Street Barracuda (StreetCuda) recumbent bike low racer HPV
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By Warren Beauchamp

I have started construction of the Barracuda street racer. The Barracuda low racer is a great bike for racing and short, high speed blasts, but the seat is too laid back and not comfortable for long rides, and it's too low for safely riding alone on the street. The idea for the street 'Cuda is for a comfortable, fully suspended bike, that is just high enough to see over the hoods of cars. Also I wanted only the largest of dogs to be able to look me in the eye. I wanted the riding position to be similar to that of the 'Cuda low racer.   

Specs were to be 406 wheels with fat tires, full suspension, mesh seat with 16" seat height, over seat steering and rear wheel drive.  I had originally planned a 44" wheelbase, as that was what fits on my roof rack, and to have the frame tube mandrel bent. I had seen pictures of some Euro-bents with bent tubing frames which I consider quite beautiful. To the right is my original design, click on it for higher resolution. streetcudaframe1_small.gif (10150 bytes)
streetcudaseat1.jpg (5826 bytes) While waiting for the frame to be bent up for me, I collected parts, and started work on items that I could build without the frame. I built the wheels with 406mm Odyssey rims, and Shimano LX hubs. The Tioga Comp Pool tires seemed rather expensive and hard to get, so I used the Avocet Free Style tires. I obtained some 7/8" aluminum tubing, bent it up with a conduit bender into a seat frame shape, and welded it up at the WISIL Skunkworks facility (Bill Murphy's house). Using some seat mesh material that I obtained from Prairie HPV Supply, I (with some help from my wife) sewed together the seat.
I made the seat 17" wide, and incorporated some lumbar curve and shoulder support in the design, which was created using my Vision seat as a base template. I used black parachute cord to attach the fabric to the frame. streetcudaseat2.jpg (3608 bytes)
Note: I have added orange lines in the seat picture above to shows how the lacing was routed. I had to insert plastic tubing into the sleeve at the seat edge to run the rope through. This looks cool but is not the best method to lace the seat to the frame. The best way I have seen uses a thick aluminum wire or thin fiberglass rod slid into the sleeve on either side of the seat fabric. The cord lacing starts at the top of the seat back, and is threaded through a sleeve at the top of the seat back fabric. Holes are punched through the fabric and parachute cord wraps through the holes and around the frames, crisscrossing in the back. See Drawing. The cord ends at the front of the seat bottom, and is tied under the seat. 
streetcudaplans2_small.gif (11096 bytes) I found that getting a tube mandrel bent is no small feat. Muffler shops do not have mandrel benders, which means the they will crimp or wrinkle the thin walled 1.75" chrome moly tubing I was planning on using. All of the local machine shops that had mandrel benders wanted $150 to $300, just to bend the tube. I finally found a recumbent bike builder who said he could get it done for a reasonable cost, and sent him my drawing. After rethinking the design, I stretched the bike 4 inches and changed one of the tubing bends.
After waiting over 4 months for the EarthCycles builder Sean Bjoralt to bend the tubing for me,  I gave up and decided to build a cut and mitered version. The Barracuda street racer has a seat height of about 16", so in a strict sense it is not a low racer, but it's about as low as I want to be for street riding. This is a quasi-low racer! Actually, it's seat height and wheelbase specs are quite close to that of the original Reynolds Wishbone. streetcudaplans_small.gif (6536 bytes)
streetcudaframe1.jpg (4046 bytes)  It's a fully suspended "Z" frame design (which means the BB is significantly above the seat) using a BMX Answer Pro-Forx suspended fork, and a rear swing arm assembly with a Fox air shock. The chain will just clear the top of the front fork, and will have one idler under the seat. Here's the main frame after welding it up at Bill's house, with the suspension fork mounted:
I had to machine a new brake bridge from 1/4" aluminum plate for the front suspension fork, as it originally did not come with cantilever brake mounting attachments. The rear swing arm took a while to make, as there were a lot of angles to check and re-check. This picture shows the swing arm assembly with the pivot tube clamped into brackets.  The rear swing arm pivot was constructed using a concentric tube design, with a 1" tube pivoting inside a 1 1/8"x053" tube.  streetcudaframe2.jpg (4991 bytes)
streetcudaframe3.jpg (4445 bytes) A 1 1/8" tube was braised into the frame, which the 1" suspension pivot tube goes through.. The 1" tube also goes through the rear suspension clamps, and through the frame and pivots inside the frame. I lubed it up well with heavy grease.  It doesn't move as freely as if I used a bottom bracket for the pivot assembly, but it's much lighter and should be plenty strong. Here's the frame with swing arm mounted, and wheels attached. 
Made brackets to mount the air shock and the rear canti-brake studs. It turned out that there was not as much room between the  rear tire, swing arm, and rear support tube as I had thought, so I  mounted the air shock to the side of the tube. The upper shock brackets is made with an adjustable clamp that had a grade-8 bolt braised to it. This actually worked better than it sounds, as the swing arm assembly and it's pivot are robust. I have the seat mounted enough that I can bounce on it, and it is working well, with no torsional flexing.

The brackets for the rear canti-brakes were cut from a 1/8" x 1.5" steel flat bar and braised in place. Braise on canti-studs were filed down and braised to the brackets. Beefy...

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I received some feedback about the 45 degree TIG welded butt joint that joins the down tube to the lower main tube.  People had concerns that when you TIG weld 4130 chrome moly tubing, it becomes very brittle at the weld, and that you must "normalize" it. Testing a piece of the joint that was removed from the bike for brittleness by whacking it with a hammer until it was severely deformed showed that brittleness was not an issue. Also concerns were voiced about possible "losenging" of the joint under heavy stresses, which may fatigue and fail the joint over time. Because of these concerns, and because I don't want to worry about the bike breaking in half,  I'll reinforce this joint. Because the other two main tube joints have tubes braised through them, they are already significantly reinforced.

I have also mounted the seat, which is held on with quick release skewers.

After yet another braising session at Bill's, I've completed the brackets for the main chain redirect idler, and the secondary return idler. I decided to use a large pulley to redirect the drive chain, rather than a jackshaft. With a 62 tooth front chainring I don't think I need the extra step up that an intermediary geared jackshaft will provide, and have opted for the simplicity and efficiency of the large pulley design. With the 11 tooth drive cog, it will have about 110 gear inches, which is about the same as my Vision. The bike is now fitted with a temporary crank boom so that I can work out the chain line while I wait for the custom aluminum Bottom Bracket. The seat height is about 17" now, but it seems very low (compared to the Vision). I'm going to leave it at this height until I get a chance to ride it on the street, to see how it feels in traffic. I can lower it another inch if I decide to later.

Bill found a way to make an aluminum bottom bracket with his lathe, and it turned out nicely. He TIG welded the bottom bracket onto the aluminum boom tube, and we made up the front derailleur post and welded it as well. The aluminum boom tube fits inside and is clamped to the steel tube protruding from the head tube. I drilled out the inside of the head tube to 7/8" to accept the handlebar stem tube, notched the headtube, and clamped handlebar stem tube in place with an MTB seat clamp. I attemped to bend up the handlebars from 7/8" aluminum tubing, similar to the seat tubing, with my  trusty conduit bender, but  messed it up when I decided to rebend it. 
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streetcudadetail2.jpg (10182 bytes) Lesson learned: don't try to re-bend T-6 aluminum!

 The handlebars on the bike now are temporary.  In the picture above you can sort of make out the derailure post, the return chain idler, the handlebar stem clamp (silver thing above the head tube), and the front fork/brakes.

Yes, the cables are a bit of a mess right now. The picture to the left shows the intermediary pulleys (Which are available from McMaster Carr), various clamps for the seat, pulleys and shock mount, and the rear suspension.

Here's what it looks like so far. I took it out for a quick ride last Saturday at Bill's house before the last snow. It handled well, but obviously needs some tweaking. A quick weigh in on the old bathroom scale places it at a heavier than expected 34lbs. streetcuda2.jpg (7181 bytes)
badbars.jpg (4167 bytes) 3/1/00
Well you know they say the fourth time is the charm, don't they? Finally on the fourth try I think I have handlebars that I really like. The first try was the botched bending attempt above, the second was the straight bars,  and the third set was some nice ones that Bill bent up for me with a new tube bending jig that he made, that were too narrow (my knees hit the shifters). I finally decided to give the conduit bender another try, this time with a simpler shape. This time I was able to successfully make a big "U" shape handlebar out of the T6 7/8"x.058" aluminum without problems. The picture to the right shows my 3 failed attempts:
I finally got a chance to take the bike on a real 15 mile ride through the 'burbs, and was very pleased with the handling (and the new handlebars!) The bumps that used to launch me while trying to keep up with the cars (25MPH speed limit) were soaked up nicely by the suspension. Due to the fact that the drive chain is parallel to the rear swing arm, no pogo effect was noticed. Still no speedo, so I couldn't tell what speeds I was averaging, but it felt fast... The bike is getting there! streetcuda3.jpg (7452 bytes)
The next step will be to add the small brace to the joint between the down tube and bottom tube that I mentioned previously. It doesn't seem like it needs it, but better safe than sorry. Then... Paint! I'm thinking an automobile touch up spray in silver would be nice, and would match the aluminum.
In the last month and a half, I've been been riding the Street 'Cuda about twice per week to train for the HPRA HPV races, and have put hundreds of miles on it. All the training must help, because I did pretty well a the last races in Selma, AL. In between the riding, I found time to add a brace to the head tube area to prevent the boom tube from wagging around while I'm cranking up a hill. While this was not a potential failure problem, the less that the head tube moves, the better the leg to crank power transfer is. Since I've been riding a lot of hills, this is important to me.  
streetcuda-paintedframe.jpg (7562 bytes) The head tube area brace was made by bending up some 4130 sheet metal into a box section, and trimming it to fit, then braising it in place. It seemed to help as the boom deflection is not nearly as much of a problem now. I braced the down tube to bottom tube joint as well. Then it was (finally) time for some paint. I picked out some silver metal flake paint at the local auto parts emporium, and after some gray primer, and a little sanding, sprayed it on.
The picture above show the painted frame (which I weighed at 8 lbs, Ouch!), with the rear swing arm folded underneath. You can also see the two newly reinforced areas. I put it back together after waiting just a day for the paint to dry, which was not long enough, as I messed up the paint in a couple of places while adjusting the frame clamps. Ideally this type of paint required a of couple weeks to harden, but I wanted to RIDE it! streetcuda-paintedbike.jpg (5905 bytes)
Oh yeah, I also made a heat and bend Corplast tailbox for it, which makes a big difference going down the hills. So much so, in fact that I appear to be coasting faster than my training partner, AA, who rides an extremely laid back Wishbone, with wheel covers. He's a lot faster than me going up the hills though... Last weekend AAl, Wayne Estes and I rode a hilly 40+ mile ride and ended up with a 19.5 MPH average. I really appreciated the suspension as some of the roads were pretty rough. Before the paint, the fastest that I had averaged in a long ride like that was only 17.5 MPH. Did the paint make it faster? Hmm, I doubt it. 

I changed my riding position a bit. I used the "adjust the seat so your heel is barely touching the pedal when your leg is fully extended" rule, and moved the seat a little further forward then it was before the paint. I think I was overextending before, which was slowing me down, and causing knee pain at the top of my knees. Apparently if you get knee pain above the knee you are too far from the pedals, and if you get knee pain behind the knee, you are too close. Also this allowed me to tilt the seat back just a little more. 

Alan now has a Challenge Jester low-racer, which he trains on and races. I do my best to keep up. Still trying to increase my speed on the road, I obtained a Reg Rodero front fairing from Ed Deaton of Fools Crow Cycles. It needed a lot of reinforcement and I have been working on a mounting system to fit it on the Street 'Cuda. As I am working in my cold garage, I also had to build an temporary "oven" to get the fairing up to a temperature warm enough to cure the epoxy. To make the oven, I used the 1/4" fanfold foam insulation as the sides, and a 2 foot by 8 foot chunk of the 2  inch thick foam as the top. A low power forced air space heater was used to heat the oven. Works nice.

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Epoxy curing oven

The ribs not only gave the fairing a little rigidity, it also provided a place to attach the mounts.

Due to problem I was having with getting numb fingers, and the inability to fit the wide handlebars into the fairing, I changed to a tiller style handlebar. It's hard to tell if the change from the "superman" arm position to the "praying hamster" position improved the cruising speed any, but it is more comfortable. 

I made a steel mounting bracket for the main mount to the boom tube, and used plastic water pipes for the front mount, which doesn't undergo as much stress. Below are a side view and front view of the fairing and bike. Also you can sort of see the tiller steering.

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The Street 'Cuda weighs 36 pounds without the fairing. I'm thinking it's closer to 40 lbs with it. In the past year I have ridden it a couple thousand miles, and it has performed well, but of course, it's still not fast enough. I had put parts of the old "practical" fairing on it for the "Harmon 100" century ride this past fall, and was able to cruise at 25MPH for most of the 100 miles. It was a hilly course though, and that, plus the rest stops and the couple wrong turns we made, made it a 5 hour century. Still not bad, but I really want to do a 4 hour century at some point in my life. Will this new fairing help? I don't know yet, but stay tuned for details...

The street 'Cuda is almost 2 years old now and still going strong! (click on the photo for a bigger image)

Over the course of the past year or so, I have changed both the front and rear brakes to Odyssey A-brakes. I like these a lot. I also changed to the Velocity Aero Heat rims. I didn't like the Odyssey rims I was using before, as the braking surface is funky causing the brakes to pulsate. The Odyssey rims are also a bit undersized. 

This means you can't use Avocet Free Style, or Comp Pool tires with the Odyssey rims as they will blow off the rim at high pressures or inopportune moments. I found this out the hard way and have the scars to prove it. Conti's or Vredstine S-Licks work fine. I'm now running Comp Pools on the Velocity rims without problems.

While this bike is pretty fast and absorbs the bumps well, the 'Cuda lowracer is substantially faster.

The MTB cranks I am using are a bit too wide to use the Reg Rodaro front fairing that I mounted to the bike, as my shoes scrape the inside a little. If I use narrower Q cranks to solve that problem, my heels will strike the front suspension fork. Sigh. The next step will be to work on a custom trailing link front suspension fork to solve the heel strike issue. In addition, this will be used a a test bed for the suspended front wheel drive solution I need for my next streamliner design.

Upgraded to Shimano 105 road cranks to solve the Q problem, and got rid of the front shock fork. As long as I'm running the big tires this should be ok. I got tired of the tiller bars and made some new handlebars, going back to more of a superman arrangement. I had moved the boom out and moved my seat forward a bit to allow the seat to recline more, so I'm closer to the handle bars now.  The new bars have a different hand position than the old superman style bars, so maybe my hands won't get numb. They seem to work fine on the trainer in any case...
streetcuda-bars2003_1_sm.jpg (7347 bytes)
streetcuda-bars2003_2.jpg (5812 bytes) The tubing is all .058 wall 6061 aluminum. I re-used the steel "T" clamp from the previous handlebars and added some old clamp on bar-cons. I had to remove the gear indicators to make the index shifter work.  I also had to make a "flip it" style handlebar mount to allow use on both threaded and threadless steerer tubes. Beside a couple trips to the WISIL Skunkworks, I machined it largely by hand from a solid block of bar aluminum. The best position ended up being a lot closer to 90 degrees than I originally thought, so I needed to add a stop. The bars do swing forward though are damped by a nylon washer.

After a nice group ride with accompanying 3 bike pileup (nothing/nobody hurt) due to slippery mud on the trail, I decided that the flip it bars were a bit too flimsy. The riding position felt good though.

I dumped the flip stem and just used the handlebars that I built for the flip stem with the stem clamped into the top of the head tube. Works great, no huhu. The only thing that has broken on the bike is the Fox air shock. It developed a crack and started losing air. I replaced it with a coil-over shock. I also got rid of the front shock fork, and have a new set of Aerospoke wheels. The thing on the boom is a Laseredge Bike light. It works nicely.
The StreetCuda is now 7 years old. I don't ride it very much any more and it's sort of morphed into my foul weather / winter training bike. It's very stable and comfortable but just doesn't give me the same ballistic speeds as the NoCom. I put the spiffy Aerospoke wheels on my folding lowracer, and have added fenders. I tried changing the fork a couple times but kept coming back to the one pictured above.

Final Street 'Cuda Specs:
Weight: ~30 lbs
Wheelbase: 48"
Seat Height: 17"
BB Height: 24"
Seat Angle: 45 degrees

In 2005, mechanical engineering students Matteo Prussi and F. Bartolini from Florence University in Italy performed an FEM dynamic multi-body analysis on the Street Barracuda. They built a multi body system with the spring unit and the suspension. Matteo recently sent me the results of their analysis:

Here is the CAD solid view of the street 'Cuda frame and seat.

You can click on the first two of these pictures for a higher resolution image, and the next 5 for movies of the analysis in action. 

Here are various views of the wireframe model.
Click on this image to see an animation of the suspension in action.
This movie shows the stresses on the various components of the rear suspension.
This movie shows the stresses on the rear suspension assembly.
This movie shows the stresses on the whole frame, as well as the slight twisting of the frame that occurs due to the offset rear shock.
This movie details the stresses in the seat mount area.

Matteo's final results were that this is not the lightest bicycle ever designed, but indeed it is strong! He said the most stressed point is the lower seat bracket shown here, and that I should take a look to be sure fatigue phenomena are not present.
Because I didn't ride  it, I sold the street 'Cuda frameset. I only ended up getting $50 for it. John from Texas built it up and sent me pictures.

Some of the other parts were re-used on the street racer2 project.

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