DIY tandem or trike
 

Looking for info on building my own tandem and maybe a solo trike.

Because of my wife's health issues regarding balance, but still wanting to ride a bike, we decided to get a tandem. BUT, good quality tandems aren't cheap, and I don't want a Walmart type bike. I've read a bunch of stuff online, mostly through Sheldon Brown's stuff... The bike won't see high speeds, and won't see trail use. Mostly flat and slow bike paths.

I'm picking up 2 Trek 950s Monday. And believe I have a line on some chromoly tubing. My intention is to use a larger diameter tube (probably 1.5") for the main bottom tube, and possibly the same tubing to sleeve and extend the rear top tube to the seat tube of the front bike. I'm not sure if the front top tube needs sleeving. But I will add a brace behind the headtube to give some support between the top and down tubes.

The other part of the question... WHAT is required and where can I find parts to build a trike from a standard MTB frame? I have an older Trek 820 that would be perfect for this.

Good luck! Sounds like a fun project, though it might be easier to build from scratch if they make lug sets for tandems.

However, I notice that unless you are making your own lugs you are probably out of luck :)

Your basic approach to the tandem sounds fine. They don't fail as a beam; they just get squirrelly if they twist, and large tubes are good for that. With trikes, there's an inverse relationship between the percentage of bike parts and general desirability. There are seldom any substantial frame chunks in common, except for the upright styles.

In addition to Sheldon Brown's info (too bad the master has passed), I found this last night...
mattsbikes - Step-by-step: How I made a home built tandem bicycle on the cheap.
AND, he is in the Salt Lake area. I will probably try this method first, out of expedience. But can add tube and reinforce as I go. Now all I have to do is be patient till I pick up the bikes tomorrow!!!

Of the various bike parts resources, none have tubesets and lugs for tandem specific applications.

I found Atomic Zombie's website... WOW! Over the top on everything...
AtomicZombie Recumbent, Trike, Chopper, Scooter and Electric Bike Plans
I've looked at great length though this site and others, and think I have a good idea how to setup a rear for a trike.

Those two sites were the ones I was thinking of suggesting. I think you've found the best sites for doing what you're doing. Get to it! If I had a welder, I'd have a tandem already.

Great idea, and good resources. Good luck :D

Picked up the 950s last night. They are a little shorter than I wanted, but I can make them work. Remember, this isn't a speed machine or hardcore downhiller. Found a source for 4130 through an aviation supply house. Now if I could just find it locally. Downside, they are lugged frames. Upside, the lugs are thicker and easy to weld to.

Anyone know what the wall thickness of the Trek double butted tube is? I have a friend with some 1.5"OD .125" wall 4130 left over from a rollcage. I'm guessing this is going to be too heavy. But if I used it, it would be SOLID!!!! Looking for some tube about half that thick, and 1.25" OD...

And I've been in touch with Matt (built the tandem in the link above...). Good guy and good info.

I'm loving that StreetFighter Race Recumbent... that thing is sick, for sure. I might have to either buy those plans, or head-game the design and see what I come up with!

There is some incredible stuff on the AtomicZombie website... 20 years ago I might have even built a tallbike! But the build your own trike hubs I found very interesting. I know I can build a trike now if I have to, but hope I can find something that I can lighten (and maybe get a hubmotor to drive the front wheel)...

And a question. Has anyone used studded MTB snow tires? I've never seen them before and ought to go get a pair of them for next winter. Novel at least...

I almost like the idea of the recumbent reverse trike better... plus, I can add any motor up to 1.5 HP and still keep the pedals, and it's a street-legal moped! (Needs lights and stuff, but still.) I bet a weedwhacker motor would drive one of those nicely, if made from fairly stiff reinforced plastic or aluminum tubing.

Once I figure out the bills, I might just have to buy myself a few of those plans.. or see if I can find them for free elsewhere... love to support an artist, but I can't see tossing out money for a simple plan like that.

Bought a regular adult trike for my wife. She has significant balance issues. First thing I notice, the riding position SUCKS! Seattube lays back a lot. I might have to get a longer post and have it tweaked. I KNOW its not a bike, but comeon... The trike is a Miami Sun, has a 3 speed internal geared hub with a coaster brake. It rolls on 24" wheels, the coaster brake hub acts as a jackshaft and has a gear attached instead of a flange for spokes, which drives the rear shaft with the right rear wheel fixed to the shaft, the left rear hub has sealed bearings and spins on the shaft. Anyway, my wife loves it, and isn't doing too bad. THis coming weekend we'll see how she does on a bike path loop...

Tandem. Still on track. Had a couple more pressing projects to clear up. Ordering the tubing this week. Enough to run a tube between bottom brackets, another from the headtube on the front to the bottom bracket of the second bike, and to stretch the top tube of the second bike. Will get some pics as the carnage/er/construction begins...

http://i178.photobucket.com/albums/w...0908150059.jpg
What I suggested as riding position sucks, is not that the seatpost is laid back so far... But the crank is so far forward of the seatpost (which is 70*, just like the Trek 950s I will make into a tandem...). Of course, we never intended this to be a serious cycling machine...

http://i178.photobucket.com/albums/w...0908150060.jpg
As my wife gets faster and has more stamina (of course, lots depend on the recent hip issue mentioned in another thread), I have been thinking of ways to make the trike faster. The easiest to do is to swap the rear sprocket for a taller geared one. After that, it gets more difficult. I might be able to swap the input sprocket on the Nexus hub just not sure yet. Next would to build new wheels at 26" instead fo the 24s... But that would look funny. I think.

We are still building the tandem, tubing will be ordered soon. But we might end up buildign the tandem as a trike. Or, be able to make it work either as a bike or a trike. Parts for the trike aren't that expensive, a rear conversion is under $200, the hard part will be gearing... But I think I have that part figured out. We'll see how that goes. Why the tandem as a trike? We are concerend my wifes balance issues might make her feel out of control relying on me for balance. And seriously, I don't intend the tandem to be a speed machine anyways.

Can't wait to see what turns out!

That riding position is worth a premium price to some people. On that trike, it lowers the CG and makes mounting easier.
Gearing alone is seldom the issue with speed potential, but I'm not going to write a new book on the subject here.

Oh yes, step in rather than over is big. Which is why one of the Treks is a small frame, but I'll still stretch the top tube out.

Looks like a fun little trike!

If you are considering going electric, I'd recommend using a hub motor, the Crystalyte Phoenix Racer 5 series is my favorite. It's very torquey, and is very clean and simple. Just make sure you use a torque arm if you are going to go the hub motor route.

EVcomponents.com sells lightweight LiFePO4 batteries for very good prices. You could use anything from a 36V 10Ah pack up to a 48V 20Ah pack. There's lots of cargo room onboard those Delta-style trikes for some great battery capacity.

Have fun with it.

-Tommy

Thanks for the link! I got into a few other projects and the tandem is on hold for a bit...