Tadpole Recumbent Trike 2 WD Application?

[Earl]

EBR and Recumbent Trike Fans:

First of all, let me say I love the EBR review website, especially the explanations on the many videos by the young man who does them. Great job! Interesting threads in the forum, as well.

Here is the reason I am writing. I'm a seventy year-old guy with a heart condition who would like to have some assistance in getting up hills and/or riding longer distances on my trike. I have an HP Velotechnik Scorpion tadpole trike with 20 inch wheels and disc breaks. I have a Schlumpf Mountain Drive upfront with a Shimano derailleur in the rear along with a DD 3 internal hub.

At the moment, I'm not interested in a mid drive set up nor a rear hub mounted motor as I would like to keep the gear set up that I currently have while using the assist only occasionally as I need it.

So, what I am hoping to do is put two front wheel hub motors on this tadpole trike with either one or separate controllers and one or two batteries for the two wheels. I know this may seem a bit crazy, but I just want to know if it's even possible and how I might proceed to get this to work for me. Anyone tried it? What are the engineering challenges and application issues?

I posted a similar message in the DYI section, but I am hoping this will garner a few more ideas/responses. To be honest, I'm not sure I would want to tackle this on my own.

Thanks so much,

Earl Harris

 

[Admin]

Hey Earl! Glad to hear the site has been useful for you and sounds like you've got an interesting project on your hands... Having reviewed the electric version of the HP Velotechnik Scorpion I've got to say, what a cool bike! Does yours have the same full suspension setup?

I linked to the review there and called out the BionX version of the trike out because the photos might stimulate ideas for how and where to mount your battery and draw into contrast how a sprocket setup would work with a singular hub motor in the rear vs. two hub motors up front. Much of the weight on upright bicycles goes towards the back wheel (especially as you accelerate) and since steering involves physical movement of the front wheels, front-mounted hub motors aren't preferred by most. Heavy hubs up front make for slower more rigorous steering. I'm not sure I'd go for a double hub design up front but a single hub there (on the left or right wheel) might work better than you think. You can see this sort of design in the E-Glide GT electric skateboard. Only one wheel is powered and although this may wear that tire faster, create some imbalance and even impact steering a bit, the board works well enough and this keeps the systems simple and cheap.

There are companies producing hub motors pre-built into 20" wheels that might be worth considering and modifying to work with your recumbent trike. One such company is Dillenger, their 360 watt hub kit would give you a lot of power and doesn't cost much. Another is E-BikeKit which actually uses their hubs in a line of recument electric trikes sold at ElectricTrike.com now with nicer display panels and pedal assist plus throttle options. At some point, all of the wires, added weight of a second hub and second battery pack just aren't worth it. But again, one hub would probably work better than expected. Now this is the sad part of the story because I'm guessing it would be very difficult if not impossible to use one of these geared hub motors on your bike at all if mounted as a front wheel because they all seem to come pre-built around an axle... and your bike already has axles in place up front. You can't just a hub motor onto the side axle of your recumbent trike. See the image below to demonstrate then look at the hub motor kits and note the pre-built axle that protrudes from both sides and requires a dropout fork to mount to.



Back to the pre-built BionX Velotechnik trike design... You don't have to buy that trike or use BionX but if you go with a hub motor it probably has to be mounted as your rear wheel because it has dropouts there. Which brings us back to the question of, are you willing to swap out your internally geared hub for a cassette in the rear in order to transform your recumbent into an electric trike? That's the easiest and most powerful approach but we aren't quite done yet, there are two more considerations. One is the Add-E which rubs on your wheel and uses friction to rotate it but requires a special bottom bracket mount. I bet you could get this working with some custom metal-mount fabrication. The other option might be an electric trailer like the RideKick which connects to the back of your bike, can be used for storing gear and has a single-wheel motor designed to push both the trailer and your bike forward. They are actually very popular with recumbent bike riders and you can take it off as you see fit!

I hope this short guide helps in your process of electrifying your recumbent trike, I wish there were easier customized options to recommend. Hopefully others will chime in with creative suggestions and you'll get something figured out. And when you do! Please update us and post some pictures