Nine Continent hub motor and vertical rear dropouts

[blue badger]

<Dr. Nick> Hi, everybody! </Dr. Nick>

I've been lurking these boards for a few months now, gathering information on electric bikes. The idea of a bike with an electric assist has always fascinated me, and the past few months, I've been quietly siphoning up information on these forums, planning an electric bike build. I got as far as getting the hub motor from ebikes.ca, a 48V 10Ah battery from Li Ping (though I missed the fact that it didn't come with Anderson powerpole connectors until a few days before the battery arrived, something I've since addressed), and I had a bike in mind to put it all together on. I got a 9C 26" rear hub motor, which I wanted to put into a Dahon Jack folding bike. The idea was to have an electric bike with sufficiently large diameter tires to ease handling, but could also be folded up and put into a car or moved indoors relatively easily.

I've hit a bit of a snag, though - the mechanic I delegated the project to contacted me, and told me that the axle does not fit perfectly in the rear dropouts - specifically, the motor's axle hangs past the dropout by 4-5mm. I haven't yet had a chance to take a look to snap any pictures, so I want to ask anyone who's had experience with installing a 9C rear motor - is there any solution that would allow me to properly fit this motor into a Dahon Jack (or any bike with vertical rear dropouts, for that matter), or is it time to look for another bike for the project, and just throw the idea of putting it on a folder out the window? I've done a lot of research, but I never came across anything that suggested this would be a problem, so I want to know what my options are.

 

[theyerb]

I ran into the exact same problem when I was installing my rear 9 Continents motor on my bike. I contacted the seller, and he advised me to bend the rear dropout arms to accommodate the extra width of the hub motor axle. I was apprehensive to do so because I didn't want to harm my beautiful bike, but I did so and everything worked out fine. My bike was steel, so bending wasn't a big deal. If yours is aluminum, it might be more difficult or problematic. Best of luck!

 

[blue badger]

Oh, damn >_< The bike's got an aluminium frame. I was aware of aluminium not being good for bending, which may have been a problem with a front hub motor even with a torque arm, which was why I went with the rear hub motor in the first place. Is there anything I can do to avoid throwing out the electric folding bike idea on the Jack? I suppose I could always put in for an exchange with ebikes.ca for a different hub motor size if all else fails, but then how am I going to be sure any given bike can accommodate either a front or rear motor?

 

[Kingfish]

Blue, Take a picture so we can see the problem

 

[John500]

Oh, damn >_< The bike's got an aluminium frame. I was aware of aluminium not being good for bending, which may have been a problem with a front hub motor even with a torque arm, which was why I went with the rear hub motor in the first place. Is there anything I can do to avoid throwing out the electric folding bike idea on the Jack? I suppose I could always put in for an exchange with ebikes.ca for a different hub motor size if all else fails, but then how am I going to be sure any given bike can accommodate either a front or rear motor?

I would clamp the frame members close to the downtube and spread the frame at the dropouts. Just use a block and two wedges. This will keep the pressure off the welds and the tubes will easily accept this little spread. You will probably have to spread it twice the amount needed, as it will spring back.

EDIT; MIs-read the problem. Depth of dropout is the problem, not width of motor. Proper solution has been posted below.

 

[Icewrench]

Some bikes have drop outs that are not deep enough for the large axles on hub motors.



This frame is made of steel so I have built up and welded in a filler so the nut will have something to get a bite on.
From what I have read it is not a great idea to bend aluminum frames.

 

[theyerb]

My initial reaction was "Ya, go ahead and bend the frame a few mm-- just try to stabilize the welds so they don't stress and crack during the process." If it's only a few mm to bend, you're probably fine, but after a bit of googling, I think you should do a bit more research before making a decision. Bending the aluminum *could weaken the frame and result in a crash while you're flying down the road. I'm about as daring as they come, but just consider all the variables before going ahead and doing it.

Some info I found on bending aluminum bikes:

http://www.bikeforums.net/archive/index.php/t-518380.html

http://www.sheldonbrown.com/frame-spacing.html: "Note, if you're not careful, you can do serious damage to your frame this way! If your frame is made of aluminum or carbon fiber, do not attempt to re-space the frame, these materials are not suitable for "cold setting. If in doubt, try the magnet test: if a magnet won't stick to it, don't try to re-space it!"

 

[c9tech]

It sounds like the issue is not dropout spacing at all, so bending the frame is not a solution to the problem. If the motor axle hangs 4-5mm below the dropouts when fully seated, it is as Icewrench has pointed out, the dropouts are not deep enough. You can usually get away with a few millimeters of overhang so long as the washers and axle nuts sit flat and are properly tightened, but 4-5mm is definitely enough to be dangerous. If you try to install the motor in the dropouts as-is, you'll spin the axle out of the bike when you hit the throttle.

If the frame has a good deal of metal above the dropout, you can take a Dremel tool and grind it a little deeper, making sure to grind an equal amount on both dropouts, and maintaining a constant dropout width of 10mm. You should also secure the motor axle with a quality torque arm, just in case. If grinding the dropout deeper is not an option, you may need to find a different bike.

 

[dogman dan]

Grinding the corners off the axle to seat deeper in the dropouts is another option. But deepening them may still be needed since the axle is so much bigger than normal, it will need a deeper dropout than normal. This may be required just to get the washers, tourqe arms, and nuts to fit properly. Another good reason to just sort of replace the dropout completely with some custom fabricated tourqe plates.

 

[blue badger]

Thank you to everyone who's posted replies with suggestions. It seems, though, that in the expert opinion of the mechanics, there is no combination of axle grinding and dropout deepening that will produce a safe fit for the 9C on this particular bike. Hence, I'm currently exploring whether an eZee rear hub motor might fit. However, I'm not really sure if I'm reading them properly, so I'm hoping someone can help me interpret them and figure out if the eZee would fit, given that the 9C's axle hangs below the dropout by 4-5 mm.

http://www.ebikes.ca/store/diagrams/M2800R.pdf
http://www.ebikes.ca/store/diagrams/MeZeeR.pdf

If the eZee won't fit either, then I'll have no options left but to throw out the idea of using the Jack entirely, and start researching into another, more appropriate bike to convert, since the consensus seems to be that it's unsafe to use a front hub motor on aluminum forks.

EDIT: At this point, I have little reason to believe that the installation will be any easier with the eZee kit, as opposed to the 9C kit, so I've pretty much ditched the idea of putting it on a folder. I suppose there was a very good reason why I've mainly uncovered BionX kits on these types of bikes... oh well, anyone have a good recommendation for a frame using 26" wheels that I could get in Toronto that would work with the 9C kit?

 

[dogman dan]

Got money? If so, the world is your oyster. Generally, I'd be looking at something in steel frame. So that runs the whole range from a 20 buck bike at a garage sale, to a really nice steel frame hardtail with front suspension built for riding off the roof. In between, the lower price range full suspension MTB's often come with a rear swingarm that is steel. Any of the steel bikes can be filed on till stuff fits, or spread some if that is the prob. The general favorite is a steel frame hardtail MTB with lots of room in the triangle for battery mounting. Often enough, the oldest frames have the big triangle. New stuff has the top bar lower and lower each year. In the new stuff, hybrid bikes still have the big frame triangles. By hybrid, I mean a 26" built more for street, rather than a 700c commuter bike.

 

[Ykick]

I like steel beach crusiers with front V brake. ($100-$200USD) Keep it under under 1000W, 48V - you should be pretty safe on a steel front fork with torque arm. That leaves the rear for battery rack and whatever gearing you need to run. With a strong motor and gentle hills - hardly any need for gearing in my experience but maybe a 3spd internal for steep grades? Suspension is nice but fat ballon tires at the right pressure offer a nice little cushion without the added components and/or moving parts.

 

[dogman dan]

He's already got the rear motor. But a nice beach cruiser is definitely an option, provided it can be geared for fast riding. Personally, my butt falls asleep after about 4 miles If I can't pedal along. One disadvantage of some of the beach cruisers are that they are one speed, and geared for , cruising. One with 5 speed derailur though, is perfect for a rear motor.

 

[torker]

I installed a rear 9c on the back of my Giant Rincon (alum) I did have to spread the dropouts a few mm. but I was surprised how easy they opened up. I didn't actually bend them, they will spring back when removing the motor. I did however use a dremel to slightly deepen and round the bottom of the dropout. I just took enough to make the axle seat evenly. I also used a torque arm. Yours however appears that it won't drop in the slot at all which would require more surgery than mine. Whatever frame you get you might check the size of the slot in the dropout first. Have you read Dogmans thread on fitting hub motors? Just make sure it is seated all the way to the bottom of the dropout or don't do it :lol:

 

[blue badger]

With a little more research, it seems that the prognosis for fitting an eZee front hub motor to the Jack are good enough to warrant further study. I do understand, though, that there is a general aversion to using a front hub motor on aluminum forks, even if it doesn't have suspension. In this case, though, I would plan to keep the power to the motor relatively low (720W max, based on 48V/15Amp max draw), and reinforce it with twin torque arms just to be safe. Justin at ebikes.ca seems to think this is a workable solution - how would you guys rate the safety of such a setup? I plan to keep this machine on roads and trails for the most part, if it makes any difference.

EDIT: The other thing that's leading me to re-assess the possibility of the eZee front hub, is the fact that almost all of eZee's own line puts a front hub motor onto aluminum forks, half of which have suspension. Granted they're rated at 250-350W rather than the 400W the kit's version is rated at, but it does seem to hint that proper reinforcement with a torque arm to account for the greater power could make it work, and I'm hoping somebody here has some experience to confirm or deny that before I forge ahead.

 

[dogman dan]

Justin has studied the problem well, and his c washers and tourque arms are working for me with alloy front forks. I'm running about 1000 watts too, 48v 22 amps. As long as you have good fit, the nuts stay tight and don't crack the dropouts. If the worst does happen, dual tourqe arms keeps the wheel on the bike till you stop.

 

[blue badger]

After yet more research, it turns out that the forks of the bike I'm looking at are, in fact, made of steel and not aluminum as I previously believed (ambiguous specs FTL!). Hence, I'm now looking at putting in a front 9C hub motor, but still using a torque arm to be safe. I've seen the blog entries of someone who successfully installed an ampedbikes hub motor onto the same bike, albeit with a little filing. Another comment notes that, supposedly, the ampedbikes' conversion kits are just de-branded 9C motors; can anyone substantiate that? I just want to be more certain that the motor will fit before I go placing an order for the 9C front motor (the last time I checked the measurements, it worked in theory, but not in practice). Also, do the C washers that Justin produces have any place on non-suspension steel forks with a quick release?

 

[mwkeefer]

Blue,

I may have missed your post on this but do you have the measurement from dropout to dropout - or the clearance on the Dahon Jack?

I saw your thread here and figured since I just ordered one to covert to electric I would just ask, save myself a trip to the LBS before my Jack arrives.

I will be first installing a 9C rear 9x7 on the bike (from e-bikekit.com but the same as most other RH205's I think) with a 7sp freewheel for starters (hopefully... I think there is sufficient clearance) and then I will go on to a geared hub of my own design and finally I plan to come full circle with the bike and install an RC drive (reductions not yet planned).

A friend said they were done with front hubs on folders because it makes folding abit more difficult... I think the Jack requires the front wheel be taken off to fold to it's smallest footprint (similar to the montague paratroopers).. in either case, I just don't want the excess weight up there...

If in fact the front fork is steel, it should support a 9C fine... really shaping either the axle or the rear dropout with a careful, slow grinder being mindful of heat levels (constantly cooling with water or oil if possible and needed) will be fine... I've done it to countless aluminum frames and forks now with no ill effects (including treks, specialized and downtube folding bikes).

In either case, I plan to do a video of proper technique for "shaping aluminum dropouts or steel hub motor axles" once the Dahon arrives.

Thanks in advance,
Mike

 

[blue badger]

The rear dropouts on the Dahon Jack measure 135mm in width. They won't take a 7 speed freewheel normally, though; you'll have to stretch the clearance to about 139mm, which is generally not recommended with aluminum because of its rather sudden mode of failure under stress, but I'm guessing you know that already. As for the fit of the hub motor itself, Icewrench's picture on the first page of this thread describes what I was told; I never got a chance to see it in person, because I delegated the assembly work to the bike shop, but the essential idea is that the 9C rear motor, when fully seated, is simply too large to fit into the vertical dropouts of the Dahon Jack, and would require about 5mm of filing, which I'm told would undermine the structural integrity of the bike significantly. Not having had a chance to see the poor fit firsthand, I'm not 100% sure of this, but I believe the problem is the diameter of the axle - if that's the case, then the Jack will most definitely not accept a 14mm diameter axle in the rear, as that's the diameter of the RH205. If you run into the same problem, you might as well take some pictures and put them up here for the benefit of the audience.

That's why I've shifted my focus to the front instead; www.stevehauck.com is a blog which shows the results of a successful fit of what I believe to be an FH205 onto the Jack, and he successfully used it as a commuter vehicle for a year without a problem. My front hub motor arrived today, and I'll be bringing it to the mechanics again, so I'll let you know of the results, hopefully with pictures of the finished product

 

[mwkeefer]

Okay...

1.) - The front fork on the Jack is steel but I caution anyone against adding that much weight on the front of a Jack, I think they called it a jack because the geometry of the frame is so Nimble (Ie: Jack be Nimble, Jack be Quick).. .the added weight in the wheel could cause a serious handling issue (part of the fun of this bike).

2.) I'm glad you decided against modifying the rear dropout to accept the 9C since the proper method is to mill or file or grind the 9C axle (carefully little bit at a time) until it seats properly into the Jack dropout... I'vedone this for Downtube 9FS, Specialized Hard Rock Pro and now a Jack...

3.) FH205 is lower speed, higher torque (I've been using one on the Specialized for months and months) which is near useless on the jack... its weight balance is more 20/80 with the bias to the rear to begin with... this causes all sorts of traction issues...

4.) I picked up one of the e-bikekit.com geared rears, a Shimano Mega range 32-14 7spd thread on and had NO PROBLEMS installing it... I did remove some paint from the dropout which will not affect the structural integrity... then I had to add a few spacers (too lazy to redish the wheel, it was damn close) amounting to about 1.5mm to regain rear wheel center... This new motor (if it survives about double it's current of 22A in testing) isn't bad for a folding bike... with a 15S pack I hit 27 hot on the flats and die out at about 24mph but... the 22A with a 26" wheel = very little torque, but enough if you don't mind pedaling a tad bit uphills...

There is also sufficient room for up to a 9sp but it will require the a DNP cassette and a minor redish or spacers.

5.) With regards to strength... I've taken pot holes at > 30mph downhill (big potholes) but most I can avoid (jack be nimble)... truth be told I thought several times I was going to break somthing, especially the 6 stairs I bunny hopped down because I didn't see them in time to stop (about 9' @ 15mph).. it just keeps on ticking and surprise to me, the geared (composite ie plastic gears) hub is holding up nicely to my levels of abuse...

The only bitchs I have about the Jack conversion:

1.) Stock front rim was trash, the butt where the rim ends join would pull the brakes each revolution... I need to replace this rim with somthing better, maybe a velocity wheelset?
2.) Due to stem length, handlebar bags hang far out over the center of the front wheel hub, I have not been able to find a mount which would attach to the actual permanent non turning part of the headstem, this would allow batteries in the front (maybe just an emergency pack of LiPo) but tuck them in and below the bars for riding.
3.) I want a quick release on the stem!! Ensuring you have a toolkit is annoying
4.) There really aren't many good places to mount batteries on the Jack... I've seen a bionx kit where they mount the batts down near the chainring on the front tube but... I would prefer to not use a rack when I can avoid it... I had hoped to frame mount or build a small rear pack behind my seat (supported by the rear downtubes)... no luck yet.

Hope this helps a bit!

-Mike

 

[blue badger]

I actually haven't put the 9C motor in the front yet, owing to a bunch of delays, but if I'm going to change anything, it would be now. Do you suppose an eZee front motor would be any better in terms of maintaining handling? I was planning on putting the battery onto a rear rack to offset the weight of the 9C in the front; as you say, there's no good place to put the battery, since the Jack's triangle is pretty much nonexistent, but I figured it would at least help to offset the additional weight in the front.

 

[mwkeefer]

On the stock Jack front fork... you will need to take 1mm of washer sufficient to fit over the axle, then cut the top off it, this puppy will require C type washers which you will need to install while the bike is right side up and this is due to the Odd implmenetation of Lawyer Lips or Tips in this case on the fork... without them you will deform the fork at best and likely will never have a tightened axle leading to inevitable failure.

-Mike

 

[biohazardman]

The old style BMC 400watt gear motors and possibly the E-zee have a 12mm axle that's a couple less than the newer units with 14mm as with many other newer motors I am thinking the 9C is included with the 14s. You can probly file out the edges of the rear dropout, on your bike, near the bottom to fit the shape of the larger 12mm axle, instead of the stock 10, and drop it in another 1-2mm without compromising the frame. Just a thought Justin would probly let you know on the axle size of the E-zee motors for sure.

My BMC 600 axle did not fit my dropouts to well and I did the outlined filing to drop it in a bit more this made the axle fit even with the bottom of my dropouts. An added feature is that my calipers hit the brake rotor a bit further in as well.