Motor Shaft Suitable For Thrust?

There may be motors so designed, but the ones I've worked with are designed to transmit torque, with maybe enough side loading for a pulley or a gear.

In fact, I briefly worked on a mechanism (designed by a consultant -- you can never trust those people) that looked like it was designed to do what we wanted, but turned out to be a motor-shaft-puller-outer.

Can you dig up a data sheet for the motor? If you can, and if it's made for OEMs to design into machines, then it'll have an axial force specification. It'll probably be much less than your 500lb, and you can show it to your customer to convince them they need external thrust bearings.

I don't believe any normal motors are designed to handle that type of loading. If you could use a dual shaft motor and provide a proper thrust bearing on the opposite end it might survive.

There are standard motors that will handle significant thrust loads, but you may have trouble locating one as small as a 5/8 shaft implies. For example:

I like the way your mind works!

I drill tapered handle holes in Beech broom blocks with a 3 HP Grainger motor with a spoon bit attached. The motor is on a slide pushed with a

Encouraging... What's the diameter of the holes?

Standard tapered broom handle, 3/4" to 1"...it take all 3 hp to do the job quickly.

Definitely yes!

They have an end bearing! This is a ball bearing placed in a small socket at the end tip of the shaft.

Make or model, I do not know but are popular among large fans for the thrust that is created.

--------------------

I've got a customer who wants me to make him a chuck to go on to a 5/8" motor shaft. No problem.

My question is whether the motor shaft is suitable to receive a chuck since he will be forcing the drill into material with around 400-500 lbs. of thrust.

My thinking is that the motor shaft may shift in the housing and damage the motor...

Am I right here or are there motors out there designed to take this type of load I'm not aware of, etc.?

Regards, Joe Agro, Jr. (800) 871-5022 x113

V8013-R

Excellent news. Thanks for the info! I suppose I can simply warn the customers that an undersized motor (and thus smaller bearings) may cause premature bearing failure, etc.

I have to agree that a fan creates "thrust" but certainly not the amount of thrist I'm talking about. My customers may be running 400-500 lbs. of thrust on that shaft whereas a fan might create a few hundred pounds of thrust only if it were large and high speed... And certainly not driven by a 1/2 to 3 HP motor like I offer.

My mistake. I thought you were asking for help, not selling something.

I have seen many smaller motors with end thrust bearings back 30 years ago. Fan have a lot of end thrust when 0.5 HP is used to push air.

You didn't think most of the energy went somewhere else.

----------------

"Joe AutoDrill" wrote in message news:PP81q.14402$ snipped-for-privacy@newsfe12.iad... I have to agree that a fan creates "thrust" but certainly not the amount of thrist I'm talking about. My customers may be running 400-500 lbs. of thrust on that shaft whereas a fan might create a few hundred pounds of thrust only if it were large and high speed... And certainly not driven by a 1/2 to 3 HP motor like I offer.

I agree. But I think you may be missing what he is suggesting.

Would it be possible for what you are trying to do to get a double shafted motor (one with the shaft sticking out both ends) and then apply the trust to a thrust bearing on the end of the shaft opposite the chuck. This would apply all the thrust to the shaft and transfer all the thrust down through the shaft and create no thrust on the motor bearings. You would still have a little bit of thrust on those bearings depending on how fast the whole assembly accelerates or reverses direction.

-jim

Joe,

A V-Drive boat has all of the prop shaft thrust taken up by an ordinary ball bearing... It is about a 32mm ball bearing in the V-Drive case that takes all the thrust. Here is a video of what they look like...

A great idea, and I understand... But it's typically not possible or logical. Most of these folks are either simply bolting the motor down to a slide plate and strokig it with air or hydraulics or bolting it to a stand and stroking the part into the tooling. They want a very simple set up with no moving parts at times (such as when they manually slide the part into the tooling.)

To set it up so that it pushes the shaft would essentially be making a more expensive and complicated set-up similar to what I sell as an AutoDrill. ...Something I'm not keen on doing. :)

You might consider replacing the outside motor bearing with a angle contact bearing. These bearing take axial loading by design

You say you understand, but it's fairly clear that you don't.

I haven't seen anyone suggest that the force to feed the chuck into the workpiece, be applied to shaft at the back end of a double-shaft motor.

A motor mounted to a slide, as you say the customers are interested in using, would still utilize the feed force applied to the slide.. but a thrust bearing could be mounted to the front or rear of the motor case.. or anchored to the slide in the case of a dual-shaft motor (or a motor with an exposed shaft end at the back).

Generally, the end bells of general purpose motors aren't designed for significant thrust loads. The customers will likely need a good supply of spare motors, unless a properly designed motor is utilized for repeated significant thrust loads.

Adding a thrust bearing to the front or rear of a motor case (supported/reinforced by the motor case) wouldn't be difficult.

You are correct... I didn't and still really don't....

Are you saying a thrust bearing should simply go outside the motor case supporting it but not tied to the shaft? If not, I presume you are suggesting replacing the existing bearing inside with one?

Geeeesh! Take a cheap drill apart and look at the end of the shaft!

You should see an end bearing in the form of a ball bearing (see the shiny object that is spherical in shape?) You know what a drill is, right?

Are you saying a thrust bearing should simply go outside the motor case supporting it but not tied to the shaft? If not, I presume you are suggesting replacing the existing bearing inside with one?

The shaft through a motor can be destabilized by putting lots of force on it (Euler buckling), so it might be preferable to put a secondary shaft with a thrust bearing on the mount plate, and a flexible shaft coupling from the secondary shaft to the motor. That moves the motor back a few inches from the mount plate, but otherwise solves the problem (moves the axial load from the motor rotor to the external thrust-rated bearing).

In all probability, both of the bearing will be deep groove. The drive end one will probably be the locating bearing, i.e. it will be held on to the shaft with a nut or a circlip, and the outer race will be held into the end plate by a circlip. The non drive end bearing will probably also be held on to the rotor by a nut or circlip, and the outer will be able to "float" in a clear bore to allow for differential thermal expansion.

OK, a mid-range 5/8 bore deep groove bearing has a static load capacity of about 725 pounds. This means that your thrust load won't put bad "dents" in the races if you apply it when not rotating. The dynamic load capacity might be about 1400 lb. This means that at a load of about 470 lb the L10 fatigue life will be about 81 million revs. I'm neglecting all the usual fudge (service) factors here, including the one because thrust loads are a bit worse than radial ones. In other words, at 1000 rpm, you would have a 10% chance of bearing failure after 1350 hours. For 50% failure rate, you probably run for nearly 7000 hours.

Assuming you know how long it takes to drill a hole, that gives you a ball park estimate of the number of holes you could drill between bearing failures.

I'm assuming here that the lubrication is OK. All bets are off if it runs really hot, or is sprayed with sand and seawater. If there's a lot of vibration from the drilling, reduce the predicted life by a factor of

1. And we tribologists don't normally claim to be able to work anything out to better than a factor of 10, so if you were paying me for my advice (and might sue me!) I'd add another factor of 10 to be on the safe side. In truth, most bearings from reputable suppliers survive ten times longer than the simple catalogue calcs suggest.

But superficially, with a simple catalogue calc of around 1000 hours of drilling between bearing failures, this motor sounds as though it might be OK in many workshop environments, although you probably wouldn't want it on a 24/4 car production line.

As others have said, adding a proper thrust bearing or even just changing to angular contact or taper roller bearings makes a lot of difference (but at a cost).

These numbers are self verified (but they are not hard to check against a bearing catalogue). Hope this is helpful.