Scoota Rebooted Pt.1 – The Big Makeover

September 7, 2012

The rebuilt scooter with Lyen 18-FET 4110 controller, 1500W motor, big Bopper 120/90 tyres and extended centre-stand

While I was dismantling and fixing the motor and had so much of the back end in pieces, it was a good opportunity to give the bike a proper makeover. With all the commuting I’d done in all weathers, and the amount of time it had sat outside my workplace in the pouring rain, it was getting a bit rusty round the gills, with the swing-arm, battery box and other frame parts in need of a clean-up and respray. There was also a broken bracket on the battery case where a crater in the road had jarred me hard enough to almost bring me off the bike.

Swing arm removed

Swing arm and stand removed

There was also the matter of the centre-stand. I’d recently decided to go for even bigger tyres than the 3.5″ K-62s, and decided that the 4.2″ equivalent Michelin Bopper would fit the bike, give me a more comfortable ride, and also increase the amount of distance covered per turn by an extra 8.5% compared to the K-62 tyre, which would aid top speed with a sufficiently powerful controller. However with Big Bopper tyres front and rear, the bike stands at over an inch higher, with the centre stand barely able to touch the ground.

I’d ordered a custom, 18-FET controller from Lyen, and while I was waiting for it to arrive I got to work on cleaning up the bike and giving it a respray. You can see the swing arm below looking a bit worse for wear from the weather.

Likewise the stand, but before the stand got a respray it would need some surgery to make the legs longer. To extend the stand, I decided to do a ‘cut-and-shut’ with two inch-long pieces of steel tubing. Fortunately my local metal worker had some of exactly the same gauge and diameter.

After sanding off the paint around the cuts with steel wool, I set to work on it with an arc-welder.

A bit of grinding to tidy up the welds and it’s an inch higher and ready for its respray. I also took care of the broken bracket on the battery case.

The nice, shiny, resprayed swing arm goes back on with the repaired motor.

After a respray, the back end is ready to be reassembled

This is where I finally get to put into commission my custom-made, heavy-duty torque arms. Because of the length and the longer adjuster slots, the wheel can be slid back a further inch or so keep it well clear of the battery box. Standard torque arms are especially susceptible to wearing out when people use regen, as accelerating and then decelerating under regen alternately turns the axle one way and then the other, which can lead to it gradually chewing its way through the retaining slot. Hopefully these much sturdier pieces will let me use regen with impunity. I might even double up with a couple of extra ones just to be ultra-safe…

While I was at it, I removed the plastic panels to get better access to the frame and battery box. While the battery bank was having a couple of weak cells replaced, I had resprayed the battery box with hammerite inside and out. Once everything was reassembled, the wiring was re-secured with fresh cable ties. To accommodate the larger tyre, the mudguard needed a couple of inches of the forward end trimming off as the tyre was rubbing against it. However that part of the mudguard serves little purpose as it’s below even the base of the battery box.

Sprayed and back in place, the extended stand gives the extra inch that the larger tyres need to allow the bike to be properly parked. The rear wheel therefore has about the same ground-clearance as it did before – about an inch, so that the wheel can be spun while the bike’s on its stand.

The stand – extended by an inch so it works with the bigger tyres

All reassembled and ready to go, there’s just one thing missing: The silver panels that came with the bike had been getting steadily more battered, and one finally broke. While I was buying my motor from Steavan, I also got a couple of fresh panels that he had for sale.

The best match he had for the bike were black ones, which I think look fine.

The Road Test

Once I’d got Lyen’s controller up and running, it was time to run it in, steadily increasing the rated and phase currents until I found a setting that gave me the power I needed, but without getting the controller to run dangerously hot. I eventually settled on 60/150 rated/phase, though a little less than that would probably have made no difference. It seemed that any setting at all above 55A or so made no extra difference to the power. But since I’m putting 4KW plus through a 1500W motor, this is hardly surprising – it seems that the motor just won’t draw any more than that. The next stage on the upgrade path is an even bigger hub motor. The controller, though, runs pretty cool, topping out at 60°C only after a great deal of extended thrashing.

The performance though, is fantastic. Very torquey, with phenomenal acceleration that’s more than adequate to beat most things away from traffic lights – I’ve recently noticed shocked boy racers in BMWs or Audis chasing me to try and make a point.

Though the acceleration is excellent, I didn’t end up with quite the top speed I’d hoped for. With the Lyen 12-FET controller I was getting 43-46 mph satnav. Now I’m getting 48-50mph satnav, topping out at about 52mph when the wind’s in the right direction. That’s the equivalent of about 55mph clock-speed though, and more than adequate for short hops between towns. I was hoping for a little more than this, as I thought my 120/90 tyres would leverage me a bit more speed, but different motors are wound for different types of performance and it’s just pot-luck what you end up with. I believe this one is better on acceleration because it’s wound for ‘torquey’ rather than ‘fast’. Still, I’m more than happy with the results.

With the new motor/controller combination, regen is a little harsher than it was before, and I might tweak the resistor value to make it a bit lighter. I’m also thinking of wiring a button into the regen self connector so I can switch it on and off without plugging my laptop in and changing the settings.

As part of my upgrade, I also built a custom heatsink for the controller. Though heat is not a particular problem at the moment, that might change if I get a 6KW hub motor or something. More about that next time…

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