An Electric Bicycle

[vtsteam]

Freezers are handy things. If you ever need to drill rubber cleanly -- like a rubber stopper, freeze it first.

[S. Heslop]

Got a bit done today. Leveled the lathe first, or got it more level than it was, which helped reduce the taper on the turned part.

Then I made a camera boom similar to doubleboost's except... junkier. I'm still working out the problems.


But it still helped get some good angles for recording.


Finished the motor shaft after that. It's probably the most accurate thing i've produced yet, but that's not saying much.


Y'know I trapped my finger every single time I put the motor together. I was trying to prevent the thing from snapping closed when the rotors got near the magnets, but there's really nowhere good to hold on to and those magnets are helluva strong. No blood blisters though fortunately, but it still hurt!


To truly finish the shaft I need to put a keyway in for the gear. But, lacking a mill, i'm thinking about just carefully drilling a hole in and using a dowel pin to spline the gear to the shaft.

[vtsteam]

A pin radially through the shaft would weaken it quite a bit.

What about drilling the shaft axially with the gear mounted at the join line, to accept a solid round pin? That would act like a square key, only round. Maybe a drop of Loctite to hold it together while drilling. Center punch on the line,  mount it solidly in a drill press, and step drill to final size.

-or-

Can you mount a woodruff cutter in your lathe, and mount the shaft in the tool holder at the right height, to cut a square groove in it?

-or-

If no woodruff cutter -- make something -- even a simple small fly cutter, and feed lightly?

[S. Heslop]

I have sometimes seen people use their lathe like a shaper, with the part held in the chuck and the tool sideways, and cutting by moving the apron back and forth with the spindle locked. I just figure it'd be awkward to make a kind of 'blind groove' that way. One that doesn't run all the way along the bar to one side.

My concern with the pinned shaft was the pin being more liable to shear than a keyway, but it couldn't be any worse than a set screw. The hole would only have to be drilled as deep as a regular keyway would too, so I don't see how that'd risk weakening the shaft any more than a keyway would.

Thinking about it, I might be able to do the shaper thing by first drilling a hole and using that to start the cut in.


With the part held in the toolpost and a cutter in the chuck, I could probably get away with using a regular slot drill with the part held in line with the cross-slide. The only problem is that i'd have to buy a slot drill!

[RussellT]

You could make a tool to cut a slot using a bit of silver steel - or even a broken drill bit resharpened to give a flat end.

Russell

[vtsteam]

Steve a cross pin is far more likely to shear than a round key -- think of the cross sections!

[S. Heslop]

Steve a cross pin is far more likely to shear than a round key -- think of the cross sections!

Would there be a risk of a round keyway 'jacking' out and putting radial pressure on the gear? The keyway in the smaller gear is cut relatively close to the edge and id be worried about it cracking.

The bigger complication though is that there's quite a bit of shaft beyond where i'd want the keyway to be, since a bearing supports the shaft on the end opposite to the motor, which would make it hard to drill a hole parallel to the keyway.



I still think compared to a set screw a pin would be adequate though.

You could make a tool to cut a slot using a bit of silver steel - or even a broken drill bit resharpened to give a flat end.

Russell

I've only got 8mm silver steel on hand unfortunately, too small to make an effective cutter. I'm thinking now that it'd be worth giving the shaper idea a go, drilling a blind hole in the shaft to give a place to start the cut.

[S. Heslop]

t=4m20s

Heres a video demonstrating the keyway thing. Shouldn't be too hard to grind a cutter to do this. I could just use a parting tool i've already got ground too and make multiple cuts. Hopefully the 4 way toolpost on my lathe will give me enough room.

[vtsteam]

Steve, I didn't realize the gear already had a square key slot.

Seems best to mill the shaft to match then.

[vtsteam]

Steve, you don't have to use the scraper method on the shaft, if you have a boring bar (as in the video).

You can mount the boring bar in the chuck as a fly cutter, and the shaft to be milled in the tool holder, and mill it.

The boring bar is just a one tooth woodruff cutter. 

Lathe in reverse so you aren't climb milling.

Very light cuts and slow feed. Try on a practice piece first.

[S. Heslop]

Tragically I don't have a boring bar, i've never had to bore anything too big and deep yet. Plus I feel a fly cutter would make a pretty wide 'scoop' that would remove material from where i'd rather keep it.

I appreciate the suggestions though, but I feel the shaper thing would work best with what I have available right now.

[vtsteam]

Well it will be cool to see you do it that way! 

[tom osselton]

We did the shaper thing in school way back when on a external thread for jackstands it worked fine on a whole keyway, I would suggest a hole drilled at the start and end of the keyway otherwise the end will be a bitch to clean up the chips have no chance of breaking off clean if you don't. How hard is the shaft?

[S. Heslop]

We did the shaper thing in school way back when on a external thread for jackstands it worked fine on a whole keyway, I would suggest a hole drilled at the start and end of the keyway otherwise the end will be a bitch to clean up the chips have no chance of breaking off clean if you don't. How hard is the shaft?

It's just EN1A steel. I've had trouble with silver steel fatiguing in the past so I thought i'd just try a more regular old steel for this one.

[S. Heslop]

Alright! The shaper thing kind of worked.



There were plenty of problems with the method though. For starters, the toolbit was digging in due to the backlash on the cross slide, which made the part slip in the chuck jaws a few times (it was held in without any shims to protect the finish since I find that tends to muck up the alignment). I had to use a 1mm thick tool shimmed to various heights to cut the full width.

The two relief holes I drilled were also kind of small. I figured i'd need to drill holes wider than the slot, but I didn't drill them wide enough. This made it hard to get the cut started and the slot ended up being a slope.




The results were messy but they seem to work. The key was filed from a round silver steel bar. It's pretty hard as is, and I'm not sure if it'd be worth trying to harden it further. The slot I cut was pretty shallow but hopefully it'll be enough. Can't be much worse than a pin would've been!




I also built the world's laziest spindle lock to keep the spindle from rotating. It works terribly but it was enough to keep the chuck steady during this.

[vtsteam]

Keystock is usually soft -- comes in a 12" long stick at most hardware stores here, and you cut it to length with a hacksaw and file the ends smooth and chamfer corners. Usually you'd rather damage the key than the shaft if it shears.

You can always replace a key. Not so a shaft.

[S. Heslop]

Ah. I was imagining you'd want it hard so that it's easier to get the gear off, but I guess protecting the spindle makes more sense. At least it won't be too hard to remake the shaft if it does shear.

[S. Heslop]

Ain't it typical for a dropped item to bounce right into the darkest and most cluttered corner of any workshop. Luckily it was just the keyway, but I guess i'll order some keystock for making a new one.




I got one of the arms mostly assembled now, and it's a real goofy looking thing, but i'm glad things aren't too misaligned that it doesn't fit together. I'm still not too certain if it's even going to work over all though. The contact wheel will be about 50mm diameter maximum, and that's not going to have alot of surface to contact the smooth metal of the wheel's rim. I don't want to have to put too strong a spring on because i'm not so sure how well these bearings will handle the radial force. I guess time will tell though!

I'm waiting on some circlips to be delivered to finish off the gearbox part.

I also had another of those brain farts and cut the plates wrong, so the gear sticks out a bit forward of the front about a millimeter. Any cover i'd make would have to have a recess in it to accommodate that.

[vtsteam]

Hey, it's looking just like your drawing. Good work! 

[PekkaNF]

looking good

You got that keyway right and if that gear is running concentric with a shaft you did really very good job. Keys are those things that look really simple but are easy to use wrongly. I'm resorting more and more on glue and shrink fit

Pekka

[S. Heslop]

Been busy the last few days but got a bit done. I'm real glad I bought those burrs at the car boot sale, just used one as a sort of 10mm reamer to get the holes in those aluminium lumps to a sliding fit. Aluminium on steel probably isn't a great bearing surface, or great in general, but i'll see how it goes.

Also note that I mucked up with the angle iron and they're not mirror images of each other.

All i've got left on the mechanical side is keywaying the larger gear's shaft, making some bars to connect that forward hole on the box section to the frame (it should be strong enough without a second set of angle iron struts like planned), and making the contact rollers. I'm short on space near the tyre though so i'll have to make them a bit different than planned. I'll probably also want to fully enclose the gearbox at some point to keep doit out.

Also in other news I hit my left ring finger with a hammer about 5 or 6 days ago, and it's not gotten any less sore. I'm starting to wonder if I've broken it but i'll give it a bit longer. I've been thinking about banjos alot lately but it's killing me that I can't actually play one without it hurting!

[vtsteam]

Simon, you gotta take it easy on yerself. You're supposed to last a lifetime! Cuts, burns, and hammer blows are no good, man! 

Bike looks great. I don't think those particular alumin(i)um bearing block will produce much friction for the requirement Seems fine to me.

[S. Heslop]

Got the gearboxes totally complete now with keyways and circlips. Might buy some loctite to stick the bearings in place though.

I'm playing with the electronic side now. Ordered some 60 amp fuses and a fuse holder.

I've had a problem with the ammeter not working (the needle just sort of twitching at the bottom of the scale), but by chance I had a 'spark' occur through what I think was the shunt contacting the wires I had leading from the shunt to the ammeter, although i'm still not sure why i'd get such a big spark (it blew the chrome off the side of the shunt and scorched the desk) from just that, but that's all that could've been touching. So I suppose the insulation on those wires isn't enough, and were shorting out before the current could reach the ammeter. The continuity itself tests fine.

I'm gonna leave testing it any more until the fuses arrive. That spark gave me a fright. But at least the motor and controller seem to be working!

[vtsteam]

Simon you've got the equivalent voltage and current capacity of a DC welder. So yes it could produce a healthy spark if you short something!

In fact it's quite possible to make a DC welder from a couple of car batteries hooked in series, a stick holder and a clamp.

A shunt is connected across (parallel to) an ammeter. A shunt and ammeter must always be used with a load that drops the current to the range they are rated for. Don't ever connect them directly to a battery with no load, since the battery can output hundreds of amps, and the shunt and ammeter are pretty much a dead short.

[kayzed1]

Bit late but look what i found..
http://www.petrolscooter.co.uk/spare-parts/electric-scooter-hobby-parts.html

Lyn.