Drive motor options

[adz600]

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

[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]

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

[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?

[mightymouse]

Chris,

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

Trev

[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

[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.

[Max]

I'm confused as to where all the gears are mounted, presumably the first gear is attached to the output shaft of the motor, the second 2 gears are on a separate shaft both attached to te shaft with a grub screw so they rotate at the same speed. Then I don't get where the last gear is connected? Is it on a separate shaft inline with the motor's shaft but only supported on one end?

[Liftoff]

Gearbox details:

2 stages with 10t and 35t mod1 gears.
Gears interference fit on shaft.
Shaft material: chrom-vanadium (a 1/4" drive extension turned down to size)
Bearings: MR126 ZZ 6 X 12 X 4Mm, 6700 ZZ 10 X 15 X 4Mm
Side plates 7075t6 Aluminium 64x41x4mm
Grease : Rocol Aerospec100

The gearbox output shaft will bear no side loads as the drive wheel is supported by its own bearings.


Gearbox.jpg
gearbox1.jpg

[Liftoff]

Christmas presents finally arrived, slightly belated but that doesn't matter now!
Been doing some sketches for the gearbox in the meantime, I'll upload them and as this is my first attempt to building one please feel free to point out any flaws etc which can be noticed


20140102_142608[1].jpg

[Liftoff]

Had a good look at Conrad and found the same items for a lower price from the UK http://www.rapidonline.com
Going for 10 and 35 teeth gears with two stages of 3.5:1 for a final drive of 12.25...that will fit in the space I got, the 48T gears will be too large and will require quite a lot of work to fit in.
I estimate the weight of the motor and gearbox to be around 340 gr each, that's a weight saving of 110 gr over my current setup...I desperately need to shed off weight!

[Liftoff]

Two 6:1 stages makes for 36:1, not 12:1. Stage ratios are multiplied to get the overall reduction. That setup would get you a bit over 3mph!

Mod .7 sounds a bit small to me (roughly the same as what's in a drill gearbox), and I'd be even more cautious at just 5mm wide. I'd expect to use mod 1, 10mm wide, or similar.

How silly of me! You're right! This will make my life much easier as I can select smaller gears with a larger modulus making the whole gearbox smaller.
Thanks to both of you, spared me a log of grief
Will have a look at Conrad tomorrow Mario, hope they have decent prices as the gears I found aren't exactly cheap!

[Ellis]

Two 6:1 stages makes for 36:1, not 12:1. Stage ratios are multiplied to get the overall reduction. That setup would get you a bit over 3mph!

Mod .7 sounds a bit small to me (roughly the same as what's in a drill gearbox), and I'd be even more cautious at just 5mm wide. I'd expect to use mod 1, 10mm wide, or similar.

[maddox10]

The NTM motors have a lot of torque, I would opt for mod 1 gears. Z12 to Z 36/Z12 to Z48.

The 12/36 double gear is one you can buy at www.Conrad.com , order number 240320 - 62
, making life easier.

[Liftoff]

Christmas shopping time!
Just need some advice before I start ordering stuff... I'm about to order gears for the gearboxes, motors and escs.
The motors I'm going for are these:
http://www.hobbyking.com/hobbyking/s...dproduct=16231
These spin at around 13500rpm on 4s. The diameter of the wheel/track is 80mm, I'm thinking of gearing it down with a 12:1 ratio.
Did some research of available gears and I'm looking at two stages of 6:1 using 5mm wide 0.7mod gears with 10 and 60 teeth.
Any suggestions if this is suitable and strong enough for the above motor?