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Electric Assist

electric assist mid or hub motor

It is not uncommon for people to want to include Electric Assist (a motor) when considering a bike or recumbent trike.
Mid Drive or Hub Motor: is one right and the other wrong? I don’t think so.

Electric Assist Considerations

For the un-initiated in the pedal power world, both bikes and trikes can consume finances and at times feels like it’s leaning a little towards the concept of a boat (a whole in the water you throw money into). Well, maybe not so bad but it can certainly be a bit more than you’d perhaps expect after shopping at BigW for a pushbike for the child’s birthday ($100 – $150).

When you start talking push bike parts, even for the two wheel cousin, you can start to spend many thousands of dollars. You could look at the end of the spending process without being able to see much if anything for your efforts. Part of the reason is the design of parts for such items as Internal Geared Hubs (IGH) is to make them small and light. In an effort not to add more rider effort than need be, on a constant basis, to push along the road or up a hill, the weight of the parts.

Generally when parts are designed, they take into account that a push bike will be ridden by a very fit person perhaps producing 250 watts of energy to motivate the bike into motion. So far there has not been much thought that a 250kg robot who can produce 1,500 watts of energy would be doing the riding.

I know I’m at the bottom end of the muscle power application ladder and I’d only likely apply that very fit person’s 250 watts to the pedals for a minuscule amount of time. Any other great bursts of speed would be in fright of being run over by a truck or perhaps a good downhill run.

My physical condition likes to have the backup of being able to get home, should I after a bit of a ride, have done a little too much. Electric assist for me is therefore pretty important. We have seen quite a number of trikes go out to others that have had a similar situation and I see no problem with the desire to add a couple of hundred watts that can be applied by other than the rider should the need arise.

Some other people just like the thrill of being able to keep up with the more athletic without the need to be burning so much winter store (fat). In any case, electric assist motors are popular but when you go make your purchase, please have already considered what your needs will be. Without thinking about do you fit on the trike, or does it fit under you, does it serve a long term purpose or similar thoughts: you can consider things like power requirements before you even look at a recumbent trike.

During the years I have seen a number of different hub and Bottom Bracket [B/B – where the pedals connect] mounted motors on recumbent trikes. My own trike has a hub motor with lots of battery storage. We have also had in the family garage, the forward mounted (mid drive or B/B) motors.

On a standard shape push bike (bicycle), the pedals are about mid way along the bike and with the introduction of this type of motor they were called mid drive to match the position of the pedal bracket (bottom bracket).
electric-assist-pushy

For a tadpole recumbent trike, the pedals overhang the front of the trike, generally a little in front of the front wheels. The same motor is used here and it replaces the pedal crank system mounted in the Bottom Bracket.

electric assist recumbent trike
electric assist recumbent trike

While it is good to have a mid mount motor to take advantage of the gearing system, sometimes an over-kill on the size of the motor can overload the drive chain system. Remembering that the average Joe, isn’t going to create a lot of power, if you put yourself on the trike and then add a 1,000 watts, you are no longer an average Joe (or Joanne). Suddenly you’re a SUPER JOE (or SUPER JOANNE) and you can almost climb Mt Kilimanjaro in a single battery charge.

Instead of having just Joe peddling you have half a dozen Joes peddling all at once. The chain and sprockets that were designed for Joe, were not designed for Super Joe and can very quickly deteriorate (fail). Add a 20 hundred weight trailer to your pedal machine and instead of the trike (or bike) being able to spring into action, it is almost chained to the spot and all that power is applied to the system more assertively and for longer.

We have met a chap recently who has added to this topic by telling us of his long and intense efforts to try and over come some of these problems, chain and sprocket wear and it is still a work in progress. Past customers who have later added reasonably high powered mid mount assist motors have reported similar and additional problems. These relate to the drive system and to the weight balance of having those few extra kilos hanging out over the front. I spend quite a bit of effort to get rid of the kilos hanging over the front (belly) so I can well sympathise with the recumbent in the same situation.

For the recumbent it can also affect the steering and wheel alignment. Part of delivery of a recumbent trike is to set “toe-in” on the front wheels to improve steering and tire wear. If you add extra kilos with additional leverage force out front, be sure to check your wheel alignment to get the best wear from your tires. Add plenty of watts up front and expect a much more limited life from your tires.

Worth Considering

My own trike has what is called a hub motor and it has given several years of excellent service. The hub motor is called this as the actual hub of the wheel has the motor built into it. On mine it is the single rear wheel, it could be the two front wheels or even all three or it could be just the front wheel on a delta trike. I think for me the hub is appropriate but where do I think a Mid Mount Motor would be more appropriate? In a situation where a motor needs to be more “high and dry” a mid mount or Bottom Bracket motor would be very appropriate:

Electric Assist Fattie
Electric Assist Fattie motor high and dry

The hub motor does not have an internal geared system so it limits the ability to have an economically priced large gear range. Hub drive can not take advantage of the gearing system to create extra torque to climb the rocky crags. It does however have no affect on the rest of the drive system as far as wear and tear goes. The hub motor takes a load off the pedal system and while making it easier for me also makes it easier for the chain and sprockets. I can’t tow a 20 hundred weight (really heavy) trailer up a hill but I am more than happy that it can get me up a long steep hill and home.

I would suggest that the Australian legal power restrictions for a bike/trike are a good place to start. There are situations where a mid mount motor is good. There are situations where a hub drive will serve you and your trike better. If you add a motor to a trike with a Continuously Variable-speed Transmission, remember there are manufacturer limitations on gear ratios and power (watt) application [i.e.: you may void your warranty].

If you have an urge to spend more money on gears and you have fitted a hub motor and need more, you can add a Pinion 9, 12 or 18 speed gearbox up front. If you have fitted a Mid Drive motor and need more gears you can consider a Rohloff Internal Geared hub. In either case, don’t be surprised if you add another $2,000 or more to the cost of the bike/trike. For me and my hub motor, I fitted a Speed Drive [$600 approx] to the pedals so I click with my heels to change gear ranges and then a standard gear shift for the rear cassette.

electric assist speed drive
Electric Assist and Speed Drive – kick one side for high, the other for low gear range

Fore-something is good …whats the word – oh yes, fore-thought, it could save you a lot of fiddling and money. One returning customer whom fitted a high power B/B motor, tried a 250 watt motor and said he wished he’d have stayed at the 250 watt level which provided all the power he’d need and would have saved a lot of hard work. Have a think then get out there and have fun.