Camera, motor, kittens

Going through the workshop, making small improvements and sorting some things out.

For one, after several months of it bothering me, I knocked together a better mount for the angle-poise webcam.

Doesn’t look like much, but now the tilt is on top of the pan pivot rather than the other way around. The previous one was smaller but meant the image was only level when looking directly forward (along the line of the arm). Turning to show what I was doing to the left or right meant the image turned on it’s side. This way the image should remain level and I’ll be able to manuver the camera closer to the action.

In my sorting, I also scrapped some broken battery drills that either had dead batteries, broken chargers or damaged electronics. So I have four sets of low-voltage motors with reduction gearboxes and torque-limiters, and one electric screwdriver with just the motor & gearbox.

I haven’t checked yet, but Wikipedia suggests about the maximum torque you can expect from a battery drill is around 30Nm.

I’d been considering using them to make a large track-mounted robot arm, but at only 30Nm it’s unlikely they’d be able to make the arm move under it’s own power, let alone do anything useful.

If I packed out the torque control spring I could have them continue to run at higher levels, but I’ll still need more powerful motors I suspect. I’ll be looking into what’s cheaply available. Initial enquiries suggest radio-control vehicle motors won’t have enough torque. Steppers may be another option.

I’m envisioning something of a comparable reach to that of a human arm, so about 30cm between joints.

And finally, we still have some kittens looking for good homes.


The legality of using an electric cart

So I’ve been trying to figure out if it’s legal for me use these electric robot bases I’ve been making. This is only my research from today, so there may be flaws. Please feel free to correct me.

Electric bicycles & scooters in the UK are legal to use at age 14 without any licence provided the motor is only capable of 200Watts of power (or 250Watt if it’s a trike or tandem), limited to a maximum of 15mph under electric power and weighno more than 40Kg (60kg for trikes & tandems).

The junk-built “Thunderbird 1” would fall under that at the moment. A 120Watt motor and it’s built as a trike. It’d be lucky to hit 12mph with the wind at it’s back.

However, I do not want to ride T1; I wanted to add a guide-handle to it and use it as a power-assist cart to move heavy stuff around. This seemed a lot safer to me.

But this would also suddenly make it a class-K vehicle; “Mowing machine or vehicle controlled by a pedestrian”, which requires a UK driving licence to use. Mine is currently only a provisional licence.

I found a case where a poor sod who worked delivering milk using an electric hand-cart was told by the police that he wasn’t allowed to, and since he couldn’t get a drivers licence (could only read a licence plate at 21 yards, rather than 25) the dairy had to get him an assistant with a drivers licence to guide the cart while he walked alongside.

I can’t find the link right now, but it was the local MP bringing up the ridiculous state of the class-K licence in parliament and pointed out the man would have been fine to use a bicycle cart, or a horse & cart, all at much higher speeds (and potential risk) than a 4.5mph trolley. The matter ended after a lot of description by being dismissed in true government fashion. Paraphrasing; “Very nice, but that’s an extreme example, it’s not worth bothering.” “That’s ok, I can tell my annoyed constituents I tried, thanks!”

Then I look at the Road Traffic Act of 1988, section 189 which explicitly states “controlled by a pedestrian” is NOT to be treated as a motor vehicle. The same portion also defines the electrical-assist pedal-cycle as not a motor vehicle.

So a class-K is a vehicle as far as the driving licence is concerned, but not as far as the Road Traffic Act is concerned.

Fortunatly this section also defines what “controlled by a pedestrian” actually means;

  • is constructed or adapted for use only under such control, or
  • is constructed or adapted for use either under such control or under the control of a person carried on it, but is not for the time being in use under, or proceeding under, the control of a person carried on it.

Now here it gets very muddy. Remote-control vehicles.

The person driving a radio-control car is a pedestrian, but they have no physical contact with the vehicle. And the only specific example given in section 189 is that of lawnmowers (as well as the milkman case). This implies that the control by the pedestrian is considered to be by physical contact with the vehicle. And there is ample proof of larger & more powerful remote-control vehicles (EG: 5000 Watts) than I’m making being used without a licence (other than that for the radio system).

Now if, and it’s a dangerous to take an if when dealing with the letter of the law, this above paragraph is correct in it’s assumptions, we’re left with an absurd situation.

  • If I ride on Thunderbird 1, I have no legal issue.
  • If I guide Thunderbird 1 with a handle, I need a full driving licence or a provisional one with a fully licensed person present.
  • If I drive Thunderbird 1 via remote-control, I have no legal issue.

Further to this I find some more explicit descriptions on the Suffolk Police website that states;

  • The term MPV (mechanically propelled vehicle) is not defined by legislation, but will include, for example, child-sized motorcycles, quads and all motorised vehicles as defined in the Road Traffic Act 1988. Note the exceptions from the definition of motor vehicle contained in section 189(1)(c) of the Road Traffic Act 1988 i.e. grass-cutting machines, certain vehicles controlled by pedestrians, and specified electrically assisted bicycles.
  • An MPV becomes a motor vehicle when it’s made or adapted to go on roads.
  • MPVs have to be registered, taxed and insured.

I think this just told me that a childs electric ride-in car (a 4-wheeled vehicle, not a bike or trike) would have to be taxed & insured.

I know I’m being facetious there.

Though there’s another loop-hole in all this mess that recently saw a man prosecuted for riding a Segway in the UK. Why is the Segway illegal to use on public land? Because it doesn’t have pedals, apparently. Quoting from the Legalise Segways website; “The Highway Act of 1835 renders the Segway PT illegal in the UK on pavements. They cannot be used where bicycles can (even electric bicycles) because they do not have pedals – and they cannot be used on the road as a motor vehicle because they do not meet any kind of permitted type approval in the UK. The only place they CAN be used is on private property (and only with the land owner’s permission).”

Their mention of the electric bicycles is a bit of a mistake I feel. Although I can’t find Segway literature listing motor power, a user forum post from 2002 however says the Segway uses two 2HP motors. So nearly 3000Watts.

With the electric-bike/trike law an absolute 250Watt limit, using the comparison here seems to provide their campaign with an immediate Achilles heel. I would be far more concerned that the Segway is fifteen times more powerful than the highest rated electric-assist bicycle, rather than it lacking pedals. (of course the Segway needs that power for rapid high-power adjustment in balance, rather than speed or loading)

But the pedal issue is why electric scooters are illegal. They’re solely electrically powered, not power-assisted. And despite being popular gifts for kids, illegal to use on anything other than private land in the UK.

Now to close with a couple of bits of speculation;

  1. The law relating to electric MPVs (but not motor vehicles) seems to take the attitude that the electric motor is solely for the purpose of assistance where the person is physically unable. Bicycle power-assistance, invalid carriages, electric wheelchairs, etc. Actual use as an independent low-risk/low-cost device for the able-bodied does not seem to be a consideration.
  2. With Thunderbird 2 looking at 360Watts of power, it should be legal to use as long as I don’t ride on it, control it wirelessly, don’t run it fast and don’t act like a cock to draw attention to myself. The whole area of new MPVs seems to be a sprawling grey-area where there’s a lot of interpretation involved on the behalf of the legal services. While this seems to sit ok as not-a-passenger-vehicle or a pedestrian-assist/controlled vehicle, it’s still an unusual variety of remote-controlled-vehicle which could invite legal wrangling. The additional robotic components will likely exacerbate that.
  3. While I can’t find specific mention, there’s some suggestion that using an RC vehicle to carry anything (person or cargo) turns it back into a motor vehicle. Which would rather stump one of the original intentions for the damn things.

If I were to make an amendment to the rules though? For a start I’d scrap the motor-wattage rating completely (Hell, scrap the ICE size limits too), but keep the speed limits on them.

It doesn’t matter if your motor is a hundred or a thousand watts; if it’s limited to twelve or fifteen miles per hour you’re only going to go that speed. The only thing it’ll effect is how much load you can carry and how quickly (or if) you can get to that top speed.

Final thought: While cat-K seems to be included on full licences by default, as many of the other categories require specialised testing it seems to imply there is a specific test or portion of test to get licensed to “drive” a push-lawnmower. I wonder if it’s possible to get a licence for JUST that?

Also, I’m aware that while not a legal necessity, public liability insurance is advisable when using powerful RC vehicles in public.

Picking up more pieces

I am officially looking for a treadmill to rip apart. I almost had one tonight but went to make a sandwich and got bid-sniped before I got back.

I know, with all I’ve said about just going straight in with your max-bid.. :P

Maybe I just want something new to mess around with.

Thinking of combining several of my existing half-done projects to conserve resources. Like taking the steering rack off the electric kids car, the motor and axle from the golf-caddy and the wheels from the big robot to make an electric go-cart. I can allways re-use it for the robot project later anyway.

Likewise thinking to combine the never-quite-functional robot dog thing with the robot camera-arm to make a sort of Scutter robot.

The treadmill I’m after with a view to fixing up the milling machine more with new head. Would be relatively easy to mount a slender DC motor on the mill’s front compared with a chunky AC motor of similar power. Plus I’d get a nice flat torque curve and less pully-gearing requirements (I anticipate at least 3 “gears” to give additional range. 8000rpm motors will probably only go down to 150rpm before stalling. Proper mills can get to low double-digits).

I suppose they’ll always be these things around, and I should concentrate on more pressing matters. But likewise I want to feel like I’m progressing. And the easiest way is to try and buy progress.

I’m acting no better than those militant Doomers who pile up their homes with survival gear they’ve never used and have no idea how to, just for the safety blanket of feeling more protected.

Robot eye tinkering II

Okay, so I’ve spent a little on the eye. I grabbed a £10 PS3 Eye while grabbing some other casting supplies for the business. And since whether the robot it’ll be attached to works out, I can still use it for webcasting from the workshop.

Also grabbed some M3 nuts; for some reason I have hundreds of M3 screws but no nuts.

Oh, and four flanged bearings. I don’t know the exact strength of these old servos, so didn’t want to make their job harder. For once I found prices cheaper than ebay. Most of the ebay flanged bearings were as pairs, so about £2.50 each for ones with a 3mm ID. Fast Lad Performance did a set of four for £4.08 (£6.45 inc signed postage).

The bearings arrived the other day along with some of the plain (not nyloc) nuts.

While I was waiting for them, I managed to do some repair-soldering on three of the servos with cut-short wires.

This is the sort of thing. Wires under an inch long from the PCB. I cannibalised the cables from some PC case-fans since they already had 3-wire cables with connectors on them at a standard 0.1″ pin spacing. Handily the wires are also the same colours as the servo ones!

Had to trim back the rubber gland a bit on one so the wire could bend sharply enough to clear the mechanism.

Why are the wires always at the end with the mechanical output too? It seems to mean robotics using standard servos end up using oversized brackets to clear the cables.

I also cut up the small servo with broken gearbox and got the potentiometer hooked up to a gear after a lot of trial, error and fusing gear & hubs together with the soldering iron.

When the cross-piece was cut down a bit I also drilled holes and bolted the pot-end to it, and then added the other half of the servo carcass to the conveniently identical-sized focus motor. Means I’ve been able to hide the servo’s PCB in that half for safe-keeping. Nice & tidy.

With the new bearings I drilled out some slices of the old shower cabinet frame and used them as brackets to mount one of the servos. The join is a bit loose because I over-filed the square hole, but it’ll do for the rough version.

I pressed the cowling on and loaded some nuts into it for weight. Weighing them after it drooped, I’ve got another 80grams before the servo gears won’t hold it locked in position it seems. I might be able to get away with that just fine, but it may mean bigger servos if I add an auto-focus mechanism later.

I then grabbed the tin-snips and made up a small mount for one of the small speakers from an old laptop. It looked okay, but I quickly realised it would foul the pan-tilt mechanism. I’ll have to go inside the cowling somewhere.

Need to fab up the pan mount next. Trying to get some weight away from the arms end I’m going to try and run it from a servo near the elbow using some old printer toothed-belt if I can find a matched set of belt gears.

I can probably clear up some of the tinier parts now and make some space again now the basics are together. It should get bigger & cruder as it goes down toward the base. Got some old printer flanged-bearings for the elbox & shoulder (8mm ID).

It’s enjoyable so far. But I really want that cheap camera to arrive. I know xmas post slows things down a lot, but I am a little concerned.

Please excuse the photo quality. These ones were grabbed quickly with the mobile phone. There’s enough loose glass-fibre in the workshop at the moment I’m loathed to take the good camera down there.