Gear reducer help me understand

I am looking into what kind of gear reducer I'll need for my wax extruder. I have read I need about 100 rpm output. Which is an 18 to 1 gear reducer on a 1720 rpm motor.

Do gear reducers have a lot of torque?

How do I match the mounting on my 1/3 hp motor to the face plate of the reducer? Do I make an adapter plate or must it be specially matched?

Can I reduce the speed of the motor to reduce the rpm output, or will that reduce the torque too much?

Any suggestions for where to buy one on the cheap? Ebay has a few but the selection seems a bit limited in the 18:1 ratio.

 

Gear reducers multiply torque, that is, except for friction losses, you get 18 times the torque and 1/18 times the speed with an 18:1 gear reducer.

I generally find gear reducers which are affordable are too lightweight to do much good. I always resort to belts and chains. Not belts and suspenders, that's different. If I wanted to go 18:1 I would use a 2" sheave on the motor driving an 8" sheave on a jack shaft (4:1), then put a 10 tooth sprocket on the jack shaft to drive a 45 tooth sprocket (4-1/2:1) on the extruder input. Chain will run at 1,725 rpm but it is hard service. Belts won't do good at 100 rpm and still transmit load. You need everything strong enough you can slip a belt or stall the motor when your wax is cold.

When you reduce motor speed you reduce motor torque.

 

Ok so I wasn't just looking in the wrong place for an affordable one then haha. Kept seeing a few hundred bucks and thought I might be looking at the retail price rather than flea market price.

I'm pretty impressed that you figured out the wheels and teeth. I had been wondering about that. Whether it would be better to make one using pillow block bearings, shafts and gears like you said. How did you figure out the wheel sizes you need? The tooth part I think just needs to be divided to get the ratio you want, but for wheels is it the circumference of the wheels that does the reduction or the diameter?

 

Pretty impressed, eh? I did use a computer to type it on.

Pretty simple arithmetic. For belts, the circumference in one revolution of the driver determines how far the driven sheave turns. But since there's a linear relationship of circumference to diameter, you can use the diameter and avoid pi. A 2" drives a 4" at half speed, or an 8" at 1/4 speed. For an A section belt 2" is a good minimum and 8" is not too large. Then sprockets, once you guessed at 1:4 for a belt you're left with 1:4-1/2 for the chain (18/4=4-1/2) so a 10 tooth is easy calculation, and a 10 tooth is practical for a #30 or #40 chain (bicycle chain is #41), the bigger the number the bigger the chain. 4-1/2 reduction is easy with 10 tooth the 45 tooth, or with an 11 tooth you need 50 tooth, or for a 12 you need 54 tooth. Lots of tooth count sprockets are available. They just need to be for the chain you select. #40 is stout, #50 is too big, #30 would do you.

 

Thanks for the explanation. That makes sense. I think that's a good backup plan if I can't get a gear reducer. I will shelve this away for the future for sure. Still impressed with how you and many others here seem to know everything under the sun.

Would this work? 1/2 hp input, 1750 rpm input, 15:1 ratio gives me about 116 rpm output, and I have a speed controller to fine tune the speed. Not sure how I would mount the motor to it. But it is pretty affordable at about $100 compared with the other ones...
https://www.ebay.com/itm/Morse-H98M...5:sc:FedExHomeDelivery!37813!US!-1:rk:49:pf:0

"Morse H98M10013 Gear Reduction Box Speed Reducer Gearbox 15:1 Ratio"




Here is a second one:


https://www.ebay.com/itm/GROVE-GEAR...AOxyeR9TKcid:sc:FedExHomeDelivery!37813!US!-1

"GROVE GEAR FLEXALINE GEARBOX REDUCER BOX D71D 15:1 RATIO .551 HP SP HMQ213-XX"

• INPUT HP: .551

• MOTOR FRAME: D71D

• RATIO: 15:1

 

It will work and is designed to have a 5/16 motor shaft go directly into the female input of the gear box. The flange is made to mount directly to the motor holding the gear box when using a motor with this type of mount. It can be mounted to a motor without the mount. It just requires proper alignment and bolting on the same base plate as the motor. If you have a shop that rewinds motors you can often pick up a rewound motor that was not paid for fairly cheep or if there is a local well driller around. They often have old damaged or pulled above ground pumps that people are replacing with submersible that often you can get for a song. Especially a small one for a pump like A .5 hp. This type pumps all have the type mount used with this gear box. Check shaft size. .5 hp is often .5 inch, it can be shimmed.

Joe

 

I've got a 1/3 hp motor at home. Not sure if it is beefy enough for this job, bit there's a place near by in CT that has stacks of motors for sale at cheap prices. In the 50 to 80 dollar range depending on the HP. I'll hook the motor up to the nice speed controller that I was sent a while back.

So just to double check, the first image is the one to get?

 

https://www.ebay.com/itm/Boston-Mot...h=item33c07e8023:g:oRcAAOSwOyJX9jfK:rk:2:pf:0

 

It will work very well. The hp rating on the gear box is a continous rating. If you have to use the speed controller. The motor will produce less torque. If the torque is not sufficient and the rpm is dropped below maximum. You might want to consider a slightly higher than ½ hp motor.
This can become a slippery slope. With a good gear box of that rating I would not hesitate to run a 3/4 hp motor intermittently such as exteuder use. This will however at maximum torque reduce life considerable. Even if it cost 50% it should still last thousands of hours if the gears are in good shape.
If you reduce speed by more than around 20% you are losing1/2 the motor torque and might consider a 1 hp motor but don’t forget if you increase the speed to maximum you are exceeding the rated value by almost 100%. At that pressure anything can and will sooner than later fail. If this is the case a small jack shaft and chain with the descried ratio such as Kelly had mentioned would be a good option. The gear box would just mechanical simplify Kelly suggestion by eliminating the second jack shaft. For low hp, ½ or 1 You can build one from go cart parts new for under $50. If you go to slow torque gets very high. A bit heavier shaft and bearings would be best It is always best to run an AC motor at or very near maximum rpm if you can.
This type of gear box was built for industry and take a lot of abuse but before use any unknown box should be inspected. Just pop the side off the output shaft and do a visual. Worn parts are easily spited. There will most be a heliacal gear on the input made of steel between 2 bearings on the input and a round gear made of bronze gear between 2 bearings on the output. There will most likely be shims or gaskets that are used as shims under the plate you removed with a bolt pattern to match. Don’t forget to put them back. They are important and there thickens determines the tolerance on the tapered output bearings. If you break one or more use some silicone and glue them back together.
Joe

 

Ok, I'm thinking this one and an adapter to go from 5/8 to 7/8" so I can fit my smaller motor into it and I can upgrade to a larger motor later if needed and the speed controller to change the speed like you mentioned Joe but still have torque. What do you think?

Also is the shaft that comes out the side removable? It might be easier to insert my extruder screw shaft directly into the socket in place of the shaft if possible.

https://www.ebay.com/itm/DODGE-TIGE...753243?hash=item4d74a9979b:g:7yIAAOSwhIZbD-0V

DODGE TIGEAR 15:1 RATIO GEAR REDUCER
1.13 MAX INPUT HP 1750 INPUT RPM 496 OUTPUT TORQUE
3/4" DIAMETER INPUT BORE KEYED
7/8" DIAMETER 1-3/4" LENGTH OUTPUT SHAFT KEYED


https://www.ebay.com/itm/Keyway-Sha...h=item3fb158ce62:g:3~4AAOSwlkpb6vnG:rk:1:pf:0

 

Yes that is a very nice gear box and adapter with a rating of over 1 hp. It will be a vast improvement over the other. Unfortunately with this type of gear box the shaft is what the gear is held between the bearings on and can not be easily replaced.
It sounds like the extruder is moving along nicely. To keep from clattering the form I will PM you on some details and let you decide if and what you want to post.
Joe

 

If the shaft isn't removable I can use a coupling of some sort. That shouldn't be too hard. Maybe one of those weird jointed ones that can spin at an angle. Might be helpful for alignment too.

The shaft coming off the screw will be about an inch or so thick. I can probably get a matching one for the shaft and a double female coupler to join it to the reducer box.

I'm going to buy this one and the adapter I think.

 

I got this adapter for the motor end, but I still need to get a coupler for the other shaft to motor shaft.

 

The motor output shaft goes into the female input shaft on the gear box. No adapter is required If the bolt patterns match. It might bolt up directly but if it does not without a motor flange mounting. It is a bit tricky but not to bad. Put the motor and gear box together and make a shim to match the motor and gear box height then just bolt the gear box down with the 4 threaded screw holes on top of the gear box to the base plate you will make for holding the motor and mount the motor. It might be best to check with a local well driller as explained in the PM.
Joe

 

I made an end piece that I can glue on to the slotted end then bore out a hole for the shaft to slot into. I'll need to key it to make it work though.

Do you prefer this versus the slotted end?

I'm just not 100% certain how I'd secure the slotted end if I was going to do it without the end cap I just printed. Maybe tap and thread the plate into the slot so it doesn't wiggle?

 

I might suggest something like this. The cylinder is what guides the screw. The coupleing would ride in the slot and be held fast with the shaft on the gear box. The Timken bearings in gear box must withstand the back thrust that will be considerable. The coupler would have to ride against the collar of the gear box or a spacer. The torque will potentially be very high depending on the wax so a shear point is highly advised. If the coupleng is made of a softer material than the bronze it will shear before damaging the screw, the most valuable part.
Joe

 

I'm not 100% sure what the above pic is showing. A cylinder and a bar through it to lock into place inside the bore of the original screw?

This is the adapter I was going to cast directly onto the back end of the screw to hold the shaft.

What do you think? Will work? Might be less machining required than the slot

 

It will definitely work but if was building it I would use the other design.
This would be made of a solid cylinder of material {X} This is then cut on one end so there is a flat bar that is the same width as the slot in the screw minus tolerance. Then the cylinder is bored and keyed to your shaft size to natch the output of the gear box. Next it is drilled and tap for a set screw in line with the key for locking the coupling to the gear box shaft. This will give a coupling that goes on the end of your motor. The coupling will have 2 “fins” divided by the bore hole. The 2 “fins” would be the width of the slot in your screw. These fins on this coupler would then fit inside the screw until flush with the solid part of the coupler. The coupler would be riding free in the slot in the screw. They would be cut so that they set deeply in the slot but do not bottom. It is important that the screw is in no way locked mechanical to the coupler. It must “float” between the coupling and your screw. As the screw pushes back causing back pressure. It will be transferred to the gear box housing, not the gear inside the box. For this reason the coupling must be push up against the gearbox output shaft fully or a collar must take up the gap between the turned down portion and the coupling. If it is not the screw when pushing on the coupling will push it back until it is possibly causing damage. In the picture of your gear box the output shaft was turned down slightly during manufacture leaving a convenient collar to push against. The output shaft on the gear box rides between 2 internal tapered bearings. This causes any lateral thrust to be transferred to the housing through the bearings, not the gear.
This is about the easiest type of coupling there possibly is to machine reacquiring minimal time and effort. If it is made of a softer metal. than your screw. Under heavy torque the “fins” will shear off saving damage to the screw. They are so simple to make that although the only way you would shear one would be if the screw was locked up such as if the extruder was let to cool full with very hard wax or if something solid other than wax is accidntly dropped in. Or a mechanical failure. I would have a spare. The extrurer should always be cleared after use. Honestly it will take more time setting the machine than making the parts.
The easiest way for me would be for you to sent me a couple of solid cast cylinders just a couple of tenths bigger than your screw of the type material you want the parts made of and I will do the machining from there.
The friction and cohesive shear forces of the moving screw and the side wall will cause heat. This will probably be sufficient for extrusion. You could possibly run into a problem with air entrapment causing voids or emulsifying the wax. This will change the properties of the wax. In this case you will have several choices. The easiest would be to bring the wax to a viscus state or possibly even a liquid state before entering the screw and then cooling the wax as it exits the extruder with air or water.
Joe

 

Testing out the forum features.

 

So you are saying something like this?

This may be difficult to cast without voids 9 cm in diameter will shrink a lot. Maybe it would be better to cast if I were to put a hole down the center to make it hollow. I could do a 3/4" diameter hole which could be widened to 7/8" for the final shaft.

This design also uses a lot more metal than the design up above. A lot more wasted bronze. Maybe it would be better to use the top design?

How deep does the bore into the end of the screw need to be to ensure the shaft has enough grip? I was thinking 1.5" is enough but I am not sure.