

[julianthegypsy]

Have a look at a raglan vertical mill, that uses variable pulleys, but without springs etc. One half of each pulley is connected by a Z bar so when you open one you close the other. Operates with a lever with a lock. Brilliantly simple and super quiet too.

 

[Maker]

Have a look at a raglan vertical mill, that uses variable pulleys, but without springs etc. One half of each pulley is connected by a Z bar so when you open one you close the other. Operates with a lever with a lock. Brilliantly simple and super quiet too.

That's brilliant, thanks.

I like to think if I can draw it I can make it, off to Google sketchup I go then.

 

[DanielW]

The wider the belt the faster the speed,obviously the maximum belt width would be about 3/4" ie this width would displace the variator plates wider than a 1/2" belt.

Most GY9? twist&go engine transmissions have a restriction sleeve on the variator shaft and that extra speed can be achieved by taking off the sleeve.

 

[Maker]

Does it need a special type of belt?

 

[DanielW]

Does it need a special type of belt?

Nope,V belt or......most common type
http://www.adrenalin-pedstop.co.uk/img/tutorials/4/2.jpg

 

[ronan]

I think that system was used on Daf cars back in the 60's and early 70's. Known as Variomatic transmission.

I knew a mechanic who had one of those daf's, it was horrible dysentry yellow in colour, but he reckoned nothing could beat it off the line in the traffic light GP .

 

[Turbo]

I used to be a fitter in a food factory and 2 new machines had variable speed drives using adjustable cone pulleys and reinforced rubber belts similar to those discussed. Right from the start we were plagued with breakdowns, usually the belts shredding and wrapping around the pulleys. The bearings failed, material from the belt wear caused pulleys to jam and not slide, etc. Complete new drives were supplied & fitted under warranty - no better. Manufacturer even sent out engineer to fit another new set of drives - still no better!

We ended up binning the drives & fitted a stroter variable speed gearbox, something we knew was reliable as 90% of the other equipment in the factory used them. Not cheap as the stroter box was £2000 but the down time was costing a whole lot more! The machines ran up up to 16 hrs a day and I guess the rubber belt drives couldn't take it!

 

[DanielW]

I used to be a fitter in a food factory and 2 new machines had variable speed drives using adjustable cone pulleys and reinforced rubber belts similar to those discussed. Right from the start we were plagued with breakdowns, usually the belts shredding and wrapping around the pulleys. The bearings failed, material from the belt wear caused pulleys to jam and not slide, etc. Complete new drives were supplied & fitted under warranty - no better. Manufacturer even sent out engineer to fit another new set of drives - still no better!

We ended up binning the drives & fitted a stroter variable speed gearbox, something we knew was reliable as 90% of the other equipment in the factory used them. Not cheap as the stroter box was £2000 but the down time was costing a whole lot more! The machines ran up up to 16 hrs a day and I guess the rubber belt drives couldn't take it!

Must have been a naff system or machines at fault? then because the twist&go automatic transmission engine has been using variable speed drive since the 80's and still in use.

 

[Turbo]

I think it was just the wrong type of drive for the application. It was a quality brand of drive, Fenner I think. It was running in a poorly ventilated machine cabinet for long periods and I think it was simply getting too hot.

 

[DanielW]

You wouldn't be on about this system would you?
http://i.ytimg.com/vi/MhFK5gfAGpM/hqdefault.jpg

This is the system I'm on about,the stiffish spring is need for the variator to apply the right pressure on the plate to keep the belt from twisting as its rotating up or down in the variator.If you don't apply pressure then the belt tends to kink even if its locked in place which is needed for the correct speed you require.
http://img-new.cgtrader.com/items/12763/large_5d0f18fa-6e0d-4972-8327-e85e46c61d74.jpg

 

[Turbo]

Something like the one in your second link. The spring loaded disc was supposed to slide on a square alloy shaft with a plastic/teflon coating. Bits of rubber from the belt caused the disc to jam, belt would slip, everything got very hot and I've seen the plastic melting on the shaft!

 

[DanielW]

Weird,Spring loaded disc sliding on a square alloy shaft with a plastic/teflon coating....thats a recipe for disaster ie friction....are you winding me up?

 

[Maker]

Here it is.

The shaft in the middle isn't for another pulley, its attached to a leadscrew in the column for the rise and fall head.

The switches have been cut inside, as has the transformer for the low voltage light, I'd guess this is so it can be used with an inverter.

The chuck is a 3/8" Rohm, I'm not sure if it's any good or how to replace it if it's not but I don't have a key for it.

It is single speed, and the motor pulley is the smaller of the two so its a relatively low speed.

Everything on it is in immaculate condition, I couldn't ask for more for the price.

 

[roofman]

Am i missing summit here...why not use the regular stepped pully system for speed changes or has the thread gone that long ive forgot half.

 

[Maker]

Am i missing summit here...why not use the regular stepped pully system for speed changes or has the thread gone that long ive forgot half.

Because a Reeves drive is cooler.

I don't have a problem with stepped pulleys, but I'll probably need help with the correct sizes to get the original speed ratings.

 

[Spark plug]

Ratio = driver / driven

So if the motor turns @ 1500 rpm and the motor has a 3" pulley, the spindle has a 2" pulley:

Ratio = 3/2 = 1.5

So the spindle will run 1.5 times faster than the motor:

1500*1.5 = 2250 rpm

 

[roofman]

or another way ive always used.. motor RPM x motor pully size divided by driven pully size gives you the end RPM
motor RPM...1425
motor pully size 2"..multiply by 1425 =2850
driven pully size 5"..divided into 2850 = 570 RPM

 

[Maker]

I mean, how do I get all six speeds from two step pulleys? I could make a two and a three step pulley but the belt would be really misaligned at some speeds.

Depending on the height of the space for the pulleys and the thickness of the belt I could have pulleys with more steps for more speeds.

 

[roofman]

I mean, how do I get all six speeds from two step pulleys? I could make a two and a three step pulley but the belt would be really misaligned at some speeds.

Depending on the height of the space for the pulleys and the thickness of the belt I could have pulleys with more steps for more speeds.

its an old bench drill,what do you need 6 speeds for..2 x 4 grooved pullys would be ample giving you 4 usefull speeds. I only ever use no more than 3 speeds on my 4 speeder,slow..intermediate and a high speed for small stuff like pin drills and anything under 5mm ect.

 

[Maker]

I probably don't need six speeds but that's what it had originally, it would have been nice to restore it to how it was.

What spindle speeds would you recommend, considering it was built for high speeds, there isn't the room for the length of larger drills and I'm hoping i can get a floor standing one to go with it for big drills?