Motor on a folding bike

[Desertprep]

I want to put a motor on a folding bike, assuming the airlines will cooperate with me (see another post). The goal is to have it weigh less than 50 pounds, ideally including all batteries, although when I check the bike in the airport I can remove a battery or two. Most of the time I will be riding on flat land but I do travel 2 months a year. When I travel I will be riding on places with hills...you can say small mountains. I want the bike to have at least 5 gears for pedaling, 7 would be better.

1. Am I better off getting a bike with an aluminum frame or a chromoly frame? There seems to be a 3-4 pound difference. I will be riding on paved ground almost all of the time, although sometimes the pavement is not very smooth. I weigh 170 pounds and will be carrying about 30 pounds of luggage with me when I travel.

2. The idealist in me would like this bike to go 25 mph on reasonably flat ground on its own accord, with me pedaling to make it go faster. Any suggestions on the size motor? I would prefer not to use a hub motor but instead use a motor with a chain so that I can balance the weight on the bike more evenly, i.e. put the motor near the center (front to back) of the bike. Any thoughts on this? Also, I have seen a 500 watt 36 volt motor like this that weighs about 6 pounds, including the short chain and large gear wheel needed to slow the speed down. The lightest 500 watt hub motors I have found were 15 pounds. Also I am not sure a hub motor would fit in a 20" frame of a folding bike.

3. I will eventually have lithium - xx batteries. I was thinking I should use a 36 volt motor because most of the lithiumxx battery packs I have seen are 36 volts. Is there more selection now? Is the Dewalt 36volt one of the best? i.e. most durable with the most charges?

4. How many batteries would it take to go 50 miles at 25 mph - assuming no pedaling? I remember seeing a post that referred to a website that had a "calculator" on it that would allow me to input certain information such as weight, motor power/volt, batteries, etc and then give me an estimate of how far/fast I should be able to go. I am pretty sure it was on this site. Can someone help me find it? I have searched but did not find it

4. How does pulling a trailer affect the weight capacity of a bicycle?

5. An ideal solution (re: weight distribution) would be to put the motor on the front fork, but I keep hearing bad things about this idea.

 

[fitek]

Hi there!

You're doing exactly what I am planning to do. Just this morning I almost finished ebike #3 and I've come to the conclusion that only two types of ebikes are useful to me: those that I can handle just like a regular bike (meaning, they are light enough that my gf can handle it and stealth enough to ride on sidewalks) and a sub motorcycle class, where I can pimp it out with large batteries and motor.

I have set a goal of 45lbs for my bike. You can go with a steel bike but only if you use lithium; and then the weight is going to be nearer to 50lbs. An aluminum bike will work with small SLAs (this is my preferred option).

Here's the link to my webpage about this bike:
http://petervieth.com/index.php?page=serial-hybrid-electric-bicycle-3

You can check out the previous builds for info on how I've arrived here and different things I've tried out.


I have put a 300W Kollmorgen on the front fork of my long wheel base recumbent, and it works just fine. I used a rear wheel, removed the gear cluster and replaced it with an 80 tooth sprocket and freewheel adapter. It's really much easier than trying to get a motor and the pedals to work on the same wheel & having to deal with double sided hubs, whatever. If you use a suspension fork, you will have to get creative, because you can't drill holes into the fork like I did to attach the motor since it contains springs. Also, a suspension fork probably won't be very happy with being spread apart to accept a rear wheel.

The Kollmorgen motor is $45 from ElectricScooterParts.com. It has a built in controller and is 24v. If you bypass the controller and use a better one it can run at a higher voltage. You need a $50 Magura throttle, the $1 3 pin connector to attach it to the motor, several feet of no. 25 chain and either a chain breaker or a couple of masterlinks and a dremel and some pliers (to set the length of the chain), an $15 8mm d-bore sprocket, a $20 80 tooth no.25 sprocket, and the $15 freewheel adapter. You can order these parts for cheaper from tncscooters.com but I found their site less friendly and their shipping slower.

If you are willing to accept the above, then go for it.

The range you want is quite high (for that speed). My LWB recumbent requires roughly 350watts to travel at 25mph on flat ground. Batteries should only be discharged 50%, so to run for two hours, you would need 1400watt hours of energy. At 24v, you'd need 60ah. This would weigh more than 50lbs by itself for batteries probably. 24v and 10ah of duct tape batteries are like $200 if I recall correctly, so you could buy $1200 of lithium batteries too.

In my opinion, it's best to keep speed below 20mph. The power requirements fall quite a bit. I have an excel file with the calculation which I'll have to dig up...

 

[docnjoj]

For the non-electric part, namely the folding bike, check out Gaerlan cycles! He really knows his stuff and has very fair pricing.
David

 

[Malcolm]

Like fitek says, it will be difficult to achieve the range you want at 25 mph without pedalling. 20 mph and 50 mile range should just about be achievable with a decent lithium pack weighing around 10 kg, especially if you're prepared to pedal a little.

That only leaves you around 12 kg for the bike and motor. For chain drives I would take a look at one of the following:
http://www.cyclone-usa.com/
http://www.elationebikes.com.au/
http://www.bike-elektro-antrieb.ch/startseite.htm

There are a few lightweight hub motors around, weighing just 2-3 kg. The best known is probably the nano/tonxing, but there have been reports of poor reliability lately. Other names to look out for are Tarn/Nuergy/Thinkar and 8Fun/BF/Suzhou Bafang. I'm looking for one of these myself so I'll be stating a thread to find sources shortly.

 

[fitek]

Looking forward to your thread Malcolm. I'm sticking with the Kollmorgen for now I think-- affordable hub motors are either too heavy or too unreliable. The Roadrunner that was posted in my cheap hub motor thread looks pretty decent when the supply of $40 Kollmorgens runs out

With a light bike like a folding aluminum bike with a few pounds of lithium (which could be made to be < 40lbs), it won't be that hard to pedal. Going ~10 mph you won't even break a sweat, so if the electric part can add another 7 or 8 mph your speed will be pretty good. I just rode for the first time from work to my new place in San Mateo, it was 8-10 miles and I went pretty damn slow and got there in 1.5 hours. Electric assist would easily cut this time down in half.

 

[gmouchawar]

Have you considered the IZIP EZGO. It may be just what you are looking for with a reasonable price.

 

[fechter]

Look for the power calculators here:
http://endless-sphere.com/forums/viewtopic.php?f=16&t=1499

You'll definitely want some lithium batteries to get the range you need.

Hub motors will fit in a folding bike, there are several members who have done it. They are heavy.
The EZEE geared hub motor looks like a good one, but not cheap.

You're in China aren't you? Close to the source for many of the parts. Seems like you should be able to find something local.

 

[Desertprep]

Thanks for the input! Yes, i have noticed that the motors with chain drives are quite a bit lighter. What do you think of using a motor like the http://goldenmotor.com/ BLDC 40S? or the 90 or 90 BlD?

As I play with designs i see two choices coming through. I either need to have a fat stubby "pancake" motor, maybe 2.5-3" (to fit between the pedals) or a longer thin motor - maybe 4" long but 2.5" thick to fit in spaces in my bike.

The 40S is a thin one but it is only about half a pound. How do i know how durable it will be? if i put 2 on the same bike would that help with the durability? I hope to be able to do 20 mile (or more) trips with this bike.

 

[Drunkskunk]

Since you plan to be checking this through as luggage, I would stay away from the BB and other chain drive motors. they would be lighter, but they aren't as robust as a hub motor. there's too many clamps and chains, and the normal tossing and banging the bike will get by the luggage handlers may mean a day's worth of work to get the bike ridable when you get to your destination.

A EZEE would work for you. its a geared hub motor, so it would have the torque, and still be in the wheel.

As for 50 miles range at 25mph, it ain't going to happen on a 50 pound folding bike.
if you could build the bike for just pure efficancy, you would still need around 2200 usable watts to do it, and that means a 2500 watt battery minimum. even if you went for LiCo batteries, thats still 35 pounds of battery. I don't know many people who whould want to get onboard a plane with an uncertified 35 pound brick of Lithium Cobalt in the belly. Thats a pucker factor of 9 at least.

50 mile range is reasonable, on a 20 pound battery with some pedaling at 10-12 mph, and the same bike might be capable of 25mph or more, but the two together would be a heavy beast.

 

[jerryt]

I have an eZee Quando II which is the folding model. It weighs in the 50+ lb neighborhood with a NiMh battery and 36v (9a I believe).

I'm heavy (230+ lbs) and carry groceries up to 30 lbs including my 5 - 6 lb panniers, helmet and bike lock and can travel 15 - 18 miles with light pedaling @ 12 +/- mph. This is only an estimate because I have never traveled more than 5 miles at one time.

The eZee is not the most compact folder but appears to be a well made bike. The only problem I've had is the brazing holding the center kickstand cracked because I put too much weight on it. I removed and replaced it with a rear wheel kickstand.

A lithium battery will save you 2+ lbs and may provide more travel distance. However at present, the lithium batteries for the eZee are poor quality and are not recommended per eZee CEO Wai Won Ching. They are presently being replaced in Great Britain by a new eZee supplier. I don't know about other countries.

An eZee with 2 batteries may be what you need to go 40 miles +/- if you are not as heavy as I am.

If you're curious, read this thread and also do a search on eZee.
http://www.pedelecs.co.uk/forum/electric-bicycles/1213-ezee-phylion-li-battery.html?highlight=sanyo

Edit: Here is an article regarding long distance e-bike travel in China on an eZee bike (not a folder).
http://www.pedelecs.co.uk/articles/88/1/eZee-Torq-Trekking-is-put-through-its-paces-from-Shanghai-to-Wuhan/Page1.html

 

[Mathurin]

you would still need around 2200 usable watts to do it, and that means a 2500 watt battery minimum.

Wait, how do you figure that? Kreuzotter using default mtb but with "wide high pressure slicks" at 25mph gives me 450w, so X2 for 50 miles is 900, plugging 75% for eff gives 1200, and say 1500 for good measure. Am I missing something?

 

[TylerDurden]

The slightest slope changes things a bit.

 

[Desertprep]

Thanks! The banging around point is well made. I have enough problems as it is with durable goods being mashed My problem...I wanted to reserve the rear hub for a hub gear so that I could pedal at reasonable speeds to get exercise. Also an ebike with pedals and only one gear makes pedaling only useful during a narrow range of the speed of the bike. The chain drive system was supposed to allow me to have the best of both worlds, a gear hub (to avoid the hasstle that many people report with rear derailer systems)..but that creates another avenue for problems, with the chain and motor combo.

The optimal solution is to find a lightweight 400-500 watt hub motor and put it on the front wheel which, I believe, has a 100 mm size on most 20" folding bikes. The bikes I am looking at are aluminum which means I have to make sure the front fork is at least steel, if not chromoly (would carbon fiber be stronger than chromoly for this purpose?). This would be a good way to distribute the weight more evenly on the bike but I am not sure I can find such a motor.

Is it possible to buy a chromoly fork (for under US$ 100) for a folding bike? Would I need something called a "torque bar" to help distribute the torque of the motor evenly over the fork? I know there is quite a bit of debate about the motor on the front fork topic.

 

[fitek]

Just an update, I had issues this weekend with my front wheel drive. The whole fork was flexing when I hit a bump and accelerated, and this caused the chain to fall off during a turn (I stopped at a stop sign, then accelerated, turn, and went over a man hole cover). I reinforced the fork with some extra steel.

I would use a BMX fork. The tubing has a larger diameter, so it is stronger, even with the same wall thickness. They are available in chromoly. I went to a local bike shop and was quoted $145 for a chromoly BMX frame and fork. I didn't ask about pricing for the fork by itself.

 

[Desertprep]

Thanks! I found a site that makes custom frames. I think it is called thick frames. I asked for a quote on a fork. Has anyone heard of this outfit?

 

[docnjoj]

Danscomp.com has a bunch of BMX forks at various prices.
Doc

 

[Desertprep]

but a bmx fork has no rake...just straight down. I think for even a moderate distance trip a bike like that is not going to be much fine to ride. If I find a new fork I would actually like to increase the amount of rake a bit.

 

[fitek]

Well the head tube angle will be set by whatever bike you have. Then there is some offset that the drop outs provide. I don't actually have a BMX fork, I have a BMX like fork that was used on a girls princess bike. That fork is pretty sturdy and the offset is about an inch or so. I think the head tube angle is something like 15-18 degrees, which seems to be pretty standard...

 

[Miles]

Maybe this will help clear the confusion? http://www.phred.org/~josh/bike/trail.html