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Converting a two person Surrey bike to Electric drive

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    Converting a two person Surrey bike to Electric drive

    I recently purchase a two person surrey bike, and want to make it electric drive and maintain ability to peddle. This will at times have two adults onboard. I am looking at a mid drive setup. I am questing if a motor designed for a single rider can handle two not small adults, and I am also considering adding a mid drive motor on each side. Currently it has two independent sets of peddles driving the rear wheels. Any comments or suggestions?

    New to ebikes, but...

    This is too cool to not comment on!
    How does it drive with only one person pedaling? If it gets along OK, it seems like a single mid drive motor, geared deep, would do the job driving one wheel. I can't imagine wanting to go more than 10 mph on one of these, so the power would be sufficient to move - just not move quickly. Gear it twice or more as deep as if the mid drive was on a single person bike.

    However, the possibilities are endless for how complicated to make it! Some of these electric conversion kits have torque sensing, so two mirrored drive systems could effectively be like having a limited slip differential I think!
    Or you could add a shaft on that rear crossmember and split the power between the two wheels, driving a freewheel sprocket to each wheel.

    Very cool proect and good luck!


      Right away, I am rather jealous.

      That thing looks awesome--and I want one to play with!

      Just sort-of thinking off the top of my head here, so bear with me...

      I love mid-drives... And maybe you could get by with only one mid-drive...

      But if you want to be able to operate that beauty (with assist) from either seating position, it'll need two mid-motors. And, as best as I can tell, you'll need to use one of the Cyclone mid-drives (there's no way the TSDZ2, or any Bafang mid-drives are going to fit on that bottom-bracket). Also, the rider on the right-hand side, uses left-side drive chain and sprockets. So, if you used two Cyclone mid-drives, one would have to be run "backwards" (not a big issue--instructions can be found).


      All that's rather complicated.

      Though not 100% straightforward, I think if it were my project, I'd opt for front-wheel hub-motors instead (geared hub motors, or perhaps even direct-drive). They'll be a lot easier to install, and though it'll take a bit of extra effort to synchronize their operation, I think ultimately it'll be much easier than trying to get two mid-motors on there.

      I've got twin front-motor systems synchronized up on my bakfiets. Two complete systems (two motors, two controllers, two displays). Both are controlled together, with a single control-dongle wired in parallel; throttle and PAS signals split, and sent to both controllers.

      A similar setup for your Surrey Bike would allow simple operation from either seat. Simplest, would be a throttle-only operation. Each seating-position could have its own throttle.

      If riding with two people, and if you're wanting to use a pedal-assist-sensor (PAS or rotation-sensor if you prefer to call it that). That'll be a little more complicated. You can put a magnet sensor on both sides, but you won't want to mix two PAS signals simultaneously. In order to make it work, you'll need to set that up with a [Right] / [Left] switch for the signal-leg--meaning that your riders will have to determine which of their pedal-inputs will be controlling it (arguments might ensue).

      If you get along well with your potential passenger, that might not be an issue. But you could just skip rotation-sensing altogether, and simply use two throttles wired in parallel.

      It looks like fun--and more fun on the way...

      Good luck with your project--whatever you decide!

      Last edited by tklop; 09-20-2019, 11:33 PM. Reason: for clarity


        I agree with Tklop as far as not being able to use the Bafang or TSDZ2 mid drives. The bar under the bottom bracket rules that out. A Cyclone would be fine. I am not sure a front hub motor will work either with just one side attachment. I think Grin might make one that allows it but the attachment has to be pretty sturdy. It looks like you have IGHs on the rear. You could use the hub motor from Grin that has an internal 5 speed built in. As far as a single motor handling the weight, I think it will. We ride a recumbent tandem trike. The 2 of us, heavy trike, DD hub and 2 batteries puts us at close to 500 pounds when fully loaded. The 1000 watt hub motor in a 20" wheel gives us plenty of power. We also had a BBS02 for awhile and it worked fine with the proper gearing. Another option would be a Stoke Monkey.


        • tklop
          tklop commented
          Editing a comment
          I was also thinking about that too--maybe rear-wheel hub-motors. But for the right-side-rider, their chain and drive-gears are on the left-hand-side. I'm not personally aware of any left-side-sprocket hub-motors... But if available, that might be a good option.

          That left-side chain-drive was also why I was hesitant to think mid-drive... Not so much for the bottom-bracket end of things--because the Cyclone models would work okay there... But if the right-hand-seat's drive components are difficult to find (all that left-side chainline stuff might be rare--and expensive), it'd be unwise to potentially overstress those components with a powerful mid-motor (like the Cyclone)... I was concerned about reliablility, and costs in that sense--although I freely admit I don't know the prices or availability--so maybe that's a non-issue in reality.

          But strength and reliability--as you point out--is also a big factor when it comes to that front-wheel-hub-motor idea I floated. You're absolutely right--those front-wheels' attatch-points had better be quite sturdy to use hub-motors! And it's true--there aren't a ton of stub-axle motors out there--but there are at least some (as you pointed out). Q-motors even makes one!

          Clearly, it's not going to be the simplest project to electrify--but I think it looks doable!

          I think powering only the left-hand seating-position's side would be the simplest way. Basically the two seating-positions are like twin bikes welded together. Although only one of the four wheels would be powered, I still think it'd work pretty well (in most conditions).

          If the original poster was okay with just powering that left-side, I do think a Cyclone mid-drive would work very well.

          Of course the machine would only be able to be operated "solo" when sitting on that left-hand side, but I doubt that's a big problem.


          If that beauty were mine, I'd probably try to figure out how to make it all-wheel-drive and soft-sand capable!
          Last edited by tklop; 09-23-2019, 12:36 AM.

        Have this project got any update?
        I am interested. I want to do the same: add PAS to surrey bike.


          Hey Hey! I'm about to embark on motorizing my Surrey Quadracycle.. I have a few of these bikes, like 15 actually - I rent them. The popular method is:

          Putting 1 hub motor on the rear driver/left side wheel. About 1000-1500 watt motor will take the bike to about 11-12mph. Finding a 1000-1500 watt hub motor with an integrated drum brake is a bit challenging but there are a couple on Alibaba/Aliexpress ( the bikes use drum brakes). You could probably use a regular hub motor w/o a drum brake and use these other skinny-type drum brakes that you slide onto the axle....cadence sensor to the bottom bracket, throttle, etc. There's a couple shops which sell this solution as a kit...they run $1500+....if anything, google it and look over the kit and what that wheel build looks like., some pics here

          For the build I'm going to do....I'm thinking of a mid-drive solution... This is my personal bike, and I'd like the bike to hit 15mph and have a bit more torque than the hub solution... I'm rather confident that I can fit a BBSHD onto the bike, resting on the top of the frame...The bike I'm building is an actual Surrey and the bottom bracket/frame section is slightly different than the one above with that horizontal bar sitting below main frame. So I think I can fit the motor part on the top frame part, leaning towards the front...I'd prolly have to make some bracket to hold motor or something.....

          There's not a lotta info on DIY motorizing these online, so chime in with any feedback and if you have any questions lemme know...!!!

          Click image for larger version

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            From their website, it looks like this has both back wheels with brakes in their drums. That's good especially since you rent these. The kit has an interesting wheel that seems very heavy duty. But doesn't match the wheels you got. The controller seems typical and sized about right, but the battery looks pathetic. They look like lead acid gell cells. The instructions say only use on easy hills, and any hill will drain these batteries quick. Especially with this ungeared type of hub motor. Ungeared motors suck down the most battery power. So you would need Lithium batteries and chargers to get better results from this kits. You could add a mid drive kit with matching lithium setup. Then you can keep the wheels and brakes you got. But the pictures are not clear how much work you would need. And maybe welding too. I did notice that the factory did neither of these upgrades, but opted to build a fifth powered wheel. That would be the smoothest drive option over powering one wheel on one side. That can make these pull to one side endlessly. I have no clue how much pull it would be but these motors have a ton of torque. Another option would be motoring both rear wheels with those included brakes. But without a connecting axle, the motors would have uneven torque and would pull either side at random and rather unpredictably as you increased throttle. The factory may have tried all that and that's why they went the fifth wheel option. You can try a mid drive kit and see how it performs for you before you upgrade the rentals.


              Yes, the factory went with a fifth wheel option..It's almost bolt-on...easy....I just dont like the look-n-feel of a fifth wheel...I regularly ride the bike on my own...doesn't seem to pull to one side or another on pedal-power....I'll just have to try it....Buy it on Amazon. good return policy....Batteries---haven't even delved into that part.....Yes, lithium ion are the best. But I wonder if there is another, more cost effective option as I have space for a larger form-factor battery...I mean, lead acids are huge and heavy...but they carts use em...thoughts?


              • stts
                stts commented
                Editing a comment
                Yea I thought about gell cells on a trailer pulled by a bike. But for all the weight, they simply have very poor capacity and take forever to reach full charge. So the performance wasn't worth the weight. So I was pretty much stuck with going the lithium route. I'll build a metal box to put my lithiums in that will contain potetial fires. And I will have a metal box on the concrete basement floor if I have to bring them in for winter. I already been burned down once. Don't want to be down that road ever again. Another idea is a bit of engineering to put an axle in the rear with a differential. You can buy motors setup like that. Then put sprockets on each axle end to engage with the chain line. Then you got twin wheel drive and no changes to your wheel setup. But I have no idea of the quality of those differentials. I plan to make my own differential with grinder gears and bearings for my own project. Those gears are solid and all ball bearings. There youtube videos of people making small differentials like that.

              Thanks for the feedback. I'll post some more info once I make some moves on this build...