Using hubmotor as middrive for quietness? Challenges?

Wheazel

Wheazel

10 kW
Joined
Nov 2, 2010
Messages
970
Location
Sundsvall, Sweden
Hi ES

Since I switched from geared applications to a dd hub, I have been sold on the silent operation.
This has to me become one of the most important aspects of a commuter ebike.

However, I am not fond of the unsprung weight a reasonably powerful dd hub brings.

So my question is, would it be possible to reach a system as functional as the ddhub, when using a beltdrive for example.
I am thinking of the hubmotor as 1:1 (or close) direct drive with fairly large beltpulleys. To minimize forces, slack and hopefully maintain a good motor braking feel.

How much power goes lost in the transmission? Is it a path of too many bad compromises?
I have seen some middrives on the ES, but the focus has been on torque, not necessarily silent and efficient operation as number one.
 
I have been considering doing the same thing. I have really come to appreciate the quietness of my BBSHD, but I miss the power of my Astro 3215 setup. I want it all! I have considered many options including running a DD hub as a mid-drive, but I still need gears as I need to climb massive hills on my off-road commute - up to 32% grades for short periods of time. I'll be interested to hear what you come up with and I'll also check out that thread linked by Spinning Magnets.
 
If you don't drive the crank and are looking into left side drive you could easily use belt. But even using chain for left side drive I think will be bearable regarding noise if you can tolerate the chain noise. The hub could be mounted anywhere on the frame if you can make up for that with a jackshaft that is mounted in a way to avoid chain growth as rear suspension works. Like the motoped prototype would work well, a jackshaft inside the swing arm pivot. That way you could also change the gearing in an easy manner for special occasions.

A dd hub as mid drive with a jackshaft gives a much larger freedom to choose any rim sizes, even 29ers without sacrificing acceleration, abiblity to climb or haul heavy loads.

I think the added usability from a mid mounted dd hub will outweigh the little losses from using a jackshaft.
 
macribs said:
If you don't drive the crank and are looking into left side drive you could easily use belt. But even using chain for left side drive I think will be bearable regarding noise if you can tolerate the chain noise. The hub could be mounted anywhere on the frame if you can make up for that with a jackshaft that is mounted in a way to avoid chain growth as rear suspension works. Like the motoped prototype would work well, a jackshaft inside the swing arm pivot. That way you could also change the gearing in an easy manner for special occasions.

A dd hub as mid drive with a jackshaft gives a much larger freedom to choose any rim sizes, even 29ers without sacrificing acceleration, abiblity to climb or haul heavy loads.

I think the added usability from a mid mounted dd hub will outweigh the little losses from using a jackshaft.
Click to expand...

Yes a jackshaft is a real option, maybe the best option for a clean install, even if the frame could house the motor in the swing pivot point potentially.
Since I am talking about this in the perspective of scratchbuilding, most ideas are possible.

What I am worried about is that the setup overall would cause enough trouble with possible belts/chainsjumps etc, and braking with the motor working less smoothly.
To an extent so that keeping the hubmotor as is would have been better all around. It also has to be clearly better overall for me to justify putting the time in to make the build.
Would be nice if there already were a well documented setup like this to read about.

I would probably stick with 26" in most cases for the large amount of tyre choices. The best spiketyres are available in mtb wheel sizes.
If I were to put a setup like this on the cargobike, I would gear it down slightly to reduce topspeed from ~65-70km/h to 55-60km/h.
 
Well if you it use belt from hub to jackshaft and belt from jackshaft to rear wheel I am certain you will not have issues with "chain jump" because those belts need to be sort of tight when mounted. And that lets you keep motor stock except for the sprocket replaced by belt pulley. Quiet and low maintenance. And using left side you could skip the freewheel and your regen breaking should be as smooth as you are custom to with DD hubs.

As for complicated, well yes. You add a jackshaft into the mix with bearings and you add belts and pulleys. But if you use quality parts and get those swedish SKF bearings in the right sizes I really think you will not run into any problems that require regularly service. Belts you can most likely run a year or two between each time you need to tighten those. Bearing should last for years.

If you use belts both in motor/jackshaft and jackshaft/wheel you will most likely have to pay a little more to change the gearing, then again doing the math correct the first time should work for most of your use. If you find you lack heavy hauling capabilities or extreme steep climbing abilities you could always just do the easy fix and add a front DD Hub motor and yet another controller. Then you have 2 wd, well suited for swedish winters, spiked tires and ability to haul and climb anything and even quicker acceleration using both motors at take off :twisted:
 
If you have the room, I highly recommend a DD as mid-drive into a IGH.

I have so far built this:



https://endless-sphere.com/forums/viewtopic.php?f=28&t=44997&start=75

I really enjoy the simplicity of having one chain for the motor, one for the pedals as you don't run into any need for jackshafts, 2nd stage reductions, and there are a few "off the shelf" options that allow you to use for example a NuVinci n171b IGH and a simple adapter from Station Inc.

3274.jpg


http://www.staton-inc.com/store/index.php?p=product&id=543

(P . S . I have heard you can also use a Nexus 3 Speed IGH as they are very robust and would be a cheaper and possibly more available IGH)

This allows you to use one of my favorite IGH's that has been proven to take very high loads of torque (95ft-lbs IIRC from a gas bike) where it only just started slipping, slight discoloration of the fluid inside and no damage to the n171b.

There should still be some of the older n171b hubs around (I also have one on my recumbent, see link in sig) they are still supported, but no longer manufactured, and other than the linkage on the outside occasionally being damaged from carelessness or a bike falling over, they have a spotless record for performance (several bike shops in Portland, OR in the USA told me they have never had to service them internally).

I am using a rather heavy bike atm to pull a trailer for a local bike shop, Classic Cycles in Oregon City (I come to customers to work on their E-Bikes at their homes) and I plan on putting 2x 20s 4p Li-Ion (Panasonic PF) to make 144v 11.6ah for the drag strip at the local track, and I have a much lighter custom made frame to really go for speed (the current bike is quite heavy, 114lbs, and the first prototype of our mid-drive design) with it in the rear wheel.

I too live near a steep hill, and my goal was a bike that could do all the work for me if I cannot pedal along, and climb 2 miles of 7% grade with out getting warm.

I have done that with the Cro Motor (Hub-Zilla it's a 9.3 KV so nice low RPM running nearly a 1 to 1 ratio between hub and IGH input) so far, and I believe I will be able to place a MXUS 3000w in it's place to get similar performance.

So far I have only run at 18s 2p 90c Nanotech Lipo, or 66v 12ah (it's a bit old and tired however) and have been able to charge up that hill at 28 MPH, this only required 1500w and that means 24a at the controller, so nothing even got warm even on a 90F+ day! 8)

Tomorrow, I get this battery from Lunacycles!

panasonic_ga_72v_11.6ah-2__01959.1465450609.1280.1280.jpg


http://lunacycle.com/hot-new/72v-panasonic-pf-11-6ah-with-luna-charger/

I expect as good or better performance, expecially since I will be pairing it with a 72v 40a controller, also from Lunacycles:

CYCLONE_CONTROLLER-1-2__66801.1463467885.1280.1280.jpg


http://lunacycle.com/motors-and-kits/mid-drive-kits/cyclone-mid-drive/40-amp-48-72v-ebike-controller/

At the risk of sounding like a shameless plug for Luna, they also provide a 6 months warranty for the controller being used with this battery.

I have been very impressed by their customer support and product (I had to return a controller that didn't have the right plugs, they gave me a store credit no problems!) built a simple DD hub motor kit for a customer with one of their 48v shark batteries, and she has been happy with it with no complaints for about 4 - 5 months.

I plan on simply adding a second controller when I run 2 of these batteries together to get 40s 4p! :twisted:
 
this is exactly what im doing on my new bike, still a work in progress at the moment. using a hub to drive a jackshaft, then to the rear wheel, in two low ratio reductions (both about 1:1.5/2) so the motor is effectively mounted in a 11" wheel, but with none of the unsprung weight and disadvantages of such a small wheel... i was thinking of doing a 2 speed but i dont think it'll be worth it, at most i may have a 2nd pair of sprockets that i can manually change the chain too if im doing particularly slow high load riding...
 
Wheazel said:
So my question is, would it be possible to reach a system as functional as the ddhub, when using a beltdrive for example.
I am thinking of the hubmotor as 1:1 (or close) direct drive with fairly large beltpulleys. To minimize forces, slack and hopefully maintain a good motor braking feel.

How much power goes lost in the transmission? Is it a path of too many bad compromises?
Click to expand...
I don't know with belts for sure, but with chains it's about 2% per stage, so if you had just one chain from motor to wheel, it's not terrible.

I've seen numbers for belts that vary widely, and it seems to have to do with type of belt and how much tension is on it. Too little tension and it just slips under high loads, too much and it robs power and wears the belts too fast. But most of the numbers I remember were higher losses for belts than for chains.


Unless you have pretty high RPMs, I don't think the belt is going to be appreciably quieter than a chain, if the sprockets on either end of it are both larger numbers of teeth.


Myself I've been plotting to add a hub-based middrive thru an IGH to my stuff for years, but events and whatnot keep settign that priority back, so I've never actually done it. What I was going to actually use is not a bike hubmotor, but rather a powerchair one, that seems to be capable of similar power as the old Crystalyte X530x series, or better. The main reason for using it is it has a flat side mounting that means the only thing I have to come up with is a modification to it's rotor to bolt a sprocket to it. No worries about making something to hold the small axle of a bike hubmotor, and it's bearings are already designed for loads pulling on it from just one side....but it's heavier than a bike hubmotor by a significant amount. :( If interested you can look at the thread for that motor here:
https://endless-sphere.com/forums/viewtopic.php?f=30&t=32838
 
sn0wchyld said:
this is exactly what im doing on my new bike, still a work in progress at the moment. using a hub to drive a jackshaft, then to the rear wheel, in two low ratio reductions (both about 1:1.5/2) so the motor is effectively mounted in a 11" wheel, but with none of the unsprung weight and disadvantages of such a small wheel... i was thinking of doing a 2 speed but i dont think it'll be worth it, at most i may have a 2nd pair of sprockets that i can manually change the chain too if im doing particularly slow high load riding...
Click to expand...

Nice, what are you using for power transmission between the wheel and jackshaft, and between the jackshaft and motor?
 
Wheazel said:
sn0wchyld said:
this is exactly what im doing on my new bike, still a work in progress at the moment. using a hub to drive a jackshaft, then to the rear wheel, in two low ratio reductions (both about 1:1.5/2) so the motor is effectively mounted in a 11" wheel, but with none of the unsprung weight and disadvantages of such a small wheel... i was thinking of doing a 2 speed but i dont think it'll be worth it, at most i may have a 2nd pair of sprockets that i can manually change the chain too if im doing particularly slow high load riding...
Click to expand...

Nice, what are you using for power transmission between the wheel and jackshaft, and between the jackshaft and motor?
Click to expand...

chain in both cases - likely 219. keeping the reduction ratios low helps with efficiency a lot too - two small stages can be far more efficient than a single large stage (of equal total reduction). down the track im thinking of doing enclosed chain, atleast for the first stage, gives the best possible efficiency.
 
wheazel if you think about it, so what if you loose a little due to reduction and or jackshaft? You are free to choose whatever dd hub you like and if you choose one of the more popular like mxus 3000 or qs 205 you will have peak power of 12-15 kw. If you loose 10% or even 15% you still be peaking 10+ kw.
And as you build your own frame you can tailor your battery to account for those losses so your range is not affected.
 
Please use a cvt with your left hand side mount. Those pocket bike kind for 49cc..I want to see this. Pitch of pulley gives reduction of two to 1at low and rises to 1 to 1.1 over drive
 
Overclocker said:
why use a DD hub that has poor cooling? just use a low-kv inrunner motor
Click to expand...

Because a dd hub is quiet, rather narrow and for my applications cooling is not an issue.
I am not trying to build motorcycles (yet).
The point that could be argued is the weight.

What alternative would you suggest for a low kv inrunner?
 
I'm trying to understand how do you attach the driving cog to a hub motor? The existing mount will freewheel, right?

I suppose you could attach it to the disc brake rotor mount. Then you have to make it left side drive or move it to the right side using a jack shaft.
 
Or spin the motor in reverse, and drive the other side of the chain (from the top or bottom), like Rassy's trike does.

Or use a very large chainring bolted to the spoke flange or the ocver bolts, or even directly to the cover in the space between the bearing area and the stator coil area.

Or flip the motor over and run it backwards, with freewheel on left side direct to rear wheel (or IGHjackshaft, etc).

There's a few ways. :)
 
StinkyGoalieGuy said:
I'm trying to understand how do you attach the driving cog to a hub motor? The existing mount will freewheel, right?

I suppose you could attach it to the disc brake rotor mount. Then you have to make it left side drive or move it to the right side using a jack shaft.
Click to expand...

My initial thought was to make a custom attachment for the discbrake pattern. I want the motor to be connected for braking so no freewheeling is wanted.
Also needed for good speedo measurement with an adaptto controller.
Regardless if I would go jackshaft (upcoming winter quad build), or rebuild the cargo (left side drive with the motor in the pivotpoint, or very close to the pivotpoint on the swing),
I strongly believe that reducing the amount of transmission steps is something to strive for, when possible.
 
Wheazel said:
Overclocker said:
why use a DD hub that has poor cooling? just use a low-kv inrunner motor
Click to expand...

Because a dd hub is quiet, rather narrow and for my applications cooling is not an issue.
I am not trying to build motorcycles (yet).
The point that could be argued is the weight.

What alternative would you suggest for a low kv inrunner?
Click to expand...


https://endless-sphere.com/forums/viewtopic.php?f=6&t=69319
wANQIPj.jpg
 
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