anyone have experience using hydraulics for speed reduction ?

[knighty]

I've got a machine at work I'm looking to copy, it's 15hp - tho that's a bit overrated

it spins a drum at 40rpm, speed reduction right now is belts and then 2 chains

I'd like to be a bit more compact with my copy, and it's tricky to find a decent gearbox for the load - worm drive is no good (too much inertia when it stops) and the load is pretty... bumpy (I can't think of the right word) - lots or jerking/bumping etc.

call it 20:1 reduction to make explaining easy

if swap to a hydraulic pump and motor

do I just need a 10cc/rev pump and 200cc/rev motor for the 20:1 reduction ?
(obv. need them both to take same pressure/load etc.)

anything else I need to think about ?

 

[rory1]

You need to determine the maximum torque that you will require, this will help you choose which type and size of motor you need. Work out what motor you will need then work back towards the pump.

 

[AndersK]

You have to consider the motor speed driving the pump is a lot higher, so rather 5-6 cc pump.

 

[Luke]

The 'bumpiness' is referred to as service factor. The required torque is multiplied by the service factor to overrate the gearbox and allow for the varying load.

Pump and motor capacities won't work out exactly, as both will leak to some extent.

Hydraulics are pretty inefficient. You will lose power, which will be converted to heat. You will either need a big tank or an inline cooler.

A planetary gearbox is both efficient and compact, but you're unlikely to find something lying around.

 

[knighty]

I'm unsure on starting load... there's a slow start fitted... starting up its pulling 32amps on two of the phase and 60amps on the third

but... I'm wondering if the slow start it just doing something weird to my clamp meter throwing the reading off on the 60amp one ? (it's a modern slow start)

starting torque is set to only just enough to start the motor moving and take up the slack in the chains, then it ramps up to full power over 10sec - in reality it's at full speed before the 10sec is up (probably 5sec tops)

running it only pulled 6amps/phase but that's wasn't fully loaded (4.5kw ish?) - it's not easy to get in to measure

I'm a bit flexible on final rpm, it runs at 40 right now, but up or down a couple will be ok... original (pre-ww2) motor was changed when I was a kid for one which was thrown away at the local shipyard... I don't know how closely matched it was to the original (probably not close at all)
that was 18kw, but I swapped it to a 20kw motor about 3 years ago when the 18kw one was destroyed in a fire - supplier had 20kw ready to ship so I bought that

motor only runs 3 or 4 hours a day, so efficiency isn't such a big deal, (tho I guess I'll have to stay motor-over-rated to compensate for loss of power)

current motor is 1400rpm, I figure I'll drop down to a 760rpm motor to help reduce the reduction needed

I've looked at gearboxes, and struggled to find one with the input/output shafts in decent positions to make it fit well with the machine, 90' would be great but almost all were worm drive, and it has to be happy living in pretty rough conditions, hot+cold, regular steam and always very humid - I've had machines which are supposed to be made for the conditions deteriorate pretty quickly and need constant maintenance

I might just stick with chains, maybe run them in an oil bath - that should make them last a lot longer, right now I think they get worn out more than they stretch (tho they do stretch)

 

[winchman]

Hydraulics shoiuld do it no problem but cost I suspect will kill it unless you can find a donor

 

[vwmark]

Use an inverter and on the last revolution slow down so the stop not so sudden.
Seen it used on a cooker that had a ton of grain in and had to stop in exactly the same position.

 

[addjunkie]

If using chains have you considered a scott oiler as used on bikes, rather than an oil bath

The gear boxes used of field toppers are 90 degrees, and robust.

Something like this

https://www.ebay.co.uk/itm/Genuine-...e-Direction-Fleming-Abbey-Conor-/112438196957

 

[8ob]

40 rpm and hi torque is Staffa motor territory used with a gear hyd pump and will diresct drive without the need for chains/belts. Staffa will handle an abrupt stop/start without running on, gear motors will run on and foam the oil in these situations. Also worth fitting a hydraulic shock absorber in the system to soak up the pressure spikes.

http://www.staffa-motor.com/products/staffa-motors

Bob

 

[Luke]

Sounds pretty typical for a 2 phase soft start. An inverter would give you more control.

A planetary with a bevel output stage would give you the 90 degree output.

If you go for a 6 or 8 pole motor, the speed would drop to just less than 1000 rpm, or just less than 750 rpm on a 50 Hz supply.

 

[winchman]

40 rpm and hi torque is Staffa motor territory used with a gear hyd pump and will diresct drive without the need for chains/belts. Staffa will handle an abrupt stop/start without running on, gear motors will run on and foam the oil in these situations. Also worth fitting a hydraulic shock absorber in the system to soak up the pressure spikes.

http://www.staffa-motor.com/products/staffa-motors

Bob

Thats the best plan if you can find one cheap!
Ideal for big heavy loads and high initial torque, often used on Fun Fair rides, big long conveyors etc, remember though the cooling and conditioning of the fluid is also very important.
You could use an inverter and gear box if you can get the combination slow enough?

 

[knighty]

Unless it's massively overloaded a chain doesn't stretch.
When people talk about stretch on a chain it's always wear on the pins or holes. This wear is also accelerated by worn sprockets, so people think it's stretch (I put this chain on last week, now it's slack - it must've stretched a bit).
If you're actually saying that the plates are deformed and elongated then your drive system is woefully inadequate.

originally (pre WW2) it was 3x V belts to single 12b chain to duplex 16b

I upgraded from the single 12b to duplex, and then later to triplex

all new sprockets on the 16b now too, since the 3 inch shaft everything drives snapped :-o
(I'm putting the shaft break down to 70+ years of use)

triplex lasts a lot longer but does get longer over time - maybe the single and duplex chains were overloaded but now it's wear making it longer

 

[knighty]

Hydraulics shoiuld do it no problem but cost I suspect will kill it unless you can find a donor

I'm expecting to spend thousands on it, just spent ~£3000 repairing the old one (70mm shaft, chains, sprockets, kick ass bearings etc. etc.)

original is galvanised, I'm planning on stainless for the new machine but I'll see what kind of quote I get for the stainless first!

 

[knighty]

Use an inverter and on the last revolution slow down so the stop not so sudden.
Seen it used on a cooker that had a ton of grain in and had to stop in exactly the same position.

I'm trying to stick with as few electrics as possible

no matter what I do, sooner or later someone manages to steam clean the inside of every control pannel


computers and sensitive things etc. are out of the way, but these machines are right in the thick of it... and they get pretty dirty so are steam cleaned every day (sometimes more than once)

 

[knighty]

Yep, there's your stretch - every time the chain goes around a sprocket those pins and holes wear a little bit.

A triplex has more bearing surface over a simplex or duplex, so the wear is reduced and load handling is increased.

oil bath vs getting wet and dirty all the time will cut right down on the ware.... yeah?

 

[knighty]

40 rpm and hi torque is Staffa motor territory used with a gear hyd pump and will diresct drive without the need for chains/belts. Staffa will handle an abrupt stop/start without running on, gear motors will run on and foam the oil in these situations. Also worth fitting a hydraulic shock absorber in the system to soak up the pressure spikes.

http://www.staffa-motor.com/products/staffa-motors

Bob

I'll email them for a quote :-)

 

[knighty]

yep, original is belts then 2 chains

I was thinking swap to slower motor, flange mount motor, then 3 chains in the oil bath 'tub' fully enclosed

will probably only have 1 chain running through the oil, but there should be plenty of splash


what I meant was, how much ware will the oil prevent... but now I've realised it's a silly question, it'll be like bearings where they last practically forever with decent lubrication ?

 

[8ob]

A bargain, go direct drive and forget the chains/belts. https://www.ebay.co.uk/itm/BIGNOZZI-BM-150-radial-piston-hydraulic-motor-210bar-155cm3/173035881338?_trkparms=aid=222007&algo=SIM.MBE&ao=2&asc=49129&meid=b0cc083bb43c4c918b7aeba0a7e97f14&pid=100005&rk=2&rkt=2&sd=352227652759&_trksid=p2047675.c100005.m1851

Bob

 

[knighty]

A bargain, go direct drive and forget the chains/belts. https://www.ebay.co.uk/itm/BIGNOZZI-BM-150-radial-piston-hydraulic-motor-210bar-155cm3/173035881338?_trkparms=aid=222007&algo=SIM.MBE&ao=2&asc=49129&meid=b0cc083bb43c4c918b7aeba0a7e97f14&pid=100005&rk=2&rkt=2&sd=352227652759&_trksid=p2047675.c100005.m1851

Bob

if that's 155cc/rev

then I need a hydraulic pump delivering 6200cc/min (6.2litres/min) to drive it at 40 rpm yeah ?


I'm leaning towards chains, I thought they were really stretching... I know what I'm doing with chains, I can keep a full set of spares on the shelf and if something breaks I can fix it quick

 

[dannyp]

it almost sounds like your runing a rotary screen / trommel

i've built, rebuilt and bodged a few of these. i'd drive it hydralicly,

step 1 get a big wheel motor, step 2 get a power pack in the 20kw region, add some pipe. when pluming it up id ether put a check valve across the motor ports that would allow the motor to freewheel to a stop, or use a motor ctop valve that connects the AB ports when unpowerd also letting the motor freewheel to a stop, personaly i'd avoid the c top as valves casue losses , id just use a power to close valve T'ed off the pessure line to start stop it.