Electrifying the Viking

Feb 16, 2020
Hello All,

I recently built and toured on the Viking Tandem Trike. While I love it, the hills in Maine really killed my legs and so I am looking to add an electric motor to the trike. The motor would be used primarily for hill-climbing assistance. Given the demands on the wheels (and the requirement for 14mm axles), it seems that a mid drive motor makes the most sense. After research, the Bafang BBSHD seems to be the motor of choice for performance and reliability. My question, however, is how to tie it in to the Viking's complicated drive system?

My first instinct would be to place the motor in front for the pilot. This would allow the motor to have access to the gears on the rear cassette (helpful for hill climbing torque). However my concern is that this would wreak havoc on the stoker's pedaling cadence, causing them to spin out of control. This could be compensated for with a larger left side chain-ring, but I already have a 46t chain-ring on the left and hesitate to go any larger as I want the trike to function well even without the motor running. While perhaps spin-out would not be an issue if the motor is used to assist with hill climbing only, I wonder if anyone has any thoughts on these dynamics? Is the solution as simple as simply restraining the impetus to 'throttle up?'

Were the motor to be placed within the stoker's BB, the problem then is that there is not room for a left-side chain-ring. One could maybe move the chain-ring way out but then the chain-line on the left would be totally out of wack (I already broke two freewheels due to a misaligned left chain-line and want to avoid breaking a third). Maybe this could be solved by extending the crossover dropouts but unfortunately my access to a welder has ended.

This Viking will be my daily vehicle on a very hilly island and I plan to haul heavy cargo, so the motor is a necessary addition. An ideal situation would consist of a 15-18mph cruising speed with a comfortable cadence for both stoker and pilot while also being able to climb up steep hills over longer distances (no single-track level grades). The trike is close to doing this as is but we pushed it up several hills on the last trip and are looking to avoid this moving forward. Any thoughts or experience is appreciated.

Apr 16, 2017
Winnipeg, Manitoba
I have the Bafang BBSHD on my fat bike that gets winter use primarily and some summer duty as well. It won't make you spin the crank any faster, what it does is add power to your effort. Each power level will take you to a set speed, ie on my fat bike with a 42 tooth chainring level one with take the bike up to about 12 kph even if I just "ghost" pedal. Level 2 goes a bit faster and so on up to the 32 kph limit. For the fattie in winter it's only ever level 1 due to the winding singletrack trails with an occasional bump to level 2 for the few hills. In simple terms all the motor does is give the effect of you having more power in your legs. For what it's worth my BBSHD has been troublefree for a few years now. If you do get one buy the gear sensor as well, your drivetrain will thank you.


Super Moderator
Apr 14, 2013
Peacehaven nr Brighton, Sussex ,UK
Only problem might be is the attachment of any middie drive into the bottom bracket shell ( overhang or rather under hang ) . Also beef up the rear triangle when installing e- assist as the extra help will try and shorten the wheelbase.
May 31, 2013
South Benfleet, Essex, England, UK
I have used BAFANG on my tadpole(s) and can attest to 2 things (as mentioned by Emma (Twinkle) above.
  1. If your gearing isn't low enough the power will often rip the R.H. Side of your drive-wheel out of the drive-side dropout. No amount of tightening of the axle nut will stop it if it does this, believe me). I is fixable by adding a "keeper-plate" with a turned over edge wrapping over the rear of the dropout.
  2. No amount of tightening the supplied mounting elements will stop the Bafang rotating around the BB-Shell axis until the motor casing rests against the front changer post.
Having said that, the benefits far outweigh these minor "niggles", the only other issue I found was that it made me far too lazy and I then relied on it too much.
This reliance was also enabled by the dreaded "Statins" which have helpfully destroyed the majority of any muscle tissue I ever had. :(
But BAFANG is great overall and I am glad I still have one.