How much interest in a 2.5kg 40kv sensored outrunner

[RWP]

#25, and for the record #35, chain does not have rollers. Bicycle chain and most other chains do have rollers.
Not sure about 219 but I suspect it has rollers as well.

Not having rollers means to me that more maintenance is required, meaning more attention to lubrication.

I am very interested in this motor option.

 

[waxman123]

I am in for two if those motors!!! Been waiting for a low kv motor!!!!

 

[johnrobholmes]

Seems that the design of a geared hubmotor is really what we are after, but with a body designed for normal mounting and chain output. It has been shown that smaller outrunners can't be spun too slow without running out of the efficient range.


Seems that what we really need is small planetary gearbox. Something that could get a 250kv motor slow enough to use a modest 3:1 geardown for the final stage.

 

[johnrobholmes]

Just thinking out loud here..

If the gears were taken from a little bafang motor with the ring gear held stationary, the reduction is 5.8 (if my counting was right). With a 3.5 times reduction on the second stage, a 200kv outrunner could put down 27mph unloaded at 36v. Not too shabby, and decently compact. It could weigh less than the comparable hub motor, but have a huge power to weight ratio advantage. The downsides that I see would be the rotating mass of the planetary assembly, and the trouble keeping everything aligned and centered.

 

[John in CR]

Hey John,

I'm approaching it from exactly the opposite direction, so hopefully we meet in the middle resulting in a variety of solid and economical options. I want simplicity and I'm having a hard enough time choking down just a single chain or belt. Plus I'm not giving up regen or the ability to turn my rig off with a key, so fiddling with brakes is the absolute minimum and my emergency shutdown is covered.

 

[LI-ghtcycle]

Hey John,

I'm approaching it from exactly the opposite direction, so hopefully we meet in the middle resulting in a variety of solid and economical options. I want simplicity and I'm having a hard enough time choking down just a single chain or belt. Plus I'm not giving up regen or the ability to turn my rig off with a key, so fiddling with brakes is the absolute minimum and my emergency shutdown is covered.

I agree, nothing wrong with a geared hub motor, but if you're going to go this far, might as well eliminate a second X-mission, just a single stage down to the wheel, where if you so choose, you can use an internal geared hub (my choice is the Nuvinci of course).

 

[arnie1]

I am in for a one of these motors. I want to drive a Nuvinci hub with single stage reduction.

 

[MitchJi]

Hi John and John,

Ramsey silent chain is out. It requires an oil bath.

Why does length matter for #25? Would it bounce more, or just because more links means more stretch?

In response to a similar post Luke said he didn't think an oil bath would be required for silent chain (he thinks very highly of silent chain).

On the length of #25 I said "I think". It was a complete shot from the hip. It could be totally incorrect. The thought was based on the facts that #25 is a pretty weak chain and that they have held up well for Matt in his drive units (very short chains). Kind of makes sense (IMO), which doesn't mean its true.

Seems that the design of a geared hubmotor is really what we are after, but with a body designed for normal mounting and chain output. It has been shown that smaller outrunners can't be spun too slow without running out of the efficient range.

Seems that what we really need is small planetary gearbox. Something that could get a 250kv motor slow enough to use a modest 3:1 geardown for the final stage.

I agree but the problem is going to be the cost of a compact, strong and solidly built solution.

If the gears were taken from a little bafang motor with the ring gear held stationary, the reduction is 5.8 (if my counting was right). With a 3.5 times reduction on the second stage, a 200kv outrunner could put down 27mph unloaded at 36v. Not too shabby, and decently compact. It could weigh less than the comparable hub motor, but have a huge power to weight ratio advantage. The downsides that I see would be the rotating mass of the planetary assembly, and the trouble keeping everything aligned and centered.

I like the basic idea (if it is an affordable way to resolve the issues I've already mentioned) but for a 200kv motor I'd prefer something like 8:1 primary reduction.

I'm approaching it from exactly the opposite direction, so hopefully we meet in the middle resulting in a variety of solid and economical options. I want simplicity and I'm having a hard enough time choking down just a single chain or belt.

If John (in Missouri) can come up with a solution thats quiet, strong and inexpensive (big if's IMO) the result would be simpler than a belt or chain to get a similar reduction.

For example Gary's direct drive was very compact and simple to mount. But the small primary sprocket was very noisy and fitting in the 20" rear sprocket (slight exaggeration) were problems. An inexpensive built-in planetary of 5:1 to 8:1 could have all of the advantages and simplicity of mounting of Gary's direct drive with none of the disadvantages.

 

[johnrobholmes]

I think the best meet in the middle solution would be a larger diameter motor. In all honesty I would love to only need one stage of reduction, but the laws of physics seem to dictate that we will needs lots of RPM to get the power we want in the size we want.

 

[oatnet]

Please sign me up for at least 1 - more if other applications present themselves as I mull the possibilities.

-JD

 

[waxman123]

When can we get them? Lead time, cost? I would love a low KV motor if they work. If they work I think you would have alot of takers. It would be a true single stage set up! Alot more compact and doable on alot more frames with out the second rduction stage!!!!!!!

I would like two right off the top!!!!

 

[patrickza]

I'd be in for one. It's exactly what I need to get my electric mountain board built!

 

[John in CR]

Ok guys it seems like there's enough interest, so I want to set mine up in the same manner you guys would want. That puts me back to asking what form do you want the output? The hollow drive shaft forces a large 1.5" OD drive shaft. I want the motor to be able to work with a single reduction to the wheel, so belts are out, because a small enough drive pulley at the motor for the reduction needed can't be affixed to such a large shaft. It looks like #25 chain is the best solution, and I'm coming up with a 15t sprocket as the largest size still offering good flexibility in gearing.

One of the compromises is the general recommendation for roller chain is a minimum of 17t. If that's an important issue please speak up, because the largest #25 sprockets I've seen are 90t, and the largest at McMaster Carr are 72t. 72 should give me great climbing but my wheel will only have a 21" OD. The other compromise is chain length. 30-50 times the chain pitch from axle to axle is recommended, which with #25 is only 12.5". I'll probably end up at about 15", but with a 26" wheel you're probably looking at 20". If chain length prove problematic, I think it will be easily resolved with idlers. I will run regen on mine, so a chain tensioner is out.

I was wrong about something earlier. We will be able to output from either side, by simply removing the housing and flipping it over. Then just change the wiring combo by swapping only two hall wires and two phase wires.

If we can source a reasonably priced die for cutting FW threads, we can cut them on the output shaft, just in case someone has a large enough sprocket to run bike chain. If someone really wants to output to their bike's gearing, I'd suggest just using a disc brake ready bike rear hub to make a first stage reduction. Connect the large #25 sprocket as if it's a disk brake, and use a bike sprocket on the other side. Such a reduction will be extremely easy and flexible with this motor, so it's right in line with the overall goal of simple and cheap.

I'm waiting on China to get back to me on pricing, and what mods they're willing to do on that end. While skilled labor is pretty cheap here, no doubt China's is cheaper. I'll push my guy here for a bargain price on the work on the shafts, and those won't be case hardened since we're not even using the outside of the shaft and some may want the FW threading.

Once you guys sign off on the output method, I'll order what I need, which takes a couple of weeks to get here. Then even if I procrastinate I can get it running and tested within a week or two. My bike that will readily accept non-hub drives is virtually ready to go. Once running, we'll know immediately how it handles the extra power I want to push through it. Let's call it end of March as a deadline for me to say here's the motor and what it does. That way I'll have a couple of weeks to hammer on it before signing off. Hauling 250lb me up hills should be a good test.

John

 

[RWP]

Some sources for HSS 1-3/8" x 24 dies:

http://www.kbctools.com/ Catalog page 126
$48.95

http://www.victornet.com/cgi-bin/vi...l+Pitch+Dies,+1-3/16"+and+Larger:1173,507,599
$51.00

http://www.travers.com/product.asp?...ss+level3+id+30318&eaprodid=119191-17-088-245
$59.86

http://www1.mscdirect.com/cgi/NNSRI...re=ItemDetail-_-ResultListing-_-SearchResults
$71.13

 

[John in CR]

Thanks RWP, that's definitely a tool I need to add.

 

[John in CR]

Sorry for the delay in the update I promised. I planned to start with the motor out of a Fusin geared hub, because it is beefier than it's Bafang counterpart, but my supplier seems to have evaporated. I went ahead and started the mods anyway on one of the Fusins I have, and I'll share the details in case someone wants to do something similar with any geared hubbie.

Updated info I do have is that the Kv is a bit higher that originally expected. The motor runs 40rpm/volt somewhere around the max efficiency point, not at no-load.

The new drive shaft attaches directly to the original sun gear. If this works well we can dump the sun gear and put a flange on the bearing supported output shaft to bolt it directly to the rotor. I'm still trying to track down the right size centrifugal fan from a scooter or motor to attach directly to the rotor and suck fresh air through the windings and air gap. If that doesn't work, I'll put 2 server blowers to blow directly on the exposed stator. The housing will be a composite of balsa wood, fiberglass, and epoxy to any fan sounds should be well dampened.

My test platform will be my Cannondale SuperV using my diy extended swingarm. Since I'm trying a variety of drives on this bike, I've added a new twist for this particular motor. I'm going to make a custom fit Konion battery to fit within the swingarm. The motor and controller will attach directly to a small framework that attaches directly to the wheel, which will guarantee me perfect sprocket alignment , and easy chain tensioning (issues I had with my first mid-drive using a 9C on this bike). The slick part will be that I can swap the motor drive with wheel out and put a regular wheel on in less than a minute...just unplug the battery mains and throttle connectors, loosen the normal bike axle nuts, and remove 2 bolts that anchor the motor assembly with housing to the swingarm.

I also started building quick attach adapters that also act as both torque arms and dropouts, so I can just as quickly attach a monster scooter hubmotor that I have to the same steel swingarm. A few small bolts for the big hubbie's controller, battery and throttle connectors, plus 4 large bolts for the motor, and it's ready to go within a minute or 2 with 10kw+, though it will need some extra battery capacity for anything other than short errands.

Back on topic, here's what the motor inside the Fusin hubbie looks like once freed from its oven roasting shell, along with the new bearing supported output shaft and sprocket. Note that I will run it initially as 20s or 74V nominal, and reasonably expect 33mph with great hill climbing from this tiny 100mm diameter sensored outrunner.

 

[amberwolf]

How did you make the mating surface to the sun gear, inside the sprocket adapter? Is it just a splined surface, or actually negative-toothed to match the sun gear (for more surface area in mating)?

I have been pondering the more permanent method of mounting, using the bolt-on in place of the sun gear entirely as I think you are meaning above, and might have a solution using some pieces I already have laying around. I have to test fit them to see if they'll even fit over the axle, as I haven't gotten them and the Fusin in the same room yet. :lol:

May be a bit before I can, though, with delays caused by my crash injury to pretty much everythign I am doing that doesn't involve laying around with my leg up in the air.

 

[John in CR]

As a quick and dirty solution, I just turned the sun gear teeth down on the lathe to mostly flatten the teeth, and then turned the high pressure pipe I'm using for a shaft open to fit the sun gear. As you can see in the pic, I didn't turn the sun gear teeth all the way off, so my attachment is 2 grub screws that bite into the valley between teeth. That should be a good enough solution for some testing. I can always drill out some better purchase points for the grub screws, and it should work ok, since they are used at a much greater radius than something like on a 10 or 12mm drive shaft. I'm actually more concerned about the 5 quite small bolts that hold the sun gear. I replaced the factory ones with the hardest steel bolts I could find in that size, because I just didn't like the phillips head originals on my motor.

Later, yes my output shaft will be essentially a piece of pipe small diameter pipe with a flange to bolt in place of the sun gear at one end, and the other end a sprocket supported by a bearing on the shaft. I found some nice small bearings online that match the motor bearings, but I didn't find any locally. That's why I had to go to a much larger diameter for the shaft due to bearing size limitations. Waiting on parts from overseas exceeds my patience level if I can make something locally fit.

In the review section, I found someone running one of these without issue with a 35A controller in a 20" wheel, and that's still a slightly steeper gearing than I'm starting with. I'm getting even more confident of being able to run it at 40-50A peak with my forced air ventilation plan, and now that I've completely dumped the original metal housing, it should end up weighing a lot less than the original thermally limited motor.

Wait till you see this wheel plan. Everyone should get a kick out of it. Pics this week I promise.

The monster hub has a 5" wide street tire and looks really bad ass with the rest of my SuperV setup, and I'm going to try to kinda copy that look with my rig with the Fusin if the motor proves out. I'm pretty sure I can pull off the quick swap ability. Then I could rig a fusin or 2 for trail riding, and the hubmonster for street racing. Since I missed the Death Race, my son and I have been taking my Little Red Racer out to hunt up cars, scooters, and small motos to crush leaving red lights. Using the hubmonster we should be able to bite off some slightly large motos, and really embarass the cars.