Lightweight folder - build thread

[Miles]

The Urban Lite II looks like a deathtrap, IMO. The tubing all looks smaller than the beefy stuff on the Downtube, particularly the headtube and seat-tube.

Hopefully, the Downtube design has been improved since this:
http://www.bikeforums.net/showthread.ph ... -Mini-died

[Jeremy Harris]

That Downtube headtube is a design disaster! Who in their right mind designs TWO stress raisers into the point where the bending stress is at its greatest (the weld and the change in section)?

It would almost certainly have been better had they chosen to keep the thinner section running up a little higher, often it's the change in section that creates a much greater stress locally and causes failures like this.

[Miles]

That Downtube headtube is a design disaster! Who in their right mind designs TWO stress raisers into the point where the bending stress is at its greatest (the weld and the change in section)?

As I said in that thread "Whoever designed that should be locked up"

[TylerDurden]

Looks improved...

http://downtube.com/images/2010_Bikes/N ... G_1285.JPG

[JennyB]

I found a useful-looking thread on bikeforums about making a Swift lighter. It seems 9-10 kg is possible without going titanium-crazy.

Much of it should be applicable to other folders, but there is one important Swift-specific point: the seat post is vital to the frames integrity. Any replacement needs to be just as stiff where it enters the frame and exactly the same diameter.

[Jeremy Harris]

Thanks for that, Jenny. The table of component weights part way through that thread was useful - I've started a small spreadsheet to try and look at options (without becoming a weight weenie in the process...........).

One snag with the Swift is the cost. I've priced up buying a frameset and then adding all the components and it's a bit more than double the cost of buying an Urban Lite II and then throwing out the all the parts I don't want. Crazy, but true..........

I'm currently pondering whether paying a lot more for a Swift, just to get slightly better frame geometry, is worth it. It might be, as the Swift seems to put the rear wheel back to a more-or-less standard hybrid bike position, and so seems to put more weight on the front wheel, which would be useful. The question is, is it worth around £250 ($380) over the cost of the Urban Lite II?

[Cargo_Tom]

I've always been fascinated by folders

Have you considered a Tern bike? I have no first hand experience, but their "link" frames and especially their hinges seem well designed. http://youtu.be/A3DwLVAaYz4

Available in various configurations in the UK http://www.evanscycles.com/products/tern/link-uno-2012-folding-bike-ec032584#features

Their "verge" frame bikes are lighter but quite costly.
-tom

[Jeremy Harris]

Decision made.

The guys at Xootr have been great, and have put together a package of parts for me at a good price, so given the better geometry of the Swift, and the way that it uses standard bike parts, that's what I've decided to get.

Next decision is which motor. I have the slightly smaller and lighter QSWXH motor on my current folder, but am leaning towards the BPM for this one, despite the extra weight, as I get the feeling that I'm pushing the little 250 W rated QSWXH by running it at over 1 kW..............

I've always been fascinated by folders

Have you considered a Tern bike? I have no first hand experience, but their "link" frames and especially their hinges seem well designed. http://youtu.be/A3DwLVAaYz4

Available in various configurations in the UK http://www.evanscycles.com/products/tern/link-uno-2012-folding-bike-ec032584#features

Their "verge" frame bikes are lighter but quite costly.
-tom

Yes, I did take a look at them. They are really Dahon's, apparently Tern was set up by the son of the chap that runs Dahon. Certainly Dahon have the best hinge, reputedly, but TBH the hing on my present, no-name, Chinese alloy folder works OK.

[JennyB]

Decision made.

The guys at Xootr have been great, and have put together a package of parts for me at a good price, so given the better geometry of the Swift, and the way that it uses standard bike parts, that's what I've decided to get.

Next decision is which motor. I have the slightly smaller and lighter QSWXH motor on my current folder, but am leaning towards the BPM for this one, despite the extra weight, as I get the feeling that I'm pushing the little 250 W rated QSWXH by running it at over 1 kW..............

Looking forward to this!

[Ykick]

Dammit Jeremy, 'got me eyeing a used single speed here in Brooklyn...

http://newyork.craigslist.org/brk/bik/3169274866.html

[Jeremy Harris]

Looking forward to this!

Me too - thanks for pointing me in their direction!

Dammit Jeremy, 'got me eyeing a used single speed here in Brooklyn...

http://newyork.craigslist.org/brk/bik/3169274866.html

Bit of a bargain at that price, less than half the price when new. Black, too, which is nice, a colour they only do the single speeds in, I've had to settle for silver.

[Jeremy Harris]

Having now ordered all the parts, I thought I'd sort out some of the bits that usually get left till last, like wiring, connectors and all that messy stuff. I hate messy wiring on a bike, it just makes the thing look a bit Heath Robinson, plus it ends up getting dirty and is hard to clean.

The Swift design presents a few challenges when it comes to mounting stuff, so I have decided to fit the controller and battery in the same box, and fit that vertically to the handlebar stem. This leaves the seat post free to move up and down to allow the folding mechanism to work, something that would be harder to do if I fitted the battery to a seat post rack (as I've done on my current folder). I also decided that I wanted a way to quickly and easily remove the battery pack for charging, without needing to unplug wires. Putting the controller and battery in the same box eases some of the messy wiring problem, but I still need to connect a fair few wires between this box and the bike, the three phase wires, three Hall wires, +5V, 0V and the throttle wire, plus, maybe, a lighting wire.

I'm only going to use a small battery on this bike, as I don't need more than around 10 to 15 miles range. 222 Wh should be fine, as my current folder only uses around 15 Wh per mile and this one should be a bit better. I've settled on just two 6S, 5 Ah Zippy packs. These are small enough to charge on a low power charger through the balance ports, so I also need to bring out 13 connections from the battery pack to connect to a balance port charger.

So, in total I needed to bring out three high current phase connections, plus about 18 other connections. I decided to have a go at making a connector that would connect simply by dropping the battery/controller box into a cradle fitted to the handlebar stem. I have to say it worked rather well. I cut out a couple of bits of 1/2" Delrin, milled some slots to accept DB25 connectors for the low power connections and drilled holes to accept RC type barrel connectors for the phase wires. One of these two bits of Delrin will be fastened to the bottom face of the alloy battery/controller box, the other will be fastened to the bottom of the cradle that holds it. To remove the battery for charging (or security) I should be able to just lift it out and the connectors will just pull apart. Here's a photo to show work so far:

Batt box and connector.JPG (205.7 KiB) Viewed 359 times

The box that will house the controller and battery is the shiny thing under the connector, laying on it's back. The bottom face will be the one to the right of the photo. The box is about 2 1/4" deep and will just fit the Zippy packs inside with "just" enough room for a 6 FET controller and the wiring, plus some other gizmos. On the top face of the box, which is about 5 3/4" wide by about 2 1/4" deep, I plan to fit a display showing capacity remaining, power, voltage, current etc, a bit like an ordinary wattmeter, but with a memory, like the CA, so the pack can keep track of itself.

To charge the pack up I'll build another of the simple foolproof chargers I made for a friend, that will have a multicore cable that connects to the battery balance ports via the DB25 connector. I'll probably also make up a lead to connect this port to a Cellog, so I can occasionally monitor individual cell voltages to make sure things are looking OK.

The frame, motor etc won't arrive for a fair while yet, I expect, as all freight into the UK from abroad is being held up by the Olympic security stuff, apparently.

[Punx0r]

I like the idea of the drop-in connector

[Jeremy Harris]

Not much to report, but the parts have started arriving. First off the mark was Accountant, with the speedy delivery of the Speed Drive:

Speed Drive.JPG (111.4 KiB) Viewed 322 times

I can at least get on and make up the tooling and jig to chamfer the BB now, ready for when the frame arrives. I should be able to make up a couple of spacers, too, in case I find I need them.

Another surprise was a call from a courier telling me that the batteries I ordered from HK earlier this week (!) will be delivered this afternoon. I've never known HK deliver in a week, I wasn't expecting to get them for another two or three weeks, at least. Should resolve the "will they fit?" question (see here: viewtopic.php?f=3&t=42306).

[cal3thousand]

Nice connector! I'm trying to accomplish the same thing for my wife's bike/battery since the LVC breaker on methods' kit utilizes the throttle.

One question, how do you think the connection that you designed would hold up to an angled loading position? I ask, because the frame I am working with will require that the box be dropped in at an angle and they stood up right. (maybe 30 degrees from vertical max). You must have a vertical drop in path due to that parallel connector right?

[Jeremy Harris]

Nice connector! I'm trying to accomplish the same thing for my wife's bike/battery since the LVC breaker on methods' kit utilizes the throttle.

One question, how do you think the connection that you designed would hold up to an angled loading position? I ask, because the frame I am working with will require that the box be dropped in at an angle and they stood up right. (maybe 30 degrees from vertical max). You must have a vertical drop in path due to that parallel connector right?

I think you do really need to try and get the pack and connector parallel for maybe 1/2 inch or so before the connector mates fully home, but there's no real reason for it to be vertical. This afternoon I've added two stainless guide pins to take side loads when the connector is mated, and to help with alignment. With these fitted I'm pretty sure that you could run this horizontally, provided you could provide a means to hold the two halves pushed together.

I'll probably have the case mocked up tomorrow, so will be able to take some photos of the way the bits fit together.

[Caliban]

I was contemplating a similar connection scenario for one of my bikes. I have an oatnet style battery mount using a pelican box strapped to the legs of triple crown forks. If I mounted the controller in the side of the box then I reckon that I could bring together the wires from the handlebar controls into a waterproof DB 9 (or 15) which could plug into the battery/controller case. The only stray wires would then be the halls and the phase wires which I could run through the frame for a very tidy look. I had considered a panel mounted 4 square Anderson connector (with the extra pin used for orientation) and a screw lock 5 pin DIM plug for the sensors, also bulkhead mounted on the battery box. A similar arrangement at the wheel would allow for easier wheel removal. I especially like this way of wiring as the "electronics module" can be unclamped and removed in less than 2 minutes. (if you have the tools).

[Jeremy Harris]

The nice thing about using miniature D series connectors is that they are very easy to mate and de-mate, the forces needed, even for the DB25, are quite low. Each pin on a miniature D is OK for 1A, so they are ideal for all the low power connections.

I've used 4mm RC type bullets for the power connections, which are are OK, but do need a hefty tug to get them apart.

[cal3thousand]

The nice thing about using miniature D series connectors is that they are very easy to mate and de-mate, the forces needed, even for the DB25, are quite low. Each pin on a miniature D is OK for 1A, so they are ideal for all the low power connections.

I've used 4mm RC type bullets for the power connections, which are are OK, but do need a hefty tug to get them apart.

I ordered some of these pogo pins a month ago, but I'm not sure if I have large enough pins. The ones I ordered were pen tip sized connections. But since the throttle connections don't require much current, I think I could get away with them.

Here's a link the manufacturer's link

http://www.digikey.com/product-detail/e ... ND/2242404

If this will work (I suspect so), I just need to get some flat contacts for the battery side as these will stay on the bike at the junction.

[cwah]

Jeremy, this connector is crazy nice!!!


I waaannt the same!

I use for now an ATX 24 pins connectors to have everything connected at once but I noticed the connector gets hots very quickly. So it has load of resistance even if it's made for computer power supply.

How did you manage to cut the delrin (black box that contains the connector) to accept the connectors exactly where it needs to be? Is there an easy way to do so? I'd love to have the same thing. I'm thinking about potentially using a polycarbonate sheet, and use a drill to put the bullets connectors. But how do I drill it to accept the DB24 connector?

Thaaanks

[Jeremy Harris]

One of the joys of having milling machines in the workshop!

The cut outs for the DB25s could be cut by hand, if you decided to use three bits of plastic rather than two. The middle bit would have a slot that was a clearance fit for the whole connector, with the outer bits having slots just big enough for the back of each one. I drilled and tapped holes in the Delrin for the screws, but you could just as easily fit longer screws with nuts on the back. The blocks were clamped together and drilled/milled as a pair, to ensure perfect alignment. The holes for the high current pins were drilled undersize and then reamed to a very tight push fit. I'm planning on adding some adhesive on the back to make doubly sure that these connectors stay in place.

[cwah]

Thanks jeremy. Good idea about slicing the plastic in 2 part to fit the db25. I'm now thinking about using the remaining polycarbonate sheet I have from my battery box, a db25 and potentially use a complete HTX 4 mm bullet connector with the plastic cover. As this cover helps the connector to fit in the hole. It could be quite practical to keep that.

[Jeremy Harris]

Another way of making a high current multipole connector that I looked at was to glue some Dean's Ultra connectors together. These stack side by side, in alternate pairs, to form as big a connector as you need. The only downside to using lots of Deans plugs/sockets is the relatively high mating/de-mating force needed. This may or may not be a significant problem.

[nieles]

these connectors would be a really elegant solution for the power connectors. not cheap though

they are available in 2 types of male plug and one type female

[Kin]

I'm a fan of http://www.citizenbike.com, and have the http://www.citizenbike.com/catalog.asp? ... duct_id=24. It's a bit too beefy to some extent on the alluminum, so it could be a bit lighter. Also, the standard gearing is set too low at top speed . (probably ~18mph, I've not checked or bothered calculating, but not >20mph)


I think you may have actually already chosen your folder, but I look forward to seeing how this goes.