BOB Pusher Trailer

[Rassy]

My trike buddy turned 70 this month and after years of insisting he didn't want any electric assist he has consented to let me put a motor on his BOB trailer. One of the turning points was taking one of my trikes on a couple of rides, including back up the steep hill to my house, combined with some right leg issues as a result of getting shot in the butt when he was a Marine in Vietnam.

I already had a Bafang in a 16" wheel that I purchased from JRH several years ago when thinking of a cross country trip. This Bafang has the winding normally used in 26" wheels so it tops out at about 15 MPH on 48V, but this makes it a good hill climber.

I purchased a used controller from EBikeBert which mates perfectly to the Bafang.

I'm using a thumb throttle because he likes his bar end shifters on bars that point straight up. see picture below. I've made a short test run and the thumb throttle feels pretty comfortable. He hasn't tried it yet because he lives about 200 miles away and won't get over to pick it up until the end of the month. He's still working full time, but retires this coming September.

At the moment I'm using one of my 48V 10AH Pings for testing, but he'll have to buy his own battery.

I'm still waiting for a 30 amp DC breaker I ordered before installing a Watt meter (one of the new inexpensive ones).

http://www.ebay.com/itm/New-Digital-60V-100A-Battery-Balance-LCD-Voltage-Power-Analyzer-Watt-Meter-/170982183517?pt=US_Radio_Control_Control_Line&hash=item27cf55125d

 

[StudEbiker]

Looks good. One of these days I'd like to see what a pusher feels like. It seems like it would feel really strange to me, but I'd have to try it to know for sure.

 

[SamTexas]

Very nice, simple and clean build Rassy. Perfect top speed for a 70 yo too. How efficient do you think it'll be? Less than 10Wh/mile?

 

[wayover13]

I experimented with a pusher trailer a couple years ago. I bought the cheapest thing I could find, since I wasn't even sure it would work. The design was similar to the Bob--an all steel thing, though. The experiment was only partly a success. It did push us ok on our tandem. We ended up doing a ca 550 mile tour with it, in fact. But the metal on various parts of the trailer started to fatigue and we ended up with tubes breaking in varying spots: the upper cargo railing with the first victim. We had a couple small welding repairs done on it, but each time we'd fix one of those, we'd get another break in the same place on the opposite side. Finally the trailer gave out on us altogether when, one day, the bike inadvertently tipped and twisted the "tongue" (linkage attaching it to the rear axle). We ended up having to trash it after that.

I can't say whether the failures of our experiment had to do with cheap quality materials of the trailer and its poor design, or whether the stress that the motor was adding played a key role. I did decide in the wake of that experiment to give up on powered trailers. I'll be curious to see how a higher quality trailer like the Bob will hold out.

How much weight will your friend be toting and how far? We tried to keep the weight in ours to about 25 lbs.

 

[Rassy]

I've built several two wheel/two hub motor and several one wheel/one hub motor pushers for different bikes and trikes. The only ones that felt weird were some of the one wheel pushers behind my two wheel recumbent bike. I actually used and liked an old style BOB trailer that I converted to a 20" wheel and used behind the recumbent bike for a couple of years. It had a nice quiet DD brushed hub and the trailer hauled the sla batteries.

With my current trike I used a "shorty" pusher for a while before installing the mid drive. In my experience any pusher trailer works good behind a trike.

As far as efficiency, I expect my buddy will do real good since he'll "pedal only" a lot of the time. That's why I used the Bafang instead of the DD I have that's also laced into a 16" wheel. I don't think he would be happy with any extra drag. You probably couldn't tell in the picture but his trike is the lighter aluminum TerraTrike Zoomer model and he sits lower and more reclined than my trikes.

 

[SamTexas]

As far as efficiency, I expect my buddy will do real good since he'll "pedal only" a lot of the time. That's why I used the Bafang instead of the DD I have that's also laced into a 16" wheel. I don't think he would be happy with any extra drag. You probably couldn't tell in the picture but his trike is the lighter aluminum TerraTrike Zoomer model and he sits lower and more reclined than my trikes.

No I couldn't tell. I have seen many tadpoles but have yet to try one. Good choice on the geared vs DD hub.

 

[MadRhino]

I love it. That trailer is neat, could power almost any bike without mod, and still has enough room for cargo.

 

[Rassy]

My buddy came over last weekend and he got to take his first trike ride with his BOB pusher trailer. We rode about 40 miles during the two days. Lots of hills, including a 1 mile steady climb on about a 10% grade and several times up my driveway 20% grade. No heating issues. He quickly mastered the throttle and was able to avoid spinning the back wheel, at least most of the time.

He mentioned how he liked his new "assist" a number of times and the grin was there.