Dahon Speed D7

[RVD]

Hi Everyone,

This started with me getting bored on Black Friday. Everyone else seemed like they were out shopping but I don't like big crowds of people, waiting in line, etc. so I just went online as usual to all of my local bike shops, etc.

I noticed an ad on performance bike that said 20% off your entire purchase. I started browsing around. Unfortunately I already own 4 bikes, my 5 year old son owns 3 bikes, my wife has a bike already, etc...but I did notice that they had some folding bikes. Hmmm...that's a bike that I don't own. I then started thinking about all of the ways that I can carry around a folding bike in my trunk at all times to whip it out to go for short rides, errands while at work, etc.

Too bad I knew almost nothing about folding bikes so I did some research. In the end, I chose the Dahon Speed D7.

This is a chromoly frame, 7 speed bike with 20" wheels. As far as I can tell, it's a pretty well made bike. At around $640 it's also not a cheap bike. But with 20% off it was $512. But then I had to pay $30 for shipping and I also had to pay tax so it ended up at $590. Not the best deal around but I figured it wasn't too bad either.

It took about 2 weeks for my local Performance to get the bike and assemble it. I drove over to the shop and picked it up. I was immediately happy. Playing with this thing was sort of like an EV grin over again. Probably just me, but it's just cool. I folded it up, put it into the trunk of my car, and away I drove.

The guys at the shop knew almost nothing about the bike. It was assembled but the guys there had no idea how to fold it, etc. It was fairly self explanatory though.

The next thing to do was figure out how to make it electric!

I had a few rules:

1) Bike must stay foldable. After all, what's the point if I make it electric and it can no longer fold?

2) Bike must be as light and as portable as possible. After all, what's the point if the bike is so heavy that you can't actually carry it around?

3) Bike must be as stealth as possible.

4) Try to conserve costs by reusing what I already have. i.e., going out and buying all new stuff is cheating.

So then it came time to buy...

[RVD]

So next came shopping...

I wanted to choose a small rear hub motor. Some potentials were the e-bikekit 350 watt geared motor. Others were motors by cellman, bafang, cute, etc. The crystalyte 209 was another candidate but I only saw this in front hub and didn't really know if they made rear hub motors. Either way, it was all way too much work to research. In the end, I went with the e-bikekit because I have a e-bikekit 26" direct drive and it's been working well. I also like the guys over there (Jason always gives great service, etc.). This was my 3rd purchase from them.

E-bikekit was having a holiday sale of 15% off everything. Then on cyber Monday for 1 day, they were having free shipping. So I ordered on cyber monday to get 15% off and free shipping. Cost was $170 for the wheel.

The bike came with stuff like fenders, rear rack, etc. I went to look for a bag to fit on the rear fenders.

REI was having their holiday sale so a $50 bag was $35. It looked like a perfect fit for the rack. Since the folding bike is so low, you have to be careful with panniers because if the bag or panniers are too wide, it will disrupt your pedaling. In addition, if the bag is too wide, the bike won't fold (and I don't want to have to remove the bag every time I want to fold the bike).

For my controller, I decided to reuse a Lyen 9 fet sensored controller that I used with my old e-bikekit direct drive hub motor before upgrading that system to a Crystalyte HS3540. The old e-bikekit motor is used as a backup now (along with a sensorless controller by Lyen).

For batteries, I chose to go with lipo. I already have a decent lipo stash of 6s and 2s 5000 mah packs. For my normal ride, I usually ride lipo of 14s or 18s on my direct drive kit. However, for this kit, I wanted to experiment with going from 6s, 8s, 10s, and 12s just to see the differences in power. I am not necessarily looking for speed but of course that's all within reason.

For electronics, I decided not to buy another CA. Instead I decided to use one of my leftover watt meters (turnigy).

As for wiring, etc. I already have a lot of extra wires, andersons, etc.

[RVD]

Builds rarely go 100% smoothly and this one didn't either.

I received the 350 watt motor and wheel from e-bikekit. When I tried to install the wheel, it was tough. The rear dropouts are 133mm on the Dahon while the wheel is 135mm. 2mm may not sound like much but when you're trying to use brute strength to get that wheel to fit, it's tough. I have no experience widening dropouts so I muscled it to get the wheel to fit.

I had some complications with installing the wheel so Jason at e-bikekit sent me another one and I returned this one. To make a long story short, I got the wheel to fit and the wheel works.

Overall, with some back and forth, this build took about 30 days from the day that I ordered the Dahon to the day I rode it on the street for a test ride. It wasn't so bad though because it took over a week or so for the bike to get here. So I'd say that from the time I had the bike in my hands, it was about a 2 week or so build.

I had to buy a new rear tire. I went with the schwalbe big apple. I also got a tube. I also got velox rim strips (I had the rubber band ones that the bikes come with).

I decided to go with a thumb throttle. I didn't go with a half twist because the bike already has twist gears on the right (for the 7 speed). I didn't want to have 2 twisters. So I bought a new thumb throttle from Lyen. I had an old 3 speed switch already so I hooked that up as well.

I had an old bell so I installed that too.

Anyway, it's all done so time for pictures...

[RVD]

Ok these pics aren't the best.

The masking tape is ugly and I'll remove most of it but it's there for now for extra padding in certain areas of the bike where there is a lot of contact during the fold. I also use it for placeholders for getting the best fold. Yes, I will probably remove most of it soon.

I took them indoors with my cell phone but whatever...here goes.



Overall view of the bike



Closeup of the rear hub motor, rack, and bag



Closeup of the thumb throttle and 3 speed switch (and the bell)



Closeup of the controller and wiring



Closeup of the rear hub motor and torque arms. Did I install this torque arm correctly? I don't think so but they wouldn't really fit well on the other side of the bike and they wouldn't fit on this side except for right there. I also have Dr. Bass's torque arms but those were way too big to fit. Any suggestions on torque arms? Is this way really bad?



Another view from the back



View with the kill switch installed. If I just pull on that red wire that is under the saddle, it will cut power to the controller and stop the bike (in case of runaway throttle, etc.).



Closeup of how the kill switch works. As you can see, the thin red ignition wire is not hooked up directly to the red square unit. It is hooked up to that other red wire which is hooked up to the long U shaped red wire that goes under the saddle. Pulling out the red wire under the saddle stops the flow of + to the thin red wire which is needed for power on the controller.



Of course the bike still folds!



Another view of the folded bike. It takes roughly 15 seconds or so to fold/unfold the bike.

[RVD]

Regarding battery, I am running on 12s lipo.

I tried it with 6s...unusable. I don't have a speedometer hooked up but it was probably going about 10 mph (or maybe even less).

8s...virtually unusable. Probably went around 12 mph.

10s...decent. Probably went around 15-18 mph. This is actually my recommended build for most beginners, etc.

12s...pretty good. I think it goes around 20+ mph. It's not as fast as my full sized bike but this is good enough and has some decent power. I don't really find myself wanting much more.

The rear bag can hold 12s3p although 12s2p is much better. 12s1p is very light but probably a bit too low in range (I'd guess that it will get around 8 miles distance).

[amberwolf]

Old innertubes would make a good replacement for the masking tape to protect the frame/etc from contact during fold. Black zipties to hold them on, if you have to slice them. If you have skinny enough tubes, you might be able to stretchfit a piece onto the handlebars for the cable rub area, and avoid using zipties up there where you'd stare at them all ride long.

Teflon tape is another option, that wont leave black marks on anything as it ages (which the tubes might), but you'd probably want to put it on both points that contact together, so that if they rub you don't wind up with shiny spots worn in the untaped contact point. It's also generally translucent.

Kapton tape is another option but it sometimes tears easy from a starter scratch.

[cwah]

Nice build RVD. I was thinking about having something similar but with a bafang 48V500W overvolted to 66V to reach 25-30mph.

Have a few questions:
- is it still easy to roll once folded with the electric kit installed?
- why don't you directly put the controller inside the battery pack? So it would be neater. And you could remove both the controller and battery together from the bike if you ever have to lock it outside
- is your motor efficient at 20mph? Is it a geared drive?

[RVD]

Nice build RVD. I was thinking about having something similar but with a bafang 48V500W overvolted to 66V to reach 25-30mph.

Have a few questions:
- is it still easy to roll once folded with the electric kit installed?
- why don't you directly put the controller inside the battery pack? So it would be neater. And you could remove both the controller and battery together from the bike if you ever have to lock it outside
- is your motor efficient at 20mph? Is it a geared drive?

1) Yes, it still rolls. However, the Dahon in general doesn't really roll all that well when folded (Brompton is better). Most Dahon owners don't actually walk around rolling the bike when it is folded. They usually just roll the bike as an actual bike and then fold it when they need to put it in their car, train, etc. There is a bit of a wobble so it's not totally smooth. However, the electric motor wheel and regular factory wheel are the same in that sense.

2) The controller usually gets warm and can get hot so it needs some air cooling. I'm afraid that it won't dissipate enough heat if it's inside the bag.

3) Motor is a geared drive. I haven't run enough tests to see if it's efficient or not.

I plan to ride this folder on Friday. On Friday I have a dinner to go to after work so I will be riding "foldy" to work. Then my wife will pick me up at my office before dinner and I'll throw the bike into the trunk folded up.

In the past, I usually had to leave my full sized bike here in the office and then come in over the weekend to ride it home or borrow the wife's car to drive to work and then put the bike in the back seat with the top down (convertible) to bring it home.

I have one of those bike carrier things that attach to the rear trunk but with an 80 pound bike, I'm afraid that the weight might mess up the trunk on a big bump, etc.

[cwah]

1. hehe I would too prefer to fold the bike only when it's needed. However, in a lot of public places, bikes are forbidden. When they are folded, they are tolerated. That's why it's so important for me to have a bike that rolls once folded or I'll have hard time carrying the bike.

And if the bike look like a luggage that's the perfect way to carry it around
http://www.youtube.com/watch?v=9ic6cssX_50

2. For the controller in the bag it would just be more stealthy. I was wondering if there was any possibility to do that. Without the controller outside (and the red cable), we wouldn't spot it's an electric bike!

Looking forward to hear more about this bike, it may be my inspiration for my next bike

[Alan B]

Nice bike. Someday I want to set up an electric folder.

Is this the one with the bad throttle?

How are you going to combine the Magura twist throttle with the twist shift?

[RVD]

Nah the bad throttle is the tidalforce s750. That bike had the same problem but I dont shift gears much so it is ok.

[Alan B]

On my ebike I put the twist shifters on some short bar-ends so they are still available but out of the way.

[beast775]

nice build rvd,why so much heat from a 9 fet? the torque arm will be fine if its flush with the frame..my next build will be a folder but very old and wierd heavy kind 16 inch wheels,1968 rsw raleigh.not much of a folder but tank like heavy.mine will get similar ingredients but different batteries, controller, motor up front.ive always like folders,and dont even know why?

[RVD]

hmmm, i haven't really tested the bike that much out on the road so i don't know if the 9 fet will get hot or not. is it pretty safe to store in the bag? i always thought that controllers needed to be out where the air can cool it so i always build these where the controller is somewhere with a lot of air circulation.

the batteries also get a bit warm sometimes so i just figured it'd be best if it didn't get too hot in the bag.

but other thoughts?

[RVD]

Ok I moved the controller into the bag. I'll be riding on this bike tomorrow to work so I'll run some tests to see if the controller gets hot, etc.



Overall bike.



The rear part of the bike



Closeup. As you can see, the throttle wire wasn't long enough to extend from the handlebars to the rack so I had to punch a small hole in the rear bag to allow the connector to go through the bag to connect to the throttle. The 3 speed switch is barely long enough to fit.

The result is a much cleaner build. I also removed some of the masking tape that was on the bike.

[cwah]

Amazing RDV!! Really stealthy, a true inspiration for my next build (if you controller doesn't get hot as your may have this problem). What I was planning to do is also to have a removable controller and batteries inside the bag. So when I park the bike I can just remove the bag to secure everything.

You should show your bike to people and ask them "Have you noticed something special about my bike" to see if they can spot the electric motor/batteries

By the way, what is the added weight to the rear side of the bike with both the motor and the batteries? Is it stable enough to have all the weight on the rear wheel?

[RVD]

One of my rules in building this bike was the keep the weight down. I haven't weighed the bike but the rear motor is only about 7 pounds (350 watt geared). I would guess that the entire rear wheel is no more than 9 pounds max with the rim, tire, etc.

Since I'm using lipo, each 6s 5ah lipo pack is about 2 pounds. if i'm riding 12s1p, it's about 4 pounds or so in battery.

so if you add in the controller and some extras, you take a 27 pound factory bike and make it roughly 40 pounds (slightly less probably because the 27 pounds included the factory rear wheel).

But the short answer is no, the rear isn't too heavy. It's stable and nice. I can actually carry the bike still while it's folded (although I wouldn't want to carry it too far).

Today I rode this bike to work. It's a fun ride but since today was the inaugural ride, I kept it at speed 2 on my 3 speed switch. I was also careful not to go WOT from the stop position, etc. to ease it in. I set it up with a 12s2p pack so 44v 10ah lipo. Riding very conservatively (under 20 mph) for my 16 mile commute, according to my watt meter, it used:

227 watt hours
4.87 ah
44.25 volts ending voltage

I pedaled here and there but 90%+ of the time I was not pedaling. The route is mostly flat but has a few small hills here and there (but nothing difficult).

The only issue that I had today was earlier as I was leaving my house, the rear wheel actually dropped out of the dropouts! I think this is because I didn't have a nord-lock on one side. I also didn't really tighten the screws that hard when I did the initial install. I didn't check the bolts regularly so they may have been loose I guess.

So I re-inserted the wheel, put a nord-lock on the non drive side (drive side already had a nord-lock) and tightened pretty much as hard as I could by hand.

I rode to work in caution mode so I stopped every 2-3 miles to check the controller in the bag (warm but never hot), motor (never even warm), batteries (slightly warm but normal), and dropout screws (stayed tight).

I wasn't riding fast and everything made it intact, etc. I will increase speed as I get more comfortable on the bike.

[cwah]

Wow that's great. Also perfect bike now then. Can you do wheelies?

So 227Wh for 16 miles commute, your efficiency is at 14.19wh/miles (8.87 wh/km). At similar speed (throttle only), Kepler BMC uses around 8 wh/km and SamTexas MXUS uses 8.34 wh/km. So you're pretty much in the average

But at 20mph, I would get bored quite easily. My actual bike has a max speed of 22 mph, and sometime I'd love so much to go faster...

Waiting to know more about your efficiency at higher speed. My next bike is going to be strongly inspired by you

[RVD]

Nice to hear. It definitely does get boring at 20mph. My other bike goes about 30 mph when I commute to work and I can get it up to 40 mph+ if I really want to (although for me, it's kind of scary going that fast). Even at my fastest this bike tops out at about 25mph. I don't know if it's really safe for folders to go much faster than that. It is definitely convenient though to have a bike that folds up and fits in your trunk and can be easily taken on buses, subways, friend's cars, etc.

This is an interesting build because it's not for everyone and definitely not for everyone in this forum where we're all about maximizing speed, etc.

[SamTexas]

RVD, nice looking folder.

... and SamTexas MXUS uses 8.34 wh/km. ...

Mine is 8.54wh/mile (5.30wh/km) at an actual moving average of 17mph (23mph top speed.)

[RVD]

Sam, I haven't seen any other pics of small folder conversions (other than the bionx type ones sold commercially). Do you have pics of yours?

[SamTexas]

RVD,

Mine is a mountain bike
viewtopic.php?f=4&t=29356

Kepler's is a road bike. I don't know why cwah use mine and Kepler's as an efficiency comparison with your folder. Anyway, have you had a chance to find out the exact weigh of your electrified folder? Enjoy.

[cwah]

I just added these bike efficiency because they are using geared motor. I though the efficiency would be quite similar. My conhismotor efficiency bad compared to yours at 14 wh/km.

[matchpoints]

I've got a D7 as well. I like how stealthy it looks. Is it possible to get the speed up to 30-35mph using that motor?

[cwah]

Matchpoint, I don't think you'll be able to reach 30-35 mph on a 350W motor. To reach this speed you need at least a 500W motor. Bafang or Mac. If you need more speed, go for a Mac. In term of motor size, you'll have Mac > Bafang > 350W motor (ebike Kit, MXUS or Cute)

RVD, I'm also planning to convert a dahon speed now. What torque arm did you use? I'm thinking about buying one too