cplager

Hi,

Does anybody know where I can find a rear rack for Birdy or Bike Friday that has wheels so I can roll the bike when folded? Most racks for Brompton's are too small.

Thanks,
Charles

joey buzzard

Paul from Origami Bikes might be somebody worth asking. He's currently developing a wheeled rack for his company's upcoming soon to be released 20" Swift folder. The rack will be specially designed for the Origami Swift, but it'll possibly work with a Birdy or a Bike Friday as well. Worth enquiring.

https://www.bikeforums.net/folding-b...n-classic.html

Pinigis 

we are still working on it. I may have photos this week.

cplager

Please do post on this thread when you do (even if you just post a link to another thread). Thanks!

Charles

cat0020

https://www.aliexpress.us/item/3256801565585320.html

https://www.aliexpress.us/item/3256803046026261.html

cplager

Both of these look to be the right size, but neither of these has wheels nor any easy way to add them (unless I am missing something).

tds101 

This is from Tern, but it's too expensive IMO:https://www.ternbicycles.com/us/acce...transit-rack-m

cplager

Agreed.

I'm hoping I can find something to use with a Bike Friday when the real wheel is folded 180 degrees (like Brompton does).

CEBEP

Birdy racks are proprietary ones and afaik are different for Birdy Mk 3, 2. I’m not sure Birdy rear rack will fit other bikes as the one I have on my R&M Birdy Mk 3 Touring is designed to collapse once bike is folded. You can see this rack in this review, wheels are mounted at the end of this rack. If that’s what you are looking for you can order them from R&M dealers. There are other options on Aliexpress from other manufacturers but I have no experience with them.

cplager

Thanks. I think you're right that a Birdy rack would not work for a Bike Friday.

I see various racks on Aliexpress, but as far as I can tell, all of them are sized to fit Brompton's smaller wheels.

CEBEP

Maybe it’s a stupid question but did you ask Bike Friday? Racks with wheels would normally be designed for a certain bike model. Or look for something like this

cplager

Not a stupid question. No, I have not asked Bike Friday.

That definitely looks like a possibility. Thanks!

Pinigis 

We made our first attempt, but we have shipped it off to a company that specializes in racks to get them to tweak the design, and then produce it for us.

cplager

Please post pictures as soon as you can. Thanks!

Pinigis 

Here is our latest effort.



Tip the back back to roll it on the trolly wheels

2_i 

No triangulation? Floppy structure?

Pinigis 

We are trying to get the geometry right first. We will be adding a side structure for rigidity and mounting of panniers.

Schwinnsta

I don't understand this criticism. It is not a perfect triangle, yes, but for a functional reason and most racks are like this. In the other direction, few racks are triangulated, Brompton, may be an exception.

2_i 

What?! it is a valid engineering criticism. I am not sure I have a rack that is not triangulated - I seem to bypass those that are not. You seem to be dismissing the history of frame construction (scaffolding, Eiffel Tower, bridges) and these days even of molecular design.

What is triangulation and why is it used in frame structures?

Examples of Triangulation

The design of Frame Structures: Triangulation

P.S. Moreover here the rack is supposed to support the bike and this just on its edge.

Schwinnsta

First off, I said it is not a perfect triangle. Many racks are not. Many have adjustable rods to connect to the chain stays that look a lot like Pinigis's. When I first read your comment, I did not know which plane of the rack you meant. I think it likely that you're letting the perfect be the enemy of the good.

BTW, I did not mean to criticize you. I very much respect you and your opinions. I just wanted to understand your comment.

2_i 

No offense and you are very welcome to criticize - it should be a discussion and I may stumble beyond the limits of my expertise.

The photos indeed show principally only one projection, but is evident that the stays supporting the rear edge of the rack stick out on their own and the edge is susceptible to swings to the side. In addition, these stays may buckle out, if the bike is tipped over so that it rests just on that edge. In any case, Pinigis stated that this is only a transient form, presumably not worthy yet of investments into greater stability.

Tourist in MSN

I am a retired engineer, and have lots of miles of bike touring with heavy loads on a bike. It is my professional engineering opinion that sometimes all you need is a light duty rack.

I usually tour with a Tubus Logo EVO rear rack on my medium or heavy duty touring bike, extremely stiff and robust. On my light duty touring bike I tour with a Racktime Addit rack, also very stiff and a weight capacity that although is less than the Logo is still more than adequate for my needs.

But both of those racks are in storage right now because for riding around near home I am looking for a wider platform and do not need the weight capacity of those touring capable racks.

Two photos of part of my light duty touring bike, the first photo is with the Racktime Addit rack that I use for loaded touring with my camping gear.




Second photo, this is the rack I use for riding around home. It serves my needs very well for that purpose. Occasionally used with one or two shopping panniers, but often just used with a rack top bag, it is more than adequate.




The prototype rack cited above on the folding bike might not be built for heavy duty touring, but perhaps it is sufficient for most needs of potential customers?

2_i 

Agreed that for light enough loads, you do not need to overly complicate. I tend to build up so that I later do need to look back. (I may throw 18kg just to go to work and this for a backpack on top of the rack.) Correspondingly, I tend to go with Tubus or Old Man Mountain. The Tubus, you give as example, has the structural rigidity built in. Most corners are widely rounded. The stays are at angles to each other irrespective of projection and these angles are fixed.

The particular rack, discussed earlier, was to carry the folded bike while rolling. According to a parallel thread the project was abandoned due to insufficient stability, not clear whether the structural stability discussed here, or just geometry.