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

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
User avatar
tangentdave
1 kW
1 kW
Posts: 314
Joined: Jun 06, 2015 11:40 am
Location: Seattle, WA
Contact:

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

Post by tangentdave » Jan 11, 2018 1:56 pm

I'd recommend 16-20Ah of Multistar LiPo's for the full 120A current (16Ah is pushing it on the small side). Don't draw huge current below 3.5V per cell. Other, higher quality LiPo's may be able to handle the current at a lower state of charge. Balance the pack every chance you get, preferably install a BMS as the cheap LiPo cells will fall out of balance quickly.

For 18650 packs in the USA, I've been referring people to Patrick at Hi-C Battery (hicbattery@gmail.com; http://www.hicbattery.com/). A little more expensive but a very nice pack. Patrick built me a 14s8p with 30q, very acceptable size:
24993375_10213112230111931_368742817613071460_n.jpg
24993375_10213112230111931_368742817613071460_n.jpg (70.14 KiB) Viewed 502 times
Pack on left is from Hi-C, 14s8p of 30q, 23Ah measured, 120A continuous, 12.5lbs. Pack on right is China, 14s8p of 25r, 150A continuous, 14lbs. For customers in Australia/NZ, I think I've talked E-max Ebikes (https://www.emax-ebikes.com.au/) into building a 14s8p pack using HG2 for us (160A/24Ah). Yes, it'd be nice to not push these packs to their limit, but carrying more weight (cells) is counterproductive.


I'll get a weight measurement of all the components soon as I can.

There is a little confustion about the 'upgrade' vs 'new' units, my fault since I'm still waiting for the first rotor/stator to be delivered otherwise there'd be pics of the 'new' unit. Unless specially requested, all kits will have the stator bonded to the Tangent housing making a one-piece motor/reducer. If you already have a 32xx engine, the water jacket version would save you the cost of a new Astro engine (I just pass the cost through). Any new kits will not require the addition of water within the housing.

-dave
Zerode G2/Tangent 6kW
Intense Tracer 29er/Tangent 3kW PAS

User avatar
tomjasz
1.21 GW
1.21 GW
Posts: 3704
Joined: Mar 29, 2014 1:45 pm
Location: Out riding, MN USA
Contact:

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

Post by tomjasz » Jan 11, 2018 3:27 pm

tangentdave wrote:
Jan 11, 2018 1:56 pm

For 18650 packs in the USA, I've been referring people to Patrick at Hi-C Battery (hicbattery@gmail.com; http://www.hicbattery.com/). A little more expensive but a very nice pack. Patrick built me a 14s8p with 30q, very acceptable size:


-dave
hicbattery link gets, "Please come back later."
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

User avatar
tangentdave
1 kW
1 kW
Posts: 314
Joined: Jun 06, 2015 11:40 am
Location: Seattle, WA
Contact:

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

Post by tangentdave » Jan 11, 2018 3:49 pm

Yep, but Patrick is real, he's building a few packs for customers already.
Zerode G2/Tangent 6kW
Intense Tracer 29er/Tangent 3kW PAS

Megsy73
1 W
1 W
Posts: 55
Joined: Mar 25, 2013 4:10 pm

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

Post by Megsy73 » Jan 11, 2018 8:23 pm

That looks amazing ! Could you share the weight of the new 3220 kit or how much weight you saved with GEN2 ? I am trying to estimate how much weight I would save by switching to the Tangent (I have a cyclone 3000W right now)
Remi why would you switch to the tangent from the c3000w as they are both 6kw capable but the c3000w is a lot quieter and a lot cheaper ! I was reading this thread here: https://endless-sphere.com/forums/viewt ... 28&t=83578 where the dude did built 15 ebikes and did opposite swap as the c3000w has more torque down low and its quieter ! in other words you can ride it anywhere and not have to look over your shoulder from the noise.

Also the total weight is not that much less than a c3000w not sure what the direct weight difference is? as the tangent has a heavy steel geared gearbox vs cyclone plastic geared one. for the $$$ you save from swapping you should rather spend that on your c3000w bike and get lighter better components from carbon or titanium eg, better battery with newer cells i.e less weight, bike frame , forks, cranks, peddles etc then you will be left with a bike that is LOWER Weight , lower cost, high torque and quiet from the coin u saved lol i.e no downsides like noise and wear from high rpm gearboxes. That’s the other thing people forget High rpm systems that are light weight are prone to wear out fast, the rpm of the cyclone3000w is half of the tangent so you would think the gearbox life and motor bearings will have drastic difference in life as well?

User avatar
macribs
1 GW
1 GW
Posts: 3293
Joined: Jul 22, 2014 5:59 pm

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

Post by macribs » Jan 11, 2018 9:07 pm

I don't know much about the other mid drive, but what I've seen here must radical support and ludicrous improvement and attention to details. From what I've read about daves drives they are both about the highest torque to the ground drive around, uses high quality Astro motor and are now available in a new and updated version for even less noise, and more longevity. The fact that the drive is made from metal as to plastic from the other kit you mentioned is not a drawback - it is a feature. Long lasting.

Weight, are you really gonna count the grams? It is a 6 kw kit. Who cares. If you need less weight take a couple of weeks on a diet. Or buy a lighter battery pack. The truth is you will not notice the grams anyway as you are riding by throttle not by pedals. Look what people who bought the drive says about the drive, for the kind of money asked I don't think you will find anything close in regards to quality. The Astro motors are even rated to 200 degree celsius temp without demagnetizing. That is not common.

The other mid drive I am sure is also a good kit, but comparing that drive to dave's drive might be comparing apples to oranges.

I've got a carrot in the other end of my weight loss program, when I reached my target weight I will threat myself to a light weight dh build with dave's drive because afaik that will give me the highest fun factor to weight ratio for a DH build. Plenty of torque and acceleration and light enough to ride it everywhere. Now that is something to look forward to 8)

Alex07
100 W
100 W
Posts: 125
Joined: Jun 27, 2016 4:00 am

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

Post by Alex07 » Jan 11, 2018 9:41 pm

~150W of drag at full speed (all tested at 55V
is that full throttle no load ? what is the full throttle no load without the gearbox i.e just the motor ?

Megsy73
1 W
1 W
Posts: 55
Joined: Mar 25, 2013 4:10 pm

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

Post by Megsy73 » Jan 11, 2018 10:22 pm

I don't know much about the other mid drive, but what I've seen here must radical support and ludicrous improvement and attention to details. From what I've read about daves drives they are both about the highest torque to the ground drive around, uses high quality Astro motor and are now available in a new and updated version for even less noise, and more longevity. The fact that the drive is made from metal as to plastic from the other kit you mentioned is not a drawback - it is a feature. Long lasting.

Weight, are you really gonna count the grams? It is a 6 kw kit. Who cares. If you need less weight take a couple of weeks on a diet. Or buy a lighter battery pack. The truth is you will not notice the grams anyway as you are riding by throttle not by pedals. Look what people who bought the drive says about the drive, for the kind of money asked I don't think you will find anything close in regards to quality. The Astro motors are even rated to 200 degree celsius temp without demagnetizing. That is not common.
I like spending my money wisely and not on show off bling bits for the sake of it as it’s like an expensive piece of jewellery , shiny when new my delicate as F_k and overkill for the purpose … all the machining cannot be cheap ? I like spending my money where its needed to last long and not what looks good to sell a product . I mean this kit does not even have chain guards on the chainring or the motor chain, so unless you are riding indoors lol this is a major downside i.e mud splash chain life and ur pants getting sucked in the chains lol people must not ride this often enough to care maybe ????

but the main deal breaker for me is the noise as others keep mentioning these things are not quiet at all and since they are so much OVER legal power I do not want to be riding around always looking over my back.. so that’s a deal breaker for me and most other people on here, especially now the c3000w 6kw peak exists that is also nearly silent and like ¼ the price…..

User avatar
tangentdave
1 kW
1 kW
Posts: 314
Joined: Jun 06, 2015 11:40 am
Location: Seattle, WA
Contact:

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

Post by tangentdave » Jan 11, 2018 10:32 pm

is that full throttle no load ? what is the full throttle no load without the gearbox i.e just the motor ?
I just ran a bunch of these tests with different lubricants. I have a 3turn 3220, a few hundred miles on it (30+ hrs). The CA is reading ~130W for the motor alone, no gearbox, just sitting in my hand (brand new is about 70W IIRC). With the Nabtesco RE0 grease, a good loading of it (25mL+), at 55V (all measurements are via CA, 225kV x 54V is 12,150 RPM) full speed the brand new unit reads 350W on the CA (via battery shunt measurement). So I was wrong, a gearbox with 4 miles on it needs 200W. Will correct myself.

Also of note is how long it takes the gearbox to spin down. The only inertia in the system is the 3220 rotor, so the fact that the gearbox+motor take just as long to spin down as motor alone...is a good sign.

Cell phone camera, small shop. Check the other GoPro video shot outside.




Some people prioritize value, some people prioritize performance. Because Harbor Freight exists does not mean people shouldn't buy nice tools. But, enjoy your value. I want nice equipment.

edit: another thing of note is this setup outruns your feet by 4x yet still makes more torque than you can. So, there's no need to run the gearbox at 12k rippims, it's plenty quiet if you want to pedal. Hold back the hooligan for when you can rip it.
Zerode G2/Tangent 6kW
Intense Tracer 29er/Tangent 3kW PAS

Remi812
10 mW
10 mW
Posts: 22
Joined: Mar 06, 2016 8:32 pm

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

Post by Remi812 » Jan 11, 2018 11:16 pm

Megsy73 wrote:
Jan 11, 2018 8:23 pm
That looks amazing ! Could you share the weight of the new 3220 kit or how much weight you saved with GEN2 ? I am trying to estimate how much weight I would save by switching to the Tangent (I have a cyclone 3000W right now)
Remi why would you switch to the tangent from the c3000w as they are both 6kw capable but the c3000w is a lot quieter and a lot cheaper ! I was reading this thread here: https://endless-sphere.com/forums/viewt ... 28&t=83578 where the dude did built 15 ebikes and did opposite swap as the c3000w has more torque down low and its quieter ! in other words you can ride it anywhere and not have to look over your shoulder from the noise.

Also the total weight is not that much less than a c3000w not sure what the direct weight difference is? as the tangent has a heavy steel geared gearbox vs cyclone plastic geared one. for the $$$ you save from swapping you should rather spend that on your c3000w bike and get lighter better components from carbon or titanium eg, better battery with newer cells i.e less weight, bike frame , forks, cranks, peddles etc then you will be left with a bike that is LOWER Weight , lower cost, high torque and quiet from the coin u saved lol i.e no downsides like noise and wear from high rpm gearboxes. That’s the other thing people forget High rpm systems that are light weight are prone to wear out fast, the rpm of the cyclone3000w is half of the tangent so you would think the gearbox life and motor bearings will have drastic difference in life as well?
Well, I have done pretty much everything I could to my bike. It is already carbon everywhere (Santa Cruz V10cc and I still find it too heavy). I like the cyclone, don’t get me wrong but it is heavy, the motor is all steel, the mounts are crap (even though mine works OK with a heavy duty hose clamp...a hose clamp for god’s sake!!! On a V10 !) I am still looking for the ultimate mid-Drive and the Tangent might be it. I don’t like the noise, that is my main concern and if it does not save me some weight I’ll probably stick with the cyclone and try to improve it.
This thing is a work of art you can’t just denigrate it like that. It might not be ideal for everybody and that’s probably what makes it even more attractive. I just wish I could test ride one !

User avatar
macribs
1 GW
1 GW
Posts: 3293
Joined: Jul 22, 2014 5:59 pm

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

Post by macribs » Jan 11, 2018 11:36 pm

Megsy73 wrote:
Jan 11, 2018 10:22 pm


I like spending my money wisely and not on show off bling bits for the sake of it as it’s like an expensive piece of jewellery , shiny when new my delicate as F_k and overkill for the purpose … all the machining cannot be cheap ? I like spending my money where its needed to last long and not what looks good to sell a product . I mean this kit does not even have chain guards on the chainring or the motor chain, so unless you are riding indoors lol this is a major downside i.e mud splash chain life and ur pants getting sucked in the chains lol people must not ride this often enough to care maybe ????

but the main deal breaker for me is the noise as others keep mentioning these things are not quiet at all and since they are so much OVER legal power I do not want to be riding around always looking over my back.. so that’s a deal breaker for me and most other people on here, especially now the c3000w 6kw peak exists that is also nearly silent and like ¼ the price…..
If you ask for custom made parts, or small series performance parts you must expect to pay extra over high volume mass produced stuff. If you don't you are either one heck of a buyer with mad skillz at getting bottom prices or living in a fantasy world. It is the same in motorsport, if you like to tune up your snowmobile, motorcycle or even car you can't expect to get great performance manufactured in small series at your car parts superstore. They sell mass produced knock offs, backdoor exits or gray paper box parts without branding and the extended warranty. The gray paper box part might be produced at the same plant as your car manufacturer does their shopping from, but the gray no brand box removes the warranty. Why? Could it be parts that didn't make manufacturers cut? Or simply the lack of warranty?

Overkill for the purpose? What you need is a 250-750w hub motor with sine wave controller. Dead quiet and within legal power. Gives you all what you ask for and even dirt cheap.

It seems odd to start bashing a quality made drive because the drive is high quality. If this drive+motor+esc combo is priced too high for your liking, that is your choice to make. But the bashing I don't understand. Would you stop by the thread for the NYX frame and complain about the size of the battery box or their choice of making it in carbon fiber?

If you fancy a splash guard nothing is stopping you from getting any and all chain guard and mount it yourself. They come cheap btw.

User avatar
Adamlivi
1 mW
1 mW
Posts: 10
Joined: Nov 26, 2016 2:52 pm
Location: Norcross, Georgia

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

Post by Adamlivi » Jan 12, 2018 11:35 am

Just got on the list for the latest upgrade to Dave's awesome Tangent 3210 (http://tangentmotors.com/tangentsdrive) for my Ti/Rohloff urban assault e-bike! The new design looks pretty incredible and promises greater durability and reduced maintenance.
Image

dtx
100 mW
100 mW
Posts: 40
Joined: Oct 02, 2014 3:02 pm

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

Post by dtx » Jan 12, 2018 1:44 pm

How's the Rohloff holding up?

User avatar
Adamlivi
1 mW
1 mW
Posts: 10
Joined: Nov 26, 2016 2:52 pm
Location: Norcross, Georgia

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

Post by Adamlivi » Jan 12, 2018 1:53 pm

Rohloff is holding up very well. About 15,000 miles on it. a few hundred with the Tangent. If you do overload it, the fix a replacement of a pin designed to break under excessive load no a less then $100 repair.

dtx
100 mW
100 mW
Posts: 40
Joined: Oct 02, 2014 3:02 pm

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

Post by dtx » Jan 12, 2018 2:03 pm

Could you post your gearing choices please? I would love to see if my math for the rohloff matches with reality

User avatar
tangentdave
1 kW
1 kW
Posts: 314
Joined: Jun 06, 2015 11:40 am
Location: Seattle, WA
Contact:

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

Post by tangentdave » Jan 12, 2018 2:56 pm

Adamlivi's new unit will be a 20:1 internal with 14/32t secondary (45:1 overall, 250RPM max motor cadence). This ratio could be increased with a larger chainring at the crankset. Having the motor outrun your feet by 2x is about right, keep the RPMs low when pedaling but still have headroom for throttle use. Much more reduction than this and you'll never be able to get 3000W into the unit (torque becomes unusuably high).

Not to butt in on the question. Unsure his exact gearing on the current setup.
Zerode G2/Tangent 6kW
Intense Tracer 29er/Tangent 3kW PAS

User avatar
wturber
1 kW
1 kW
Posts: 389
Joined: Aug 23, 2017 8:52 pm
Location: Fountain Hills,AZ
Contact:

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

Post by wturber » Jan 12, 2018 3:05 pm

Megsy73 wrote:
Jan 11, 2018 10:22 pm

I like spending my money wisely and not on show off bling bits for the sake of it as it’s like an expensive piece of jewellery , shiny when new my delicate as F_k and overkill for the purpose … all the machining cannot be cheap ?

I think you kind of miss the point. "Overkill" is the purpose. :) (Or at least one of them.)

Nothing wrong or necessarily unwise about buying or using one of these motors. Everyone has different priorities, wealth, and preferences. I'm not buying one either. But I think it's a pretty cool motor.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
7 x 36v 4.3ah 10s 2P battery packs - Wangdd22 1500W 30A DC Boost Converter delivers 54v and about 1175 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
https://endless-sphere.com/forums/viewt ... =2&t=90369

Buk___
1 kW
1 kW
Posts: 392
Joined: Jul 28, 2017 5:59 pm

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

Post by Buk___ » Jan 12, 2018 5:17 pm

Comment withdrawn.

It was a passing response to an early post; not a criticism.
Last edited by Buk___ on Jan 12, 2018 7:31 pm, edited 1 time in total.

StinkyGoalieGuy
100 W
100 W
Posts: 236
Joined: Apr 23, 2008 3:53 pm

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

Post by StinkyGoalieGuy » Jan 12, 2018 5:36 pm

Buk___ wrote:
Jan 12, 2018 5:17 pm
wturber wrote:
Jan 12, 2018 3:05 pm
But I think it's a pretty cool motor.
I agree; but starting out with a 3.6kg solid billet of Al to form what is essentially a 400gm tube, rather than starting with (say) a ~1kg piece of tube, just seems wasteful.

I can't see any good engineering reason for it.
I'm guessing it's because you need an end cap on the tube for the motor output support bearing. So it's not really just piece of billet hollowed out to a cylinder.

User avatar
tangentdave
1 kW
1 kW
Posts: 314
Joined: Jun 06, 2015 11:40 am
Location: Seattle, WA
Contact:

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

Post by tangentdave » Jan 12, 2018 5:53 pm

need an end cap on the tube for the motor output support bearing
This.

It's only machine time. As the machines get bigger, a 4x4 in pocket in aluminum takes seconds. Solid billet reduces the number of parts and lets me make it as light as I can; solid billet makes the best product.
Zerode G2/Tangent 6kW
Intense Tracer 29er/Tangent 3kW PAS

User avatar
macribs
1 GW
1 GW
Posts: 3293
Joined: Jul 22, 2014 5:59 pm

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

Post by macribs » Jan 12, 2018 6:00 pm

Buk___ wrote:
Jan 12, 2018 5:17 pm
wturber wrote:
Jan 12, 2018 3:05 pm
But I think it's a pretty cool motor.
I agree; but starting out with a 3.6kg solid billet of Al to form what is essentially a 400gm tube, rather than starting with (say) a ~1kg piece of tube, just seems wasteful.

I can't see any good engineering reason for it.

As for wasteful, the savings are still Al and worth is weight so it is not waste.

As for engineering, hard core design often tend to be made from billet. I am no engineer but I certain there is good reasons for that. After all it has been done for 3 decades or more. Stronger, lighter maybe? Better finish then casted parts? No seems. Probably less expensive to manufacture as you don't need to come up with money upfront for tooling used for casted parts?

User avatar
recumpence
100 GW
100 GW
Posts: 5323
Joined: Apr 19, 2008 8:33 am
Location: On Earth right now. That can change at any time, though..........

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

Post by recumpence » Jan 12, 2018 6:08 pm

Okay, I've got to chime in here. I've been in manufacturing for the last 12 years. I used to manufacture RC helicopters using carbon fiber flat sheets and Billet aluminum as well as titanium for all of the bolt ons. On top of that, I've been making my e-bike drive systems for close to nine years now. Billet aluminum CNC machine parts have a strength benefit versus castparts as well as being much easier to manufacture in small numbers. I've been observing this drive system that Dave has designed from its Inception. I must say I am highly impressed with the quality of this drive system. Also, I know what it takes to design this type of product. I don't think you guys have any idea the magnitude of time and knowledge and energy and expense that goes into this type of thing. My hat goes off to Dave. He is essentially Manufacturing extraordinairily high quality Equipment in small quantities. That is difficult to do because in small quantities it is nearly impossible to cover your engineering time. Dave is doing this more as a self-supporting hobby than anything else. I for one hope this becomes something that he can rely on as his full-time business for years to come.

Lastly, I work with these Astro flight Motors on my drive units as well. They are extremely expensive Motors. For Dave to be making his own housing and having astroflight epoxy their laminations and windings into the motor housings, he is very committed to this design. I have done the same thing in the past. It is a big step and it is very expensive. Honestly, though tangent Drive systems are relatively expensive compared to other Drive systems, they are actually very reasonably priced considering the engineering involved.

I just had to chime in.

Game on.........

Matt
Last edited by recumpence on Jan 12, 2018 6:56 pm, edited 1 time in total.
1% of the world's population can think "Outside the box". The rest are firmly stuck within the box. Where are you?

User avatar
wturber
1 kW
1 kW
Posts: 389
Joined: Aug 23, 2017 8:52 pm
Location: Fountain Hills,AZ
Contact:

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

Post by wturber » Jan 12, 2018 6:20 pm

Buk___ wrote:
Jan 12, 2018 5:17 pm

I agree; but starting out with a 3.6kg solid billet of Al to form what is essentially a 400gm tube, rather than starting with (say) a ~1kg piece of tube, just seems wasteful.

I can't see any good engineering reason for it.
I'm not an engineer and don't know what drove his decision. Maybe that's a good question to ask the guy who designed it.

... oh! I see he answered the question.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
7 x 36v 4.3ah 10s 2P battery packs - Wangdd22 1500W 30A DC Boost Converter delivers 54v and about 1175 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
https://endless-sphere.com/forums/viewt ... =2&t=90369

Buk___
1 kW
1 kW
Posts: 392
Joined: Jul 28, 2017 5:59 pm

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

Post by Buk___ » Jan 12, 2018 6:33 pm

Comments withdrawn.
Last edited by Buk___ on Jan 12, 2018 7:29 pm, edited 1 time in total.

StinkyGoalieGuy
100 W
100 W
Posts: 236
Joined: Apr 23, 2008 3:53 pm

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

Post by StinkyGoalieGuy » Jan 12, 2018 6:48 pm

Buk___ wrote:
Jan 12, 2018 6:33 pm
macribs wrote:
Jan 12, 2018 6:00 pm



As for wasteful, the savings are still Al and worth is weight so it is not waste.

As for engineering, hard core design often tend to be made from billet. I am no engineer but I certain there is good reasons for that. After all it has been done for 3 decades or more. Stronger, lighter maybe? Better finish then casted parts? No seems. Probably less expensive to manufacture as you don't need to come up with money upfront for tooling used for casted parts?
I am an (ex)engineer of some 40 years experience. And I didn't mention casting.

And assuming that you use the same grade of aluminium for both, there is no engineering benefit to cutting a thin tube out of a rod shaped billet, than cutting the same thin tube from a thicker tube. None.

And the time, energy, tool wear and waste disposal costs, of machining away 2.6kg of material that you didn't need to start with, is just extra expense.

There may not actually be any saving in the cost of the tube over the solid rod -- tube tends to cost more -- but the other costs are avoidable expense and waste.

Maybe he couldn't find a suitable tube; or maybe he just didn't bother to look. I'm not criticizing him either way, and as I'll never be a customer for his product he can safely ignore me.

But as an engineer, it still seems like his costs could be cut substantially without compromising his product in any way.

Back of the envelope calculation, outside diameter of the motor housing looks to be about 4 inches, output shaft of the reduction is maybe .75 inches. So you need a 4 inch tube with a wall thickness of 1.625 inches? And you'll want to bore out that hole so that it is precisely concentric and also meets the tolerances required for the seal? What are the chances you'll find tubing in that size. If I were were making thousands of these, I would seek to reduce material/manufacturing costs to this degree. But for now, I'm sure he's done the mental cost/benefit analysis and it's not a big deal.

*edit* - I'm also an engineer, though of the EE variety, but I did work in a machine shop as a machinist for a while, and I still dabble with my lathe, mill in my home shop.

User avatar
tangentdave
1 kW
1 kW
Posts: 314
Joined: Jun 06, 2015 11:40 am
Location: Seattle, WA
Contact:

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

Post by tangentdave » Jan 12, 2018 7:45 pm

We want to locate the rotor bearing precisely. And seal the gearbox well. I can finish the housing in two machining operations and be done. The more work I can offload to the CNC machine, the better. I would argue the billet housing is cheaper to make.

Besides, who doesn't want a one-piece housing? I'll make the version with a water jacket for anybody who wants to use a separate motor, the difference in machining is minor. There's an army of small shops that do excellent CNC work at excellent pricing, stuff like this is nothing to them, it's what they live for. If I ever can't keep up with demand, the operation will scale easily.

And thanks Matt. It's because of you and LR that I could even dare attempt this. Your builds showed showed us how awesome these bikes can be, I'm copying you.


-dave
Zerode G2/Tangent 6kW
Intense Tracer 29er/Tangent 3kW PAS

Post Reply