Rigidity of donor bike

[Shahmatt]

Hi all,

I'm considering building a cheap folding commuter bike with the converter kit. I'm not good mechanically (I can change a tyre and align my V-brakes but that's about it). And I don't have many tools. So I'm looking to buy as complete a bike as I possibly can before attempting the conversion, as opposed to building it up from scratch with a frame.

I currently commute with a folding bike. The folding frame has been immensely useful to me since I can put it in a train or bus if I am stuck in the rain somewhere. My bike also has a 3 speed internal gear hub, which is great for the stop-start riding I have to do in the city. So I'm hoping I can get my future cruzbike to be able to do the same.

I'm trying to make my ride a little easier and improve on the range - presently around 8 miles before my rear starts to feel sore.

So I've found the following at a Chinese website: http://www.cnjalon.cn/product/244677565-200141975/20_folding_bicycle_JL_Z20148.html

So what I like about it is the:
1. Full suspension
2. Shimano Nexus 3 speed hub - so I don't have to buy it separately
3. Folding frame

The cost of the entire unit is around $200 excl. shipping. My main concern is the frame quality. I'm not very sure what type of rigidity I can expect from something of this price - though good quality stuff from the mainland can probably be had for cheap prices anyway.

My question though is should I care? Since the MBB design would only necessitate stiffness at that front triangle, and most of that's from Cruzbike anyway and should be ok, would a flimsy rear bit make a difference? Also it doesn't have fenders - but maybe I can make do somehow. Possible issues regarding the donor bike would also be greatly appreciated.

 

[Eric Winn]

Minimum order quantity: 200

Minimum order quantity: 200 pieces - I don't think you are planning on buying 200 of these bikes so you might want to look at Chris Blessings thread here:

http://cruzbike.com/speedone-fs-mini-velo-suspension-folding-frame-set-20406

The one I found is still listed on eBay:
http://www.ebay.com/itm/Speedone-LFS-Mini-Velo-Suspension-Folding-Frame-Set-/271038973035

Here is the one Chris used:
http://www.ebay.com/itm/Speedone-FS-Mini-Velo-Suspension-Folding-Frame-Set-/271058421551?

Or Charles Plager's Cruzigami thread here:
http://cruzbike.com/introducing-cruzigami-mantis

Here is the bike Charles used:
http://shop.origamibicycles.com/Mantis-3.htm

Charles and Chris know more about the conversion kit than I do - I haven't used it but this might be another viable candidate:
http://www.citizenbike.com/catalog.asp?product_category_id=1&product_id=24

And here is another of their bikes for $199:
http://www.citizenbike.com/catalog.asp?product_category_id=1&product_id=1


I believe the main issue with a folder is the conversion kit seat and how it attaches. The seat mount ma interfere with the folding and require you to remove part or all of the seat.

Let us know how it goes - photos are always appreciated!

-Eric

 

[Shahmatt]

Thanks for the reply

Thanks for the reply. I did indeed see the order quantity. But I'm hoping they'll sell me an individual unit. Surely it must just be a matter of money.

Chris and Charles's work is brilliant, and I've been through their stuff. Lots of useful information there.

I prefer to convert a fully constructed bike. I don't think I'd do a very good job building from scratch. Also there's the expense. I understand that purchasing individual units may cost more than if I were to get everything together in one package.

I want a bike with an internal gear hub. These are useful in traffic. Trouble is they can be beastly expensive if bought separately. So I've been trying to find one stock. So my requirements are -> folding, IGH, suspension and fenders.

Also, they've got to be able to send it to me in Singapore.

Unfortunately the Mantis and Citizen use derailleurs. I would prefer to avoid this if I can.

So are there any obvious problems with the frame? Would the seat fit do you think? Is a mediocre frame a problem after conversion?

 

[Charles.Plager]

I'm a little worried about

I'm a little worried about where the seat pan will go and what the angle will be, but I'm sure that could be worked out.

I think (but could be wrong) that Chris is located in Singapore. It's worth PMing him to see what advice about obtaining frames, etc. he has. Yes, you're right that buying piece meal is more expensive, but that's only if you don't end up replacing the pieces that come on the original bike.

Cheers,
Charles

 

[jimbo3b]

Stiffness should be fine

I've put my kit on two different donors, with vastly different springs. The one with the weaker spring was mildly irritating, as I would pogo up and down after a bump. My new one is stiffer, and it's better. However, I believe your assumption is correct that the stiffness that matters (and where all Cruzbikes excel) is in the front triangle, and it should end up quite stiff.

 

[Shahmatt]

@ cplager,
Thanks for the

@ cplager,

Thanks for the info on Chris. Maybe I'll give him a buzz.

I guess that I'm trying to minimize the need to replace parts and try to save some money. Hopefully the IGH will satisfy, because that's likely to be the most expensive component on this bike.

On my current upright bike I believe I have the same, if not similar, Shimano Nexus 3 speed hub. I do not have a front derailleur, just a single 46T cog. It has a good lower-bound that makes climbing and controlling at low speeds very easy - quite important in traffic and sometimes amongst pedestrians. But the upper limit leaves a little to be desired. I top out at around 18mph - pedalling furiously.

So I am considering a wider range hub. But stock bike options with better hubs are few. As you've said, piecemeal is more expensive and I'm trying to stick to my budget.

Then also, there's the improved efficiency of the Cruzbike to consider. Would you reckon that, with a Cruzbike, I could raise that lower-bound just a tad bit and not compromise too much on hill climbing effort?

If not then I guess the next option would be to convert the front cog either into a derailleur or Patterson CVT.

@ jimbo3b,

Thanks very much for your input and confirming about the stiffness. I do not know much about the quality of suspension. I wonder if the suspension can be swapped out and replaced with something better in the market. Have you tried doing this?

 

[hamishbarker]

Looks like the headset is a

Looks like the headset is a threaded 1", so you would need a 1" threaded to 1 1/8 converter, (about $10-15 on ebay). That's assuming that the original folding steerer is removable. Downside is that with a cruzbike you won't be able to fold the handlebars down, because it must be rigid enough (by using the Cruzbike steerer extension tube which comes with the kit.).

It looks likely that the seat support bracket will need to be attached on each side of the hinge, which will make folding a bit of a pain.

It may be possible to release one of the rear shock attachment bolts and swing the rear swingarm under the frame, a bit similarly to how a Brompton folds, so perhaps that would make up for the loss of main hinge function for quick folds. Perhaps a quick release pin could be used in place of that bolt.

Another point worth investigating (but not a show stopper if you can get mechanical help (possibly including cutting flat steel!) is, what the rear dropout spacing of that donor bike is? Some folders have smaller rear dropout spacing, while the front fork is likely to still be 100mm, so that may complicate the use of the cruzbike conversion brackets which are normally used to convert the 100m front dropout spacing to 135mm (as well as provide the mounting points for the new front chainstays.

Rather too many questions I guess.

 

[jimbo3b]

Swapping Suspension Components

Swapping out suspension components is a big hassle for the short shocks like you're looking at on the donor bike. The cheaper acceptable shocks sold online are in the $100 range, and the good, light ones are much more than that. But the main issue is finding a short one.

On the cheap mountain bikes that most people convert, spring stiffness is adjustable by turning the backing nut. That doesn't look like an option on your proposed bike.

However, I think you'll be fine. The folding bike will be designed for a weight ratio of something like 60% rear 40% front, and converting it to a Cruzbike will switch that ratio. Therefore, it will already feel like the rear shock is a little more stiff than it would be in stock configuration. This is a double-edged sword: the downside is that if you are heavy, then you'll be riding with the front shock compressed most of the time, and bottoming out all the time.

If you think the bike will work for you, then don't worry about suspension. Build it, ride it, and at worst you'll have to find a machine shop to pull apart either the front shock or the rear and insert a stiffer spring.

 

[chrisblessing]

Folding Cruzbike

Hi Shammatt,

I'm in Kuala Lumpur, and, as you've noted, put together a pretty nice folder that both climbs and has respectable high end. The frame to which Eric Winn referred (see his post above) was shipped to me from Hong Kong. Two advantages of the Speed One frame are: 1) seat placement and 2) rear suspension.

Although the frame is square rather than round, I had no issues securing the seat, although I do have to remove it to fold. As I don't use hose clamps it only takes a moment to remove. The hinge is below the seat and doesn't compromise the positioning of the seat at all.

Secondly, the rear suspension of the Speed One is superb. It's so well integrated with the frame you almost don't see it. I don't have front suspension, and I can't imagine I'd want it.

IGH is certainly an option. I'm using a Nuvinci N360, which is a bit heavy, but it's a gorgeous piece of machinery. With a gear range of 360 gear ratio it would be ideal for Singapore, even with a single chainring. Possibly a Sturmey Archer 8 speed, with a gear ratio of 325, would work as well, at less weight and cost. Either choice would eliminate the derailleur.

A local bike shop could do the assembly for you. Aside from the conversion kit itself, everything about your bike would be off-the-shelf components. You could continue with your own basic maintenance as you do now.

As for the bus and train, I don't know. But, after popping off the seat, I can bag my bike pretty compactly and lash it to the back of my 150cc motorbike with ease.

Good luck in making a decision. You'll find a tremendous amount of encouragement and support on this forum. And should you find yourself up north drop me a line.

Chris

 

[Shahmatt]

Thanks for comments

@ Hamish,

Points to ponder. I was willing to compromise on the handlebar fold but not being able to fold at the main hinge is a problem. Would fitting the seatpan in front of the hinge be too close?

@ Jimbo3b

Thanks for the info on the springs. Having never owned a suspension bike before I'm afraid my knowledge is rather lacking, and I hadn't thought about the weights being redistributed as such. From what you say I imagine that on the Cruzbike the tyres will wear at the same rate - the rear slower and the front faster, in comparison with regular uprights. So replacements will need to be done on both tyres at once, as opposed to just the rear every so often. That's more convenient I think.

@ Chris,

Indeed your recumbent looks like a fine, purposeful machine.

The rationale behind the front suspension was to improve road holding on rough terrain - in my case, roads under construction and roads covered with steel plates. Maybe this could be mitigated with wide big apple tyres or the like though.

Or, if the "loop wheel" (look it up) were to go into production soon I might consider that also.

Edit: Sorry they appear to be in production now. See here:
http://www.loopwheels.com/shop/

I have read much about the N360 and I am certain it is a dream to use. I am a huge fan of IGHs, but in general I prefer the simplicity of 3 speed hubs to 7 or 8 speed ones or even the Rohloff. The N360 is not unreasonably priced but pushes me just out of budget right now.

On your frame, would you say that the square shape/rectangular of the top bar is an advantage in providing lateral stability to your seatpan? Or does it not contribute at all?

Incidentally all of this talk has given me pause for thought on budget, and I may revise to accommodate what is needed.

I will consider putting together a bike from scratch and talking about this with my LBS.

I am looking at another frame. Will post up soon if it seems to match what I want.

 

[chrisblessing]

Nuvinci IGH

Hi Shahmatt,

Just a couple of notes: done right, your seat can be easily removed to allow folding. It may in fact be preferable to leaving the seat on. As for the simplicity of the hub, I believe that that Nuvinci is profoundly more simple than any geared IGH. It has far fewer moving parts and no gears to break or wear. And it's far, far cheaper than the Roholff. More importantly, eliminating "stepped" gearing means that the bike can "shift" under load, with no loss of momentum.

 

[Shahmatt]

On front and rear suspension

@ Chris and others,

Thanks for all your comments so far.

I've been wondering about the front and rear suspension.

How do you reckon your weight is distributed between your tyres?

Jimbo3b suggests 60-40 in his previous post, front to rear. I imagine that this might vary dependent on the height of the rider.

I am not tall (around 5"8) and weigh 75kgs. My guess is that I would be seated nearer to the steering column. Would this mean that my weight will be more heavily distributed towards that front tyre? If so, would a front suspension fork hardtail be more suitable?

 

[Charles.Plager]

Hi Shahmatt,
I have my seat

Hi Shahmatt,

I have my seat very close to the steering column, but have the seat angled quite low so my head is just about perfectly over the rear wheel (I have a lay back seat post). I'm significantly heavier than you (~95 Kg) and I find my (cheap) front suspension fork isn't bottomed out (but it's close at times). I think it still adds something.

I don't think you'd go wrong not having a front suspension fork, either. Chris' bike that has rear but not front suspension isn't a bad choice at all.

Regardless, you do want to make sure your center of mass (CoM) isn't too far forward as it is still possible to fly over the handlebars on a SWB bike (if I'm sitting up on the Mantis and braking, I can feel the rear wheel losing contact with the road and that's not entirely pleasant).

Cheers,
Charles

 

[chrisblessing]

center of mass

Charles, I've made an art of flying right up to the entrance of my condo, jamming the front brake and going right into a standing position. It's greatly entertaining to the Bangladeshi security guards and whichever tenants happen by.

 

[Jake]

OP said "So I am considering

OP said "So I am considering a wider range hub."

I'm not aware that 3 speed hubs come in wide and narrow ranges, but it's cheap and easy to change the sprocket to a smaller, or more likely, larger one resulting in all 3 gears being relatively higher or lower.

One thing you should be aware of though is that, in my experience, recumbents require wider and more populated gears than uprights - that same 3 speed that served you well on your current folder might be a bit lacking on a 'bent. Big gaps between gears results in peddling rates (cadence) outside of the normal comfort zone. Err on the side of peddling too fast rather than too slow is the best advice I can give you if 5, 7or 8 speed hub gears are out of budget,

Jake

 

[chrisblessing]

Gears

Jake is on the money regarding the applicability of an IGH on a recumbent. I'd also add that the "steps" between the gears can really be bothersome on a recumbent, particularly in climbing. The more gears/smaller steps, the better (or, in the case of the Nuvinci, no steps).

 

[Shahmatt]

Noted on IGHs

Noted on IGHs.

I read up on the Nuvinci and have decided, despite the weight, it's probably a good way to go. Thanks Chris for the suggestion.

My aim is to try to achieve a gear range of 37.4 to 134.5 inches with 52T and 13T cogs. Or similar.

 

[John Tolhurst]

That is a total range of

That is a total range of 3.64. A 50/34 and a 32/11 will give you 4.15; so you'll easily get the range, its just the spacing you need to manage. on a 700c wheel, my favourite for my riding is 50/34 and a 12/25. That only gives me 3.06, which I could get on an 11/34. but I wouldn't have the close spacings that I like.

 

[Charles.Plager]

How 'bout a Nuvinci and a

How 'bout a Nuvinci and a triple? Not as crazy as it sounds...

(You just need (1) chain tensionner and (2) make sure the granny gear on the triple isn't too small for the Nuvinci, but that shouldn't be too hard).

In any case, I hope I run into you guys with the Nuvinci - I really want to try that puppy out.

 

[chrisblessing]

Nuvinci n360

If the Sheldon Brown calculator is to be believed, I have a gear inch of 15-99.5. That's with 20x1.25 wheels and a 15t sprocket on the Nuvinci, and a Patterson-Metropolis, equivalent to a 28 and 45.

I folded and loaded the little guy onto my motorbike this morning to meet some other folks for a ride, and it was great to just unfold, mount the seat and be ready to go in about 10 minutes. Not as quick or easy as prepping my Dahon, but a much nicer ride.