Building a compact cargo bike

General Discussion about electric bicycles.

Re: Building a compact cargo bike

Postby IdleMind » Mon Feb 15, 2016 6:16 pm

Your frame still lacks bracing behind the seat tube. Maybe the tubes have enough beef to be loaded as beams, but that's less than ideal in any case


I didn't think anyone would notice that and I agree. I was mostly concerned about the situation where you stand up on the pedals and apply a heavy force to the bottom bracket and I think that case is now addressed. I weigh 150 pounds so I am not a heavy load and I am way past my prime so not a strong pedaller. Those tubes are chrom-moly so they can withstand bending and there is enough of them to share the various loads. Anyway I am glad you made that observation.
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Re: Building a compact cargo bike

Postby Chalo » Mon Feb 15, 2016 7:36 pm

Yeah, the pedicab I have helped to design and develop has a transition from space frame to flat frame partway along, basically underneath the passengers' feet. The weight and cost penalties for doing it that way are less than they would be to incorporate more complete bracing.
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Re: Building a compact cargo bike

Postby dogman dan » Tue Feb 16, 2016 7:08 am

Some relatively small gussets would help brace that frame, if you notice a weld starting to crack. Unless carrying passengers, looks ok to me. But a diagonal across that bottom trapezoid would easy to add, so why not?

On the other hand, you have enough steel there to be pretty strong, so if you welds don't crack later on, why bother? The worst hits will be absorbed by the rear shocks.
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Re: Building a compact cargo bike

Postby IdleMind » Sun Feb 28, 2016 4:35 pm

It's been slow going since I last posted. The battery box from my recumbent was about a 1/2 inch too wide to freely clear my heals so I made a thinner wood box which will eventually also fit the recumbent. Then I also made a smaller wood box for the controller. I didn't like the derailleur I was using for chain tension so I made a new one from scratch, it took 4 tries before I got one that worked. Also added a bottle bracket.

Then I got fenders from ebay and mounted them, but they will need more work when I get wheels. The rear fender is mounted to the swing arm so it will fit close to the wheel. I didn't leave enough room between the fork legs for the fender to ride up and down between them so the front fender is mounted to the fork with lots of wheel clearance for suspension travel. Here's what it looks like now.
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Re: Building a compact cargo bike

Postby Wheazel » Sun Feb 28, 2016 6:56 pm

Lookin good! One thing I have struggeled with in the past is having too little support for the rear fender and it will vibrate until it breaks.
Pretty much need 3 supportpoints well spaced out to make sure it wont break from fatigue after riding on umpy surfaces.
Im talking about standard plastic fenders, some have a thin aluminum inside. Ive broken a few.
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Re: Building a compact cargo bike

Postby IdleMind » Mon Feb 29, 2016 9:02 am

Thanks for the heads up. I haven't had a bike with fenders since I was a small child. When I get the wheels, I will take another look at the fender mounts and beef them up.
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Re: Building a compact cargo bike

Postby IdleMind » Wed Mar 09, 2016 6:45 pm

It rained a few days ago and washed the road salt away and then warmed up a bit. So, I got my recumbent bike out and dismantled the bike I had been riding for the winter. I laced the rear 3 speed hub into a 20" rim and, put on the handle bars and seat. I don't have spokes yet for the front hub motor. Here's how it looks now.
Image

With the rear wheel in place and because I was warned about their importance, I made 2 new fender stays. I made them from 1/4 inch brake line tube. Flattened the middle and ends, bent it around a tube, and drilled some holes.
Image

I didn't take photos of the battery, The box is built for 10s 15p 18650 cells. As it is now it is 10s12p with some wood blocks holding places for future additions. At the bottom of the page of the following link shows how I made an 8s7p battery, I used the same approach for this one.

viewtopic.php?f=14&t=69738
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Re: Building a compact cargo bike

Postby IdleMind » Tue Mar 22, 2016 3:18 pm

Took it out yesterday for the first test ride and I liked it. The motor is a smaller Bafang (swxb?) which I bought a few years ago on ebay. With the 10s battery and 20" wheel it goes 18 mph on its own. The bike handles nicely at all speeds, but the steering is a little heavy at times, I might have too much trail but also the headset was real loose and may have been part of the reason. But it wasn't a problem for me for now. The rear suspension feels just right, the front feels good when seated but too soft when standing and pedaling hard.

My biggest concern was how the chain would behave when using the coaster brake. I never threw the chain but it does rattle when braking so good enough. Today I took it all apart for painting.

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Re: Building a compact cargo bike

Postby IdleMind » Wed Mar 30, 2016 1:59 pm

It's about as done as a homemade bike ever get's done. A new properly adjusted headset corrected the heavy steering. I gave it a really ugly flat black brushed paint job. I've ridden it over 80 miles with no problems, just a few rattles that need attention. So now I am starting on a big box to put on the rack. I am happy with how it performs, but it's not going to get any prettier.

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Re: Building a compact cargo bike

Postby IdleMind » Wed Apr 06, 2016 1:20 pm

What's a cargo bike without a big ugly box. There are 4 nuts welded to the rack so this box can be added or removed in about 2 minutes. The plan is to build other cargo attachments, say a structure that can carry 2 grocery bags pannier style.

But for now I am done, too many other things I have been ignoring to find time for bikes.


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Re: Building a compact cargo bike

Postby Lurkin » Sun May 22, 2016 4:08 am

Dude, check this out! http://www.gumtree.com.au/s-ad/joyner/b ... 1108944176

couldn't help but notice a few similarities! 8)
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