Drive motor options

[mightymouse]

Chris,

0.2mm on diameter is perfect. When drilling pre-drill to within a couple of mm of finished size. If the reaming drill has to do too much work it may cut oversize and ruin everything.

Get the ream holes dead size for the bearings and loctite 603 or similar will hold them in the plates without needing retaining plates.

The gears should Loctite well but if not make a small collar and loctite that to both the gear and axle as well.

Trev

[Liftoff]

Great, thanks again Trev. Ordered the remaining parts I needed (bearings, silversteel shaft, loctite, drills and reamers). Will go on with building the boxes as soon as I have everything...and keep you posted

[Liftoff]

Any idea from where I could get some laser cutting on acrylic done, at a reasonable price? I'm being asked silly prices locally for a couple of pieces 64x34mm 10mm thick...

EDIT: No longer required - alternate method suggested

[Liftoff]

Update: finally found some free time and got the motors and escs rigged for a trial, looks fine running on no load and looks quite powerful. One thing I noticed,full fwd to full reverse the motor will come to a stop in a fraction of a second (with a big jerk), but you have to give it a reverse command again to spin in rev. Well, I'll see to that when I get the programming card and have everything connected...

Gearboxes almost done, had a problem with the pinion gears which I just couldn't drill through! Dont know what material they were made from, for me its some type of cast steel or similar. Tried with a cobalt drill, no success, so I machined a new face on the lathe, no swarf came out, just a golden powder...tried to drill again, with some success...again golden powder instead of swarf. I bored about 3/4 of the length of the gear and then again, the drill refused to cut any further...like trying to drill a piece of hardened steel.
I the end I found that the gears had cracked the gears are made of some type of steel for sure as its magnetic and flies yellow sparks when ground, like these:
http://www.modelsport.co.uk/hpi-pini...roducts/363296

I ordered a new set from a different shop and I'm sure these are normal steel and the hole size is correct so I dont need to drill anything... after that the boxes should be done...

[Ellis]

Sounds like they are sintered steel (the one you linked looks like it), like drill gears, which are equally impenetrable with a cobalt drill. Nick, in Aus, intended to mod loads of drill gears to make more rugged drill gearboxes but found the same thing as I did, simply not drilling. He ordered a carbide drill and reamer from US, don't know how that went, will ask.

I think the way they do it is they mold and compress fine powder to form the gear and then to make it at all viable they harden it to hell and back, or it may just be very hard from the casting. Either way, I'm quite sure the gears from places such as Technobots and Beltingonline are "proper" machined gears from steel and not cast. Likely to be more expensive but at very least they'll be practical; they can be welded too.

[overkill]

Hi Ellis! You reminded me how slack I've been so I tried out some new drill on the drill gears. It worked brilliantly, see the details here: http://www.robowars.org/forum/viewto...?p=85652#85652

[Liftoff]

Nice work nick. Could be it was as you said Ellis, some type of sintered steel... strange material to work with!
It's also most probable my fault as well as I drilled them without coolant and the two that cracked clearly overheated!
That material has got some sort of case hardening tho, I could cut through the central part relatively easy with a black HSS drill and reamed to a good finish. The ends were a different story!

I was also drilling slightly larger holes than you were Nick, 6 and 5mm. The 5mm holes came out fine, but the 6mm holes were at the limit a 10T mod 1 gear can take!

20140207_090836.jpg

[overkill]

My gears look different to the ones in your photo; they have a surface finish that couldn't have come from any milling or turning method I know of and they were definitely hard all the way thru. Your gears would probably benefit from the carbide drills as well; I had the lathe set for 200 rpm and used a slow feed as I don't have and data for working sintered steel with carbide. The gears only got slightly warm.

[Liftoff]

My gears look different to the ones in your photo; they have a surface finish that couldn't have come from any milling or turning method I know of

Originally they looked like this:

HPI gear.jpg
I couldn't drill through it at that stage so I turned it on a lathe and cut a new face, that took the hardened piece off and I could just about drill it.
What type of drills did you get Nick, there are loads of different shapes carbide drills around! What worked for you?

[overkill]

Ah, now your gear looks exactly like mine. I used drills like this: http://www.mcmaster.com/#standard-drill-bits/=ql6bw5 and I am sure you can find the same thing locally in the UK or Europe. I tried facing one of these gears and only succeeded in ruining a carbide insert.

[Liftoff]

Could be they are different materials then, as I did face it with a carbide insert. I needed the gear 5mm wide so I cut it off with a Dremel type cut-off disc, no problems there either.
Good choice of drill on that website, thanks...

[Liftoff]

Gearboxes almost ready now. Have not tried them out with the motor yet, but they turn freely by hand. Had to do some modifications to the original design, namely introducing thrust washers to reduce gear rubbing on the side plates. Looks good enough though, considering its a precision part manufactured using hand tools a lathe milling combi would have come very useful! will have to wait a bit more for that...
Will try to find some time tomorrow to couple the motor to the box and give it a go...hoping it will stay in one piece - fingers crossed!

20140222_130223[1].jpg20140222_140743[1].jpg20140222_141635[1].jpg

[Mouldy]

looks good!

[overkill]

For a gearbox made with just hand tools, that is fantastic work.

[daveimi]

Is there any chance of getting a run through of how you got it so accurate with hand tools?

There is hope that mere mortals may be able to make something like this!