Introducing the Electrom

[Dauntless]

If that's the actioncam mic, that's interesting sound. Seems to sound better when it's facing AWAY from you.

Three words: Solid Medium Transfer. When there's any little rattle of the selfie stick or whatever, it vibrates up to the camera and the capsule floats around and we hear it. Wind noise, what can you do? Well you can 'Loop.' You wear headphones to listen and rerecord your narration afterward. Or just don't say it while you ride, do it later.

I'm sorry, I do this for a living. Or used to, not doing so well at the moment. You really got me with the jump cut to someone handling the camera after it being all selfies up until then. Not sure if it's so jarring to the uninitiated.

 

[tigcross]

Hey guys, I absolutely appreciate the feedback on my video, and will work to do better next time. I have to find the comfortable medium between professional looking video and not spending too much vehicle development time tinkering with videos. After all, the idea is to create the vehicle of the future and save the world, not become a youtube star. :lol:

 

[LeftieBiker]

You should be able to get a good result just by taping the selfie stick super tight, and putting microphone foam over the mic or mic hole. And do try to drive more straight-ly.

 

[SlowCo]

Very nice build!
Although the steering cables could maybe attached directly to the plate under the fork?:





That would minimize failure points.

 

[bige]

look in to the rake trail vers length. the forks have to much rake for what it is. look into chopper Harleys should be the fasest place to find this info. a bike can turn and be stable if the geomentary is right I am gessing when u turn sharp is wants to flop over.

 

[tigcross]

Very nice build!
Although the steering cables could maybe attached directly to the plate under the fork?:
That would minimize failure points.

The problem is that there needs to be a turn-buckle in the system to adjust the cable tension. One could put the turnbuckle elsewhere in the linkage, but as the system is currently designed, it needs to be in-line somewhere.
To be honest, I already know that the system as it is could be improved by using round pullies (also called a sheave) on each end of the cables instead of lever arms. This would yield a smoother action and allow for a tighter steering circle. I knew this to be the case before I built it this way, but hoped that the lever arms would work as they are simpler to build. The lever arms do work BTW, but pullies would be better.

look in to the rake trail vers length. the forks have to much rake for what it is. look into chopper Harleys should be the fasest place to find this info. a bike can turn and be stable if the geomentary is right I am gessing when u turn sharp is wants to flop over.

Thanks for the feedback but actually this is not the case at all. There's a pretty big difference between a Harley and a long-wheel-base recumbent. This version of the Electrom is version 5 of an idea I've been pursuing for quite some time and I did a lot of investigation into head-tube angles with version 3. I tried much steeper and much slacker, the angle as it is now is a good trade off between stability and turning radius.

 

[LeftieBiker]

look into chopper Harleys should be the fasest place to find this info.

And don't forget the Ape Hanger bars! :wink:

 

[tigcross]

look into chopper Harleys should be the fasest place to find this info.

And don't forget the Ape Hanger bars! :wink:

funnily enough if I wasn't using an under-stear system I would need Ape Hangers to clear my knees while pedaling.

 

[ThatWarrenGuy]

I have some particular interest in how the generator was wired into the electric system.

I have an electric handcycle, a Horizon recumbent trike ( Horizon handcycle - Outrider USA ) and it's very hard to keep the handcranks geared to be right with the electric motor's output. It has an Alfine 11-speed rear hub with the push button electric shifting.

A little bit of the thumb throttle (currently the only input) and I speed up enough that I'm needing to go up 2 or 3 gears up. Similarly when slowing down - Unless I'm riding at a constant speed I feel like I spend all my time shifting to get the hand cranks in a gear that will let me provide a bit of input without being bogged down. It has a Cycle Analyst v3 so I'm interested in remapping the throttle response or adding a pedal cadence sensor.

So I understand the mechanical setup, but how do you use the motor as a generator, and how does it's output get turned into rectified current at a voltage that can charge the battery? From what I think I know, there would have to be field current in the stator to go from free turning to generation, as in regenerative braking. It's kind of like there'd need to be one 3 phase controller for the generator and one for the drive motor, and a DC-DC converter to get the generator output to the right voltage to float on the power bus.

Is there a way to control the physical resistance of the generator, kind of like setting a gear ratio? Like by varying the field current to the motor coils...

 

[justin_le]

So I understand the mechanical setup, but how do you use the motor as a generator, and how does it's output get turned into rectified current at a voltage that can charge the battery?

I'll speak for Tig here since he came by the shop with the Electron a couple weeks ago. In the end he's got it setup so that the gearing to the generator motor causes it to produce a back-emf volage that just exceeds the battery voltage at a comfortable cadence level and that charges the pack through a rectifier bridge. When you pedal harder than this it puts more and more torque on the generator and current into the battery while the cadence increases somewhat, while if you pedal slower than this then the resistance just drops right off completely.

Previously he had been working to use a Phaserunner controller in regen mode so that you could just dial in the pedal torque that you wanted and it would maintain that fixed resistance regardless of how fast you were pedaling, but this didn't feel very natural to the rider. There would be resistance even when you started pedaling from a stop and you'd have more pulsations in the pedal stroke velocity as you passed through the deadband with the legs, and if you tried to pedal harder it would just make the cranks spin faster but the resistance was the same so it wouldn't generate that much extra watts. You'd need to manually increase the regen intensity via the phaserunner's control input if you wanted to step up from say 100W to 300W of generation.

It's kind of like there'd need to be one 3 phase controller for the generator and one for the drive motor,

That is correct, although in this case rather than using an actual controller on the generator, the controller is just being used as a passive rectifier bridge (6 mosfets is the same thing as 6 diodes in this regards)

and a DC-DC converter to get the generator output to the right voltage to float on the power bus.

No, there is never a need for a separate DC-DC controller for this. If it's just a passive rectification, then the generator output voltage is set by the rider's pedal cadence, so they just spin up to the generator speed that causes the battery to start charging. If you want to have the controller doing active regen, then that will step up whatever back-emf voltage is present on the generator to the bus voltage automatically, there's no need for a separate DC-DC to do that, the controller itself is the DC-DC (well AC-DC) boost converter.

 

[minimum]

Previously he had been working to use a Phaserunner controller in regen mode so that you could just dial in the pedal torque that you wanted and it would maintain that fixed resistance regardless of how fast you were pedaling, but this didn't feel very natural to the rider. There would be resistance even when you started pedaling from a stop and you'd have more pulsations in the pedal stroke velocity as you passed through the deadband with the legs, and if you tried to pedal harder it would just make the cranks spin faster but the resistance was the same so it wouldn't generate that much extra watts. You'd need to manually increase the regen intensity via the phaserunner's control input if you wanted to step up from say 100W to 300W of generation.

Would there be a way to close the loop by adding PAS (/encoder/resolver/etc) to take pedal position into account to make controllers regen input variable, so the deadband would require less torque to overcome? Or use 1-stage reduction with oval chainring?

 

[justin_le]

Would there be a way to close the loop by adding PAS (/encoder/resolver/etc) to take pedal position into account to make controllers regen input variable, so the deadband would require less torque to overcome?

Yes, most definitely if you're up for a custom electronics control project. In any higher volume product development I'd think it would be totally worth the effort to develop an active control loop circuit for regulating the generator drag force in such a way that the human experience is optimized.

If you do it that way, then you don't really care about matching the gearing and motor KV to to a specific battery voltage so that you get regen at just the right cadence. Instead you'd do it under full electronic control and allow the rider to tweak with a dial at what cadence range they want to ride, and also have them be able to tweak the relation for how rapidly the torque increases when they try to pedal at a higher cadences.

 

[tigcross]

So I understand the mechanical setup, but how do you use the motor as a generator, and how does it's output get turned into rectified current at a voltage that can charge the battery? From what I think I know, there would have to be field current in the stator to go from free turning to generation, as in regenerative braking. It's kind of like there'd need to be one 3 phase controller for the generator and one for the drive motor, and a DC-DC converter to get the generator output to the right voltage to float on the power bus.

Is there a way to control the physical resistance of the generator, kind of like setting a gear ratio? Like by varying the field current to the motor coils...

Thanks Justin for covering off some of the questions Warren had. Here's some additional info for Warren.

As Justin said, I'm using a separate generator from the drive motor. The drive motor is in the rear wheel, the generator is up in front of the bike underneath the pedals. I'm using a low RPM 3 phase wind generator, and just running the three phase current through a diode rectifier to make it DC. The model I'm using is rated as a 48 volt, 300 Watt generator from Ali Express https://www.aliexpress.com/item/32878945779.html?spm=a2g0s.9042311.0.0.11c94c4digF7CB

Because I'm running a 72 volt system I needed a generator that would produce about 80 volts when pedaled at about 80 RPM at the cranks, but I think if one was running a 48 or 52 volt system one could use a smaller and lighter generator. To accomplish the speed increase the rider's energy goes through a two-stage speed increase to multiply the rpm by 9, which results in about 800RPM at the generator shaft. You could vary the resistance through variable gearing, but I have found that if I want more exercise I just pedal a little faster and the resistance goes up considerably.

The generator energy is being monitored by the Cycle Analyst using the solar charge function (thanks Justin and the rest of the Grin crew for that) at a gentle pedaling effort I am producing between 100 and 150 Watts, if I really pedal hard I can produce 500 Watts for a few seconds.

As discussed by others, you could use a controller and circuit to handle your generator energy, and that would allow you to tune the resistance electronically, however, I found that it was very difficult to do with off-the-shelf components while maintaining a natural feel. The simple solution was to mechanically increasing the generator RPM to get the generator output to match battery voltage. I think if this concept takes off it would be feasible to make a control circuit in larger volumes.