'lightest.bike' 1.7kg 1000w mid drive
- Thread starter Grantmac
- Start date
raylo32
100 kW
I have never used an IGH but the idea is intriguing. What kind of shifter do you need for this Shimano or for a Rohloff? Do the hubs come with them?
I have never installed an IGH on an ebike before myself.
AFAIK it's typical to need to buy the shifter separate.
The downside of most IGH hubs is lower transmission efficiency than a chain. But if you do an ATF fill or some other lubrication upgrade, then you could bridge most of that gap and also likely improve the long term durability of the IGH beyond what it is stock.
Approximate cost of entry, all parts except wheel build included:
Shimano 3 speed: $133
Shimano Alfine 8: $275
Rohloff entry level model: $1250
I think i would be unhappy with a 3 speed drivetrain in the long run.
I think the ideal bang/buck case is the Alfine 8 with an ATF fill to reduce friction + a tune for the lightest controller that either adds a very slow soft start to the power ( if not present ), + a reduction in initial torque by intentionally running a lower battery amp : phase amp ratio.
Tuning down the initial torque would mean you need to use more of the gears to accelerate, but this would have a side effect of optimizing the efficiency you get out of the lightest and lowering the heat produced by the drive.. which would probably allow you to bump up the continuous power a little more.
In effect you would be making the motor feel a little laggy in trade for:
- Ideal gearing range to take advantage of the higher speeds
- Ideal efficiency
- Higher durability than a chain + derailleur setup ( unless you make a shifting boo-boo )
If i had an additional 20-35mm of length on the mid mount then i can just run oversized gears and forget about the extra cost of an IGH & all these concerns about making a non-bulletproof IGH durable enough to handle 1200W of power for at least 1000's of miles.
AFAIK it's typical to need to buy the shifter separate.
The downside of most IGH hubs is lower transmission efficiency than a chain. But if you do an ATF fill or some other lubrication upgrade, then you could bridge most of that gap and also likely improve the long term durability of the IGH beyond what it is stock.
Approximate cost of entry, all parts except wheel build included:
Shimano 3 speed: $133
Shimano Alfine 8: $275
Rohloff entry level model: $1250
I think i would be unhappy with a 3 speed drivetrain in the long run.
I think the ideal bang/buck case is the Alfine 8 with an ATF fill to reduce friction + a tune for the lightest controller that either adds a very slow soft start to the power ( if not present ), + a reduction in initial torque by intentionally running a lower battery amp : phase amp ratio.
Tuning down the initial torque would mean you need to use more of the gears to accelerate, but this would have a side effect of optimizing the efficiency you get out of the lightest and lowering the heat produced by the drive.. which would probably allow you to bump up the continuous power a little more.
In effect you would be making the motor feel a little laggy in trade for:
- Ideal gearing range to take advantage of the higher speeds
- Ideal efficiency
- Higher durability than a chain + derailleur setup ( unless you make a shifting boo-boo )
If i had an additional 20-35mm of length on the mid mount then i can just run oversized gears and forget about the extra cost of an IGH & all these concerns about making a non-bulletproof IGH durable enough to handle 1200W of power for at least 1000's of miles.
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The only problem is an 11t gear will wear extremely fast.. and also wear the chain more.. at this power level you're probably replacing your drivetrain multiple times a year with regular riding.. i don't think that's acceptable. it's one of the main reasons i dislike mid drives.
The only way to overcome this is to run as large of gears in the front and rear as possible.
I wonder if adding soft start/ lowering initial torque would have a significant impact on the durability of a derailleur setup. I can't recall seeing anyone report on this.
..this would also improve the durability of the lightest.. especially since you and i both have 52v batteries and we're pushing it harder than stock in the first place.
But the question is how is how much room do we have to improve on the lightest' default tune?
I think you can answer that - with the throttle, does the motor have a nice 'kick' to it even if you're in the wrong gear for the situation?
The only way to overcome this is to run as large of gears in the front and rear as possible.
I wonder if adding soft start/ lowering initial torque would have a significant impact on the durability of a derailleur setup. I can't recall seeing anyone report on this.
..this would also improve the durability of the lightest.. especially since you and i both have 52v batteries and we're pushing it harder than stock in the first place.
But the question is how is how much room do we have to improve on the lightest' default tune?
I think you can answer that - with the throttle, does the motor have a nice 'kick' to it even if you're in the wrong gear for the situation?
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Interesting about the box drivetrain, $16 every few months makes this continual drivetrain wear problem more bearable.
I would guess we don't have an IPM motor but a typical brushless because this kit was once offered with an external ASI which doesn't support IPM.
To a point almost every motor on the market can benefit from higher voltage and therefore higher RPM. It's too bad we don't have a control group person running 48v so we can do efficiency/thermal comparisons but it's a pretty safe bet that we both improved continuous power with +/- .5% max efficiency difference.
Nice, i imagine if you can do that then it's tuned for high initial torque which means we probably have room to detune for higher drivetrain reliability.
I have a thermal camera and my weather ranges from -10F to 110F yearly so whatever findings i have with thermals should be good.
Now if only my battery from grin would ship..
I would guess we don't have an IPM motor but a typical brushless because this kit was once offered with an external ASI which doesn't support IPM.
To a point almost every motor on the market can benefit from higher voltage and therefore higher RPM. It's too bad we don't have a control group person running 48v so we can do efficiency/thermal comparisons but it's a pretty safe bet that we both improved continuous power with +/- .5% max efficiency difference.
Nice, i imagine if you can do that then it's tuned for high initial torque which means we probably have room to detune for higher drivetrain reliability.
I have a thermal camera and my weather ranges from -10F to 110F yearly so whatever findings i have with thermals should be good.
Now if only my battery from grin would ship..
rhauff
100 mW
My 48V battery is ready & waiting........and waiting..
@Pilot Engineer when does our control group get his kit?
It's very good to hear my math was off.
I took 15% off the unloaded speed and assumed that was the correct RPM given that this was the loaded RPM of a pretty similar motor. Definitely approximate!
I have all the tools to make proper measurements and will report back when i have ones from the real world.
100rpm difference between loaded and not loaded is within the range i'd expect.
I took 15% off the unloaded speed and assumed that was the correct RPM given that this was the loaded RPM of a pretty similar motor. Definitely approximate!
I have all the tools to make proper measurements and will report back when i have ones from the real world.
100rpm difference between loaded and not loaded is within the range i'd expect.
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While i am waiting for the battery i was admiring the view of this drive today.
I can't believe how narrow i can get this drive with this 123mm bottom bracket. The pedals look incredibly narrow for a BB and i haven't even tightened down that right crank, so it goes in a few more MM.
Absolutely love it, i'm biomechanically most efficient with a very narrow stance and this is within a single digit % of perfect for me. it's a dream come true because i remember the BBS02 effing up my knee muscles in 2014 and i would never touch a mid drive until now, but always wanted one.
I measured my 123mm bottom bracket and it has an additional 3mm on the right side. This is approximately the amount of inset the freewheel needs. If you are using the bikee crank with this extra length then the addon PAS sensor should work. If you aren't, you probably lack the appropriate clearance.
The motor sprocket can also be flipped so it will line up perfectly with this narrower width.
I love that we can just use bike stuff!
I can't believe how narrow i can get this drive with this 123mm bottom bracket. The pedals look incredibly narrow for a BB and i haven't even tightened down that right crank, so it goes in a few more MM.
Absolutely love it, i'm biomechanically most efficient with a very narrow stance and this is within a single digit % of perfect for me. it's a dream come true because i remember the BBS02 effing up my knee muscles in 2014 and i would never touch a mid drive until now, but always wanted one.
I measured my 123mm bottom bracket and it has an additional 3mm on the right side. This is approximately the amount of inset the freewheel needs. If you are using the bikee crank with this extra length then the addon PAS sensor should work. If you aren't, you probably lack the appropriate clearance.
The motor sprocket can also be flipped so it will line up perfectly with this narrower width.
I love that we can just use bike stuff!
Lightning rods are ipm and do great with ASI
rivers
1 W
I have seen photos of the Bikee motor. It is a conventional brushless inrunner.
I have seen these pictures but will not share them out of interest of keeping the motor design outside the view of copycats for the manufacturer/designer. ( sorry )
This is a very well engineered kit and that motor looks super high quality with great heat shedding.
It has a smaller stator than Bafangs but easily double the pole count and therefore the torque will be higher and also the pitch of the sound will be higher.
Something constant about electric motor designs is that, the lower the RPM, the heavier, less efficient, but also quieter.
Human hearing is very strong in the 1000-8000hz range with a big peak at 3000hz and this motor is very likely loud not because it has a lot of sound energy but because it is in a high spot in our hearing range.
It's the same issue many geared motors have, especially if they don't have helical gears.
If we are running a sine/foc controller than we can expect the contribution of the motor to this sound is pretty low and the gears are the highest contributors to the sound energy.
This system has 2 gear reductions. The first stage is helical, the second looks straight cut and the interfacing is metal to metal.. so this is probably the loudest for sure.
Because this straight cut gear is bolted to the case, then this gear will transmit this extra sound through the case.
At least they made the highest RPM gear helical otherwise the gear noise would be unbearable.
The case is either magnesium or aluminum and these materials are great at conducing sound. The thinner, the better it is at conducting sound.
So are aluminum bikes, sound can transmit through the frame, the frame will act like a speaker. It won't amplify the sound, but give it more area to output the sound, increasing the distance and angles the sound can be heard from.
Here's some strategies for noise reduction i would consider trying.
General principle: use material to reduce the sound energy as close as possible to the source of that energy. It would be ideal to do this inside the case but it may be too hot inside to add rubber.
This is a very well engineered kit and that motor looks super high quality with great heat shedding.
It has a smaller stator than Bafangs but easily double the pole count and therefore the torque will be higher and also the pitch of the sound will be higher.
Something constant about electric motor designs is that, the lower the RPM, the heavier, less efficient, but also quieter.
Human hearing is very strong in the 1000-8000hz range with a big peak at 3000hz and this motor is very likely loud not because it has a lot of sound energy but because it is in a high spot in our hearing range.
It's the same issue many geared motors have, especially if they don't have helical gears.
If we are running a sine/foc controller than we can expect the contribution of the motor to this sound is pretty low and the gears are the highest contributors to the sound energy.
This system has 2 gear reductions. The first stage is helical, the second looks straight cut and the interfacing is metal to metal.. so this is probably the loudest for sure.
Because this straight cut gear is bolted to the case, then this gear will transmit this extra sound through the case.
At least they made the highest RPM gear helical otherwise the gear noise would be unbearable.
The case is either magnesium or aluminum and these materials are great at conducing sound. The thinner, the better it is at conducting sound.
So are aluminum bikes, sound can transmit through the frame, the frame will act like a speaker. It won't amplify the sound, but give it more area to output the sound, increasing the distance and angles the sound can be heard from.
Here's some strategies for noise reduction i would consider trying.
General principle: use material to reduce the sound energy as close as possible to the source of that energy. It would be ideal to do this inside the case but it may be too hot inside to add rubber.
- I think some rubber or other 'damping' material, if applied on the case near the output shaft, and placed under slight tension could absorb a good % of the noise close to the source. Gluing the material may not work. A wire wrap would be a cheap/easy way to do this for an experiment.
- It may be possible to attach a damper or additional damper to the 2nd gear reduction's main gear. This is the best place you could absorb this noise!
- More drastic: you could possibly put soundproofing material on half of the motor case ( where the output gear is ) and then add heatsinks on the opposite side to counteract the loss of air cooling and also concentrate the heat away from your soundproofing material ( rubber? ) which can be damaged from high heat.
- You could design some metal piece that covers the motor and is lined with sound deadening material. This would work, but there has to be a nice airflow to the motor still.
- Re-engineer the gear itself for these attributes: How to reduce Gear Noise | KHK Gears
Maybe adding some rubber between the frame and the motor and put it under a bit of pressure could reduce the noise. I will try that on mine.
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Watching this video on the owners group, and to me it sounds like this one is not bad at all.
I think and hope this motor will be great for me. Its good to hear that it is a inrunner and probably has good heat dissapeation. My current x1 stealth sometimes throttles down when running about 1000w for some minutes at steep climbing. This is a outrunner. With not the best heat transfer to the outer casing.
If this lightest 1000w motor has about the same power as a stock BBSHD as @nervagon describes I will have about the same power as I am used to also. With this little weight added to the bike.
I am going to build a 14s2p 21700 battery at about 2 kg so I will probably add only 4kgs total to my bike.
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Watching this video on the owners group, and to me it sounds like this one is not bad at all.
I think and hope this motor will be great for me. Its good to hear that it is a inrunner and probably has good heat dissapeation. My current x1 stealth sometimes throttles down when running about 1000w for some minutes at steep climbing. This is a outrunner. With not the best heat transfer to the outer casing.
If this lightest 1000w motor has about the same power as a stock BBSHD as @nervagon describes I will have about the same power as I am used to also. With this little weight added to the bike.
I am going to build a 14s2p 21700 battery at about 2 kg so I will probably add only 4kgs total to my bike.
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The location of the controller is close to the motor and separated by a plate. Both have great contact with the case and use the case as a heatsink. There would be a great benefit in adding heatsinking on the part of the drive on the side opposite of the output gear.
Even more drastic would be to remove the controller, but the additional power we can output is limited by a plastic gear, so you may not be able to use much of this extra ( and significant ) heat reduction.
But you may not need to do any of this - unlike these other mid drives it seems the power rating lines up with it's thermal capabilities in stock form at least
Even more drastic would be to remove the controller, but the additional power we can output is limited by a plastic gear, so you may not be able to use much of this extra ( and significant ) heat reduction.
But you may not need to do any of this - unlike these other mid drives it seems the power rating lines up with it's thermal capabilities in stock form at least
