Mid-mount Hubmonster Madass

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Re: Mid-mount Hubmonster Madass

Post by John in CR » Feb 15 2017 11:34pm

You can't run 30kw at 20s without running into heat issues. Heat is the enemy and it compounds, since the resistance of copper goes up by 0.4% per degree C of temperature increase.

Heat is difficult and slow to disperse to the environment, so the one best solution in the battle against heat is to create as little as possible. Steveo runs 400A combined from his controllers and surpasses 100°C with a couple of hard pulls of the throttle. Hillsofvalp did the same thing. At 400A you're creating over 5kw of heat with a cool room temperature motor, and almost 7kw of heat with a 110°C HubMonster. When you can shed maybe 1kw of heat continuously with a stock motor, it's easy to see how heat problems are such a problem for every forum member pushing performance. With winding heat going up by the square of current, heat created decreases much faster than performance as you lower current.

While HubMonster has a lower phase-to-phase resistance than other motors, which makes it better able to handle high current, there's still a finite limit. OTOH HubMonster has such a well designed and constructed iron core and slot and pole combination, that going to higher power via higher voltage costs only hundreds of watts of heat, not thousands of watts like pushing current creates.

I may sound like a broken record about this topic, but going up on current without appreciating the true consequences is a widespread mistake that's easily avoided, especially with HubMonster in a mid-drive since it's rpm limit is way way above the reach of even a 150V controller.

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Re: Mid-mount Hubmonster Madass

Post by Ohbse » Feb 16 2017 4:36am

John in CR wrote:You can't run 30kw at 20s without running into heat issues. Heat is the enemy and it compounds, since the resistance of copper goes up by 0.4% per degree C of temperature increase.

Heat is difficult and slow to disperse to the environment, so the one best solution in the battle against heat is to create as little as possible. Steveo runs 400A combined from his controllers and surpasses 100°C with a couple of hard pulls of the throttle. Hillsofvalp did the same thing. At 400A you're creating over 5kw of heat with a cool room temperature motor, and almost 7kw of heat with a 110°C HubMonster. When you can shed maybe 1kw of heat continuously with a stock motor, it's easy to see how heat problems are such a problem for every forum member pushing performance. With winding heat going up by the square of current, heat created decreases much faster than performance as you lower current.

While HubMonster has a lower phase-to-phase resistance than other motors, which makes it better able to handle high current, there's still a finite limit. OTOH HubMonster has such a well designed and constructed iron core and slot and pole combination, that going to higher power via higher voltage costs only hundreds of watts of heat, not thousands of watts like pushing current creates.

I may sound like a broken record about this topic, but going up on current without appreciating the true consequences is a widespread mistake that's easily avoided, especially with HubMonster in a mid-drive since it's rpm limit is way way above the reach of even a 150V controller.
Totally agree with everything you're saying John, just to clarify - I will not be running this on the highway for protracted periods (registered as a moped, so that's a quick way to big fines) and the 30kw *potential* power peak will only be utilised whilst drag racing and perhaps the very occasional blat. In the case of drag racing I will be fully cooling off the motor between runs, which obviously will be limited in duration for <15 seconds (all going well)

I'm very familiar with the numbers around resistance and heat generation and fully anticipate heat issues if I was attempting to run at this for anything other than limited bursts.

My reasons for sticking with 20s are many, but primarily it's around controller selection. With the new generation of Mobipus controllers I do not require the voltage to get the RPM (at the expense of further heat generation of course). I don't really want to compromise the day to day function, safety, charging practicalities etc for a requirement that's only going to come up a handful of times a year. Like my other bike, this is a practical, primary means of transportation FIRST, toy second!

Rest assured I won't be cooking this hubmonster!

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Re: Mid-mount Hubmonster Madass

Post by John in CR » Feb 16 2017 10:35pm

Ohbse, I figured you were on top of it based on previous discussions. My post was more for everyone else, because the general thing on ES for the non-pedalists is to tread current settings like a di#k measuring contest. Another irritant is treating phase current peak limits as something belonging in a power calculation, where only battery current (or RMS phase current) is something to multiply by voltage.

Imagine if we could get cheap 250V controllers. I'd cut my current limit down to 100A per controller for a cool running 50kw. :shock:

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Re: Mid-mount Hubmonster Madass

Post by Animalector » Feb 17 2017 2:09am

Am I really missing something? I thought the torque was determined by the phase current, if you want acceleration it's torque that is required? A 250v motor running 100A will have less torque at low rpm.

Or are you basing your assertion that a high V is better only in situations where you can get the toque multiplying benefit of some sort of gear reduction?

For a hub motor we're stuck right? So long as we design the peak voltage of the system so that we can reach our target max speed it's only current that's going to get us there faster...right? Taking this same hub motor and throwing 250v across it might give us 50kW but benefits are only going to be higher max speed, at the cost of acceleration torque... Right?

Thanks

Andy

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Re: Mid-mount Hubmonster Madass

Post by Ohbse » Feb 17 2017 4:27pm

Animalector wrote:Am I really missing something? I thought the torque was determined by the phase current, if you want acceleration it's torque that is required? A 250v motor running 100A will have less torque at low rpm.

Or are you basing your assertion that a high V is better only in situations where you can get the toque multiplying benefit of some sort of gear reduction?

For a hub motor we're stuck right? So long as we design the peak voltage of the system so that we can reach our target max speed it's only current that's going to get us there faster...right? Taking this same hub motor and throwing 250v across it might give us 50kW but benefits are only going to be higher max speed, at the cost of acceleration torque... Right?
That's correct. In my case I can change ratio very easily, with a hub motor this is only achievable by varying the diameter of your wheel.

With my current gearing (30 tooth front, 49 tooth rear, ~600mm tall tire) the wheel torque required to lift my front wheel off the ground (with my weight shifted all the way forward etc) takes about 600 phase amps. As RPM increases you get into your battery current limit and you can no longer produce 600 phase amps required for peak acceleration.

Were I to swap out my 80v pack for a 160v pack with no other changes, it would have zero effect on the amps required to produce this torque, however it could produce that torque to a higher RPM before running into battery current limitation. It would also have the ability to spin the motor twice as fast, but without adjusting gearing to suit that's not really a win. If I doubled my gear ratio at the same time as I doubled voltage, I would also require half the phase amps to produce the same wheel torque, but with my original limitations around speed. In reality, things aren't that simple - as motor RPM increases so do RPM related losses. While low in the hubmonster, they still affect things. You would also have controller issues, as with current technology the sweet spot for switching efficiency is around 80v. As I can't magically fit double the number of cells that fit on the bike, re-configuring for double the voltage I'm halving the AH. That effectively halves my ability to produce amps as well, so there's no inherent power advantage there.

All in all, a hypothetical double voltage/double gearing build would see the same effective acceleration (because I'm limited by lifting the front wheel) and then would run into the same limitations with battery power. It would produce less copper loss heat in the motor, however it would do that at the expense of higher iron losses, bearing losses, noisier, less chain engagement if using a smaller front sprocket or much more expensive gigantic rear sprocket, potentially lethal pack voltages, higher controller switching losses, increased pack complexity around monitoring, charging etc. I also can't buy a super power dense, cost effective, highly reliable controller for 40s voltages - but I can for 20s :)

I have tried to optimise the whole system, not just one or two facets. What I've done here might be completely different for your requirements. This system is pushing the hubmonster to its current based limits, but that's intentional because it makes everything else better.

Here's what a sim looks like for my bike configured with an 84v pack, 16mOhm pack resistance, 30/49 gearing, 600mm tire, 185 total weight (me included), 400a battery current limit, 600a phase current limit for an example.
Madass graph example.gif
Madass graph example.gif (46.88 KiB) Viewed 1697 times

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Re: Mid-mount Hubmonster Madass

Post by John in CR » May 16 2017 11:51pm

It's mid May and you need to be out riding. You've invested so much time in a great build, and I assure you that once you're going that you'll regret every spare second that you used doing something other than finishing your Madass beast.

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Re: Mid-mount Hubmonster Madass

Post by Ohbse » May 17 2017 5:28pm

John in CR wrote:It's mid May and you need to be out riding. You've invested so much time in a great build, and I assure you that once you're going that you'll regret every spare second that you used doing something other than finishing your Madass beast.
Absolutely agree John - the trouble is just life getting in the way :) I am still riding every day on my other bike, because I don't *need* to finish this it's taking substantially longer.

I have also been distracted by changing jobs, starting a CNC business, leasing a building, purchasing machinery etc. I'm also travelling a bit with new role initially so that's pushing pause for a while as I'm on the other side of the planet.

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Re: Mid-mount Hubmonster Madass

Post by macribs » Jun 15 2017 11:22am

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Re: Mid-mount Hubmonster Madass

Post by John in CR » Nov 07 2017 11:22pm

MadAsses are few and far between down here, but I was lucky enough to pick up a low mileage gem that had electrical mods go wrong and was 3 years behind on road taxes for only $440. The backlog on the plates doesn't matter to me due to the liberal legal status of electrics, and my converted electric will be street legal without plates.

Mine is getting a HubMonster as well, but it's going in wheel. I plan to cut off the bottom 2/3rds of the main tube and expand it to fit 20s or 21s of 25ah electric car batteries. I may decide to go 30s and make it a real motorcycle killer, but I gotta mock it up first as I want a clean look.

I got it this afternoon and hope to be riding by the end of next week.
Here's what it looked like upon delivery and as of this evening.
MadAss stock es.JPG
My MadAss in stock form
MadAss stock es.JPG (100.82 KiB) Viewed 1777 times
MadAss day 1.JPG
My MadAss after day 1
MadAss day 1.JPG (95.84 KiB) Viewed 1777 times
I think my controllers will go under the seat where the muffler was, and the battery box will be something like this, not as deep at the back if I go 20s and probably slightly more triangular if I go with a 30s pack, since I'll need a 9 or 10s second row of cells.
MadAss day 1 with batt box.JPG
With battery box
MadAss day 1 with batt box.JPG (95.2 KiB) Viewed 1777 times
Wish me luck with the aggressive time schedule, but I look at it as almost everything is done. It gets the modded HubMonster from my SuperV. Suspension, brakes, wheels, seat are all done. So all I have to do is slight mods to the rear wheel attachment point and a battery box, plus a day or so of reworking the lighting and throttle.

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Re: Mid-mount Hubmonster Madass

Post by wineboyrider » Nov 08 2017 10:58pm

What about the empty gas tank? There is room in there for something?
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Re: Mid-mount Hubmonster Madass

Post by John in CR » Nov 08 2017 11:22pm

wineboyrider wrote:What about the empty gas tank? There is room in there for something?
I'm cutting mine in about half lengthwise, so the terminal ends of the long top row will protrude into what is left of the tank. All of my wiring will also run thru whats left of the tank as well as the seat tube for an ultra clean build. Mine has a shorter wheelbase than later years, so to fit all of my cells in a trim form I'm moving the shock attachment and swingarm pivot rearward 3-4". I'm also going with a 2 sided pivot support instead of thru bolt for the swingarm to allow the pack to extend more rearward.

Using 18650's you could fit a good amount of batts in the tubes. The only problem is that the motor and swingarm support primary 2 bolts run thru 2 horizontal tubes near the bottom end of the main tube, so you can't just slide a cylindrical battery in there. I can't believe Sachs' electric version just hung a triangular battery pack under the main tube. That's just pure laziness of non-believer engineers to waste all of that space inside a MadAss main tube.

I don't have a clue how Ohbse plans to fit both a motor and a sufficient pack to power it in the limited space under the main tube. Sachs only fit a triangular battery powering a 1500W motor mounted at the wheel on theirs...for the pregnant guppie look that I don't like much.

I still can't believe Ohbse didn't go hubbie with HubMonster on his MadAss. It's the perfect conversion candidate with even the stock dropouts for the motor axle matching HubMonster so closely in both size and width. The modding required is quite limited.

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Re: Mid-mount Hubmonster Madass

Post by Mad Matt » Dec 24 2017 3:38pm

Hows the build going Ohbse?

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Re: Mid-mount Hubmonster Madass

Post by Buk___ » Dec 24 2017 4:53pm

John in CR wrote:
Nov 08 2017 11:22pm
wineboyrider wrote:What about the empty gas tank? There is room in there for something?
I'm cutting mine in about half lengthwise,...
Seems like a crying shame. If you cut through the tube at the back/bottom end just in front of the dome, you could slide 7 groups of 13 18650s inside and hinge the dome back on; and keep the nice aesthetic.

I guess as it's you, and you're looking at 20s or 30s, neither 7s13p (easy) or 13s7p (awkward) would not satisfy; and using a dc-dc booster to get the V would leave you lacking in range.

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Re: Mid-mount Hubmonster Madass

Post by John in CR » Dec 30 2017 8:59am

Buk___ wrote:
Dec 24 2017 4:53pm
John in CR wrote:
Nov 08 2017 11:22pm
wineboyrider wrote:What about the empty gas tank? There is room in there for something?
I'm cutting mine in about half lengthwise,...
Seems like a crying shame. If you cut through the tube at the back/bottom end just in front of the dome, you could slide 7 groups of 13 18650s inside and hinge the dome back on; and keep the nice aesthetic.

I guess as it's you, and you're looking at 20s or 30s, neither 7s13p (easy) or 13s7p (awkward) would not satisfy; and using a dc-dc booster to get the V would leave you lacking in range.
I realized I couldn't get things to fit right and decided not to hack it up. Instead I built a frame from scratch, though not a MadAss replica. I do have a replica with larger dimensions for batteries in process too, though that's a few weeks away.

The biggest issue (other than limited size unless you're going 18650's) with trying to use the MadAss main tube is there are 2 tubes running perpendicular through the main tube down near the bottom end. They're for running 2 big bolts through the gas tank for the main bracket for the motor mount, swingarm pivot and foot pegs. After all the work, my biggest issue with the MadAss is the weight of the main parts...wheels, fork and steering stuff, and even the seat assembly are all quite heavy for what is essentially a pretty small motorcycle. My steel sheet enclosed frame that holds a ton of batteries is ending lighter than the Sachs original.

I'm at the wiring up stage of my monocoque MadAss-ish steel frame, so pics and clips coming soon. Fingers crossed I'll be riding Monday morning, the best street ebiking day of the year with almost no cars on the road.

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Re: Mid-mount Hubmonster Madass

Post by Rube » Dec 30 2017 5:12pm

John in CR wrote:
Nov 08 2017 11:22pm
I realized I couldn't get things to fit right and decided not to hack it up. Instead I built a frame from scratch, though not a MadAss replica. I do have a replica with larger dimensions for batteries in process too, though that's a few weeks away.
A testament to your skills when designing a new frame is easier than modifying the original. Will you use any components from the Madass or is everything too heavy for your goal?

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Re: Mid-mount Hubmonster Madass

Post by John in CR » Dec 30 2017 6:21pm

Rube wrote:
Dec 30 2017 5:12pm
John in CR wrote:
Nov 08 2017 11:22pm
I realized I couldn't get things to fit right and decided not to hack it up. Instead I built a frame from scratch, though not a MadAss replica. I do have a replica with larger dimensions for batteries in process too, though that's a few weeks away.
A testament to your skills when designing a new frame is easier than modifying the original. Will you use any components from the Madass or is everything too heavy for your goal?
I'm using the headtube and full front end (handlebars, fork assembly, wheel, brake, etc.) I'm also using the seat itself that the previous owner just had redone, as well as the swingarm and shock. I read that the MadAss had steering on the sensitive side, so in addition to lengthening and lowering the ride height, I gave the headtube a more slack angle since I prefer handling on the more stable at speed end of the spectrum.

Here's what mine looked like originally:
MadAss originally sml.JPG
MadAss originally sml.JPG (99.39 KiB) Viewed 1531 times
A sneak peek of my electrified version with which I'm hoping will match LFP's 111mph Deathbike top speed:
HubMonsterExpress sml.JPG
HubMonsterExpress sml.JPG (77.01 KiB) Viewed 1531 times

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Re: Mid-mount Hubmonster Madass

Post by Ohbse » Dec 31 2017 7:30pm

Looks awesome John! Seems likely you'll beat me to it!

I've now got my workshop somewhat set up, CNC up and running etc. Unfortunately still limited time to work on the bike, but have made a little more progress on the swingarm modifications. Need to do some routine maintenance on the daily ride however, it's now ticked over 20,000km and most things need a good clean and a service.

It will be very interesting indeed to do a virtual dragrace once both of our interpretations are up and running :D

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Re: Mid-mount Hubmonster Madass

Post by Chalo » Dec 31 2017 9:42pm

Aww, it's cute!
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Re: Mid-mount Hubmonster Madass

Post by John in CR » Jan 01 2018 6:43am

Chalo,
It won't get pink paint, and my helmet definitely won't be a cat, so I don't think your definition of "cute" will apply. It already looks much better than any of the pics I too portrayed, but in addition to the paint job, a huge hurdle in the looks department IMO is how I integrate a place to put put my feet, whether it's pegs, pedals, or left/right side platforms.

Ohbse,
The HubMonster and controllers are pulled straight off my SuperV with no changes in tuning other than a gearing change being a 12% larger tire diameter along with a 3% increase in voltage. My all up load should be close to used with my run that peaked at 172kph at 700-750m. Yes, the virtual drag race will be interesting, but I fully expect that a real 29kw geared for an estimated 180kph top speed will blow by you in the first 100m (assuming you get a jump off the line), because I have strong opinions about the real effects of field weakening despite no direct experience in the saddle. To me anything that sacrifices torque for speed is a killer in a short race, and anything that sacrifices heat (ie efficiency) for speed is a killer in a long race. If I'm wrong about it, I definitely want to know.

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Re: Mid-mount Hubmonster Madass

Post by ElectricGod » Jan 03 2018 7:16pm

John in CR wrote:
Jan 01 2018 6:43am
Chalo,
It won't get pink paint, and my helmet definitely won't be a cat, so I don't think your definition of "cute" will apply. It already looks much better than any of the pics I too portrayed, but in addition to the paint job, a huge hurdle in the looks department IMO is how I integrate a place to put put my feet, whether it's pegs, pedals, or left/right side platforms.

Ohbse,
The HubMonster and controllers are pulled straight off my SuperV with no changes in tuning other than a gearing change being a 12% larger tire diameter along with a 3% increase in voltage. My all up load should be close to used with my run that peaked at 172kph at 700-750m. Yes, the virtual drag race will be interesting, but I fully expect that a real 29kw geared for an estimated 180kph top speed will blow by you in the first 100m (assuming you get a jump off the line), because I have strong opinions about the real effects of field weakening despite no direct experience in the saddle. To me anything that sacrifices torque for speed is a killer in a short race, and anything that sacrifices heat (ie efficiency) for speed is a killer in a long race. If I'm wrong about it, I definitely want to know.
Unfortunately you are using a hub motor so gearing is not an option. Your hub delivers the RPM's and torque it does until it runs out of KV's. A mid drive with a modded Peerless 700 transmission will give you both...speed and torque and do it for cheap. Shifter kart racers use this little transmission extensively. You can buy one on ebay for $150 and then upgrade the bearings and shifter for another $50-100 to turn it into a speed monster. Of course quite a few riding mowers have one in them too. Go find a couple of junked mowers and salvage the 700 out of them. All the Peerless transmissions use interchangeable gears and many other parts. Pretty much if it says Peerless on the case, you can use it for parts for your DD transmission if/when you break something.

I love this bike frame! I really wish I had one. I'm going to have to find this frame some where.
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Re: Mid-mount Hubmonster Madass

Post by Ohbse » Jan 03 2018 10:56pm

ElectricGod wrote:
Jan 03 2018 7:16pm

Unfortunately you are using a hub motor so gearing is not an option. Your hub delivers the RPM's and torque it does until it runs out of KV's. A mid drive with a modded Peerless 700 transmission will give you both...speed and torque and do it for cheap. Shifter kart racers use this little transmission extensively. You can buy one on ebay for $150 and then upgrade the bearings and shifter for another $50-100 to turn it into a speed monster. Of course quite a few riding mowers have one in them too. Go find a couple of junked mowers and salvage the 700 out of them. All the Peerless transmissions use interchangeable gears and many other parts. Pretty much if it says Peerless on the case, you can use it for parts for your DD transmission if/when you break something.

I love this bike frame! I really wish I had one. I'm going to have to find this frame some where.
Transmission is definitely not required here. The hubmonster is capable in stock form of lifting the front wheel under power at virtually any speed with the stock wheel base. What exactly is the point in increasing wheel torque at the expense of substantial amount of weight/complexity/failure points when you're unable to use full torque when geared 1:1?

You're vastly better off taking that additional ~10kg that you'll be adding with the transmission you're describing and adding that much more battery or controller in the pursuit of performance. Not to mention this motor will SMASH those transmissions with ease.

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Re: Mid-mount Hubmonster Madass

Post by John in CR » Jan 04 2018 12:19am

Ohbse wrote:
Jan 03 2018 10:56pm
ElectricGod wrote:
Jan 03 2018 7:16pm

Unfortunately you are using a hub motor so gearing is not an option. Your hub delivers the RPM's and torque it does until it runs out of KV's. A mid drive with a modded Peerless 700 transmission will give you both...speed and torque and do it for cheap. Shifter kart racers use this little transmission extensively. You can buy one on ebay for $150 and then upgrade the bearings and shifter for another $50-100 to turn it into a speed monster. Of course quite a few riding mowers have one in them too. Go find a couple of junked mowers and salvage the 700 out of them. All the Peerless transmissions use interchangeable gears and many other parts. Pretty much if it says Peerless on the case, you can use it for parts for your DD transmission if/when you break something.

I love this bike frame! I really wish I had one. I'm going to have to find this frame some where.
Transmission is definitely not required here. The hubmonster is capable in stock form of lifting the front wheel under power at virtually any speed with the stock wheel base. What exactly is the point in increasing wheel torque at the expense of substantial amount of weight/complexity/failure points when you're unable to use full torque when geared 1:1?

You're vastly better off taking that additional ~10kg that you'll be adding with the transmission you're describing and adding that much more battery or controller in the pursuit of performance. Not to mention this motor will SMASH those transmissions with ease.
+1. The only electrics that need multi-speed transmissions are under-powered vehicles. Early on even Telsa tried a 2 speed tranny while developing the original roadster, but they couldn't hold up to the torque. This bike will go faster than I ever want other than a few runs to record its capability. Yet with gearing for well over 100mph, I'll still have the acceleration I love and remain just tame enough to ride safely as primary transportation.

There's a nice thread in the motor section about the topic. Ohbse hit the nail on the head...you're always better off adding more motor than the weight of a transmission. Locomotives don't have transmissions, and neither will the new Tesla Roadster with its 1.9sec 0-60mph and 250mph top speed. By now I'm sure the few production emotos that had multi-speed trannies have dumped the idea.

I want to do a 2 speed retro-direct drive some day, but the purpose of the tranny will be to make it a dual use ebike, one fast enough to be safe mixing with traffic and still be able to crawl slowly up mountain goat off road ascents.

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Re: Mid-mount Hubmonster Madass

Post by liveforphysics » Jan 04 2018 12:34am

A controller setup with heavy field weakening could perhaps double your current speed, while compromising no torque over your lower speed ranges, and typically only a small efficiency penalty to achieve that RPM doubling (though some motors evidently suck at it, some motors barely take a hit in efficiency).

Multi-speed transmissions are just for people who didn't use an adequate motor.
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Re: Mid-mount Hubmonster Madass

Post by liveforphysics » Jan 04 2018 12:49am

John in CR wrote:
Jan 01 2018 6:43am
Chalo,
It won't get pink paint, and my helmet definitely won't be a cat, so I don't think your definition of "cute" will apply. It already looks much better than any of the pics I too portrayed, but in addition to the paint job, a huge hurdle in the looks department IMO is how I integrate a place to put put my feet, whether it's pegs, pedals, or left/right side platforms.

Ohbse,
The HubMonster and controllers are pulled straight off my SuperV with no changes in tuning other than a gearing change being a 12% larger tire diameter along with a 3% increase in voltage. My all up load should be close to used with my run that peaked at 172kph at 700-750m. Yes, the virtual drag race will be interesting, but I fully expect that a real 29kw geared for an estimated 180kph top speed will blow by you in the first 100m (assuming you get a jump off the line), because I have strong opinions about the real effects of field weakening despite no direct experience in the saddle. To me anything that sacrifices torque for speed is a killer in a short race, and anything that sacrifices heat (ie efficiency) for speed is a killer in a long race. If I'm wrong about it, I definitely want to know.

Field weakening is something that doesn't effect your lower motor speed operation at all, it's something that only begins to take effect after your motors at an RPM where the BEMF it's generating starts to equal your battery pack voltage. At that point normally your torque would begin to fall off quickly. However, with timing the phase current to build the magnetic field just ahead of the bemf rising above pack voltage, it can continue to make torque for a lot more rpm range. For IPM rotor motors like Nissan LEAF and Zero and Volt/Bolt, the large amount of added rpm range is only a couple percent. Surface PM motors tend to eat more efficiency loss from lower rotor reluctance.
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John in CR   100 GW

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Posts: 13510
Joined: May 20 2008 12:58am
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Re: Mid-mount Hubmonster Madass

Post by John in CR » Jan 04 2018 1:24am

liveforphysics wrote:
Jan 04 2018 12:49am

Field weakening is something that doesn't effect your lower motor speed operation at all, it's something that only begins to take effect after your motors at an RPM where the BEMF it's generating starts to equal your battery pack voltage. At that point normally your torque would begin to fall off quickly. However, with timing the phase current to build the magnetic field just ahead of the bemf rising above pack voltage, it can continue to make torque for a lot more rpm range. For IPM rotor motors like Nissan LEAF and Zero and Volt/Bolt, the large amount of added rpm range is only a couple percent. Surface PM motors tend to eat more efficiency loss from lower rotor reluctance.
Thanks for the explanation, and happy new year my friend. At some point I guess I'll have to open up my wallet in terms of controllers. I guess I've been too patient waiting for cheap Chinese controllers to come around. I have a hard time getting past a box of electronic bits costing more than 15kg of premium motor.

If it's just a timing advance, I could actually do it cheaply and make a manual set of switches to swap the halls between the controllers with the correct combos of firing sequence for neutral and advanced and pick up a 3 degree timing advance at the flip of a switch. I ran with the timing advanced for about a month one time after a crash mangled my wiring hardness leaving me with no way to identify which set of halls went with which set of phases, and I got the 50/50 choice wrong at first. Normal riding torque was off, heat was up a bit, and there was a bit more sound, so I knew something was wrong and to try swapping the hall sets. Of course the factory made it hard to get away from using their controllers, so they're wired to it's not just a simple swap of the connectors, the sequence is different too. I can't remember if a phase wire change was required too, but if so, that would screw up the idea.

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