electric tandem bike

[james1979]

Dec 19, 2022 15:40:12 GMT -8 vance said:

The motor wants to rotate all the way up to contact the frame. Usually, this is the way these work. However, this is a special build. I need to utilize the eccentric BB in order to tension the chain that connects the two riders.

I need a way to hold the motor in place well below the contact point between the motor and the frame. Sucks that there's no rigid, adjustable mechanical stop for it that works, nor one I've come up with, yet. But this might work.

A wedge can be stuck in between the motor and the frame, which is a "Hail Mary", meaning that you're hoping the chain is tensioned correctly by it. Not easy to accomplish. The problem with this method is that proper chain tension is very difficult to achieve without blind luck .

Thing is, you want optimal chain tension so the components don't get ravaged by being too tight, or, if too loose, having the chain slip off.

So, you need a way to use the eccentric BB, which allows proper chain tensioning, but only if it won't move under load.

How about a bracket bolted around the frame with a stop bolt in between the motor and the frame... serving as your wedge would, just as an adjustable stop.  I think I described that clear as mud!

[vance]

That's pretty clear! It's a good idea, but clearance is tight. I'll look at it and see if I can come up with something along those lines!

[vance]

I'll try a split piece of pipe that fits over the bike tube with an elongated nut brazed to it at the necessary angle. A bolt with a rubber foot over the head will be the motor stop. That will allow some adjustability, and a different length bolt can be switched in if more is needed.

Attaching/clamping the half pipe to the frame might be fussy. Maybe a rivnut?

[james1979]

Dec 20, 2022 14:38:45 GMT -8 vance said:

I'll try a split piece of pipe that fits over the bike tube with an elongated nut brazed to it at the necessary angle. A bolt with a rubber foot over the head will be the motor stop. That will allow some adjustability, and a different length bolt can be switched in if more is needed.

Attaching/clamping the half pipe to the frame might be fussy. Maybe a rivnut?

How about a hose clamp (screw clamp) with heat shrink over it... No mod to the bike frame needed?

[vance]

Yeah... Hose clamps are notorious frame damagers. Rivnuts work well, and are a bit more professional.

I got the strut today, and it looks promising. It was only $7 shipped, and it's a nice looking part. I'll work on that tomorrow.

I got my motor controller back today and installed it on the lathe. Booyah!

Back in bidniss.

[vance]

Here's what I went with. Strut and custom stainless steel clamp. Works great, and is adjustable.

[vance]

Now that the motor is firmly held in place, and the chain tensioning problem is worked out, I need to start cleaning up the installation so I can sell the bike. All this was mostly in aid of keeping this sweet classic off the scrapheap. I think its a really good cruiser, and will work great for casual rides.

I did this partly to go to school on this kind of installation on a tandem bike. I might want to install a mid drive on my other tandem, but after doing this one, I'm not quite sure. There are pros and cons.

The hub motor works well, but hub motors are very tough on spokes and rims. I think I have that sorted, but I went through a lot of broken spokes until I changed them all to stainless steel. I am satisfied, for the most part, with the electronics, but they are very cheap, and are not the most reliable. The firmware has issues, and so far I haven't found any alternative firmware or reflashing instructions. But, no big problems so far.

I like the hub motor for several reasons. It is plenty powerful. Maybe too powerful? I do want to get some exercise...

A hub motor turns the wheel, not the drivetrain. The mid drives cause wear and tear on the chains, chain rings, cogs and derailleurs, because the motor drives via the drivetrain.

The hub drive doesn't require any changes in the drivetrain to accommodate the motor. I changed the stoker/captain synchronizing chain over to the other side for the mid drive due to lots of chainline issues. That works ok, but you only get one ring gear, since the other is used for the synch chain.

This won't work if you want to retain a double or triple front ring setup. If you're running a 7 speed freewheel or cassette, this could drop you from 21 (triple) or 14 (double) speeds down to 7. Didn't matter for this conversion, b/c I'm using a 7 speed internal hub which doesn't work with a multi ring front.

I do like the alternative firmware you can use with mid drive motors, and I think the electronics are better quality than the hub motor kit I got.

[vance]

I did some cleanup today. It's raining like crazy, which is very unusual, and is supposed to continue for 9 more days! We need it.

So, I did some finish work on the aluminum spacer. I made the outside diameter round and clean, and faced both sides.



I also needed to remove and replace the battery holder, which I stole off the Burley tandem in order to test the setup.

The new battery slide needs a wiring harness and I need to make a new stainless steel clamp for the strut, which I'll work on tomorrow. But, the Burley is back on line!

[vance]

I sold the Gary Fisher tandem bike a while back. It is a pretty cool bit of history. I'm happy that I was able to save the frame, even though it probably cost more than I got for it. IDC. It was a fun project and I learned a lot.

The Burley with a rear hub motor is still the bike we're riding, but I just don't like the cheap electronic controller with its sketchy firmware. The bike and hub is also very heavy, and it's too small for me.

Being slightly too small isn't a huge problem with a tandem frame. I have some spacers that raise the handlebars, and the seat can be raised high enough, but the length of the cockpit is too short.

Being very heavy (80 lbs) is a big disadvantage. Amp draw necessary to make climbs causes heat problems, but the big issue is going down steep hills. I weigh 230 and my lovely stoker weighs in at... well, never you mind.

But, our combined weight, plus the heavy bike is scary. Heat produced by friction on the brakes is off the charts. This means routes have to be chosen judiciously.

In aid of improving a few of these problems (and the fact that I want to do a lighter mid-drive conversion on a lighter bike) led me to scouring the local Craigslist ads for a BIG, light tandem. I might have found it.

More to follow!

[SeaRat]

This is my favorite tandem. It's a Wenonah 18 foot Sundowner canoe we've had for decades.

ScanImage156224-2 by John Ratliff, on Flickr

Also, it's getting that time of year when a lot of folks go out on the rivers, fishing or later in the year, tubing, to remind them that they need lifejackets worn, not just "handy."

RST-Nathan-2 by John Ratliff, on Flickr
I got this photo floating down with Nathan in my wetsuit, using my Nikonos II camera.

Fishing_North_Umpqua by John Ratliff, on Flickr
Here's Nathan, fishing on the North Umpqua River. Note the lifejacket.


John

[vance]

As is often the case with this mob, topic is veering off to where-ever. That's cool, we can hang.

I love the photo of Nathan, perched on top of a 3 ft. island?

[vance]

I bought the Cannondale tandem. Pretty sweet. I spent the day just looking at options, which included a lot of disassembly. I fought to get the forward eccentric bottom bracket loose for a long time.

Did it!

I temporarily installed the motor assembly up front, which isn't the best place, IMO. I didn't like it, so the rear cranks and chain rings, bottom bracket, and all came out in order to try the motor back there.

I think getting the mid drive motor situated in the stoker bottom bracket is the way to go. My Gary Fisher conversion had the motor in the captain's position, and it worked ok, but it required a strut to keep it in position.

[SeaRat]

I'm thinking of getting a tandem bicycle, as that could get my wife back into bicycling. She's worried about a fall on the bicycle she has, and so hasn't bicycled in several years now. She forgot how to lean to turn, and tried to turn on her bicycle without leaning, resulting in a slow fall. But it freaked her out. So maybe a tandem bicycle would help get her back into my "other sport," of bicycling.

John

[vance]

Riding a tandem is a whole 'nother experience. The stoker has NO control over the bike which freaks a lot of people out and makes it difficult for them to tolerate a tandem.

When I took the guy who bought my Gary Fisher conversion out for a test ride, he dumped us b/c he panicked when a car passed in front of us at a T intersection. I was shocked that he still wanted to buy it, but he said since he'd be in control, it would be different.

Even getting on and off the bike, starting to pedal from a stop, and coming to a stop require a lot of unfamiliar co-ordination between the riders. You get used to it, but there's a learning curve some people can't get through.

[nikeajax]

Everything is compounded on a tandem, especially falling off, but in a wreck, the stats climb exponentially. You're no spring chicken John, ride solo, just like diving; yeah, not as fun, I know, but it's safer. 

Just my opinion

JB