6X10 Mid Drive Trike

[Rassy]

Zenon, I don't know anyone with a TerraTrike Rover, which only became available in 2010.

But my son lives in Eugene and has a TerraTrike Path, I have a TerraTrike Path, a friend in Medford has a TerraTrike Zoomer, and another friend in Medford has a TerraTrike Tour. Met a man casually a couple of months ago that also had a TerraTrike.

The only other person I know that has a tadpole has a GreenSpeed powered by an EcoSpeed system, both high end units.

I think the TerraTrikes are popular because of the low prices. Of course you get what you pay for and their components are also fairly low end.

 

[jbond]

The neatest (imaginary!) solution to a mid drive on a 'bent or trike is a mid mounted geared hub motor with two sprockets. A fixed sprocket with the chain back to the rear wheel and gearset and a freewheel with a chain to the front chainset. The big problem is that the threaded mount on a typical hub motor is quite narrow. And the thread means that the motor will try and wind the fixed sprocket off the thread. Perhaps it's possible to put the fixed on first and use the freewheel as a locknut, maybe with a grub screw as well to stop the fixed sprocket from moving. See Miche Quick Change Track Cogs and Adaptor on this page for one possible solution. http://www.velosolo.co.uk/shoptrack.html The adapter is pretty narrow, and the picture below shows about 5 threads visible which might be enough to mount a freewheel.

If you turn the motor over and run it backwards, it would take an adapter mounted on the disk holes. That adapter could be made wide enough to take both sprockets. Then I think you have a problem that the internal freewheel is running the wrong way. So you have to either fix that or mess around with chains that cross.

I don't like the idea of freewheels in the chainset for safety and elegance reasons. And it makes it hard to change gearing. I don't like lots of angles and idlers in the drive side of the chain. And I really want enough freewheels to use pedals, or motor, or both or pure freewheeling.

 

[drifter]

Don't know if you have considered a cyclone but this worked good on my KMX

Robbo

 

[jbond]

Don't know if you have considered a cyclone but this worked good on my KMX

Cyclone do a dual sprocket version for 'bents and trikes. Has anyone seen one? I'm curious if one or both sprockets have a free wheel and how it's attached to the shaft.

 

[zenon]

I agree there are many style and configurations that can be done on a mid drive system. The main concern about many commercial built tadpole is room for adoption of the mid drive.

Zenon

 

[zenon]

Don't know if you have considered a cyclone but this worked good on my KMX

Robbo

Hi drifter,

Is there any chain issue with this setup?

Zenon

 

[drifter]

no issues at all, just works.

 

[Warren]

jbond,

"See Miche Quick Change Track Cogs and Adaptor...The adapter is pretty narrow,"

The adapter is exactly as wide as a normal track cog. It is intended to make changing cogs easier for racers, who do so often. It is easier on them because they don't need a chain whip to remove the cog.

"and the picture below shows about 5 threads visible which might be enough to mount a freewheel."

That is a track hub. The threads you are seeing are smaller diameter, and left hand...of no use for your freewheel.

Warren

 

[Warren]

jbond,

"Cyclone do a dual sprocket version for 'bents and trikes. Has anyone seen one? I'm curious if one or both sprockets have a free wheel and how it's attached to the shaft."

http://www.cyclone-tw.com/images/recumbent-s.jpg

It has two standard freewheels. The threaded adapter has a shoulder on the outer end. This allows the whole thing to work. With the adapter off the motor, the first freewheel (to cranks)is threaded on with the four removal notches facing the shoulder, as you can see in the picture. The second freewheel (to rear cogs) is threaded on with the notches facing the other way. If you pedal without the motor running, the outer freewheel tries to screw the inner freewheel towards the motor. But this is resisted/prevented by tension on the chain to the rear wheel driving the inner freewheel towards the outside shoulder. If you ride with the motor running, again, tension on the chain to the rear wheel is trying to drive the inner freewheel toward the outside shoulder. The adapter is probably keyed to the planetary gearbox output shaft. The bolt, and fender washer you see prevents the adapter from sliding off the end.

Most freewheels are not threaded all the way through. This setup only works with Dicta style freewheels, which are relieved beyond the threads, or threaded all the way through. This allows them to be threaded on backwards.

http://www.evanscycles.com/product_image/image/b26/d86/4b9/26289/product_page/4-jeri-dicta-bmx-freewheel.jpg

http://americancycle.com/merchant/1384/images/large/freewheel_dictametric14T.jpg

Most freewheels can not be threaded on backwards.

http://images.jensonusa.com/large/cs/cs409c02eng__13t.jpg

If there were an easy way to attach an adapter to the right side of a hub motor, that would be great. Unfortunately, fronts have nothing on that side, and rears only have a right hand thread, which wants to unscrew. You could file flats on the thread, then make a threaded adapter with set screws. But the adapter would be bigger around than your freewheels, so no way to thread them on from the inner side up against a shoulder. So you are right back where you started. And if you did figure out how to hold them on the adapter, they would be hanging out past the normal hub threads, putting lots of flexing load on the side cover. You'd be better off with the fixed cog/freewheel/Loctite method we discussed.

Warren

 

[jbond]

Warren, Hey ho. Thanks for the explanation.

Couple of other things I found on my travels round teh interwebz.
Stainless steel end covers for BMC and Bafang motors. These seem to include the freewheel thread for rear motors. http://www.cycle-motor.com/sonstiges.htm Perhaps a batch could be made with a wider thread section. The steel should make them stronger and reduce worries about the sprocket mount fracturing.

http://www.tppacks.com/proddetail.asp?prod=EBKE-zz-FWAdapter
An adapter for mounting an extra freewheel on hub gears. Perhaps something like this could be mounted on the disk side outside a disk mounted fixie sprocket.

In the middle of this page are a couple of photos of a cyclone dual sprocket set up but on a Dahon folder. Crank to motor to rear wheel is a real packaging problem on conventional bikes, but perhaps it's possible.

There's a holy grail in here somewhere. It might even be possible to eliminate or reduce the drag from the motor when just pedalling. I guess that's why I (and others) keep worrying away at it. There don't seem to be any simple answers though.

BTW. Amused to see you linking to bikeweb.com I run that website! The Partridge Luge machines are fascinating. John Partridge built at least 3 of these and the chassis are believed to be out the back of his house. Unfortunately he's a classic Brit eccentric and an awkward cuss and he won't let anyone see or ride them.

 

[Warren]

jbond,

"Stainless steel end covers for BMC and Bafang motors...Perhaps a batch could be made with a wider thread section."

If they are made in the EU, it would be cheaper to have a custom one-off made here in the bucolic south.

"Perhaps something like this could be mounted on the disk side outside a disk mounted fixie sprocket."

Yes, thought of that, but the thread of the adapter is only 1.375" diameter (34.9 mm). The problem is, at least on the MAC I ordered, that the cover extends out past the disc brake bolt holes. The axle bearing is pressed in there. And the diameter of that extension is 33 mm. You would need to bore out the adapter. You'd be left with nothing but a very delicate helix of thread. :-(

"Amused to see you linking to bikeweb.com I run that website!"

Coolest site on the web! I got to see a Monotracer at the TTXGP at VIR. One of the things I wanted to do before I die.

Warren

 

[Rassy]

The other day I was thinking a cadence meter might be interesting to have. While looking around, I ran into several suggestions to use a regular bike speedometer with the display in KM and the wheel size set at 1667 MM. This results in the display showing your cadence using the tenths digit but ignoring the decimal point. I.e. a reading of 8.2 KPH would represent a cadence of 82 RPM.

Since a had an extra speedometer on the shelf I went ahead and installed it on the trike. The magnet is stuck on the crank sprokett, which was easy, since my alloy 56T is bolted to a steel 48T. So an old but strong retangular magnet was just placed into one of the fancy cuts in the 56T that is backed by the 48T, no glueing required. Then the pick-up was placed on the unused derailer post.

Since my motor has a 16T and is directly attached to the 56T via the chain, the motor RPM is exactly 3 1/2 times the cadence RPM. When the motor is used without pedaling it still spins the freewheeling 56T chainring, so the motor RPM can still be observed.

I just took a little test ride, and now I have to determine my optimum cadence, particularly when going up hills. I don't have a CA and my Watts Up is attached at the battery so I can't observe Watts or Amps while riding.

In low gear on level ground the motor alone tops out just over 90 cadence, or 315 RPM. Riding up a 15% grade in low gear the speed varies a little over 6 MPH and the cadence a little over 70 RPM, with little change based on my pedaling effort. I will eventually do more tests that also involve the Watts used. My long range goal is to find the most efficient cadence for longer rides when battery consumption is important.

I am currently thinking I will shift up when my cadence exceeds 80 RPM and shift down when my cadence drops below 70 RPM. The tenths digit on the speedometer is fairly small and a little hard to read, so using easy points to read helps.

 

[gogo]

A peek at the ebikes.ca simulator suggests that about 75-85% of no-load RPM is the sweet spot for efficiency. You could put a video camera on your watts up and call out your cadence to test the correlation.

 

[Rassy]

gogo said:

You could put a video camera on your watts up

I actually had that thought earlier today, but about a year or so ago I made up a little harness and put my Watts Up where I could read it. I didn't like it because it was so busy with constantly changing values plus I didn't really like running my main negative between the battery and controller that far. However, I'll probably do that again for some tests just for fun. My hook up is different now so I'll have to make up a new harness.

 

[Rassy]

Hi Joseph,

I haven't had the Veltop long enough to see any UV problems.

When the side wind is over 20 MPH it moves around a bit, but I don't normally ride on higher wind days. As far as drag, I haven't done any definitive tests yet. But I recently moved a Watts-Up meter from the battery area to the front of the trike so I could do some general efficiency tests. I plan to run the same course without the Veltop, and with the Veltop with and without the side curtains. When I get some good data I'll share it. The trike tops out just over 20 MPH, so there won't be any "higher speed" tests.

On a bright note, it does keep me dry with the side curtains on. I'm glad I got the top, and expect to get years of good service from it.

 

[gogo]

The trike tops out just over 20 MPH, so there won't be any "higher speed" tests.

Tests into headwind count as high speed. I deal with 30 MPH headwinds on my "legal" 20 MPH bike frequently. I'm hoping none of the cops in my town take me to task on those physics.

 

[Rassy]

Joseph, I wasn't able to get good performance tests. In addition to the grade constantly changing, the wind is also constantly changing. So the amps usage never remains constant enough to make meaningful comparisons. performance "seemed" to be about the same with any configuration.

Since my motivation for the Veltop was mostly for rain protection, plus a little wind and sun protection, any performance differences don't really matter to me.

 

[Rassy]

I've never been real happy with the noise emitted from the ENO freewheel on my mid-drive motor. It was the noisiest item on the bike, particularly at slow speed when I just wanted to pedal without using the motor. Then every now and then when I applied to much motor torque, like when going up a steep hill without shifting down enough, something would slip a cog, making a loud bam sound. I was never sure if it was the ENO freewheel or the freewheel built into the NEXUS IGH. It sounded the same as the noise the original Shimano freewheel made after only 30 miles of use.

So I replaced the 16T ENO freewheel with a 16T track cog, plus a bottom bracket lock ring secured with Loc Tite. The lock ring only has to keep the track cog from unscrewing during pedal only operation, where the chain forces the 9C motor to turn, even though the motor isn't in use. So now the motor turns whenever I pedal, with a little drag. However, when pedaling along at a fixed speed the spinning (but not under power) motor seems to have a positive effect, smoothing out the flat spot as you turn the cranks.

After half a dozen short rides, the track cog has stayed tight and the bam sound has not occured, even when trying to force it on steep hills in higher than normal gears. I am happpy that the IGH seems to be okay, and I don't think I'll miss the extra freewheel. On most of my rides I don't have to conserve the battery, so if I use it a little more to overcome the drag it doesn't really matter, and I may get that back with the smoother pedaling once up to speed. And of course the drag is no more than you would get if the 9C was built into a wheel like it was intended to be.

Strangly enough the freewheeling crank I use from Sick Bike Parts has the same ENO freewheel built into it, but is fairly quiet. Perhaps they put a different grease in it, or changed the pawl pressure, etc.

In a week I am signed up for a 100K ride in Eagle Point (Medford, Oregon, USA). So that should help me determine if this setup is really okay. Of course my buddy, who rides a tadpole with no motor, has already set me up for the possibility of not going the whole 100K. Out of three 100K rides we have been on together since he got his trike, we have only completed one.

 

[jateureka]

How did your system hold up on the 100km ride?

 

[Rassy]

Wow, it's been a full year since I've posted on this thread.

The trike has been performing great and suits my needs to a T. My buddy and I took that ride last June without incident.

I don't have any modifications planned at this time, but I think the chain may still be slipping a cog under certain conditions, such as hitting full throttle when at 4MPH on a 20% grade. It only happens once in a while, and after one slip or whatever it settles in and pulls smoothly.

There have been several modifications over the last year.

It now has a NuVinci auto shift CVT set up as an 11 speed transmission. The NuVinci keeps my cadence between 60 and 70 RPM and the motor between 180 and 210 RPM between the speeds of 5 and 20 MPH.

I fabricated a bracket and now have a rear disk brake. I was using a roller brake on the Nexus, and the roller brake fit on the NuVinci but interferred with the NuVinci speed pick-up. I like having the rear brake for long down hills plus it's nice to have a back-up brake since the front brakes are operated from one dual cable lever.

The return chain is now in a tube since it is so long and was whipping around a lot. My tensioner may not be quite strong enough, which may contribute to the slip I mentioned earlier, but I haven't figured out a better tensioner yet.

 

[rearengine]

Nice going Rassy... That's one fine vehicle ... How many miles on it now ??

 

[Rassy]

Thanks rearengine (Corvair?).

My odometer shows over 1700 miles now, but I don't know when that may have been reset since I had some issues with it early on. But my estimate would have been close to 2000 miles, so close enough.

Being an old retired guy I just ride for fun and exercise, so I don't rack up the kind of milage regular commuters do.

Edit: Yep, just did a search and see it is for Corvair.

 

[jmygann]

http://www.evalbum.com/4095