Sunday, 21 July 2019

battery compartment preventive maintenance

I have often stitched up my clothes and I can attest to the correctness of the adage "a stitch in time saves 9"; so I decided to do a bit of quick maintenance on my Mercane Wide Wheel (dual motor) while I was pulling the cover off for an inspection of battery (for evidence of heat damage, and I found none).

Basically I found that the battery is actually held in place by that bottom cover, so its actually important to not break it (because it serves an important purpose too). I also observed that the battery is already sagging (well why wouldn't it) and putting weight on the wire that runs underneath it (see video). So I decided to give it some additional supports (other than just pressing on the wire).



While I was in there I actually noticed that there are holes in the bottom of the base, which is a good thing as that's going to help ventilation and allow water to drain. I'll have a closer look at my single motor one when I get back to Brisso tomorrow.

Saturday, 20 July 2019

Mercane Dual Motor Torque Steer

I currently own both the dual motor and single motor Mercane Wide Wheel, I leave one down where I work (200km from here) and one here for the weekend (saves hauling one around and that seemed a valid excuse to try the other when I bought the single wheel first ;-).

Which is better?

It turns not a straight forward question of money vs power (although on the surface it may seem to be).

One of the major differences is that the dual motor has more torque (like double heh) works out to be plenty for hills with my body weight. In fact for all but the steepest hills the single motor works out to be sufficient (meaning that if you're not seeking thrills then it does the job quite well). I mean looking at this trip, I would doubt that the dual wheel would bring much to the table in terms of getting there and back in any significantly shorter time. Interestingly I found that going up the steepest parts of the steeper hills that kicking made a difference on single motor Mercane but curiously it didn't do anything on the dual motor Mercane.

Now part of that is probably that its going almost as fast as I could possibly propel any scooter with my foot, but it feels like I'm putting in substantial energy but that's being absorbed by something. My suspect is the extra weight and the extra resistance provided by having 2 motors instead of 1 (and a very low rolling resistance front wheel).

Weight

The dual with its extra motor and 50% more battery (and extra controller) weighs about 5~6kg more and you do notice this lifting it in and out of the house. I don't think I'd like to lift the dual in and out of the boot of a car, indeed I could barely get the box out of the back of my wagon by myself when I got it home.

Handling

Then there's torque steer, the dual wheel has a substantially observable change in steering reaction under power compared to the free wheeling front wheel. I've noticed that almost nobody (even motorcycle riders) seem to get what's going on in geometery, so lets look at this quickly (and you can read this link if you're interested (which you should be).

Basically the front wheel of a bicycle (scooter, motorbike, whatever) has by its steering geometery built in stability by the same way that castor wheels work on chairs, shopping trolleys you name it. This is clear on a castor wheelsbecause the wheel is clearly behind the bit that spins, but on a bicycle perhaps not so obvious and its done like this:



So on a scooter, the smaller wheel makes the geometery harder to see but its still there.

Now when you have the front wheel pulling, especially when in a corner things get interesting because suddenly there is another force on that wheel pulling the castor around.

Unsurprisingly this makes the steering want to follow the straigh line and you feel that kick in the handlebars quite strongly. I would liken it more to front wheel drive vs rear wheel drive in the pre power steering days, but I guess younger readers just won't even know what that means.

However in a straight line, belting along a flat grassy field (heaps more resistance than the road in case that didn't jump out at you) the dual wheel just hoots along at 21kmh, while the single struggles along. When climbing my drive way the dual wheel power provides some great benefits by not just spinning the back wheel or causing the front to lift ... so its swings and round abouts.

 As it happens I'll be needing that this weekend when I'm doing traffic control at an event up here where I live.

Sunday, 14 July 2019

Mercane Dual motor underbelly

being one to always like to look under the covers (as well as check all the screws) I decided this afternoon to to pull the cover off the battery pack on the Mercane and have a look. Compared to the single motor its quite "pregnant" under there. Basically everything below the red line is unique to the bigger battery system of the dual motor.


Its certainly made the whole thing heavier, with my scales suggesting that the weight is actually more like 23kg. Interestingly it has a front rear weight distribution which puts 14kg on the front and 9kg on the back (bathroom scales under each wheel and confirmed with my digital luggage scales and also with my holding it and getting onto the bathroom scales). Update: my single motor variant is 11kg front.

Interesting.

So what's under the cover?


In this shot we see that the battery runs the full length of the available tray, as well as the wonderful webbing cast that strengthen that entire platform and the controllers.

plural you say?

Yes, two controllers, stacked one atop the other and thus hanging down lower than the battery pack.


as well as seeing where the plastic belly pan screws into we see the location two controllers. Which is interesting and confirms my suspicion that the way the dual motor version was implemented was to just double the controllers and bung on a back wheel on the front with its own controller. Simple and quick upgrade, run some more wires and voilla. Indeed that cable that powers the front wheel jutting out of the goose-neck at the front sticks out like an after thought to me when I think of it.

The basic maths on the controller is that being rated at 15 Amps it can handle 720W which is more than the peak draw of each motor, so there is built in margins there, which is nice.

Now its interesting to look at these controllers and observe that they are passively cooled (fins give that away), given how much heat controllers need to shed (from switching as much power as they do) is this a bad thing in an enclosed and sealed case? Perhaps, lets recall that the Wide Wheel has its origins in a indigogo campaign (link here) and when it was envisaged it was a single motor design.

Now owners of Mercanes may have noticed this set of 4 bolts directly above the controller ...



which look to me a very tidy way of making use of that big cast aluminium frame as a heat sink. Cunning and well designed!

So it would appear that the original single wheel version planned for this from the outset, but the dual motor version just whacks that contoller onto the bottom of (not a big heat sink) but the other side of a hot controller.

I'd hope that this was tested before being done, but somehow I have some reservations. Indeed I've seen examples of burnt out controllers on the dual wheel on YouTube already (by perplexed non technical owners).

I dunno ...

Anyway, moving up front we see more clearly that lovely webbed cast plate which is the main chassis of the scooter. It actually looks fantastically well designed and made. Looking at the lip around the bottom of the chassis you can see that the belly pan fits snugly into that. However also you can see that any water throw up from the front wheel will be likely to gradually work its way into that crack and down into the belly pan (where there is no way out). This is why I put duct tape over that join to prevent such (as I've owned old english cars in the past ;-)  (post on that here)


as well we can see the underside of the XT60 charging port (so clearly no problem if a little moisture found its way in there past the plugs and cover)as well as one of the belly pan mounts and holy moses look at the bracing around where the goose-neck mounts.


I'd have to pull it apart to see, but it looks like the goose-neck goes down into there and mounts somehow. I'm keen to pull that apart and look (especially after seeing a few Zero's bite the dust exactly due to insufficient engineering there (this is a shot from the internet):


as an engineering sort of guy that even looks inadequate before it broke. Sure, the front part looks solid, but you know what they say about the weakest link in a chain right?

Round up

Well that about rounds up what I've got to present tonight. The Mercane chassis looks great, I love the way the controller uses the chassis as a heat sink, but I have my reservations about the piggybacking of the second controller down there.

Then theres the weight ... its a lot heavier to heft around than my Single motor version ... which to me is shaping up as the sweet spot of the design (and indeed closer to the original conception of the designers. As I see it the original concept of the single engine 8.8Ah battery is not only sufficient (as I've already found) but robust.

I'm starting to feel like the move to dual wheel was more about being seen as "not competitive" in a market which is more interested in bling and "hot looks" than in good robust transport.

So basically I'm saying I'm thinking of seeing if I can send the dual motor one back and sticking with the single ... but then again, maybe I'll just keep it longer. Besides, its convenient to have two right now.




Saturday, 13 July 2019

Mercane Wide Wheel dual motor up the range a bit

So with my first day riding around on the 1000w dual motor version I've been experimenting with what I can do with that extra power (aside from just simply go faster and hurt myself or maybe blowing it up as I mentioned in my previous post). Hill climbing is the obvious answer, and so I rode out of town and went up here for a quick test. The ride is done on the "Power" setting (but with the speed restricter re-enabled because I just don't want this to be a weekend wonder...


The stats on the journey are this:


You can see that I didn't actually go back to my starting point, I instead went to a different place in town to visit a mate.

However this time it climbed 184 meters and I hit a maximum speed of 40kmh (probably on the way down the mountain).

Here's a bit of video I started after I was out of town just before starting the main climb up to Daggs Falls



So theres some incoherent ramblings about stuff (you can tell I don't script this stuff right?) which does however show how well the bike goes up ... and up ... and up

And of course then there's down...



My views on the increased rolling resistance of the motor (vs the wheel without the motor) and that the wide wheel having two motors will have more resistance may actually be a great benefit on steep long descents like this because I didn't actually touch the brakes.

So ... probably something tomorrow too