Folding LowRacer
Fold-Racer  =>

By Warren Beauchamp  started 1/30/03

It's winter in Illinois, and while it's too cold for my feet to be spinning, my brain still is. One problem with lowracers, and with bikes in general, is that they don't travel well. You often need to use car racks, bulky shipping boxes or large vehicles to transport them. This object of this project is to design and build a bike that can be easily disassembled and then compacted into a package that is easily transportable. After some consideration, I threw the folding part right out the window. This bike will be easy to take apart and put back together, but tools will be required. This allows me to make the bike lighter overall, as well as much easier to build. Most of these images can be clicked on for a bigger picture.
This scale drawing shows the initial front wheel drive lowracer plans. The frame comes apart into 4 sections, one section being the FWD assembly. This keeps the chain and all the cables except the rear brake cable together when the bike is disassembled. The frame sections are held together with a combination of tubing clamps and sliding concentric tubing.

foldracer_sm.jpg (5267 bytes)

The main frame tubing is 1.5"x0.049" chrome moly tubing, the 4 boom tubes and the frame braces are 3/4"x.049" tubing, and the rear chainstays are 1"x.049" tubing. The two main frame tubing clamps are made from 1-5/8"x0.058" tubing.

foldracer_apart.jpg (7800 bytes)

This bike will utilize 406 mm wheels and a hardshell seat. It's 44 inch wheel base will allow a total length within the 2 meter maximum for USCF racing. The seat height will be about 9 inches.

When the bike is taken apart, the pieces, including the hardshell seat, can be compacted into a package approximately 2ftx2.5ftx1ft. This should make it able to be taken on a plane trip as luggage.

Here's a detail of the proposed sliding concentric tubing joint. To disassemble, the two tubing clamps are loosened and the concentric tube is slid out. This design is a holdover from when I was intending for this bike to actually fold...

Errata:
Tubing sections, lengths from horizontal
Rear stay, 20, 13"
Bottom tube, 0, 18"
Up tube, 75, 20.5"
Top boom tube, 10, 24"
Bottom boom tube, 5, 18" (to head tube)
Seat angle ~35
Rider size > 6ft

slider_joint.gif (7941 bytes)

12/23/05
I'll bet you thought that this was another of those partially thought out blue sky designs that would never get built, didn't you. Well you were partially correct. The design above will never be built. After thinking about it for almost 3 years (!), it was time to revisit this project. 

I first considered a spiffy carbon fiber composite version that would unbolt at the bottom of the down tube, and have a rubber snubber rear suspension to allow the rear stays to fold up. This would be very cool, but would take a long time to build. As my goal is to have it ready for the Feb 2006 Florida HPRA races, this needs to be a fast project.
So, I went back to the original drawing, did an inventory of my parts bin, and came up with a new steel design. This version uses rather thin 1.5"x.035 tubing, with .058 wall lugs in the high stress areas where the tubing joins. A hacked up MTB fork will be used for the rear stays and a Barcroft FWD fork will be used in the front. I'm trying a Swanson composite seat to see how well it fits my long backside. I'm still planning on the magic 44" wheelbase.

I bought a cheap but very functional tubing notcher from Harbor Freight tools, which saved hours of time filing and makes more precise angles than I could do manually. Things are progressing quickly, I now have all the tubing cut and ready to be braised. 

Today was a good day. It was warm enough to braze outside so I took full advantage of it. This picture shows the rear fork. I cut a hole in the bottom frame tube that's the same size as the legs of the fork, cut off the fork's steer tube and inserted it into the frame tube. I left the steer tube stub that the fork legs attach to to keep the fork rigid. I'll cap off the area shown here later to prevent water from getting inside the frame. 
This was a nice wide 26" fork, so I was able to cut off the ends of the fork legs, cut out the dropouts, and then braise them back in in the correct location for the 406mm wheels I will be using. I'm using the canti-brake mounts, so I cut off the fork so that the wheel rim is 1.5" from the canti-studs. That seems to be the correct distance needed for the brakes.

Here's the lug that attaches the down and bottom frame tubes together. I still need to cap the bottom of the tube, add a gusset, and add the tube clamps later. The tube clamps will allow the frame to be disassembled for travel.

 The carbon fiber that the lug is sitting on is destined to be a wheel disk for the NoCom. 

Here's the bike with the lugs all braised, and just laid out on the floor to get an idea of what it will look like.

I'm waiting on a 1-1/8" head tube and some other parts before I can do much more.

12/30/05
The 1-1/8" head tube and headset arrived in the mail, so it was time to miter the tubes to fit. Seen here is the tube miter in the drill press. It's currently set to 40 degrees. The frame tubes and the head tube are both 1.5" OD.
Here's the head tube laid out for a test fit in the frame. I need to cut it to 6". I broke my old trusty hacksaw, so I had to go out and buy another. How traumatic...

 I spent my free time during the past week cutting out tubing caps and gussets, so now I need another nice day to do a bunch more brazing.

On this bike I'm using all metric hardware, so I couldn't just run down to the hardware store and pick up some ubiquitous 1/4" hardware for the clamp. Instead I laboriously drilled out 1" sections of 3/8" steel rod, and tapped them to fit the 6mm bolts I'll be using for the clamps. This method is cheaper but more time intensive. I filed a semicircle into the side of each clamp tube so they fit the frame tube better. Here's a couple of them placed on the BB lug for observation.
Here's the lug between the down and bottom tubes with the tubing cap, reinforcing gusset, and clamp tubes taped in place. 

I'm planning to add a bolt to the frame that keys to a cutout in the lug to allow easy alignment.

Here's the frame laid out again, this time with the head tube in place. 

My poor abused broken hacksaw lays in a disheveled heap on the floor. I'm planning a proper burial.

1/02/06
We were graced with another day in the 40s, so I was able to go outside and  braze up all the bits that I had been busily cutting and filing for the past week. This bike has gone together extremely well, and I have been able to keep it all straight without resorting to dragging the frame jig outside. 

I did have a couple problems, one of which was that the rear stays shrank in after I added the cap on the back of the bottom tube. I should have kept the dropouts spread apart with a threaded rod while I was brazing it. I had to do some manual spreading of the fork to get it wide enough for the wheel. The rear fork now sports some lovely vise prints. Also I made my head tube too long. I wanted it long so the drive train would be extremely rigid. Unfortunately, the steerer tube on the aluminum Barcroft FWD fork was shorter than I thought. I'll have to take a bit off the top of the head tube, file down one of the bearing races, and use an internal riser to get around this faux pas. Arg.

On the plus side, the frame, wheels, tires, seat, drivetrain parts, and brake parts collectively weight 20 lbs. I'm sure I'll be able to add at least a couple pounds to that before it's done, but I will be very happy if it weighs under 25 lbs when I'm done.

 

Here's the bike with the seat sitting on it. This week I need to make the front derailleur tube, drill and tap the tube clamps that hold the various frame sections together, and start thinking about the steering.

1/3/06
Here's the foldracer "folded". The fork is not as compact as the one I originally envisioned, but close enough! 

The BB is not built up yet, I just stuck the cranks in there for a visual. I have some old Shimano 105 175mm road cranks that I'm going to have cut down to 155mm or so. 

Here's the pile 'o parts with the seat on top. The whole thing will fit into a container 30"x20"x11". Soon I will need to begin the search for a suitable suitcase or heavy duty bag from the thrift store.

Also I did the "hop on the frame" test to check for frame flex, with my foot at the lowest part of the frame, where the seat bottom  will attach. There was only about 1/4" of flex. That's about right for not having any of the frame members bolted together.

1/8/06
It occurred to me that I never actually showed how the frame came apart. As seen it the picture to the right, the frame sections slide into the lugs, then 2 - 6mm bolts in each lug clamp the lug tightly around the frame. Take apart the frame, remove the wheels, remove the seat, and cram it all into a suitcase.

Something else I have been thinking of, is that this bike could easily made into an SWB bike for riding to and from lowracer friendly locations, by simply replacing the down tube. The green "SWB" tube and joint would simply replace the orange "Lowracer" one, and the seat back angle would be cranked up accordingly. One more small tube in the suitcase won't hurt, right? Cool.
I worked out the steering / handlebars, and will be cutting the brackets for the drivetrain this week. Apparently I installed my BB backwards, Arg! It was labeled L and R, but it was L and R hand threads, not L and R side of the bike... I would have gotten a lot more done this past weekend but I ran out of acetylene. Looks like it will take two (small!) bottles for this project.
1/11/06
This bike will have a traditional FWD drivetrain. I'm using a 8" McMaster Carr pulley for the drive side and a inline skate wheel idler for the return side. This will allow low speed turns without the chain hitting the tire. I'm using 175mm cranks for now, but plan to use 155mm cranks when I can obtain them.

1/12/06
Here's the foldracer with the handlebars, spiffy but heavier wheels from the StreetCuda, brakes, derailleur, and cranks. It now weighs 20 lbs, 3 lbs of which is the BB & cranks. Incidentally, a set of RotorCranks weighs the same amount. Hmm...
1/16/05
We were gifted with another January day in the 40s, so I went outside and did some brazing. Here's a bad picture of the seat clamp. I also brazed brackets onto the rear fork close to where it's attached to the frame to anchor the rear seat stays. 

I will be building up the CF seat mounting points on the Swanson seat this week. I'm using CF arrow tubing for the rear seat stays. I can't wait to actually sit on the bike! I will have to modify the steering (again) to actually ride it. A quick seat test confirmed that the handlebars will need to be mounted further back.

I brazed the drive-train mounts into place, and cut a new inline skate wheel idler. So far so good. Looks like I will not be using the RotorCranks unless I  build a new BB section, as that crank requires the the BB threads be on the correct side. Doh! Maybe I'll just drill out that beefy 67T chainring more.

I scored a set of Forte mountain bike brakes from Performance on sale for $10 each, then modified the front brakes to switch them to a left hand cable. I also had to shorten the right brake arm a bit for clearance by chopping off the cable clamp and drilling and tapping an new 5mm hole a bit lower. 

1/23/05
I epoxied a CF tube onto the seat with CF reinforcement over the past week to be used as a seat base mount. Unfortunately, it failed testing so I had to rebuild it, this time using an aluminum tube, reinforced with floxed epoxy/fiberglass/CF. 
Last weekend I mounted the seat. It's starting to look like a bike!  

The weather did NOT cooperate this weekend, so I wasn't able to get outside to do any brazing, so the handlebars were not redesigned. 

I mounted the aluminum rear stay brackets to the seat with a methodology similar to how I mounted the seat base bracket. I built the seat rear stays from CF arrow stock tubing and reinforced the ends with CF and JB Weld. 

Basically the handlebars will be similar to  the existing ones, but with a longer tiller. Plus they will will be made of steel instead of aluminum, and will be a bit lighter. That's a good thing as the bike now weighs 25 lbs. It will be a bit lighter after I change out the cranks.

While sitting on the bike and bouncing on it, I noticed that the down tube flexes a bit. It's 1.5"x.035 tubing so it's not too heavy duty. I'll have to ride it a while before I figure out if it will need reinforcing with some carbon fiber or not. The drivetrain and the bottom tube are both well reinforced, there is no flex in those sections.
1/29/06
While out-and-about my wife found a nice big Samsonite bag on clearance. It has rollers and a handle for easy carting. The bike fits in it like it was made for it. You can see the new handlebars in the upper right corner of the bag. I packed it once with the fork completely removed, and it took nearly as long to untangle the chain as it did to put together the rest of the bike. Here it's shown with the new handlebars removed, and the fork still attached. It comes apart in about 5 minutes, and takes about 10 minutes to put back together.

Here's the whole bike in the bag. Pictured here it has 175mm cranks. It will fit even better with the 155mm cranks that I have ordered from BikeSmith design. There's room for my helmet, shoes, and a bunch of clothing between the components. It doesn't move around much but the clothing should help to keep it all from rattling.

The AeroSpoke wheels are heavier than traditional spoked wheels, but they nest and pack really flat. Cool!

Here it is closed and zipped. The bike is 25lbs, and the bag is probably under 10 lbs, so that means I can cram 15 lbs of clothes and stuff in the bag before going over the airline 50 lb weight limit.

Good thing there are still 3 weeks until the Florida HPRA races! The bike needs things like cables, a front derailleur, paint, and tweaking before it is ready!  

 

Also I took the bike for it's maiden voyage around the block this weekend. My knees hit the handlebars, heels hit the front derailleur, bike felt squirrelly, yada yada.  This will all be worked out in the "tweaking" process. I shortened the down tube about 1.5 inches. This gives the bike more trail to reduce the squirrel factor (now about 2.25"), but also raires the seat.  The knees and feet issue will be resolved with the shorter cranks. All I have to do is wait!

2/5/06
After changing the headset, installing the new shortened cranks from Mark Stonich, brazing on the front derailleur post and cable stops, and cabling it up, the bike is done (except for paint).  I took it for a test ride, and it was quite nice, no body parts hit the bike while pedaling, and it rides, steers and behaves nicely.  
For now I set it up so I can position the downtube in two locations, one with a 7 inch seat height for racing, the other with a 9" seat height for rides. I'm not sure I really need a higher SWB version at this time. The bike really feels nice on the road, and amazingly, the Swanson seat fits me well with a pad. I'll have to wait for warm weather to paint it. It now weighs 26 lbs. Maybe I just need a lighter seat...
2/22/06
In addition to the multiple height adjustability, I'd like to create a leaning FWD delta trike version of this bike. It will be easy to switch between bike and trike as the rear section of this bike is easily detachable. Leaning trikes are faster than fixed trikes as the side to side tire scrub that occurs while pedaling does not occur. I may need to add a mechanism to keep the trike upright when stopped. This will probably be the chassis for a velomobile of some sort. Another leaning trike method

Leaning FWD Tadpole Trike mechanism
I think this would be a cool design to be picked up by a manufacturer. They would just have to build one drivetrain section, then they could sell different back end parts to allow the customer to tailor the bike to their individual needs. If their needs changed, they wouldn't have to buy a whole new bike, just some different rear end pieces. But I digress....

Picture by Willie
3/01/06
The Foldracer performed admirably during the Feb 2006 races at Brian Piccolo Park near Ft. Lauderdale, FL. It packed all up into the suitcase, along with my aero helmet, shoes, and assorted tools and clothing. Though I had weighed it at home, I had to remove a couple pieces of clothing at the airport to get the suitcase down to the 50 lbs weight limit. Aside from some issues with my cleats not working properly (dang Florida sand!) and associated unexpected unclipping, the bike performed without incident. 
The only issue I noticed was that the down tube has enough flex that when I'm really cranking hard during a sprint, the bike bounces enough to allow the front tire to hop which allows some wheel slippage. I'll need to wrap that tube in a layer of CF to stop that (and make it look spiffy too!).
4/15/06
I took the bike all apart to paint it, and reinforced the down tube with a layer of CF. Seems to be less bouncy now. I installed a new set of brake levers too, and moved the bar end shifters to the ends of the horizontal handlebar tube. It looks much cleaner now. No cables looping all over.
 

11/03/07
Ok, so the Swanson seat really was too small for my long backside. I rode it for the past year without any padding on the seat because that felt better, but still, ouch. Time for a new seat. I bought an XL velokraft seat, and it was lightweight and plenty long, but too long to fit in the suitcase.

 I saw the HP Velotechnik Body Link seat at the bike expo in Las Vegas in 2005, and though it would be cool as it adjusts to fit "anybody". I bought one this spring, but found that it would be a bit short with a pad, that it was floppy in the middle, and that it was not exactly light (4.5 lbs). HP Velotechnik bikes have fairly upright seats, and it was not designed for the laid back lowracer position. After agonizing over it for 6 months, I decided to reinforce and lengthen the seat. You can see the new set of bolts I added through the reinforced area, about an inch down from the slots.
Taking out the 4 bolts allows the seat to be broken in half. You can see the tabs at the end of the reinforced area, which trap the upper seat half for extra rigidity.

To reinforce the seat I covered a carbon fiber arrow shaft with several layers of carbon fiber.

Here are the seat halves nested together. The padding is made from Zote foam. I rounded the corners with my belt sander after an unsuccessful router experiment. The seat has a deep valley and holes for the spine, so I cut out that area. They should fit nicely in the suitcase.
Over the past year I also lengthened the boom to prevent my heel from striking the derailleur, and lengthened the frame bottom tube to allow the seat to be laid back more.  

Now I need to get 165mm cranks for this bike. The 155mm cranks are too short for me...

11/24/07
I traded cranks with Bruce Gordon to the 165mm cranks. The bike feels better, but I still have heel strike annoyances. 

Moving the BB further from the derailleur would mean a complete rebuild of the front subframe.
This will allow me to:

  • Use a thicker boom for more rigidity
  • Raise the BB 1.5" to eliminate heel strike and make the bike closer ergonomically to the Cuda-W streamliner.
  • Shorten the head tube to reduce frontal area and fix "too short steerer" problem.
  • Make it look a little nicer!
What the heck...

I unbolted the front sub-frame and removed the shiny bits. Using the angle grinder, I hacked off the old boom and brace tube. 

After this surgery, the BB will be 3 inches higher.

11/26/07
I made the new boom using heavy 1.5" x 0.058 wall tubing, and cut 1.5 inches off of the head tube. Here, it's just sitting on the floor for a test fit before brazing.
I brazed it all together, and added some aero tubing bracing to the top of the shortened head tube. Except for the handlebar, it looks much better now, and it should be stiffer too. Now it has the classic Z-frame look.

The bike is about the same weight as before, but only because the boom, head tube, and chain are shorter. Heel to derailleur clearance  is much better, no annoying heel strike.

I need to build a new handlebar, since now the old one hits my freakishly long legs.

12/2/2007
This weekend I reinstalled the drive-train and cut down the head-tube. Temporary handlebars are clamped on with vice-grips for now, as I'm all out of oxygen for brazing.
12/26/07
With fresh tanks of brazing gases, I built up the new handlebars. I decided to go with the center mount brakes as the are very clean looking, aero, and provide plenty of stopping power. The brakes shown are just temporary until I pick up the $13 Forte mountain bike brakes from Performance, hack them up, and make the bracket.

The handlebar stem is now attached to the head-tube by a tubing clamp. This will may it easy to detach when it's time to stash the bag in the suitcase.
Another shot of the whole bike, this time with the new handlebars. The bike looks much better now. After it gets a coat of paint it will look even better.

Here are the Forte brakes, after the tube clamps were cut off and the copious amounts of hand filing were performed.

Also pictured is the mounting bracket which will be brazed to the stem of the handle-bars, the long bolt which replaces the brake's pivot pins, and the various washers which make it all work nicely.

Here are the brakes attached to the mounting bracket.

12/30/07
Today I brazed on the brake mounting tab and reassembled the new brakes.

Also I attached the bike computer to the center of the handlebar using a metal screw. It looks much cleaner than the traditional plastic tubing clamp.

The bike is all done now except for the painting.

Current specs:
FWD Lowracer
Weight: 27 lbs
Wheelbase: 45 in
Seat height: 9 in
BB height: 19.5 in
Seat angle: ~25 degrees
Disassembly: 5 min
Reassembly: ~15 min

Fits in suitcase. No huhu.

1/13/2008
More pictures of things-in-bags. When I had the bike apart for painting I decided to make sure it all still fits in the bag. Here is everything but the wheels.
It fits even better now than it used to. Now I don't have to remove the cranks, pedals or the derailleur to get the front subframe in the bag. There is still room to stuff shoes and clothes in the bag as well.

The top of the bag has another couple inches of clearance built in.

Now all I need is a trip to take it on.

3/1/2009
I took the bike to Battle Mountain 2008, and used it for warming up. I also took it for a ride one day. The bike rode well, but feels a bit squirrely at low speeds, and feels a little noodley. I think if make some stiffer seat stays, and change to remote steering that will help.

Picture by Jun Nogami.

 

11/23/09
Looks the same, but I took it apart, painted the handlebars, added heavy duty rear seat supports and reinforced the front seat mount. I also adjusted and lubricated the headset as it was squeaking. Now it feels more solid.

Even though it has approximately the same riding position as the NoCom, it's about 4 MPH slower. Probably due to boom/frame flex and some aero considerations.

6/21/10
Complicated? Dennis Grelk built me one of compact his bolt-on leaning trike units. It uses Sturmy-Archer drum brake hubs. I added the brake cables and now need to source the 406mm rims and spokes. I'll finally have a bike to race with the trikers.

7/19/10
I built up the wheels. The spokes I ordered were a couple mm too short as Wheelsmith made ones shorter than what the calculator said, or longer. I chose shorter. This means that one or two mm of threads show, but I am confident that they have enough threads gripping so that it won't be a problem. Alternatively I could have used long nipples, but I had the short nipples "in stock".
I then mounted the tilter unit to the bike. Done! Er... not quite. The tire to seat clearance was fine until the bike tilted over about 20 degrees and then it would rub. Arg. To fix it I cut the bike frame under the seat and brazed in a nice heavy sleeve, which added 2" to the frame length. It was probably good to do that anyway as the folding lowracer was kind of darty, probably due to the fact that the rear tire was pushed up under the seat. Having the rear tire further back means it probably handles better now. I installed the tilter unit, hooked up brakes and took it for a ride around the block. Nice! It handles well and feels like a bike, a heavy bike, but still a bike. If I concentrate, I can balance on it when stopped. The front Comp-Pool and rear Scorchers should be plenty beefy for cornering. In a few weeks I'll try riding it hard at the North Manchester racers and we'll see how it does there.
2014
Over the past several years I have raced the foldracer as both a bike and a trike. I added some wheel covers to the tilting trike and raced the trike at a trike only event in 2014. In events with wide corners the tilting trike is always faster than a traditional trike, but in events with tight corners like a go-cart or trike specific track, traditional trikes are faster. Why? The leaning trike can only lean so far. Once it is leaned all the way over in a tight and fast corner the rear wheels start skidding. It's very controllable and I have never crashed it, but its still disconcerting.

Click here for the foldracer 2 project, with more carbon fiber goodness.

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