Trying to attach a gear to a motor

Hello people. I am trying to make a gear turn with a basic DC motor, and I don't really know what I'm doing. Eventually I'll be hooking this up to an Arduino but for now I just need to figure out the mechanical part.

I obtained a bunch of cool gears from an old lathe, and I'm trying to hook them up. I'm pretty flexible on the form, I just need the things to turn. In the picture, you can see my motor and a sample gear next to it. This particular gear has those little holes I can put screws in for holding on to something, but of course the motor shaft is much too narrow for that.

One option I considered was getting a gear like this pinion gear (http://www.servocity.com/html/32_pitch__5mm_bore__gearmotor_.html#.VC794SldUmY) but the DP is wrong. These are 32 pitch and my gears are 15. I don't know a good way to connect two different pitched gears and my internet searches have been fairly fruitless.

Thanks for any advice!

Unless you have a lathe you can make parts with, i would suggest you dont bother.

Thats a tiddly motor any way and you are trying to driive heavy gears desinged for a large 700w plus motor.

Try model suppliers for more suitable gear parts.

From the look of it it looks like the innards of a screwcutting gearbox and they are normally used at very low rpm compared to the thousands of your motor.

Thanks for the reply. I should mention that I'm trying to go at a very low RPM actually. My motor here is 60RPM and I'm planning to gear this down as much as possible with gear ratios. I'm eventually going to be turning a large clock face and that obviously needs to turn really slowly. I would be fine with getting a different motor if necessary. I would like to keep the gears though since they are kind of key to the project for aesthetic reasons. Thanks!

Ok, i get it.

Its possible to get coupling adapters within a range of sizes but thats a huge jump.

These gear types are normally sold with a pilot hole which is bored out to suit an application.

Iv done it myself by making adapters but it really is a lathe job.

You may need to make an adapter that fits the D shape of the motor shaft. I've made a crude adapter in the past by carefully drilling a hole the size of the round shaft in a small block of wood, then drilling a hole thru the side of the wood block to the center hole in the wood block. Then I screwed a small flat tipped bolt into the side hole to go against the motor shaft flat side to act as a set screw. Lot of possible ways, but surprisingly haven't really seen much on DIY approaches.

This is how metal adapters work often.
Big problem is matching the bore with the shaft which will be ground to tight tolerance.
Drilling dont work, and concentricity is important.
Reaming may help with diameter but not concentrisity.
You need a lathe.

Well here's how I'd do it.

Get an offcut of flat aluminium bar (say a few mm thinck) then by means of an undersized drill and rat tail files create a hole that fits the profile of your shaft perfectly.

Now using this as a template, get a piece of wooden dowel and file it down to make an exact copy of your shaft.

Now get a piece of wood whose thickness is about equal to your shaft length.

Cut a hole in this piece of wood a bit larger than the hole in your gear.

Find a piece of tin plate (such as the discarded top of a baked bean can and screw this down over the hole you just made.

Make a small hole in the centre and use this to screw into the end of your replica shaft.

Laying this flat on the bench you should now have a well with a wooden shaft sticking up in the centre.

Now finish off the baked beans, wash and clean the empty tin.

put it on a gas ring on the cooker and put in some scraps of die cast.

Once this has melted, pour it into that well that you've made and allow to cool.

Once set, drill, scrape, file or whatever it takes to get the moulded diecast out of your mould.

Push it onto the motor (ideally it wants to be a very tight fit, but it probably will be as die cast shrinks as it cools.

Clamp down the motor on a bench and power up the motor. Using files (or ideally some turning tools held against some kind of stop) turn down the adapter until it is perfectly round and just the right size to fit into your gear. Before you test it, however, you want your gear to be hot so keep it in the oven between tests.

Once it's a good tight fit, leave it until the gear cools. It will then tighten up onto the adapter and should be solid as a rock.

I do think, however that THOSE gears are much too large for that motor. They'll struggle to turn them with any worthwhile load on them. Just the power required to accellerat them from a standstill will cause some hefty strain on the motor.

One other possibility would be to buy a small pinion with a smaller bore if you can find the right dp and module.

very simple lathe work.. there are lots of machine forums and you should be able to find someone willing to make that part for you.

Yes quite,

Iv done similar in the past and had good results from offering beer vouchers and postage.
In the end its worth a tenner or two to save hours messing around.

I have a local machine shop who sometimes does some small machining jobs for 20 which can include milling rectangular holes , boring pilot holes etc.

Saves hours in the end.

If you need the project to operate very slowly, the best arrangement is using a worm drive.

Not only does it give very slow output but also large torque.

http://www.ebay.com.au/itm/Tamiya-72004-Worm-Gearbox-H-E-High-Efficiency-TAM72004-/111145058895?pt=AU_Toys_Hobbies_Educational_Toys&hash=item19e0c3024f

Image gives you how it operates if you are not sureā€¦

wormDrive.jpg

I'd probably try to mold an adapter to fit the shaft using some type of epoxy and a good release agent on the motor shaft. Maybe some other approaches using drilled holes and epoxy. JBWeld is pretty good stuff.

zoomkat:
I'd probably try to mold an adapter to fit the shaft using some type of epoxy and a good release agent on the motor shaft. Maybe some other approaches using drilled holes and epoxy. JBWeld is pretty good stuff.

I've already suggested something similar, except my idea was diecast and also making a dummy shaft to mold it around.

Another similar possibility is to use a screw on flange adapter.
The biggest problem in all cases is getting the holes concentric.

Boardburner2:
The biggest problem in all cases is getting the holes concentric.

Which is why I suggested making the adapter oversize, then attaching it to the motor itself, for the final shaping.

I actualy used your idea once to make a coil winder.
Turning on the motor shaft proved to be very difficult though t get right, a faster turning motor would probably have worked better i guess.

I ended up using a rubber bung and conpressing the ends to compress it thus making it expand.

Not particularly concentric but provided a useful way of securing the bobbin.

The bung was made from the rotary band sander tool from a dremel.

Everyone -- thanks so much for all the suggestions. This gives me a lot of different directions to try, and I appreciate that. It sounds like I would probably make my life easier if I chose a different motor, and that is something I'm completely willing to try. Thanks!