Dave's 80:1 RC mid drive kit build log

[fellow]

Having 40:1 or 80:1 reduction on a light weight high revving hub (<2.2kg) would be very interesting (market share)!
[youtube]q1v7a0jsp1I[/youtube]

 

[Thud]

Harmonic drives have been discussed before (very well done, BTW), but I have a question. As odd as this may sound, I am wondering if there is any potential to make a similar drive that is only 40:1, rather than 80:1

Its in the OP spinbuddy:

What we have is an internal 40:1 reduction and a secondary 2:1 reduction between the drive unit and crankset

bazinga....40-1

 

[spinningmagnets]

I need to read slower and drink less beer before I post!...thanks!

edit: found the post I was thinking about, from 2011. It was a 14:1 reduction, and the builder speculated that it might be limited to 500W (using his variation of the principle). for this thread, I am imtrigued by the higher potential power rating, the smaller size, and also the possibility that it could be run inside a housing with an oil-bath...

"Another way to take drive through the normal chainline" (bobc, 3 pages)
http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=27132

 

[tangentdave]

Wow. I couldn't get the flexing double wide chain to work. And its awesome its inside the sprocket.

 

[kfong]

Spinningmagnets, I remember that post. Even turned down getting the unit. Too large and too many projects going. What Dave has created isn't the traditional flexing coupling I'm use to seeing. The use of a cycloidal reducer is a very cool idea. It will be hard to keep the noise down with such a design. The traditional flex coupling seems fairly quiet, we have them running on our CNC. But as you can see in the videos, they don't look as heavy duty and I'm not sure how well they wear for ebike use. I have a 50:1 reduction I can play with but it probably is better put to use in the shop.

 

[flathill]

Nice kit! Remember folks... the competition for this kit is the EGO from Austria which looks like crap and cost 3000 bucks. Still I would copy their marketing (target demographic). They are now teaming up with redbull and running the first extreme offroad ebike races

If you want to reduce drive noise you need to add elastomer to the frame tube mount. Also offer black anodizing for stealth. Justins FOC controller will also reduce noise and is very compact

 

[kfong]

To me Ego kits are overpriced repackaged cyclones. They do address the poor quality mounting issues that cyclone had. Noise is still there.

 

[recumpence]

Nice kit! Remember folks... the competition for this kit is the EGO from Austria which looks like crap and cost 3000 bucks. Still I would copy their marketing (target demographic). They are now teaming up with redbull and running the first extreme offroad ebike races

If you want to reduce drive noise you need to add elastomer to the frame tube mount. Also offer black anodizing for stealth. Justins FOC controller will also reduce noise and is very compact

I agree it is too loud. The noise will not go away with just elastomers. This type of reduction is just noisy. That being said, Cyclone has sold many drives despite the noise.

The quality looks good. Props for the "From scratch" reduction.

Matt

 

[tangentdave]

I haven't had a chance to try many controllers yet. The Castle Creations seems to rock the rotor slightly when starting to determine position (guessing), this rocking isn't so hot for a geartrain but the load is almost nil. Would love to hear a sine controller, has anybody tried these on an Astro motor? The CC ESC has quite a bit of starting power- yesterday it pulled me away from a stop on a hill too steep to pedal up; the bike was in 6th gear.

Wonder if the Ego guys would welcome some competition...

-dave

 

[flathill]

Nice kit! Remember folks... the competition for this kit is the EGO from Austria which looks like crap and cost 3000 bucks. Still I would copy their marketing (target demographic). They are now teaming up with redbull and running the first extreme offroad ebike races

If you want to reduce drive noise you need to add elastomer to the frame tube mount. Also offer black anodizing for stealth. Justins FOC controller will also reduce noise and is very compact

I agree it is too loud. The noise will not go away with just elastomers. This type of reduction is just noisy. That being said, Cyclone has sold many drives despite the noise.

The quality looks good. Props for the "From scratch" reduction.

Matt

The noise should be reduced with a isolation mount, but definitely not eliminated. He should download a spectrum analyzer for his phone and then first measure it with the unit hanging in free air, and then mounted to the frame, to see how much the frame is amplifying the drive vibration. From there you might play around with touching parts of the the drive kit to find the main source of the "irritable" sound. The goal is not to totally eliminate the sound, but reduce the level and make it more pleasant. I'm guessing couple damping pads on the two large side plates or bracing could also help, in addition to the isolation mount(s). The plates could be acting as a sound board.

 

[StinkyGoalieGuy]

I agree with Flathill. Depending on all kinds of variables, contact with the frame can increase the sound. When I had a Cyclone kit, isolating the four bolt mount points with some rubber grommets made a huge difference. There's no doubt that this type of drive makes a different type of noise, but it should help none the less.

 

[aCeMadMod]

hi i use alot of cyclone motors. it sound better when you use a crmo steel frame it got a lot to do chian picth on the freewheels and how they cut and chian wheel to get it not get to lose , if set up right it not a bad sound , unlike i like it , use carbon or alloy frame . one best is Mag caster frame but less them 5 kind made in the world .

once i get one his gearbox drive i show u, it not that bad vs cyclone for sound

hold on this going to be fun ride ,

 

[spinningmagnets]

Here's the best video I could find on explaining a harmonic drive (2:20 minutes).

The drive gear in the center is about the same diameter as the two idler gears. If you made the idlers smaller / drive gear larger...it would give the drive less reduction. If you made the drive gear smaller / idlers bigger...it would have more reduction. As it sits, every time the motor makes one rotation of the drive gear, the flexible oval skips one tooth in the fixed outer ring-gear. Doing it this way, it has 95 teeth (which have to be short, so short teeth require a lot of them to reduce the amount of flex needed in the flexible oval. taller teeth require more flex, bigger disparity between the oval short axis and long axis)

The bicycle-sprocket/chain based harmonic drive shown above has a chain to make up the flexible-shape part. It is likely to handle more power than the 500W the designer claimed, but its "oval" can have a large difference between the long axis and short axis, meaning taller teeth can be used.

Noise aside (in the chain version) I can't help but to wonder what could be developed by using #219 chain.

https://www.youtube.com/watch?v=vzc53n0ssik
[youtube]vzc53n0ssik[/youtube]

 

[kfong]

Unlike the video, what Dave has done was to create a cycloid center. This allows for a much bigger tooth engagement. This creates the offset needed for the gear reduction. This also creates gear noises that are in harmonic with the offset. I would try filling this with oil to see if it can dampen the sounds, but since he hasn't shown the rest, his design might not be easily setup for this.

 

[panurge]

Hello Dave
Wow your is really a smart approach and an artwork realization.....the Harmonic drive is a beauty.
Although it seems noisy, the results is awesome. If you'll be able to attenuate in some way the noise and it really survive a 3210 continuous use, it will be very competitive.
Would be good to have a comparison with a cyclone, or a standard Astro separated 2 stage belt/chain transmission on the same video to better judge the noise level....
Have you tested the drive with a 3220 too? I think the 3210 is yet on the border even for a reliable derailleur/freehub usage.....another potential problem I could see with this system is the freewheeling BB unit....with the projecting/machining skills shown with the harmonic, shouldn't be hard for you to realize a freewheel support bearing adapter for a sealed bearing HD unit.....

 

[made_in_the_alps_legacy]

Here's the guts of the unit, I'd rather not talk about the alterations I've made to adapt the cycloidal reducers to run at 10kRPM and be this tiny for this cost. This is real, it works great. Sorry it's a surprise.
-dave

Welcome, Thanks for sharing, and congrats for your successfull prototype, wish you luck for the future

 

[flathill]

Guys this is a cycloidal drive not a harmonic (strain wave) drive

About the noise...does the reduction have a counterweight to reduce vibration and extend bearing life?

 

[dirkdiggler]

Is there an option for this drive unit to be used with a more popular motor such as the 80-100? Even better would be a test of the 6364 size motors that are even more common. Likely that size would lack the punch, but would be super stealth. Plus those aren't $400 motors. Might be worthwhile for all the tinkers here to just sell the reduction unit that fits a certain motor shaft size, if that is possible.

 

[whereswally606]

http://visforvoltage.org/forum/13629-concepts-ebike-propulsion?page=8

post #248 a 1/3 down the page is a good diagram for a dual rotor cycloidal gear reducer. apparently upto 95% efficient according to one youtube clip I watched earlier.



Anyway my hat of to you Dave, excellent execution and as said above can we have one for a 80/100 now please?

 

[recumpence]

I'm not sure why the 80-100 motors are pushed so heavily. They are low quality. This is an expensive reduction unit. Why would anyone couple that with a garbage motor? Astro isn't the only game in town. But at least the quality is high.

The 80-100 motors are fine for budget builds. But, for high end applications, Itty is best to go with something that does not require surgery to make it run reliably.

Matt

 

[Punx0r]

Is there an option for this drive unit to be used with a more popular motor such as the 80-100? Even better would be a test of the 6364 size motors that are even more common. Likely that size would lack the punch, but would be super stealth. Plus those aren't $400 motors. Might be worthwhile for all the tinkers here to just sell the reduction unit that fits a certain motor shaft size, if that is possible.

From the For Sale Ad:

The kit is provided Ready-To-Run, just add your choice of batteries. Bare drive units will also available if you already have an Astro Flight 3210 and controls. The RTR kit is available at early adopter discount for $1400 and includes the following:

• Tangent drive unit, side mount plates and universal downtube clamp
• Astro Flight 3210 7turn
• Castle Creations HV80 ESC
• Cycle Analyst V3 w/ twist throttle
• Freewheel crankset with ISIS BB, 16t ACS Southpaw freewheel driving a 32T SS Surly chainring via KMC Kool chain
• Assembled, wired and pre-configured-- mount, connect batteries, go ride

Each unit will be assembled and tested by me prior to shipping. The retail price of these existing components is over $1000, I'm only asking $400 for my time designing, manufacturing and integrating the kit.

From that I would assume a minimum of $400 if you wanted to buy just the drive unit/mounting assembly.

 

[kfong]

Wow, what a great thread you pointed out. It's what I was imagining but never knew it had its own classification. I like the hypercyclodal reduction design. Very easy to CNC, going to have to make one now.

Never thought visforvoltage had something we don't cover!

http://visforvoltage.org/forum/13629-concepts-ebike-propulsion?page=8

post #248 a 1/3 down the page is a good diagram for a dual rotor cycloidal gear reducer. apparently upto 95% efficient according to one youtube clip I watched earlier.



Anyway my hat of to you Dave, excellent execution and as said above can we have one for a 80/100 now please?

 

[made_in_the_alps_legacy]

The huge reduction allows for the full 10kRPM range of the Astro, and is it fun. Rated for 1350W continuous, 4000W peak, this thing moves. A Castle Creations HV80 is run sensorless without issues or overheating and can get me started on any hill so long as I can manage to stay on the bike (low gears and a steep hill make for hill climbing fun). The motor has turned several times before the slack is even taken out of the chain- hard riding doesn’t heat the ESC over 120 deg. A Cycle Analyst with shunt provide throttle input (current control) to the ESC. Power is very controllable- I power wheelie that Kona in the pictures in every gear but 10th. The CA allows for easy tuning of the throttle response and power limits.

Range and efficiency are very good.

@ Dave,
I would love to experience the 10krpm motor sound, must be like a formula one

without being picky or nasty, may we get further detail of the efficiency evaluation?
I see the efforts that were made improving cooling apparatus (completely ribbed casing with significant area enhancement)
...with the specified mechanical power, I believe even few percent of loss could make quite some heat... so just asking.

 

[macribs]

For those of you that made comment about the noise, see this video and notice the sound of the freewheel, tires etc.
It does not sound that loud to me. Maybe the mic on his cam is too sensitive?

Forgot what time these sequences where sorry you need to view all of it
Let me know what you think after watching, maybe my ears are too old.

[youtube]mkCdpRgi9Wc[/youtube]

 

[kfong]

Sounds like an angry swarm of bees, higher pitch and even louder than the cyclone. I wouldn't be able to get away with it in the trails around here.