Hub to Mid conversion for a trike - talk me out of it.

I have previously converted my older tadpole trike to hub drive - using 52v battery, generic 9C clone 1000w motor and KT sine-wave controller. Works well, and I able to do about 30mph throttle alone. What I don't like is dealing with the larger controller, the weight of the big hub motor, and the lack of gear choices etc. I have the battery mounted down low and to the side, which works well, and have the controller and other electronics in the rigid tail box: see build here: https://endless-sphere.com/forums/viewtopic.php?f=6&t=112009

My plan: replace the hub motor and controller with a BBSHD mid drive up front, and use the original 9 speed rear wheel/cassette and hub at the back. This would allow me to loose the tailbox, and continue using my battery arrangement.

Pros/Cons/Considerations
-Cost- the motor and needed pieces will be 700-1000US, but maybe can resale the hub motor and supporting pieces?
-Speed - I think geared correctly, it appears I will have similar top-speeds, and likely better climbing
-Weight reduction, at least a bit
-Efficiency for power usage - no real idea here?
-Reliability - the current setup has been reliable, the mid could be harder on the chain and driveline, I know
-Regen braking - will lose this, but now only use it set at a very low level as I have no good way, at least yet, to incorporate a good torque arm for the hub motor on this frame
-Noise? not sure how big a deal this is

Would love expert opinions on this plan.

Ergo, add a new smaller battery, your range is about to double.

You will loose the triple chainrings. Its possible to run a double ring with a Fat Bike Derailleur.

Or you could build a wheel with a 3 speed internal hub that accepts a 8-10 speed cassette like Sturmey Archer RSK.

Get an Idler from Terra-Cycle the OEM one will wear pretty quickly.

At speeds below 12 MPH the BBS02 will be twice as efficient as the Hub will be. Above about 23-24 MPH the Hub will be more efficient than the BBS02.

My experience with a mid-drive has been that the loss of the triple chain rings up front rendered my ICE Adventure useless without electric assist.

The rear cluster alone did not give me the low gears that I needed to climb any sort of hill.

Lucky me: my bike-riding days are over and I had a Rohloff hub on my (now-retired) road bike.

With the Rohloff back there and a 38-tooth front chain ring, I am a-ok on hills and don't get spun out until somewhere over 18 mph - which is approaching my perceived safety envelope of the ICE Adventure anyhow...

I switched over to a PC-1 chain (singlespeed, beeeeg links) in hopes of mitigating any drive-train failure issues.

Noise-wise, the nylon-geared TSDZ2/OSF is entirely acceptable - and I regard myself as being a bit neurotic about noise. Maybe I just got lucky, but the noise level is about the same as the Rohloff in seventh gear - lower-pitched and maybe a little less in volume.

So life is good for this slow rider with a mid-drive, but I would not even think of doing a mid-drive without adding a wide-range (Rohloff's is 500+ percent) geared hub or some functional equivalent.

YMMV - especially if you are ok with being battery-dependent in some situations.

So glad to have trikers chime in - the idler I have is upgraded over stock already, so good there. I have only a 7-speed on the hub motor, and its 14-28 - with assist I am always in the big ring up front - which is very big. I'm thinking that my 11-32 9 speed cassette will pair nicely with a 44 or 46 up front and give me broad range. It will, I think be an easier no-power pedal that what I have now, as I never use the small ring up front. The 14 at the rear currently means I pedal out at speed too often, and the smaller 28 will be improved a bit to 32. The screw-on 7 speed was about the best I could do on the current hub motor, but realize I could do 11-32 freewheel if I was to keep the current setup. An IGH could be an option down the road. I tool along at around 15mpg when riding with my wife, and don't want to over power then, but I regularly pedal up to the high 20s and even thirty now on solo rides, so I do want a combo that let me do that. I'm also in central VA where the hills are not that strenuous. My trike is quite stable at those speeds, but given it has no suspension, I look for smooth roads and trails.

So, is it a good idea to include a shift sensor? Also, how important will it be to add something like Utah trikes makes - the BBSHD-specific torque arm that ties the motor to the frame? Can the motor often be mounted in such a way the frame geometry can help resist twist-back without such a piece?

Hmm,, build another trike with the mid drive because what you have is nearly perfect? The number of bikes is the number you have, plus one of course.

The way I see this,, you want a lower gear, but its because you decide not to use the middle ring? So you plan to go from 21 gears to 9 to get more gears? I'm confused now. You can put a freewheel on your motor with different ratios, if you feel the stock ones are too big a jump between gears. And you can pick anything you want up front as well.

Efficiency won't change much, unless you ride the hub motor up extreme hills. But you live in east Virginia, not West Virginia. If you want more range, choose a lower gear, and pedal your most comfortable cadence in that gear. Use the throttle only enough to lessen the pressure on your feet pedaling, not eliminate it. At 15-18 mph, you double your range vs full gallop, in your highest gear.

Your controller is big, but I assure you there are some out there that are not a box the size you need a rear rack to mount it on. Id just hang it off the back of the top of the seat, or make a rear rack taller so it can mount under the rack, with a bit of something between it and the wheel to keep it dry.

You have one major reason to go mid drive. VERY steep hills that your current motor chokes on. Thats damn steep, or maybe not so steep if you weigh 300 pounds. If you do weigh more than 250 pounds, then you are indeed a candidate for a mid drive, or if you plan to tow a trailer that makes you and the loaded trailer weigh more than 300 pounds.

As for the torque arm, its part of the fun to fabricate something custom made. You only need a drill, a hacksaw, a small flat or triangle file, and some flat sheet steel just a bit thicker than 1/8 inch. And some creativity. Make your prototypes from cardboard. Then you could go to a welder, and say make me this in steel.

Thanks - I did ask for someone to talk me out of it! Simplifying the trike is what I'm after, and it is true what I have functions fairly well. I do feel eliminating the big outboard controller will reduce complexity and maybe make the whole thing more reliable. Gear range is not a big issue now, nor do I think it will be if I go mid-drive. I don't need a lower gear under assist at all. Power-off riding could be smoother given no drag like the current set up has, also. Not least among these things is that I am looking for another project - so fashioning the torque arm myself makes sense. I do think my current setup is a bit cobbled together, so I plan to rebuild and be certain all is done well with ultimate goal of reliability.

I do weigh about 235, and the machine is no lightweight, so climbing is an effort. I am still a strong peddler, however.

One other factor - is there an online marketplace for used components, beyond the usual ebay and craigslist type of things? Selling my current stuff could offset the cost a bit. I notice there is no buy/sell forum here, maybe for good reason.

There is a buy/sell forum on ES. Go to the board index page, scroll to the bottom.

I would just feed higher power. Then it won’t feel heavy anymore. :wink:

You have a nice clean Trike don't put a wart on it's nose.

Don't know how much power you are using with that big controller. Have you thought about a Baserunner from Grin. It fits under a battery. you could lose that big controller and storage container. If the Baserunner is to small the Phaserunner is really small.

If you don't want to spend any money here is where I mounted my controller so it gets air. Be warned my trike is not as clean as yours.



I have long legs so my feet come no where near it. This about the only pic I have that you can see the controller. Looking down on it the battery, wheels, frame and my legs block the view of it. The panniers only carry water, tools and tubes.

I would like my 9spd back also. I will find a pic of Grins torque arms on my trike, not very clean. Have been wanting to make some torque plates to replace the arms. Have been thinking that I could gain the few mm that I need to run my 9spd if design right.

I like the clean look of your trike, hard to tell its a E-trike.

Keep your big clunky controller, we all need spares eventually. But do shop around for something less clunky, that can be mounted in other places. In my climate, putting that controller in a box without vents would kill it.

Like bike + one, controller + one applies. Battery + one too. You could have that second battery for more range in that box.

Like that TA modification Zero Em, it shows how a bit of creativity can replace fabrication tools. One good easy thing to do is take a good TA such as Grin's, then just cut the second piece yourself to make it fit your bike.

If you want freewheeling and coasting back, then replacing the hub motor with a good strong geared motor would do the trick. But for now, if you have a throttle, you can simply tickle it with a tiny bit of motor power to make the DD motors cogging go away. If you do the math, less than 100w of power takes forever to drain a battery coasting, or just removing the resistance while pedaling. So its going to extend your range, not shorten it, to tickle the motor with just enough power to make the resistance go away.

:lol: They were laying around, did not even drill the holes. Was going to get back to it, no point in fixing what is not broken.
Have a TA on the other side that pulls the other way for Regen.

Ah, you have a 26 inch rear wheel which is unfortunate. Hub motors have higher power density in 20" wheels, which means you can use a smaller and lighter one for the same power.

A BBS02 is going to be less efficient on the flats but handle steep hills much better. The downside is the cost and higher lifetime maintenance requirements, versus a hub, which only has a few failure modes and parts that can fail.

One big upside with a mid drive is that taking the weight out of the rear wheel makes the rear suspension work much better due to the elimination of unsprung weight.

Since you have a 26" wheel, a nice compromise between both of the ideas would be grin tech's GMAC or a regular MAC motor, at 9 and 10 pounds respectively. A 9lbs motor makes for easy tire changes and decent rear suspension characteristics. It should be power equivalent to your 9C, possibly has more torque making potential too, once you start boosting the amps.. but watch out for heat

Thanks all for the input! The current trike platform has no suspension, all all the weight is "unsprung"! Where I ride is fairly smooth, fortunately. I think if I hit the big time some day I may use a mid-drive on a fully suspended trike like a Dumont or Scorpion FS.
After looking over all the options, I think I will stick with my hub motor, as everything works, and the faults that exist can largely be remedied easily. They are, as I see them:

- Weight - minor savings going mid, and what's there works fine.
- Gearing - I can swap the 7sp 14-28 for a 7 speed 11-32 easily - same stack height. Even easier than trying to cram a 9-speed freewheel in the already "cold swaged" dropout. I'm using a bar-end shifter in friction mode now and it works fine. Get to keep the triple up front.
- Hills - few enough of them now that current set up is fine.
- Torque arm additions - main reason to beef this area up is that I use regen, but at a light "non-braking" setting. If I were to have a solid axle-to-frame connection, I would ramp up regen braking and save the disks, which are effective at stopping as-is. I can add a torque arm to the inside of the right axle if I pull the wheel, and I think it makes the most sense there as the left side is a hollow axle for the cable pass-through.
- Cargo-box mounted controller - I have it ventilated and it does just fine, and does add some storage utility - it locks from the outside, has a switch lock in it to immobilize, along with some other wiring bits and pieces, and keeps the birds nest out of sight. I did have my big 22ah block battery in there, but didn't like that much weight up that high. Phaserunner or Baserunner could be added down the road at battery swap time.

Regarding wheel removal for maintenance, has anyone spliced in a connector in the motor cable to make wheel removal easier? Currently the one cable, with phase and halls, goes to discrete connectors at the controller. It won't easily pass through the axle washers or nuts and makes removal a pain. I'm thinking of either splicing in a 9-pin "Julet" motor connector (iffy at 35 amps?) or even one of Grins L1019s. after I solder and heat shrink that thing in, easier to drop the wheel for flats etc (have not had one of those on the road yet). A Grin extension that I can hack in is just $22, but costs that much to ship here.

So I think I am going to drop the wheel, splice in the connector, add torque arm, swap the freewheel, and even reseat the tire in the rim (finally!). Then I can ride and enjoy what I have and use the savings for a future endeavor - wait, no - to pay my bills!

I like the L1019's, would like to upgrade but it is way down the list. Splicing in is done all the time. Just keep track of your wires, Wires out of you controller may not be the same color as the ones going into your motor. Do what you must. we can always make it better.

If I put a 20" rear wheel on would need a skid plate for the bumps and unable to reach the speed limit with out changing motors. I have rear suspension and love my 26" wheel. Think about a 24" about as small as I would go. My back wants a 29er with 24" front wheels with catrike suspension.

Go tilting FS, mean machine.

22" BMX rims/wheels are a nice compromise as they come out to 23" in bike diameter.
You can also fit 18" moto tires to them and trade a little efficiency for really good puncture protection and a cushier ride out back, since all that rubber acts like a tiny suspension in itself.

Gear down, volt up

Grin's Motor simulator shows my 26" wheel is more efficient than a 20" on my setup. But a 24" beats both of them.

With my motors that have longer wires, I just used a velcro strap instead of zip ties to route the wiring. Yeah, its a pain, but not really that big a deal. Only to put on torque arms did I have to take the housings off the plugs. The one on the torque arm side can just remain on the wire permanent, once you have fabricated a really good one.

But if you do splice, by all means use an improved plug! Solder the wires at the current plug eliminating that set of connections. Then use something reliable for the plug closer to the motor. Don't make it too close to the motor though, give it 16 inches or so.

Didn't realize your controller was 35 amps, that explains the size some. The smaller one I was thinking of, with the round plug, is only a 22 amp.

I still like the idea of mounting the controller under the rear rack, It worked good for me on cargo bikes. But I did not have the switch on the box. Definitely possible to remote mount a switch, making it work with a jumper plug that makes it a bit like a keyed switch. You just put the jumper in your pocket when you park.

Always lots of room to improve your rig, but yours is pretty damn good right now!

dogman dan your a genius. Have been battling buying more switches. Most are not used very often so a inline fuse as jumper would be great.

My controller mount is simple. Have a Aluminium plate bolted to the bottom of controller. Cut 4 tapered slots to run hose clamps thru and around the frame with padding between clamps and frame as not to scratch it and stop any grounding.

ZeroEm said:

Grin's Motor simulator shows my 26" wheel is more efficient than a 20" on my setup. But a 24" beats both of them.

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Yes this all depends on motor design.
Geared motors tend to be designed for larger wheels and do progressively worse in efficiency, the smaller the wheel. This is mostly because the ratio of gear friction climbs per mph. My eZee gets horrible efficiency in my 20" wheel. But it does make a boatload of torque.. :lol:

With common 9C type motors, 24" or a bit smaller is typically where you see the sweet spot of power capability and efficiency. These motors were designed for Chinese motor bikes with 20"-ish wheels. They just happen to work well enough in 26". Some Chinese companies even dyno their motors in a smaller wheel size, and this makes specs look a little rosier. The MXUS '3kw' was actually tested in a 20" wheel. In a 26", it's more like 2.25-2.5kw rated.

The 9C with a couple more poles ( RH212? ebikes.ca sells it ) or magic pie would be better in a 26" wheel if you wanted more power without an additional weight penalty.

But 20" wheels are still where it's at for making the most power with the least weight
23" is an easier compromise too

Laying on your back with a 20" wheel with no suspension is not a smooth ride.

by neptronix » Aug 11 2021 10:47am

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Can't leave this alone yet. Yes a smaller wheel makes more power. I follow your projects and enjoy them almost as much as you. Glad you found the world of recumbents, I could not ride with out them. As you know it's a balancing act to get all that you want out of a bike/trike. Built my trike over two years ago and listened to everyone here and it has worked so well for me that I don't want to change anything. Mostly ride it on trails and with groups around 15 mph and below 1000w is all I need. I have and do take it out on the roads outside of town. My trike has a top speed of 33mph with a 7T 1500w 72V @ 40a up and down hills here. Now get on a trike and ride above 30 mph with 20" front tires and hit some pot holes almost as big as your wheels.
You start thinking I need bigger wheels or slow down. Power is not an issue with me. Have a three speed switch 950w, 2050w and 3200w. I spend 90% of the time in level 1 and level two is all I need on the Roads at 28mph "speed limit here".

I think "ccihon" has a great setup and looks good. Bet he can do 35mph if he wants to. Now a 20" wheel with lacing issues and almost no TA he would have problems not to say what it would do his steering and dropping his speed down to 30mph, which would be good with the rougher ride. But yes he would have more torque.

Before this inexpensive trike, which I have ridden unmotorized for around ten years previously, I had an early TerraTrike (3.2?) - steel frame non-suspension, 20" wheels, drum brakes. I was younger then, but the ride did not feel pzrticlulary more harsh than the current 26" rear one. I enjoyed it, but don't think I would have if electrified - some joked it should have been called "Terror Trike" as they had not quite figured out the steering geometry, and the thing felt super-twitchy at anything over 25 mph. I actually installed motorcycle steering damper up front to calm things down.

I recall the issue with the small rear wheel is that strong riders wanted really big chain rings up front so as not to pedal out. I had a Shlumpf drive unit up front that made the double ring provide four ratios, the biggest the equivalent of 62 teeth or something - anyway...

My current trike is quite stable at speed, though it has a fairly unsophisticated direct-steer setup. I wouldn't want to give up torque for speed with my riding style and surroundings. I definitely goes fast enough to make make you a bit worried about striking something in the roadway. The trade-off is that high available speeds make me feel safer in auto traffic etc. I do think low recumbents offer a greater "sense of speed" than uprights. I can go downhill on an upright at 30 and it still feels pretty leisurely.

by ccihon » Aug 11 2021 1:24pm

Before this inexpensive trike, which I have ridden unmotorized for around ten years previously, I had an early TerraTrike (3.2?) - steel frame non-suspension, 20" wheels, drum brakes. I was younger then, but the ride did not feel pzrticlulary more harsh than the current 26" rear one. I enjoyed it, but don't think I would have if electrified - some joked it should have been called "Terror Trike" as they had not quite figured out the steering geometry, and the thing felt super-twitchy at anything over 25 mph. I actually installed motorcycle steering damper up front to calm things down.

I recall the issue with the small rear wheel is that strong riders wanted really big chain rings up front so as not to pedal out. I had a Shlumpf drive unit up front that made the double ring provide four ratios, the biggest the equivalent of 62 teeth or something - anyway...

My current trike is quite stable at speed, though it has a fairly unsophisticated direct-steer setup. I wouldn't want to give up torque for speed with my riding style and surroundings. I definitely goes fast enough to make make you a bit worried about striking something in the roadway. The trade-off is that high available speeds make me feel safer in auto traffic etc. I do think low recumbents offer a greater "sense of speed" than uprights. I can go downhill on an upright at 30 and it still feels pretty leisurely.

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Have direct steering on my trike. Took months and getting the toe-in right. Now it's no big deal, think about turning and it turns.

You and neptronix may have me talked into a smaller rear wheel for my trike.

Just wondering what you decided to do? move your controller or get a smaller one?

Zero, i get your point about small wheels being a different story on a full recumbent versus my semi recumbents.
I guess my recommendations assume you care about comfort and have full suspension already. And aren't lying on the back wheel.

Suspension makes a much larger difference than wheel diameter, but if you don't have suspension, it's a very good idea to not shrink your wheel diameter.

A 22" bmx rim with a moto tire might be as comfortable as a bike tired 26" though because of all the extra rubber acting as a suspension in itself.