Hi Don,

Crank speed would only reach it's maximum under the lowest possible load condition.
I would never be using the power under that condition.
On the contrary, I would only be using the power where the load is substantially higher.
The way I'm intending to use it crank speed would never reach it's maximum.

But, it is good to be aware of what COULD happen and be ready to react. It is simply a
matter of letting go of the throttle, a very natural response.
I have a lot of experience avoiding "SPD tattoos" from years of mountain biking.

And, remember, I will be using the 250w motor not the 450w.

I understand why someone would be giving the advice not to use a crank driven setup.
The market seems to be going the hub motor route, it's safer, there will be less liability
issues.

I'm simply not interested in a wheel driven setup. I want that power to be assisting me at all times.
If the top speed of a wheel driven setup is 17 mph you get no assistance from the motor
over that speed. I'm thinking of the effort it takes to go 25 mph and how easy it would be with
250 watts of assistance. At 25 mph there would be a substantial load on the motor due to the
wind resistance.

I think it will work for me.
George

Not sure if this is of use to you but, Ecospeed now makes a Mountain drive and they do sell the drivetrain only for those who wish to use their own motor.

http://www.ecospeed.com/prodemtndu.html

Geo

More power to you, literally and figuratively. Best of luck with it.

One thing I didn't make clear, I guess, both of my last two notes referred to applying power to the back wheel through the bike's transmission (derailleur, chain). They were just techniques that powered the bicycles drive chain without turning the pedals.

I guess if my Ping LiFePO battery hadn't satisfied my need for greater range I would have gone with the SickBike Shift kit to allow using at least 7 of my 21 gears. My desire to use the gears was all about efficiency. I still don't need more speed or torque. With my nominal 24 V LiFePO battery really 28 - 30 volts, I can average 20 mph over hill and dale. 30 mph on a bike reminds me of the time it would take for my old bones to mend after a break.
With ~29 volts the motor will still contribute at 22 or 23, but I rarely use it at those speeds.

misslexi

Ecospeed's Mountain drive, sans motor, looks good but $920 or $1020 seems pretty pricey. $200 more gets you a BMC 600 W motor and controller. I don't think they really want to sell their hardware only.

Thanks Don,

Now all that remains is for me to buy the kit and the bike to go with it.
I was at a bike shop yesterday and I asked the owner, my buddy, to find me a cup for a loose
bearing BB. It was Campy and sure enough a freewheel screwed right on. The hole for the spindle seemed bigger than 10 mm, however. I'll be thinking on that. I Googled 13 tooth freewheel and indeed such a thing exists for a standard hub, by Odyssey.
I will start with the biggest chain ring that will clear the chain stays. It may be 53 or slightly smaller.
Thanks for all your help, you've been wonderful.
George

Yes it is pricey. I've been to the shop where they make these parts with a CNC machine, quite fascinating to watch. Judging from experience, because I own an Ecospeed mid-drive, I can say you do get what you pay for. Since I haven't tried any of the lower priced stuff I can't make the same claim; in other words, the less expensive stuff may be a better value.

Hi Don,
I missed this post somehow. It looks really cool.
Is a possible alternative to mounting a freewheel on the motor.
I guess I could even fashion my own bracket and use a flipflop hub as the jackshaft.
I could drive a second chainring on the crank on the right side, no stoker crank needed.
Do me a favor and look back through my posts. In one of them I described a scheme to utilize
the "no pedal no throttle" mode of the new Currie kit.
Tell me what you think of that.
Sincerely,
George

Geo

I will read that scheme again. I have to run now. I just wanted to point out this is NOT an alternative to the freewheel on the motor, that one protects the motor from being driven by the pedals, gear reduction motors don't like that. This second freewheel is to protect YOU.

Back early, some thoughts:
Geo some of what you suggest is there now, if you were to buy an eZip. On the eZip there is a switch in the Front (left) brake lever that cuts the motor while the lever is held in. Also there is an encoder down on the left crank arm that sends a pulse signal to the controller if the pedals are turning. On old controllers a Black Box and a White Box interpret this info. On new controllers it is all in the one box. Unfortunately the kit lacks the brake switch and the encoder. You could probably buy the necessary parts from Currie.
On factory eZips if you set the PAS/TAG switch to PAS, Pedal Activated System, the throttle is disabled unless the pedals are sensed to be moving. Full throttle would be ignored.

So, you might have to change controllers to get one with PAS/TAG $54.99. The other one is probably in kit $49.99. Need PAS/TAG.
The throttle with PAS/TAG switch $15.39 probably could jumper controller to always be PAS.
Left brake lever w/ switch $10.99 could use two $22
Cadence sensor $6.99. You’d have to remove left BB cup to put ring around BB axle then replace.

You might want a KILL switch on the handlebars. If anything failed, you wouldn’t want flailing pedals. This idea would surely work most of the time, if the pedals aren’t driven, that’s good enough.



Don

New idea
 

George

I have to thank you. You have kept me thinking about this long enough that I think I’ve stumbled on a plan I will pursue someday.
I’ll buy a good road bike and make MY OWN Currie, no, O’Brien Electro-Drive Conversion Kit. I would use the same Unite 450 Watt motor, same controller and the same throttle, but that’s all. I would use the SickBike Shifter kit or a homebuilt version of it, to mount the motor in the triangle in front of the seat tube.
The motor would be output shaft toward the driver side, not the passenger side as it is in the Currie version, so the wires would be hooked up the other way around (a plus of Brushed DC motors). The same 9 T sprocket would be on the motor. A freewheel sprocket on the driver’s side end of the jack shaft would protect the motor from being driven.
Between the 9T to jackshaft freewheel sprocket and the jackshaft output sprocket to crank freewheel sprocket ratios it would be easy to get the 10 to 1 reduction in rpm. I could even have two chainwheels for the bike drive chain giving me 18 gear combinations

Advantages:
I could use a “good” rear wheel and freehub not the Currie compromise. I'm thinking "Roadbike"
I wouldn’t have to worry about removing the Currie freewheel from the back wheel (for chain clearance), probably a destructive process (no spline in Currie freewheel).
I won’t have another LONG chain down the driver’s side of the bike.
I’ve moved the weight of the motor and bracket forward making the weight distribution more even.

I’m liking this. I might move the batteries to a front rack making the weight distribution even more even.

My pleasure, Don, I was hoping that you were enjoying it, I sure have.
I haven't had a lot of time, I will contemplate your idea in a day or two.

I won't be using the Currie wheel at all, I'm free to use any wheel I choose.
With the freewheel on the motor there won't be any chance of driving the motor, I think(?).
There will be a long chain and there is the possibility of having to use a chainstay mounted
chain tensioner but such things are available.

If you're going to be using a road bike, are you going to be using a drop bar?
I am contemplating that but I'm aware of the incompatibility with flat bar controls.
I think the Raleigh Sojourn would make a nice conversion.

I'll comment soon.
George

Geo

You're right. Some time to simer makes sense.

One additional thought, instead of buying the kit for $299

A person could buy:
The motor $99
The throttle $18
Rack which has controller inside $50
A Currie battery $130

tot $297

So, $2 savings ????

NO! don't spend $130 for 24 V 10 AHr Sealed Lead Acid
Spend $200 for 24 V 10 AHr Ping LiFePo REALLY Good battery

So for $367 you have a "KIT" with a GOOD battery, you'll need to make some little hose clamp doodads and buy a pre-enjoyed Currie Battery case empty

Really good thinking, Don.
So the rack includes the controller and the motor plate comes with the motor.

There is a complete bike with the 250w version of the Electro Drive but unfortunately the 250w motor is not listed in parts and accessories.
Ezip Ecoride $1149 Lithium Ion battery http://www.currietech.com/currie-tec...ctric-bike.php

I emailed ElectricScooterParts and asked if the 250w motor that they sell, that looks exactly like the Currie 450w, will work with the Currie kit. No answer yet, best to be certain. It's $90.

What do you think? Will it bolt in to the Currie motor plate?

You could do drop bars with only an on/off switch on the handlebar, that would be so cool.
You'd have to somehow put switches in road bike brake levers and run it in PAS.

Geo

Re. 250 W:
Having looked at the Unite (manufacturer's) web page which I posted here before, I'd say that externally they are identical.

Yes, I would use drop bars with a non latching push button switch, hand off switch (say to reach for brake) switch comes unmade, motor drops out.

I don't think the brake switch on my eZip has ever killed the motor, my hand comes off the throttle before I hit the brakes. It's like your right foot in a car doing accelerator and brake. I would never, in a car, leave my right on the gas and hit the brakes with my left. Who would?

Don

Hi Don,

ElectricScooterParts replied and the said they and their supplier were out of the 250w motors and that the 250w motor WOULD NOT work with the Currie kit.
Perhaps there is another supplier. Do you know of any? If so, send a link.
A hands off switch, I was thinking the same thing. But, with a drop bar there are three hand positions, drops, tops, and hoods. It would be hard to have a switch that could be reached in all three positions.
I saw some Magura switches, somewhere, that could probably be adapted to road levers, somehow.
I have an idea. Mounting the motor plate OUTSIDE of the dropout.
That way I could use a bike with disk brakes.
I would get an extra long axle with more axle sticking out the left side than the right.
Another idea. Have a bottom bracket cup welded to the motor gear, open side out. If the 9 tooth is too small for this then get a bigger gear.
The fixing nut should fit inside the cup.
When removing the freewheel a chainwhip could be put on the gear that is welded to the cup.
That would offset, somewhat, mounting the motor plate on the outside of the dropout.
There will be such a long chain that I don't think chainline would be an issue.
And, I will be using the big chainring which is the furthest out on the crank.

You could use 3 switches wired in parallel. If any of the three were held in the motor would run. They ARE NOT hands off switches, your hand must be on them for the motor to go = Dead Man's Switch.

Again I think the brake switch is just a "Fail Safe" normally has no effect. It only becomes important if switch, throttle or a controller circuit part malfunctions.

OK, but the chain stay and seat stay would have to flush with the dropout plate. Mounting a rear rack might get awkward.

Sounds good.

Hey Don, what about undervolting an motor? Run a 36v motor on 24v.

I found Unite MY1018Z 250w motors on ebay for around $50.
All the sellers are in China.
Seems like all domestic internet retailers are sold out.

I was looking at Crystalyte motor stats and realized that hub motors turn pretty slow.
Using one to turn the cranks would be pretty easy, gearing wise.
And, that is exactly what Stokemonkey is doing.
It is a hub motor they are using. The motor body spins while it runs.
The motor mount is basically a set of dropouts.
Give you any ideas?
I was also perusing V is for Voltage. It is amazing the naivety about a crank driven system.

Been doing some thinking.
I came to the realization that the freewheel has to be for left hand drive.
When you pedal with the motor off you want the freewheel to freewheel.
With the power on, it will drive the crank.
You won't be able to backpedal.
There is the possiblily that you could drive the motor if you tried to backpedal.
But, surely there would be some resistance and you would have to be pretty deliberate which
I don't think is very likely.
Another oddity is that the bottom bracket cup will have to be the left threaded one.
That's not good because the motor will be turning clockwise which will have the effect of
loosening the freewheel.
I could use Locktight or find some kind of fastener solution.
I think the best approach to adapting the freewheel to the motor shaft is to have a BB cup welded to the motor gear.
When it comes time to replace a worn out freewheel you could use a chain whip on the cog that the BB cup has been welded to.
I know a bike shop where the owner is very handy with a welder. He repairs frames.
I also know another bike shop that shares the property with a manufacturer of high end downhill racing bikes.
I saw a freewheel adapter for a 15mm output shaft but I don't know how you would remove the freewheel.
I was shopping around on the Internet for things Currie and I saw the Walmart sells Currie bicycles.
You buy it via the Internet and it can be shipped to your local store FOR FREE or to your home for only $30. If you buy from the Currie site the shipping is $99.
The Walmart price for the Ezip Trailz bike is $349.
That's $50 more than the kit but you would be getting the TAG/PAS feature, the brake lever with the cutout, and the cadence sensor, things that you don't get with the kit.
I would take off the electric stuff and give away the bike.
I am thinking of giving the 450w motor a try and if it doesn't work out replacing it with the 250w motor.
I did the math. The cranks would have a POTENTIAL speed of 135 rpm with a 13 tooth freewheel and 53 tooth chainring.
But, of course there is the load and the ACTUAL speed the cranks would attain.
I think, at the very least, the load would be no less than 40% because I would only be using the power where there would be a substantially greater load than on flat ground.
If I'm right the maximum crank speed would only be 81 rpm (135 - 40%).
That may still sound fast but I can assure you that I routinely reach those crank speeds in casual riding.
And, besides, if things get out of control you just let go of the throttle.
It's worth a try AND it would mean 450w instead of 250w of power.
I realize the to those accustomed to wheel driven setups will think it risky but the mindset of riding a crank driven setup is entirely different.
You only use the power when you need it AND you would only be using the power in high load circumstances where the cranks could not reach their maximum potential speed.
If I get the complete bicycle I will be getting the lead acid batteries. Might as well give them a try and use them up before moving up to a Ping battery.
I have read that the SLA battery will give 10 miles of range on battery power alone.
If so, that is a long, long way if battery power was used only when it was needed.
To exemplify what I'm trying to say.
I visit my mom daily in a rest home about 10 miles from home.
I would estimate that I would be using the power for 1 mile each way, 2 miles total, round trip.
On the way home I could be pretty liberal with the power and be really lazy.
Even if I run out of juice pedaling will not be a problem. I routinely ride a 50 pound bike, my utility bike which weighs 26 pounds with 25 pounds of racks, baskets, 2 dogs, and 1 cat.
I will be not be using the Currie bike. I will be installing it on my own bike which is light and fits me perfectly which allows for maximum pedaling efficiency.

Geo

Whoa, you've gotten yourself turned around. Try thinking this way.

First all clockwise/counterclockwise descriptions are looking from the right side toward the left.

On the regular 7 speed freewheel on the right side of the bike. The freewheel is a right hand thread and threads toward the left side as you tighten. The crank turns the wheel clockwise through the locked freewheel by putting tension in the top span of the chain. So clockwise = locked.

If the wheel tries to turn the crank it would need to have effective tension in the bottom strand of the chain. Tension in the bottom span of chain would turn the freewheel counterclockwise so it freewheels. Counterclockwise = free.

Now, on the motor, The motor turns clockwise. We need it to turn the crank clockwise. So we need a freewheel that is locked for clockwise force. That's just like the 7 speed freewheel. The only difference is that for motor to crank/chainwheel the tension transmitted is in the bottom span of chain. On the 7 speed freewheel the tension transmitted is in the top span. Both freewheels transmit force if it is clockwise.

So regular freewheel, regular threads as we have said all along.

Don

Geo

2008 eZip Trailz cost $299 plus shipping at Target while they last.

Hi Don,

The way that I determined that it was counterclockwise was that I held a BMX freewheel in my hand. I have them laying around because I ride a single speed cyclocross bike.
Hold it in the air the way it would be mounted on the bike with fingers inside simulating the motor shaft. Simulate motor stopped, you want the freewheel to freewheel, it does not.
Simulate motor running, you don't want it to freewheel but it does.
Not flip it around, now it works like a left handed freewheel.
Simulate motor stopped, you want it to freewheel, it does.
Simulate motor running, you don't want it to freewheel, it does not.

If you don't have a freewheel laying around go down to a bike shop and ask them to let you handle one.
I was surprised too.

I think what I was not considering is that, in this case, the freewheel is driving the crank.
Normally the crank drives the freewheel.

An easier way than going to the bike shop is envisioning the whole setup installed on the bike.
The motor is stopped, you pedal, the freewheel would try to turn the motor, which is exactly what we don't want. We want it to freewheel, exactly the opposite of what we want the freewheel to do on the right side.

It's amazing how a simple little device like the freewheel can confuse and I was totally surprised to find out my thinking was wrong.

I got on Target's web site and yes, $299.
There's no way to determine shipping until you go through check out which I will do later.
If it's $50 or less for shipping it would be worth it and it would be delivered to my door.
I will see. Currie charges $99 for shipping so I wouldn't be surprised if Target charges more than $50.

I got the green light from "she who must be obeyed" for going ahead with the project.
She was actually rather excited by it. She's environmentally conscious and is aware of the concept of peak oil. She's having part of the lawn torn out to save water!
She also has a friend who wants a bike so he will get the Currie bike after I have taken off the electric stuff.
That means I get to buy the kit and a new bike.
I'm going for the Motobecane Outcast 29. It's a single speed but I will convert it to a 1 x 9 using DMR chain tugs with a derailleur tab. If I run a full length cable housing from the derailleur to the shifter the lack of cable stops is not an issue. I will also have to get a cassette rear wheel but wheelsets can be had for as little as $99. I'm going for the Motobecane because I just like it. It sells for $349 with free shipping and no sales tax from Bikesdirect.
When I get the cassette rear wheel I will try to swap axles with the single speed wheel which is a bolt on. The thread pitch of the axles might be the same, they might not.

I will post new comments as I progress though the project.
Thanks again for all your help and interest,
George

Geo

I still disagree. You said the words yourself. Flip the freewheel so that the writing on the side is away from you. Hold the cup as if you were going to screw it into the drive side of the Bottom Bracket. Thread it into the freewheel, clockwise. When it bottoms out continue turning it clockwise. The sprocket turns clockwise too. That's what you want: when the cup is turned CW the sprocket turns CW. When the cup is turned CCW (yes it could back out, but if bound in) The sprocket DOES NOT move. This is in effect what happens when the crank tries to turn the motor sprocket CW, that is drive it.

No muss, no fuss.

I see, you've had the cup the other way around, that's why you've been saying the nut would be inside the cup. I thought that was something you see when you tried it. Sorry, I didn't explain things well.

See, the way I envision it, The sprocket is around the shaft. It would be about as far from the motor bearing as it is in the standard setup. The way you were thinking, if you could get the parts (there are only 16T left handed freewheels and no left handed BB cups) the sprocket would be a lot farther from the motor bearing (bad thing).

Don

Hi Don,

Odyssey makes a 13 tooth freewheel in both left and right hand drives.
The right cup of a bottom bracket is left threaded.

We are both right. You are thinking the BB cup is welded to the inside of the motor gear and I am thinking it is welded on the outside of the motor gear.

Actually your way would be better because the freewheel would be closer to the motor bearing.
But, it doesn't look as if there would be enough room between the motor gear and the motor for a BB cup.
You have the kit, measure the distance between the motor gear and the motor itself.

It would be better to have the BB cup welded to the inside of the motor gear for another reason.
You could then use the lock ring that comes with a loose bearing bottom bracket to keep the freewheel from coming loose. The freewheel is, in effect, left threaded on a clockwise rotating shaft and it would come loose without Locktite or some sort of fastener.
I suppose I could find a 1 3/8" left threaded lock ring if the cup has to be welded to the outside of the motor gear.
I suppose the BB cup could be cut narrower to fit between the gear and the motor or to minimize the the additional distance from the motor bearing if the cup has to be welded to the outside of the motor gear. I think you could get that additional distance down to 1/2".

Are we having fun?
Cheers,
George

Yes, it is fun to see how differently two people can see the combination of just a few elements.

The distance from gear case to end of shaft is about 30mm.
Outside of gear about 15mm
So with cup on outside, the close side of FW would be about 20 mm away

I picture gear gone, cup trimmed to 10mm to fit inside FW
Add a washer to make sure cup is stopped by shoulder (maybe added raised center to keep things concentric)
So farther face of FW is about 25 mm from gear case and close face is about 9mm from gear case.

I think 9mm is better than 20mm.

Distance gear box face to center of gear teeth:
The 9 puts the gear teeth at about 21mm, the 20 puts it at 32mm. Present set up gear teeth are about 12mm.

Taking the FW off the cup is not a biggie. Take cup off motor shaft, use wrench on cup flats, use FW removing tool on FW notches. With my idea the FW will be tightening all the time, like normal, no lock ring needed just muscle.