Mid motor, BB or non-BB?

Drizzt321

10 mW
Joined
Jul 14, 2014
Messages
31
So I'm looking at an interesting used cargo trike on CraigsList, delta upright, cargo area back, and it's got a transaxle in the middle which the pedals (above the front wheel) go to with gears, with 2 separate chains going back to each rear wheel. If I get it I'm going to electrify it, and I'm considering if I should just go with a basic BB type mid-motor, which I bet will work fine, or try and do something with a completely separate motor which sits in between the pedals and the transaxle (with the gears), and then from the motor to the transaxle, or even just figure out if I can add a freewheel sproket on the transaxle and do the motor direct to there and leave the pedal drive path alone.


I do already have a low end, cheap ~500W front hub I've been using on a regular bike and a CAv3 & up to 48v (max 58v actual) 20a controller from e-bikes.ca, so mostly need to figure out where to put the motor. Given it's fairly large trike and I'll be adding a storage area on the back (currently open frame) I was thinking at least a 1000W 48v or 60v motor, start with my existing controller/CA and upgrade the battery & controller eventually. Basically oversize the motor, and kick up the power if it seems to need it.


In some of my basic looking around I found https://lunacycle.com/cyclone-mid-drive-ebike-motor-with-freewheel-sprocket/ which looks great, can handle all the power I might want, and compact, efficient, relatively quiet, and seems to be a built-in freewheel so I might even be able to mount it to the transaxle with a static sprocket direct, or I'd have to add another sproket axle in front of the transaxle/gearing and do the double sproket as if it was attached to the BB/cranks.


So I know without pictures it's kinda hard to see, but I'm looking for general feasibility thoughts, so nobody snatches it up from under me ;) If I buy it I'll definitely be posting lots of pictures
 
If there's space for it, you can even use the existing hubmotor as a middrive (see the Hubmotor Mid Drive Media Group thread for a good starting point, or Rassy's old trike thread).

Without pics of the trike itself, I couldn't make any specific suggestions. Or if it's a manufactured unit (rather than a one-off), you could post the name / brand / model and I could see wha'ts posted on the web about it.


My custom-built (one-off) SB Cruiser cargo trike is presently using DD hubmotors in the rear wheels, but at some point I'll be using one of those methods above to drive the chain instead, after I get a differential/transaxle to pass it to both wheels instead of just the leftside wheel.
 
It seems like it might be a custom build, I'm going to see it tomorrow and intend to take some more detailed pics and measurements.

It's already got a transaxle (yay!!!) so DD rear hubs make less sense. Frankly I'm planning to do this as a Burning Man build, and possibly do it effectively as a light (but large) EV Trike for regular commuting. I've got some good bike lanes just about to work, except for one or two spots where it'd be a bit tight :\
 
So got some pictures last night (https://imgur.com/a/pT3XD0g), pretty cool design...but it's big. Large. And where the heck would I keep it when not using it?! I'm in a small 1 bedroom apartment, no real space to put it, and no way it can fit in my storage spot without paying a lot more for a much bigger one.

About 105" (8.75 feet) long from furthest back to all the way at the very front. 44" tall if the seat back is all the way back and the handlebars are folded down. 40" wide counting the wheels/hubs/etc. And the rear wheels aren't really possible to take off without crazy work, likewise the mid-axle with the transaxle (see photos). Been sitting around for a while, so needs a new front 20" tire, possibly whole wheel, needs LOTS of cleaning & fixing up of the chain system, not counting me adding a motor into the mix. Also only has a front disc brake, I'd need to get 2 for the rear wheels.

I do like the drive system design, in general. That is if he hadn't spray painted/welded _everything_, so the axles/shafts could come off easier. The mid-shaft which functions as a transaxle (gears + differential) is a smart idea, and he said he actually had 1 of the chains to a rear wheel break once and didn't really notice it because the other one was still hooked up. The whole thing is janky (spray painted over everything, ugh), but it's a cool janky.

As it stands, especially with not really having any storage space at all, I think I'm going to have to pass on this. Plus some of the design bits I'm not a fan of, the front is actually a bit higher than the back, not sure how I feel about the car seat, although it'd be kinda cool for Burning Man, relatively small front wheel which needs a solid foam inner because otherwise it pops (he does a new foam inner for it).

Does inspire me to come up with a custom design of my own, possibly making it so it can break down and be taken apart. Maybe some heavy duty hinges (sorta like folding bikes), or very well fitted attachment points so I can break it down so it's flatter for storage/transport.

Original posting, if anyone is interestinged:
https://losangeles.craigslist.org/wst/bik/d/cargo-trike/6618414448.html
 
Drizzt321 said:
[...]relatively small front wheel which needs a solid foam inner because otherwise it pops (he does a new foam inner for it).

After over 125 years of engineers and designers using pneumatic tires and trying alternatives, why do inexperienced people continue to believe that they know a better way? It's baffling. Look-- cars, trucks, motorcycles, airplanes, bicycles, golf carts, and even furniture dollies all use pneumatic tires. If there were an easy, viable, lower maintenance way to go, don't you think you'd see it on more commercial wheeled vehicles?

Do you really want your contraption to ride like a shopping cart and beat its wire wheels to pieces? Use good, puncture resistant tires and be glad that lots of smart people spent generations doing your homework for you.
 
It's a standard BMX 20", and according to hike at ~40psi it was almost flat/compressed due to the weight. And the foam thing is the equivalent of 120psi. Why he didn't go with a high pressure tire/rim, I dunno.
 
Drizzt321 said:
It's a standard BMX 20", and according to hike at ~40psi it was almost flat/compressed due to the weight.

Yeah, that's not good. It's probably worth trying a fatter tire at higher pressure (e.g. Odyssey Path Pro 20x2.4" rated up to 100psi) before you go for the solid tire.
 
I can't see the imgur page, but the CL ad pics show me enough to say that for ride quality and maneuverability, you'd be better off copying the basic idea of either SB Cruiser (first pics below) or my brother's Raine Trike (second pics), which I built based on what I learned from SB Cruiser combined with his lesser needs (so it's open-deck cargo area is very small, but it's still got the cargobox under the seat with a few cubic feet of space, but it's larger rear wheels ride better over bad roads than the smaller ones of SB Cruiser (even with the larger moped tires SBC uses)).

If you need something with more heavy-duty cargo space, then replace the back end of either design with something more like my Mk IV.5 trailer (or just use it as a trailer). (third pics)

See after the pics for some thoughts on the CL ad design.


SB Cruiser with a powerchair seat in the cargo area for passenger carrying
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SBC cargo area empty:
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SBC with teh dog crate in it
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SB Cruiser (left) and Raine Trike (right)
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Raine trike (left) SBC (right)
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raine trike by itself, still in building stages
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Trailer after hauling piano home (hooked to SB Cruiser)
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Empty (incomplete decking surface)
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The CL ad trike has a few possible issues with handling/ride quality based on what I've done that's similar to that. Delta Tripper used a similar front end, and while it functioned, it had handling problems (some of which would've been fixed by a longer version) and it sucked on bad roads; that's part of why I went with the bigger front wheel (with pedals behind it rather than in front and above it) on the SB Cruiser. Weight on the wheel is another reason--the bigger wheel has longer spokes which can take more load with less wheel distortion.

The whole mass of the CL trike sits above it's wheels, which makes it more tippy at speeds higher than some point (my guess is 5-10MPH based on my experiences), which will be worse the more cargo is back there, and the heavier the rider. Dropping the deck down to axle height (or below) will change that dramatically, which is why SBC and RT and the MkIV / V trailer are built that way. It's also why the cargo box is built below the seat, so it carries all the stuff I normaly need on there, batteries, tools, common small cargo, etc.

Took me a while to get to the cargo seat box design but it's much better with it.


That solid-strut wheel up front is part of the reason it can't bear weight properly. It needs a spoked wheel that's built correctly (thin spokes under correct tension), and if a wide rim is used then if you don't mind the weight you can use 16" moped tires on the 20" bike rims (or just use a 16" moped front wheel).


The car seat might be comfy, but it probably weighs 50lbs by itself, and you can make a much much lighter suspended-mesh seat that will be just as comfy, doesn't retain heat from sitting in sun, and will breathe so your back and butt aren't left soaking with sweat in the heat, or drowning in the puddle of the soaked seat padding when it rains. http://recycled-recumbent.com (or the waybackmachine's archive of it) shows how you can make such a seat; you don't even have to bend the tubing like they show to make a usable seat. (see my Crazybike2 for a version of such a seat).

These days I'm just using a Stadium Chair folding portable suspended-mesh seat bolted to SB Cruiser's cargo-seat-box top and it is just fine, after one small modification to a rear cross-support to clear my tailbone.


I can't clearly see the drive setup in the CL pics, but zooming in on the pics that are there it sort of looks like it's using a pair of regular freewheels on the rear axle (and maybe the transaxle) to drive a single solid live axle. This seems redundant, as the whole axle will move as one object with even just one chain. I guess it does halve the torque each freewheel and chain has to deal with, if that was a problem.

If each wheel were independently driven (for less scrub in turns), then this method is a worse idea, because then only the inner wheel of a turn is actually being driven (the outer wheel is spinning faster and so is overrunning it's freewheel), when you really want the outer wheel to be driven, with the inner freewheeling.


Some other thoughts later; gotta go feed the dogs before they decide I'm dinner. ;)
 
Thanks amberwolf, those are some nice, interesting designs. Not sure I'll be doing them soon, but definitely something I'll come back and reference when I get ready to do my own :)
 
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