Little giant motor question

[Rberry1911]

I know the reccomended motor is some1700 rpm what i want to know is if i could use a motor that has 3450 rpm and use a bigger pulley on the shaft to slow down the rpm?

[macbruce]

You've got it backwards....A bigger pulley on the motor shaft will speed things up. Problem is you can't put a small enough pulley on a 3450 motor. 1750 motors generally require the smallest diameter pulleys ( 2.5'' or less) to run a hammer and you're thinking of doubling the rpm?...Think again.....

[Rberry1911]

Thanks for the info i was just hoping for way to slow it down since i had a lead for a cheap motor.

[Jack Evers]

In North America, AC electric current is 60 cycles/sec or 3600 cycles/min. An AC motor under no load will run at 3600 rpm or some sub multiple such as 1/2, 1/3. 1/4 of 3600. With load there is a slowing to the often used 3450 rpm or 1725 rpm, but nothing in between. If the motor is cheap enough, it might be possible for a good motor shop to halve that rpm. I don't know what that entails, but you might ask around.and see what it might cost.

[Madmike]

Jackshaft or a VFD (Variable Frequency Drive) if the motor can run on three phases  :rolleyes:

[swedefiddle]

Grant's answer was to mount a second motor. Motor #1 drives small pulley to, big pulley on Motor #2. Small pulley on motor #2 drives the machine. Motor #2 is only an idler with a mounting flange, base and multi-shive pulley, not wired in the system.

 

K.I.S.S. :) :)

 

Neil

[HWooldridge]

Grant's answer = cheap jackshaft.  Same principle, all you are doing is doubling the pulleys to get more reduction, like a transfer case in a 4wd vehicle.

 

Re the OP, a 3600 rpm motor will work if you can get enough reduction - regardless of how you accomplish that.

[ThomasPowers]

The original motors for them ran around 900 rpm IIRC, hard and expensive to get a new one like that and so most folks have to play with pulleys or jackshafts, more RPM means more bother getting it down to usable 

[onetreeforge]

Go to a scrap yard, they have piles of electric motors if you want a cheap one,

[peacock]

Several people I have repaired hammers for have tried this. 2 extra pulleys a shaft 2 bearings more belts all adds up to almost as much as the right speed motor, unless you can get all that stuff cheap.  On the other side of this story once you get it built it works just fine.

[Jack Evers]

While we're on this, I have a 50# LG, got it tuned up now, don't have much experience using it. I've searched the site and seen numbers around 300 RPM for the hammer speed. Mine is about that, but I would like opinions on a good speed for a newbie at hammer use. I might be able to conveniently slow mine to the 220-250 RPM range, , more than that would require a jackshaft. Any suggestion? My motor is single phase, 1725 RPM. 1-1/2 HP.

[peacock]

Thats just a little slower than LG said to run them but it will be fine .  If your clutch is right you should have any speed you want from 0 to 300.  I use 2 horse on 50# hammer but if its a good 1 1/2 it will run it fine at faster speeds but may not have quite as much control at lower speeds.  I use a brake and if you want good hard single blows you need plenty of power in the motor.  An old repulsion/induction motor a 1 hp will do it they have so much more torque. Think 'bout it

[macbruce]

While we're on this, I have a 50# LG, got it tuned up now, don't have much experience using it. I've searched the site and seen numbers around 300 RPM for the hammer speed. Mine is about that, but I would like opinions on a good speed for a newbie at hammer use. I might be able to conveniently slow mine to the 220-250 RPM range, , more than that would require a jackshaft. Any suggestion? My motor is single phase, 1725 RPM. 1-1/2 HP.

What size motor pulley are you using and what is the diameter of your shaft? If you're using the smallest cast iron sheeve you can get, be aware that you can get smaller sizes in a machined steel pully/sheeve. Boston Gear has them.

[Jack Evers]

3/4 shaft, Pulley is 2-!/2 OD, probably about 2" effective pitch diam. Clutch does a good job regulating speed down to perhaps 100 BPM, then gets a bit sticky, may be old lubricant and low temps. We've has a cold spring and my shop is an old milk barn with a lot of concrete i.e. thermal inertia. Good in the fall when it's slow to cool off, but also slow to warm up in the spring.

[macbruce]

3/4 shaft, Pulley is 2-!/2 OD, probably about 2" effective pitch diam. Clutch does a good job regulating speed down to perhaps 100 BPM, then gets a bit sticky, may be old lubricant and low temps. We've has a cold spring and my shop is an old milk barn with a lot of concrete i.e. thermal inertia. Good in the fall when it's slow to cool off, but also slow to warm up in the spring.

You got it made. You should be able to get a machined steel sheeve that is 1 3/4'' dia, which will reduce rpms by 30%. The smallest cast iron pully made for a 3/4'' shaft is 2'' or -20% rpm. Both way cheaper and easier than a jack shaft......I'd wash the old oil out of your clutch with wd40 or mineral spirits and re lube with oil that ain't real heavy.

[Jack Evers]

Thanks for the help!!

[Frosty]

Jack: I'm currently messing with my 50# LG and just bought a larger pully because mine is a bit slow. Clean the old lube out of your clutchs but sticking can mean it's too dry. Heck, I think that's the more likely reason it's sticky but I'm new to LGs so my opinion is suspect.

 

If you use a low temp oil on the clutch cold weather won't matter. No reason to buy low temp oil, a little synthetic or hydraulic fluid will do the job. ATF or brake fluid fill the bill but they can strop paint so I'd pass. The thing that bit me was the old adage about a well lubricated LG sling oil all over so oil the heck out of everything. I tried it that way and it so soaked my clutches I couldn't get it to move, let alone strike a blow. I keep it greased where it wants grease, good low temp lithium grease. The oil I use is either Stihl or Oregon chainsaw bar oil with about 3-4 oz. of Duralube mixed in. Duralube is one of those super friction reducer additives and works nicely so I don't need the LG slobbering oil and it moves free and easy.

 

I learned about adding Duralube to chainsaw bar oil by seeing it on commercials and adding some to my bar oil. This was back when I did a LOT of chainsaw work. If you're familiar with chainsaws, you know how much you have to adjust the chain to keep it properly snug in the bar. After working it a few minutes you have to stop and tighten the chain some because the chain has warmed up and is now longer so it gets floppy and you do NOT want it floppy. When I added Duralube to the bar oil that ended, the shain and bar stopped more than just warming a few degrees. Seriously, cutting at temps near freezing you can lay your saw in the snow after hard use and it won't even melt on the bar.

 

Anyway, I'm a firm proponent of bar oil and Duralube on my LG. I use so little oil in the main bearing cups now I need to actually drip a little on the clutches every now and then. Before it slobbered enough oil to keep the clutches from engaging.

 

Frosty The Lucky.

[Jack Evers]

Well, Frosty, I have lots of Stihl bar and chain oil, I'll try to get some Duralube in town. The reason I suspect old lube is that on cold mornings like today, about 30 degrees in the shop, the clutch really doesn't disengage. Turned it on this morning,it set there running about 25 BPM, not hard strokes, barely touching 1-3/4 metal, but not disengaging. After running a while it was hitting a little harder, but still not disengaging. Works fine at speed, just doesn't totally disengage when cold.I need to pick up some zerks too. Several are missing. I'll get it cleaned up and some light oil, see what happens. Thanks.