Dual 700
  Carbon Fiber Dual 700C Quasi-Lowracer

A project by Warren Beauchamp

Over the past several years I built and refined a Steel quasi- lowracer that performs well and rides nicely. It weighs about 30 pounds and I thought it would be even better if it weighed 20 lbs. Here's a concept of what it would look like in CF. Not much different. I'd like to make it separable at the bottom of the down tube so it can be transported in the trunk of a car. It would be faster as a RWD bike and this layout would support that, but the FWD is so convenient.
A 1X frame layout was drawn and it was decided that I could not proceed without the fork. Here it is with some wheels on it.



After some lively discussion on the web forum, I decided on this fork via Ebay from China.

Once I get the fork I will finish the layout, trace the 1X layout onto 2" polystyrene foam, cut out the front subframe, and start sanding.

I redrew the 1X drawing, traced it onto some thick plastic sheeting, cut it out, traced the cutout onto the foam, cut out the foam, and glued it together. I am using the 3M Polystyrene Insulation 78 spray adhesive. Works great. Time for some shaping/sanding.

It's not going to be easy to build 1-1/8" internal bearing CF head tube. Internal bearing head tubes have a beveled ledge inside the tube, and that's a hard thing to find. I ordered some CF tubing from China to at least give me a head start.

Thinking about how to widen the CF front fork to widen it to 130mm. My first thought was to use clay to build up the outside of the fork legs (as pictured) and then lay up CF over the outside, and trim the inside.

Now I am thinking it will be easier to just add a 15mm offset to each fork leg by cutting the legs and bonding in some CF plate. This should be much easier. 

Here are the specs for the CF head tube for an internal bearing headset.

Garrie Hill is building me a CF head tube to fit the internal bearings. Woo Hoo!

I located a titanium BB shell in my parts bin, I wasn't sure if it was aluminum or Ti, so I hit it with the grinder to check for sure. It shot off white sparks, which means Ti. Aluminum would not have any sparks. It's pretty thick so also not very lightweight. I may have to drill some holes or something to lighten it up.

I have rounded off the edges of the foam frame and now need to add some convex fillets.

Here's a drawing experiment to see how much more the forks would have to be expanded to get to 130mm. This looks like it will work ok. I will need to reinforce the chopped areas with many layers of CF. It will probably be overkill.

I spent many hours filing and sanding and adding bits here and there to get good filets. The fillets under the seat are very important to keep the airflow down there as clean as possible.

The seat and rear seat stays still need to be widened a bit so I am not near done. It's pretty well roughed in otherwise. Next I will fill in the rough areas with drywall compound and do a bunch more sanding.

Once the shape is decent the current plan is to first paint the foam with green mold release and then lay up 2 layers of CF over the bottom half of the bike. A test was performed to see if the alcohol based green mold release will eat the foam, it does not. No vacuum bagging now, I will do that for the final layers after I have a solid structure, otherwise the pressure of the vacuum could warp the foam.

I had some discussion with Thom about fairing the drivetrain. I think this has merit and I can add that on later.

The bike was laid out on the floor and propped up some wheels to idiot check the sizing. Looks good. The back wheel will slide up another couple inched forward when I finish the stays.

More sanding foam, The seat was 3 sections of foam wide - 6 inches. I widened the seat by the shoulders to 10 inches and faired it into the seat stays. I also widened to seat butt area to 8". Started applying the drywall compound to fix some issues and fill cracks and rough areas. It will take a several days to dry.  I hope it sticks. It's looking pretty sexy.

Here it is after the second coat and a bunch more sanding. This is probably the last coat before I coat it with mold release

Here it is from the back side. I'm pretty happy with how it is turning out.

The "Campagnolo Front Aero Brake Lateral Pull, For Time Trial/Triathlon Bikes" I ordered from amazon to use for a front brake did not look like the picture. I think the one they sent me was either a rear brake or it was meant to be mounted behind the fork. I had to terrorize it by drilling an extra hole to get it to work with my fork.. Par for the course in recumbent land.

Laid up one crappy layer of CF over the bottom of the form in my dark and cold garage. The epoxy was cold and thick so I was worried that it would not wet out two layers properly.

For epoxy to cure the temperature should be at least 70 degrees F. An unheated garage in Illinois in December is no where near there, so I had to build a foam box "oven".

Here's the bike form in the oven, doing its impression of an emaciated turkey. I added some plastic wrap to hopefully stick down some of the CF that was sticking up and hopefully reduce the post cure cleanup and sanding. Hopefully one layer will be enough to vacuum bag over.

The halogen light in the box keeps the temp at about 75 degrees.

I cut out some CF dropouts for the rear of the bike. I have committed to FWD, so the dropouts are only 100MM wide. I put the bike in the frame jig, glued them to the foam stays, put the heat lamp on them and crossed my fingers hoping that it was really lined up properly.

Several hours later I removed the bike from the jig and tried it with a real wheel in the dropouts. Nope, it was off a bit. I accidentally broke off one of the foam stays but that turned out well and I was able to trim it down a bit at the break to bring make the wheel straight and re-glue it. Once it cures again I will re-check it to be sure it is true before I cover the rest of the rear stays in a layer of CF.

The Garrie Hill CF head tube arrived and it's very light. I tested it with the bearings and fork and it all fits together well. Here it is with the internal head set that fits into it. Basically the head tube also serves as the cup portion of the headset.

I still need to sand down each end of the headtube until it is flush with the bearings. Garrie sent me some wet and dry sandpaper and noted that it's best to sand CF with wet sandpaper to eliminate the dust issue. Great idea.

This is the top and bottom bearing of the headset assembled with the races, cap, etc. It's tiny and lightweight and very low profile.
I added a layer of CF to the rear stays and down tube area and used the belt sander to clean it up out on the driveway. I'm sure my neighbors were impressed with the racket on a cold New Years morning.

I found another great use for old inner tubes. They can be used to compress composite layups. I cut a slit in the tubes lengthwise and wrapped them around the down-tube area. They are just stretchy enough to give decent compression. I did have to use the aforementioned belt sander to remove some artifacts after it cured.

Today the head tube was bonded into place with some PC11 epoxy. Things are lining up fairly well but it looks like I will need to tweak the rear dropouts just a bit. Once that cures and I make sure its all straight  I will be ready to add the front boom section.
I didn't have much PC-11, so there wasn't enough surface area to bond to and it didn't hold. I mixed up some epoxy and micro balloons today and bonded the head tube in well. After it cured it seems to be in the right place. Yay!

The boom tube was fitted into place. I taped the template to the side of the frame to ensure it was in the correct location, and that the crotch to BB distance was 34" as per the 1X drawing and the steel version of this bike. Apparently the head tube is a bit more upright than on the template, so I have about 1" of trail instead of 2". That should be ok.

Before I attach the boom tube I will need to cover it in a layer of CF.


We had some nice above freezing temperatures over the past week so I took advantage of them and covered the boom with 1 layer of CF. I cut up some plastic grocery bags and used them to cover the resin impregnated CF. This seems to work better than the food grade plastic wrap as the plastic bag plastic seems to not wrinkle as easily and peels off better. I used the inner-tubes to compress the layup again. I won't use this method for the final layup as it leaves stripes in the epoxy that need to be power sanded off. I used the "oven" to cure the epoxy on the boom tube.
Before I added the boom to the frame I used 2 layers of CF to wrap around the head tube onto the down tube, then I bonded on the boom tube with a thick slurry of epoxy and micro balloons. After curing under the heat of the quartz halogen lamp and ensuring that everything looked straight I added a layer of CF to each side of the head tube area to fasten the boom more firmly.

In this picture the front wheel is turned slightly so the gap in front and back of the wheel appears larger than it really is.

Next step is to further reinforce the head tube area.

I laid up 3 layers of CF over the forward half of the bike. This is the minimum layup for this section, I may add more later if it's flexy. A large layup like that is a real ordeal. After laying up the CF I wrapped it in nylon peel ply and breather ply, then wrapped it with the old inner tubes and put the whole mess in the foam box out in the garage to be warmed enough to cure properly by 200 watts of quartz halogen fury. 

After curing I found that the peel ply does peel, but I used way too much epoxy and the bleeder ply was saturated, which meant that I had a thick coat of tough material on top of the peel ply. This took several hours to remove! There were many large large wrinkles on the sides where wrapping did not provide adequate pressure. It would have been better to vacuum bag.

This is also where a female mold would have really been nice. Nobody cares how ugly it is on the inside!

A fantastic day in February gave me the opportunity to go outside and sand off the wrinkles that I added last weekend. I will need to add a couple more layers to the sides of the boom to replace what I sanded off.

I had been doing some experimentation to see if the vacuum pump I got from Rick several years ago would pull enough vacuum and suck enough volume to allow me to use it on this project. I bought a gauge and some 1/4" ID tubing and fittings and did some experiments which showed good vacuum but very low volume. I was concerned it would take a long tome to evacuate the excess air from the vacuum bag and the any pinholes in the bag would make the vacuum ineffectual. Rick noted that I need to use 5/8" ID tubing with this pump. Today I did some experiments with 5/8" tubing and it seems to work well, so now I am ready to use the vacuum bag technique to mash several layers of CF to the under-seat portion of the frame.

I laid up a seat pan (partially visible in the lower left side of this picture). Another hand layup in the cold garage so is was very epoxy-heavy. Finally we had a couple warmer days and I was able to sand down the seat pan.

I partially carved out the foam on the inside of the under-seat area and gave it a coating of CF. Yes, another hand layup. This will be a nice area to store a pump, tools, water bladder, phone, etc.

It's stiff enough now that I think it can withstand a vacuum bagging without chance of deformation. I think 2 more layers on the entire bike should do it. it will take 3 separate layups - rear stays, bottom of the bike and the boom.

Also I opened a hole from near the head tube down through the frame to the under-seat area to allow me to run a brake cable inside the frame.

Peter Heal gave me some good tips for vacuum bagging. He makes his bag out of the thick clear plastic that comes in a roll, and uses a glue to make a custom bag out of a flat sheet of plastic. I wasn't able to find the glue he gets in Australia, but I think I found something that is similar. We shall see. The 6 foot long frame is a very large object to vacuum bag all at once.
The rear stays were covered in two more layers of CF, then peel ply and bleeder ply and then placed in a vacuum bag under about a 14" Hg vacuum. Several hours later the epoxy has cured. Like a kid at Christmas I tore open the bag and began to remove the bleeder and peel ply. Woo Hoo! It looks great! Some small wrinkles but most just epoxy in the wrinkles. Ok, now I am a believer in vacuum bagging. The layup and application of the peel and bleeder ply were a PITA, but the results make it worthwhile.

Laid up a couple more layers on the center section and bagged it. I couldn't get any vacuum and it took forever to find the leak. It turned out to be the hole I drilled in the frame to run the brake cable! The middle section turned out well, with just minor wrinkles. I'd post a picture but it looks almost exactly like the January picture...

I stuck some wheels on the bike and bounced on it a bit to check the stiffness. The rear stays and center section seem very stiff even without the seat pan. The front section seems to be a bit flexy but it should be plenty stiff after I add the final two layers.

Before I install the seat pan I have to mount the rear brake. It will go between the rear stays and only be accessible from the inside of the frame, through an inspection hole in the seat.

I am using extra large and thick garbage bags and Gorilla tape to make the vacuum bags. It's working well except around the vacuum hose. I need to buy or build a "port" for that.

Added 2 more layer to the front portion of the bike and vacuum bagged it. Today I used double sided carpet tape to seal the bag. It worked well.

The vacuum pump is chugging away, and doing a nice job of maintaining 15 hg, despite the small leak I can hear hissing.
Several hours later, here's the front of the bike after removing the bag. The white stuff is the bleeder fabric. Now is the tough job of peeling off the bleeder and peel ply.
The front part of the bike is all peeled. You can see some of the  wrinkles that will need to be sanded off. The white stuff is some bleeder ply that wasn't adequately insulated from the bike by peel ply.
Over the past couple weeks I sanded the wrinkles off the outside of the bike and started cutting out the areas needed to mount the rear brake.  Mounting up the wheels and doing the bounce test on the bike showed that it's still a bit flexy. I think mounting the seat pan will make it considerably stiffer.

This weekend I was able to get the rear brake mounted. To do this I had to cut a hole in the space under the seat pan and make space for the brake arms. Very fiddly work. I fabricated a CF bracket to mount the brake. It will be accessible through a hole in the seat pan. 

Also I confirmed that I can jam a brake cable down through the two foot long hole I cut through the foam in the down tube portion of the frame, and that it would snake through the under-seat area without snagging anything.

Once the brake bracket reinforcement has cured I will be finally be able to attach the seat pan!

Mixed up a batch of thick epoxy and glued on the seat base. It needs a couple more layers of CF which I will need to add before I can give it the bounce test again. Here's a picture after the epoxy cured. The next day I laid up 2 more layers onto the seat base and vacuum bagged it. I think I am getting the hang of it.
After removing the peel ply, I see that the layup turned our pretty well. The seat base looks good. Where the CF wrapped around the seat onto the frame it will need some cleanup in areas.

This was the first time I was able to sit on the bike in the actual riding position. While a bounce test showed that the bike is plenty stiff now (yay!), the seat lumbar bump and the up tube are closer together than I would like, so the position is extremely intimate. It may be better once I get the cranks on, but I am not used to pressure in that area. Maybe adding the seat pad will help. Here's the area that I would tentatively cut out and redo the layup on.

I weighed the bare frame without wheels or front fork - It's about 7 lb, which is about twice as heavy as a lightweight steel diamond frame.

In any case, Woo-Hoo, time to add the BB shell.

Today I roughed up the titanium BB shell with a course file and then cut the BB hole using a hole saw and a bench drill press. I used a level to determine if the BB shell was square to the frame and to make the slight adjustments with a file after the initial hole was cut.

I added some 172mm cranks temporarily and sat on the bike to see how far off the leg length is. It's a bit long, which is ok because I'm planning on using 165 mm cranks.

Once the JB-Weld cures I will make some fillets from a CF/Epoxy mixture to permanently secure the BB shell.

Whipped up a batch of epoxy mixed with chopped CF to create a fillet between the BB shell sticking out of the sides of the frame and the frame itself. This should firmly attach the BB shell.

Later, I installed a BB and some 170mm cranks to get a picture of me in "the position" on the bike. That looks pretty reclined. By using highly technical "hold a protractor up to the screen" technique, I can see that the seat seat is about 15 degrees from horizontal.

Next step is terrorizing a perfectly good fork to change it to a FWD fork.

I was pretty apprehensive about this step but so far it is working out fine. Over the course of the last week I did the following:
  • Jigged up the fork
  • Cut the fork legs
  • Re-jigged it
  • Added some CF plate to bridge the gap temporarily
  • Checked for clearance and straightness with a wheel
  • Wrapped the fork jog area in CF (Very stiff!)
  • Made a CF derailleur hanger
Here's the fork with the derailleur hanger being bonded on. That's some peel ply and electrical tape on the right fork. They still need a little cleanup.
Here's the front fork with a derailleur installed. Now I need to figure out how to mount the idler.
I'm also working on the handlebars. Tillers bars need a steering tube clamp, a handlebar riser, and the handlebars. The first thing to make is the clamp. Surprise, I'm making it from CF!

First I made a mold to form the CF around from a chunk of aluminum steerer tubing that was the same diameter as my CF one, and some chunks of aluminum for a base and the clamp as in this drawing. The CF was wrapped around. The gap left by the flat plate will allow some bolts to clamp it securely.

Next I wrapped a lot of layers of CF onto the form and compressed it with some foam.  

Here's the completed clamp, on the CF steering tube. I have some 3/4" CF tubing left over from the last CF bike project that I will use to build the riser stem and handlebars from.

I need to finish the drivetrain before I can work more on the handlebars so I can sit on the bike and pedal backwards to determine leg to hand clearance.

Today I worked on the power idler mount. Brazed a chunk of 10mm bike axle and nut to a holy steel plate and bonded it to the side of the frame. I'll cover it in a couple layers of CF to make sure it stays attached. You can barely see the axle stub in this picture.
Over the past weekend I tried several return idler locations, finally settling on this one. It keeps the chain clear of the tire and allows reasonable steering. Yes, the chains do cross but there is (barely!) clearance.

I also worked on the handlebars. After chopping off the excess steerer tube it is starting to look like a finished speedbike.

The handles were JB Welded together a couple days ago and tonight I am gluing the steerer clamp to the tiller tube.

In this picture I am spinning the pedals backward while holding the handlebars to determine the CF tiller tube length and angle.

I weighed the bike and it's 21 lbs as pictured. This is with the heavy wheels and without the handlebars, controls, and brake cables.

Here are the handlebars under construction. I initially glued it all together with JB Weld epoxy. I use JB Weld because if I mess up I can always break the bad part off later and re-set it. In this picture you can see the handlebars which were made from 3/4" OD CF. I added some lightweight epoxy putty to some areas as these will be high stress areas I will sand those areas a bit before covering in several layers of CF. After the bars are strong I will work on attaching the bar-end brakes and the SRAM 9 spd twist shifter from my parts bin.
The handlebars are finished except for the grip wrapping. I decided to use the same layout as the handlebars I built in 2012 for my NoCom. The only difference is that I am using a SRAM 9 spd twist shifter from my parts bin instead of a bar end shifter for now.

I removed some of the frame in the crotch area as it was pretty tight there. I added 4 layers of CF over that area.

I also had to file more clearance for the front brake as I discovered that when the brakes are engaged they expand upward. This took yet another layup to reinforce the filed out area.

After re-assembly and way too much filing to make things fit properly, it was time for the first test ride!

After getting the front dropouts reamed out enough to allow the wheel to be properly seated, the test ride around the block went well. The bike does feel a little floppy so I may need to add another layer of CF or two somewhere. The boom should be pretty stiff so I thinks it's the rear stays or the boom/seat interface that will need some reinforcing.

Also the return idler is crooked so I will have to cut and file it off and then re-add and reinforce it. This was a PITA last time.

I had a nice ride on the e-bike down to watch the 4th of July parade today. Without any set plans for the day, my attention of course drifted toward the beast in the garage.

I decided that the return idler I was using was too wide, so I started looking for a replacement. I located a steel track cog, aluminum BB screw-on end cap, and a 1" OD bearing. The track cog has the same threads as the BB cap, and the 1" bearing fits snugly in the shell with a strip of sheet aluminum for a spacer. It should work much better and be adjustable too. The only caveat is that it's a bit heavy at 100 grams.

Hack sawed off the old CF bracket and filed off the old composite that was used to mount it. This time I made a jig to hold it straight while the goo cures.

The brakes are all connected and the handlebars have grips installed. I bought a bag of flexible brake noodles and used them to put a sharper 90 degree bend in all the cables coming off the controls. It worked out nice and really cleaned up the handlebars. 10 noodles were pretty cheap from Amazon.

The Zote seat pad was cut to match the seat pan. I used a belt sander to clean up the edges and then used my vintage router to give it the ribbed look. I was suffering from dark and hot garage syndrome (which apparently is even worse than dark and cold garage syndrome!) and routing out the ribs did not go well. Built a lexan chain keeper disk for the idler. It stays on fine now except when back pedaling with the wheel turned sharply in high gear. That should not happen often. Wet sanded the back half of the bike to remove the worst of the imperfections and re-coated with a thin layer of epoxy. Reinforced the idler mount.

I noticed on the left rear chain stay I can see the foam through the CF in a couple spots. That's probably too thin.

The bike does have some flex so I decided I needed to do a bounce test video to try to determine where it is flexing. I rode the bike to the short trail in our subdivision to made a video showing riding position, handlebar detail, a low speed turn, and bouncing.

Here are some specs of the "finished" bike:
Wheelbase: 55"
Seat height: 16"
Seat angle ~15 degrees
BB Height: 21"
Weight: ~23 lbs

After viewing the video it appears that most of the flex is coming from the under seat area, and also from the rear chain stays. I will need to add some CF to those areas but I'm not sure if that will get done before the Northbrook races.

Dennis Grelk posted this picture on FB today. It's his FWD laid back dual 700C racer. It looks very fast and like it will be ready for the Northbrook races next weekend.
Racing on the Northbrook velodrome was hot but fun and I came in first place in the 50 lap race. Lucky for me all the faster guys were either absent or already tired from racing in a second class! The new bike worked well.

Sunday I was not so fortunate and I finished in 5th(?) place. It was partially that I was not recovered from the previous day's race and also because of the front wheeldisk. Saturday  there has hardly any wind so it was fine, but Sunday it was windy and I had to go slow to stay on the track. The deep-dish wheel I was planning on using in the front had a valve extender failure on Saturday.

Photo by Tony Levand

This may have been in the last lap of Saturday's 50 lap race when I was trying to get away from Joe, who was drafting me for much of the 50 lap race, but I couldn't shake him. With one lap to go I gave it everything I had and started pulling away, but then Joe did the same and was coming around me when we crossed the finish line. It was a photo finish.

Because the frame has more flex than I would like, I think I am losing some power on the sprints. I'm not a good sprinter, so I can't afford to lose any power to frame flex. Last week I received some unidirectional carbon tow from Mark Anderson which I will use to reduce some of the flex in the bike. Also I need to add a small protrusion to hook my finger over on the left side handlebar, as my hand got cramped up holding the grip.

Photo by Tony Levand via Jeff Hann

Here's picture that Dennis took of his new bike and mine. Apparently he re-used the frame from his dual 20" racer and just needed to build a new fork. Wow!

Dennis says "My seat height and bottom bracket are higher, but my seat angle is lower. My wheelbase is longer due to the laid out seat angle. My head tube is longer, pushing the headset and idlers higher, but the bars end up roughly in the same place. Mine Is currently around 30lb, where Warren's is around 23."

After the Saturday HPRA race around the North Manchester, IN high school, I had to fix the rear brakes as they had come loose. While doing so I noticed a crack in the left rear chain stay. You can see it in this picture. The crack was in an area that I had over sanded and could see some blue foam poking through the CF weave (upper left corner in the picture.  This track has a sharp bump in the back straight that must have stressed it during the race. I'm lucky that I caught it when I did! I put the bike aside and just raced the trike that Garrie loaned me for the rest of the event.
Today I finally got around to fixing it. I sanded the area and added 3 layer of CF over the cracked area, then added the peel and bleeder plies and wrapped it with inner tube to provide pressure. It turned out nicely. Now I will be ready to race it in Cedar Rapids, IA later this month!

The Cedar Rapids races went well and the bike held together. A lot of fast racers showed up and the weather was great. I felt good and did well in the lap races but other folks were faster and my sprint speeds were horrible.

I came in 1st place in the Bartlett, IL Kickstand Classic bike race this morning. My time was 46:09 for the 19.2 mile race for an average speed of 24.96 mph. I finished almost 2 minutes ahead of the next fastest racer for the overall win. 232(?!) racers total. It was a great race course. Dora Cortez and Chris Cortez raced too, Dora was first in her age category and 3rd woman overall.

Here's a photo of the start of the race, by the Daily Herald.

The course was wide and there were a ton of volunteers and police to block off the four laps of the 4.8 mile course. I took off at the 6:30 am start and kept expecting to see the peloton coming up behind me. It was just light enough to see the road, but brightened up quickly. The corners were wide and you could take them at speed. Temps were perfect and no wind. There were lots of people cheering along the route. I kept on the gas the whole 4 laps and they never caught me.

Chris, Dora and I all had a free beer at 8:00 am.

Here's a photo of me crossing the finish line, by the Daily Herald.

 At the last minute they decided not to give me the top overall winner, and instead they gave me the "top recumbent finisher", even though their website stated "any kind of bike" and I was top overall, I got the same exquisitely crafted plastic trophy as the first place roadie guy that finished almost 2 minutes behind me though, and FREE BEER, so I'm not complaining! A marvelous morning!

Here's a photo of me on the podium, by Chris Cortez.

Since it's cold and snowy here I am not riding outside, and am rapidly losing my mojo. While I was not able to use my previous FWD bikes with smaller wheels on a trainer for indoor training, with the 700C wheels my legs clear the front wheel mounted trainer without issues, so this is my trainer rig to train for the February races in Florida.
I was the top finisher overall at the 2017 kickstand classic. I didn't stick around for the award ceremony this year but they sent me a nice certificate in the mail. I traded off drafting with a group of 3 fast roadies. I rode off the front of their mini-peloton on the downhill sections and then they slowly reeled me back in on the uphill sections. We had a huge sprint for the finish line and one of them passed me right before the finish line but it turned out I still got the overall win because they started before I did. I finished the 19.2 mile race 00:45:49 which was 25.15 MPH average. This was just a bit faster than the previous year.
Here's a shot of me behind one of the roadies.

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