Drive motor options

[leorcc]

The motor pinion is just below the final stage shaft. The final stage shaft has a bearing in each plate and is supported on both sides.

[Liftoff]

Thought it would be confusing with just a drawing, 3d is better! Let my try to explain...
The first 10t gear is press fit on the motor shaft. It's not supported in anyway other from the motor bearings (looks solid enough as its got 3 bearings inside)
This 10t gear drives a second gear cluster (35t and 10t). These gears are press fit on a 6mm Crv shaft and turn together (driven by the 10t gear on the motor. This shaft is supported at both ends by two 6x12x4mm ball bearings.
This gear cluster in turn drives the final 35t gear. This gear is press fit on the output drive shaft. The output shaft is supported at both ends on ball bearings. One side is 6x12x4mm, the bearing on the other side is larger in diameter (10x15x4mm) because of the square portion of the shaft.

Here's a couple of pics from different angles...does it make sense?

gearbox2.jpggearbox3.jpg

[mightymouse]

Chris,

Perfect sense and well engineered. I am assuming there is another support plate wheel side not shown on the model?

Trev

[Liftoff]

Hey Trev yes there's another plate, the drawing is on pg6 of this thread...its supported on both sides. My thinking behind all this is to get it built without the need of complex machining (milling etc) I got no access to. My intention is to drill all holes on a pillar drill, then ream to size to get the bearings fitting properly. The gears will heat them up and press them on the shafts, should not slip I think?

[adz600]

Looks great,just a quick tip if you bore oversize by accident very easy even on a miller, centre dot all around the the hole and using bearing fit adhesive sets like rock. Good look bearing fitment tolerances are very small

[Max]

Personally I wouldn't trust a press fit on the final gear, for the gear on the motor it is fine as there is little load on it, the gear cluster shouldn't want to spin on their shaft as there is no load on that axel it shoudo just spin freely but the last gear has lots of torque and will want to slip on the axel- it may work but it could easily fail, I would go for something like a keyway, or weld it to the shaft, or a pin going thought the shaft or drill half a hole down the axel and half on the gear and put a bit of rod into the hole if you see what I mean- but like a keyway.

[adz600]

Grub screw on an angle grinded flat would hold,ceros uses roll pins

[maddox10]

On the NTM's, just weld it on the shaft. The NTM shafts are cheap.
And to make the shafts yourself, just buy silversteel of the right diameter, and go for it.

[Liftoff]

I'm afraid of welding tiny parts Mario, got a habit of fusing small things into one single part! Yes I thought about getting spare shafts, can use the 6mm silversteel shafts for the gear cluster, but for the output gear it has to be machined to size because of the square drive. That's why I'm using a 1/4" extension for the shaft, the material should be strong enough (chrom-vanadium), the problem might be as Max pointed out, the gear slipping on the shaft... welding is out of question for me - just dont feel at ease welding tiny things where you just cant go wrong!

@ Max

or a pin going thought the shaft or drill half a hole down the axel and half on the gear and put a bit of rod into the hole

I see what you mean, and I think its possible to do with a small modification to the shaft. If I increase the shaft diameter from 6mm to 10mm I could put a 3mm dowel axially to act as a key...

something like this:
gearbox4.jpg

[Max]

@ Max

I see what you mean, and I think its possible to do with a small modification to the shaft. If I increase the shaft diameter from 6mm to 10mm I could put a 3mm dowel axially to act as a key...

That's exactly what I meant- should work well I think.
With the pinion gear I'd use some thread lock or bearing fit adhesive as well as the press fit then should be fine.

[maddox10]

It's finicky work,welding such small things, and best done with a TIG.

The solution with the dowel will work, in combination with some good metalglue.

[Liftoff]

and best done with a TIG.

Wish I had spare money to have one!

You mentioned metal glue Mario, did a quick search on the subject and found this:

http://www.loctite.sg/sea/content_da...g_Compound.pdf

Looks exceptionally strong and can be installed on interference fit items, will get a some and lock every thing with it.

[maddox10]

I would use simple 2K glue. But that loctite is ok.

[mightymouse]

Chris,

been trying to reply all weekend but home pc refuses to connect, work pc is ok.....

If you are making this set-up without a mill then follow a few simple steps;

1; Bolt the 2 side plates together and drill the shaft holes together to ensure they line up.

2; Drill the bearing holes as near to finished size as you can so the reamer cuts dead size.

3; Fit the bearings with Loctite - I prefer 603 - but make sure none gets in the workings.

4: Use silver steel for the shafts and loctite again for your gears.

trev

[Liftoff]

Thanks for the tips Trev, will surely come useful.
For the idle shaft will use silver steel as that comes ground to size (6mm), I just cut to length with no need for machining. The output cant be made from silver steel though, for ease of machining I'm using a 1/4" drive extension turned down from the original 8.2mm to 8mm. That is because I need a square drive to couple the gearbox the the wheels.

One question regarding reaming before I purchase any drills, how much smaller should I get the the hole drilled? The final sizes of reamed holes shall be 14mm, 12mm, 8mm, 6mm, and 5mm. Would say 0.2mm in dia less be ok?