rench123

Hi guys,

I've been thinking of this bike design and I want your opinion. Feel free to tell me if this plan is crap and I'd like some ideas on how to make it better.

I'm thinking of a custom built frame, as the title says, a break-apart, minivelo longtail with an integrated rack and front suspension. I wanted a longtail, something like the Surly Big Dummy or the Kona Ute, because of its practicality - but I'm not sure I'd like to own a bike of that length. I think one way of reducing the length of the bike would be to use 20 inch tires, and make the rear chainstays not too long. Xtracycle extends the wheelbase about 15 inches but I think I'll be happy with an extra 8 to 10 inches of extended wheelbase. If an xtracycle bike would have 30+ inches of chainstay length, my plan would be to go 22 to 25 inches - this brings the BB to the center of the wheelbase.

I also want front suspension, and plan to use standard (26") MTB suspension forks with 20" wheels, and use disk brakes.

My initial plan is to use the Be-Bike Haze frame as a template, at least for the front of the bike:


Keep the geometry for the front of the bike intact, build an extended rear with an integrated rack, and find a way to break apart the front triangle for easy transport. Standard bike parts keeb the build costs down.

Here's an illustrated guide to what I want to do:


The "ghost" of the be-bike is there so that you can see where the changes were made. The red frame is the front of the bike with be-bike geometry, while the blue rear part shows the extended longtail with the integrated rack.


This shows the bike broken apart. The fork rests on top of the looong seatstays, while the rest of the front triangle falls to one side of the stays. The rear rack can be built wide to accomodate the front triangle. The front wheel is strapped to the side. Skate wheels are shown attached to the rear rack like a brompton.


This shows the bike top side down, so that it can be rolled around. A soft cover can be made, open at the bottom, with straps connected to the rear triangle. When padded with cardboard or newpaper, it should be a large alternative to a suitcase, since the rear rack protects most of the components anyway.

There are a couple of concerns. A bashguard should be sufficient to protect the chainwheel during travel. Disk brakes will give good stopping power, but the rotors might get bent during transport.

The size of the folded package is approx. 40" X 25" x 8" - Narrow but long. Not really it's airline recommended baggage size, but it could go through without excess baggage fees, maybe.

The budget is also a concern. Since there's a definite small budget to making the custom frame, I don't think I can go with S&S couplers for the breakaway angle. I'm thinking the ritchey/dahon system might be easier to replicate, or maybe copy some other coupler that uses bolts instead.

Comments?

thanks!

14R 

Interesting idea. It has been (somehow) executed in a very cost-effective way:

Please see this one

K6-III

For the type of bike you're building, drum brakes may be a better option than discs.

Looks like you'll want a Sturmey X-FD hub in the front and an 8 speed X-RD8 (w) internal in the rear.

As for a frame to start with, its almost better to start from scratch.

rench123

Thanks for the link. The shopping cart bike on the link is a front loader, so its a bit different. I like the way the bike halves are connected together.

A cheaper alternative for me would be to cut up an old BMX frame and put together a DIY xtracycle.

rench123

Thanks. I'll look at those products. Not sure if they'll be available locally (Philippines) or at what price they will be over here.

gnome

Very cool, thanks.

twentysixtwo

Great Idea. The Madsen is like the Big Dummy except it uses a 20" in the rear for lower load height and CG. At the same time the longtail problem is storage and transport so a foldable longtail with 20" wheels starts to make a lot of sense.

The biggest challenge I see is how to make the folding joint stiff, sturdy,and safe. The conventional longtails are pretty much bulletproof, and if you're hauling kids and krap you want to know you're getting there in one piece.

The next challenge is keeping the chain off the ground. The Madsen has a scary long and low chain. I've seen 'bents with an interesting hack involving a length of PE tubing...

rench123

the connection between the front triangle is a concern, especially since I don't want to go through the S&S route because of the cost. Good thing you mentioned about the Madsen's chain. It is one of the things I've been concerned about. My 20" bike is single speed, but I think that some form of geared setup will be necessary. An internal geared hub should be ideal, and since the frame is custom, then I can spec the right dropout.

sqynt

If you are considering a custom built frame, why are the S&S couplers a monetary concern? The seemingly high cost of the couplers are that they require someone to retrofit them to an existing bike. They are probably only going to be 10% of the cost of the custom frame.

Reconsider why you want a suspension fork, especially one designed for a 26" bike. Many Xtracycle owners start off with a suspension fork that was mated to the donor bike, only to switch to a rigid fork later. An Xtra put much more weight on the front due to the elongated rear, even without a load. My guess is that these stock suspension forks can't handle the extra weight. I personally opted to use a suspension corrected rigid fork on my Xtra build.

If you just want a cargo capable 20" wheeled bike, consider a custom "cycle truck" style build. There are builders out there who are familiar with this type of front load cargo hauler.

rench123

Thanks for the suspension fork comment. I was thinking of using the bike for some touring, and some of the places I would like to go to would benefit from having a suspension fork. Using 20" wheels with a 26" fork isn't much of a problem, as long as you use disc brakes. They larger forks are also easier to find than 20" specific forks. There are a few commercial bikes that use this setup - Kuwahara Gaap, Airnimal Rhino and that Be-bike I posted. the other advantage of using 26" forks on the break-apart design is that the headtube could be made as small a normal MTB - a front triangle with a larger headtube won't fit in the rear wheel and the seat tube when the bike is packed up.


The reason for my avoidance of S&S is my location. I'm in the philippines, and the cost of this custom frame would probably be less than $300. I've been quoted for less than $200 for a normal custom steel frame. S&S couplers would double the cost. I also have a few spare parts in my closet for this build. I'm trying to keep the budget low, as my wife thinks I already have too many bicycles.

badmother

I also wanted a shorter longtail. Look at the homemade longtails in the Utility forums.

I made one from a 24" detatchable frame but then ditched the project since it ended up almost as long as the 26" one.

This winter I am making a 20" longtail, using the rear triangel from a 20" full suspension MTB. Same way as the homemade longtails in the Utility forums, but 20" all the way. Easyest solution, at least for me.

Edit: This s the bike I made but gave up on. https://www.bikeforums.net/showthread...light=longtail

The one made into a longtail in this thread is a 24". The purple one in the first picture is the same type bke but 20". This one plus the rer triangle from the 20" MTB is what I am using. I am sure that is going to end up much shorter than the 24".

Also I agree to not using a suspension fork plus I agree on using a drum brake in front instead of a disk brake. Much better since the whole system is protected innside the shell.

I use a Shimano7 on my present (28") longtail and like it a lot. So much more simple chanline plus coaster brake.

rench123

thank you for posting the link, badmother! that 24" bike does look long with the 26" rear. I think all these ideas will help me when I start with the bike. Please post photos of your 20" longtail when it's ready.

rench123

bad mother, I looked through the homebuilt xtracycle thread on the utility board and it's so interesting what other guys have done! I might try the diy route first just to try out if I like the way a longtail handles - since I alredy have a 20" bike that I ride all the time.

badmother

I started the 20" longtail. My main problem is to figure out how to connect the mounting for the wideloaders to the bike. I want wideloaders