Trek 7.3FX Electric Conversion

[nomad85]

(I posted this in the wrong section earlier)
I just bought my bike its just like this one http://www.trekbikes.com/us/en/bikes/2008/bike_path/fx/73fx/
The front fork is an aluminum alloy, stronger than aluminum, not as strong as steel. My wheels are 700c. I have a topeak rack and
bag for the battery. I have narrowed my choice down to the Yesa 110U.4820F LifePO4 Battery Pack 48V 15Ah, a 48v12Ah pack from ebikes.ca or
a Ping duct tape 48v 15Ah pack, these will fit in my bag.
I need some advice on the best way to go about this. Motor in the rear(will an 8 speed freewheel fit in a 135mm dropout?), motor in the front(better stability?), what controller/throttle to get...Where to get it... I need help.
I have been thinking the 406 is the best choice since it gets .97kpv. I just need some reassurance that it will do what I want.
I am a pretty strong rider, and I weigh about 160, just need the motor so I'm not sweaty arriving at work which is about 13 miles away, and I want to try to eliminate the need for a car as much as possible.
I would like to be able to go at least 30 mph(with pedaling), and have a range of at least 35-40 miles per charge.
What would you do.

 

[Toshi]

Take a gander at my thread (see Seattle commuter bike in signature). My 407 in a 26" wheel takes me about 25 mph on flat ground with no pedaling, as my gearing was too short prior to tonight to pedal along. I'd guess that the 406 would be a good fit for you, provided you don't have any steep grades on the route.

I'm not sure if an 8-speed freewheel would work with a rear 4-series hub motor, but then again ebikes.ca/store does seem to have one up. I went with a front hub motor myself and have been satisfied with this choice and the resulting better front/rear balance.

 

[nomad85]

Yeah from what I am learning the front hub seems to be the way to go. Is there a motor ideally suited for a 700c rim, I live in Indiana(flat) and I can tackle most hills in my area at 10mph on my own, I am mostly concerned with top speed on flat ground, and not breaking my aluminum fork.

 

[Drunkskunk]

A 500 watt hub motor would break an Alloy fork. Its 500 Watts continuous, but on acceleration, its hitting 1200 to 1400 watts. Thats nearly 2 horse power. Literally, the force of 2 horses yanking you forward by the end of the fork. Alloy forks will fatigue and fail under that kind of stress. You need steel.

On the rear, the frame is triangulated, and won't suffer fatigue failure like the front fork.

 

[kbarrett]

A torque arm on a clyte front hub just ain't optional.

Get one. I got a factory torque arm from powerridestore.com, but they are out of stock again. The damned things seem to be unobtainable.

I didn't need it, so I am selling it.

 

[nomad85]

Looks like I need a rear motor(which was my original preference) My only issue is my shifters are 8 speed and I would need an 8 speed freewheel(unless a 7speed will work, my LBS said it wouldn't..) My dropout in the rear is 135mm, will a 8 speed freewheel fit?

 

[Toshi]

Looks like I need a rear motor(which was my original preference) My only issue is my shifters are 8 speed and I would need an 8 speed freewheel(unless a 7speed will work, my LBS said it wouldn't..) My dropout in the rear is 135mm, will a 8 speed freewheel fit?

Your LBS is correct: 7 speed freewheel and 8 speed shifters don't work together. 135mm is the standard for all non-downhill mountain bikes including those with 8 and 9 speed cassettes, so I imagine it'd work.

You can make a front motor work, however. Just use a torque arm (which you really should have anyway), +/- a steel fork. I'm having a torque arm custom made for my rig and am switching from the stock alloy fork to one with both canti mounts (for my V brakes) and disc tabs (where the torque arm will be anchored).

 

[Drunkskunk]

Looks like I need a rear motor(which was my original preference) My only issue is my shifters are 8 speed and I would need an 8 speed freewheel(unless a 7speed will work, my LBS said it wouldn't..) My dropout in the rear is 135mm, will a 8 speed freewheel fit?

8 speed "should" fit. I've measured out my 7 speed with a disk brake adapter to still fit, and thats wider than just an 8 speed. YMMV

 

[Ypedal]

I think the problem is that the 8 speed shifter is indexed for 7 speeds and the chain won't always kick exactly into the right spot all the way from 1 to 7 type thing..

Honestly.. you don't need all those gears anymore with a hub motor.. 3 speeds is plenty. 5 is fancy.. 7 is wasteful lol...

As long as you got juice to spare, a single speed would be all you need with the 3 front chainrings. Low , medium , Go-baby-go !

 

[nomad85]

As long as you got juice to spare, a single speed would be all you need with the 3 front chainrings. Low , medium , Go-baby-go !

That is something I have been considering, I just don't know how to do it.

 

[lazarus2405]

They make 8-speed freewheels? I thought they went up to 7, with freehubs fitting 9speed cassettes. *shrug*

Yes, it will fit. Is it necessary? Not at all.

As for the shifter, if you don't shift much the 8-speed shifter will be "good enough" on the 7-speed freewheel. I'm using a 9-speed shifter on my 7-speed because although I bought a 7-speed shifter for it, I just have no need; I rarely need more than three gears, and when I do the rear shifter does the job "close enough". It helps that I baby the chain, not putting any shock or much torque on it.

The front fork is an aluminum alloy, stronger than aluminum, not as strong as steel.

Any aluminum front fork can snap under the power of a motor if torque arms are not used. In the rear, generally aluminum dropouts are "okay" without torque arms at less than 1kw continuous. Any more and you're inviting disaster without torque arms. A failed front or rear dropout can mean anything from nothing to a damaged motor, frame, a destroyed controller, possible bodily injury, and other collateral damage. You want to be safe from bodily injury, and protect your investment.

Anyway, enough of that. On to the guts of the build:

If you're really concerned about top speed on the flat, you're looking at the wrong motors. At 48v, a 406 in a 700 rim will get you to 30mph, maybe a hair more. If you want to go faster, you need more power than a 400 can continuously output. If it's your cup of tea, 5300-series motor will do 45mph effortlessly, and can be pushed far higher.

Range is a completely different matter. With the batteries you mentioned, you should be able to do 35-40 miles if you stick to 20mph and pedal a little. However, speed will kill your range. Power needed to maintain a speed increases with the cube of the speed (to go twice as fast you'll need 8x the power), so you'll need a bit more energy capacity to get 35-40 miles going 30mph (About 1100watt-hours for 30 miles at 30mph (800w, 80% motor efficiency, 90% DoD), or about a 72v15ah battery. You could eke out 40 miles from a 72v20ah battery, or a 48v30ah battery). It can easily be done, but it isn't cheap. For your budget's sake, I hope you meant 30mph for that 13-mile commute and 35 miles at a much more efficient speed.

Of course, please feel free to ask any questions you might have.

 

[nomad85]

Thanks for the reply Lazarus. I figure I can put enough human power in that with the 406 motor I'll be able to get 30mph for 30 miles, if not 20-25 will do fine as well. I dont think I want to put a 5000 series on my aluminum frame, maybe when I get a cheapy steel bike and have money to burn I'll try one, for now I need this to work and be reliable or I'm in trouble. Basically I have enough money to get a cheap car, or a decent e-bike. I am thinking about putting the electronics in a cargo trailer like the burley nomad, to keep the weight off my bike and low. That way I can just remove the rear wheel and put my old wheel back on for real riding, and it will be just like a stock bike... with a mysterious throttle and watts up meter...(are those CA units any better than a watts up meter?)

 

[recumbent]

Your bike looks like a hybrid road bike, like the one i have. The Bionx system fits perfect on these bikes and have everthing including regenerative braking.
If you choose the Clyte motors you should get a 407 or 408 model so you have the torque to turn your large diameter wheels.

Good luck with your build.

 

[lazarus2405]

are those CA units any better than a watts up meter?

Absolutely. In addition to the stuff Watts Up measures (watts, amps, wh, ah, voltage, min voltage, peak amps, peak watts), the CA has a speedometer (current and trip average), odometer (lifetime and trip), energy gained from regenerative braking, efficiency (Wh/km), lifetime battery info (Ah used and number of cycles), programmable speed and current limits, and a programmable LVC. The 2.1 version has even more goodies. If you can afford it, absolutely get a CA.

Basically I have enough money to get a cheap car, or a decent e-bike.

That sounds like an x5 budget.

Really, I didn't mean to scare you with the torque arm business. There are a number of ways you can make, buy, jurry-rig, and attach one, so don't be discouraged. The power of the x5 is no doubt worth the trouble. Just, you need to consider it if have an aluminum frame.

The trailer idea is always a good one. It has several benefits (low CG, detachable, easy battery mounting,, ability to carry very heavy batteries with impunity), and there are a number of ways you can go about it. Several folks here have built battery trailers and pusher trailers (with the hub motor in a trailer wheel, leaving the bike completely stock except for a throttle and CA). Look around and you can find plenty of ideas.

The weight itself on the bike, at least when not using SLAs, isn't that big of a deal when actually riding it. Finding a good place to put that weight is the challenge, and trailers can make that a terribly easy task.

What sort of tires are on your donor bike? Skinny superlight road tires won't last very long, and with a motor and torque arm replacing tires and tubes goes from being a tack to being a chore. :|

 

[nomad85]

That sounds like an x5 budget.

I might be able to afford the motor but not the battery to power it for 30 miles... They are appealing... but the less I spend the better off I am.. need to save for retirement... I hear if you start in your early 20's you are golden... I think I will buy a 15Ah pack from ping, and if it works well I may add another in parallel for 30Ah at only 30lbs... The ping pack wont power a x5 from what I have gathered so I will stick with a 406 or 407(which will be faster in a 700c rim)

Really, I didn't mean to scare you with the torque arm business. There are a number of ways you can make, buy, jurry-rig, and attach one, so don't be discouraged. The power of the x5 is no doubt worth the trouble. Just, you need to consider it if have an aluminum frame.

Have any pictures of a torque arm setup(front or rear) I don't understand the way it works, or how it is implemented.

What sort of tires are on your donor bike? Skinny superlight road tires won't last very long, and with a motor and torque arm replacing tires and tubes goes from being a tack to being a chore. :|

I have commuting road tires but I wont be using them on the motor, I plan to use maxxis hookworm tire for the motor(does that require a special tube?). I want to keep my extra wheel stock so I can swap it out when I ride with my father to train and for the bike tours we do. I want the battery and controller to fit into my topeak bag and rack system as well so I can use the trailer or just a bag, more flexibility.
I am changing my mind every few hours but... Basically I want to put more of the money into the "bike" aspect so that if I am disappointed in the "electric" aspect I still have a kick A$$ commuter bike since I can go about 17mph or so on my own without too much sweat(on flat ground and light wind).
So far I have gotten: I got these sweet folding metal baskets that attach to the side of my rear rack and fold away when not in use, look kinda silly, but maybe it will keep someone from stealing it... I ordered a new seat with some springs to protect my behind. I got a topeak system, and some head and tail lights from planetbike as well as a nice fender set for rainy conditions. I got a new camera so I will post some pictures once my parts come and are installed(better deals online but you have to wait...)
Keep the advice coming I need it...
I am savoring the thought of riding my zero emission e-bike to a flying field and taking my electric rc plane out of my trailer and enjoying my zero emission hobby...(love lithium battery technology...)

 

[nomad85]

I was able to order a 48v 15Ah pack direct from Li(pingping227) so I have that coming in a few weeks.
Just need the rest.
Heres my current thought(from ebikes.ca)
406/407(can't decide) 700c rear motor-280$
24-72V 20A pedal first controller, IRFB4110 mosfets-145$
Basic twist throttle-15$
8 speed freewheel(if it will fit)-30$
Cycle Analyst standalone unit- 150$
Total-620$ + shipping

What controller would you guys recommend? will the 20A limit be a problem with my battery and motor choice?

Thanks,
Kyle

 

[lazarus2405]

Well, some thoughts:

You're doing it backwards for a first build. Don't use a nice road bike; get a craptacular cheapie mountain bike and spend all the money on the electric components. :wink:

All else equal, the 406 will go faster on the flat and the 407 will have slightly better acceleration/hill climbing.

If you're getting your controller from ebikes.ca, there's no reason to get the stand-alone CA; the direct plug-in model will simply plug into the controller.

You may find a half-twist throttle to be more comfortable. It'll last longer, too; if you hit a bump and jam the handlebar with your hand, you can damage the rotating mechanism of the throttle, but with a half-twist most of your grip is on the non-moving part.

For the controller, make sure to get a unit with IRFB4110 fets. They're more robust than other models with worse fets. For the 20a current limit, it won't hold you back much unless you want to push above 30mph. If you think that later you will seriously want to go much above 30mph (which, believe me, is very fast on a bike!), consider investing in the 50a controller now (you could add another battery sometime down the road for more voltage, and thus more speed). You might have to get into a racing tuck to make 30mph, but it's not a bad idea to do that anyway for your efficiency's sake. You won't have a problem with that controller and battery combo.

 

[nomad85]

Thanks for the tip on the half throttle, I'll get that instead.
Regarding my choice to start with a nicer bike... I want to be able to ride the bike without power too, and cheap mountain bikes suck(I used one on a century ride as a kid and it was miserable)... Maybe I'll get a cheapy bike from goodwill to test on first, but I really want to get the trek electrified, I think it will be more efficient than cheap mountain bikes and it'll be different I just hope its not different because it ends up in pieces :lol:

 

[dermot]

I've been using a Heinzmann 500/750W brushed and geared motor in the front of my Trek 6045 for around 4 years now with no problems - there is, of course, a torque arm for safety.

The Shimano 7 speed internal hub in the back is grumbling a little, but that's all.

 

[Drunkskunk]

24-72V 20A pedal first controller, IRFB4110 mosfets-145$
Cycle Analyst standalone unit- 150$
....
Thanks,
Kyle

Skip the pedal first, and get the imediate start. You can use the imediate start like a pedal first if you want to. But if you brake a chain, or twist your ankle, or lose a shoe to a vicious escalator, you can ride the bike home with just the motor on an imediate start controller. Thats imposable with a pedal first. -- Its happened to me a few times. Once in a wreck that destroyed the derailer, and once when I hurt my back and couldn't pedal.

20A is fine, more amps would be better accelerating, but since you wanted pedal first, i'm assuming acceleration isn't your priority. 20A is as fast as 40A for top speed, just smaller, lighter, and cheaper.

Get the direct plug in CA. it has features the stand alone doesn't like being able to set your max current draw, and max speed, as well as draw your speed and milage from the motor instead of external sensors.

 

[nomad85]

Great point about the immediate start, I will definitely get that as well as the direct plug CA. Anyone know where I can get a good torque arm for a rear wheel? I still don't understand how they work or how to set one up.

 

[Toshi]

Great point about the immediate start, I will definitely get that as well as the direct plug CA. Anyone know where I can get a good torque arm for a rear wheel? I still don't understand how they work or how to set one up.

Unfortunately there aren't really any off the shelf torque arms, as each bike's geometry is slightly different. The concept is that it extends the length of the lever arm from the distance from the axle center to the edge of the dropout (6 or 7mm) to ~100mm. Recall that torque = force * distance, so increasing distance will decrease force for a given torque, and thus decrease the chance of your dropouts self-destructing.

 

[nomad85]

I have my battery and its all wired up 48v 15Ah LiFePo4, used deans connectors, I have my motor coming in the mail along with the controller and CA. I have been looking into torque arms and found some at http://www.texaselectricbikes.com and I am thinking about ordering one(or two if thats what you are supposed to do) If anyone has some tips I would appreciate all info, thanks.