[August - September 2007]
When I found that the Worksman 20' frame was going to be too small for me, I pondered selling the frame for a while and just buying some new frame parts (a headset and bottom bracket) and working with them. Two problems with this were that I didn't know anyone who would immediately want to buy such a frame, and that when I measured the Worksman head tube and bottom-bracket thickness, I found that they were significantly thicker than anything I could find from online sources (which were more oriented towards building ligher-weight road bicycles more than anything heavy-duty). I decided to cut the head tube and bottom bracket out of the Worksman frame and use them.
The basic frame is together; engine still needs mounting. The gas tank still needs making and I decided to order a bobber motorcycle seat and mount that instead. There are some bicycle seats still available that pretty much nail the period look - saddles like the Brooks B33 and B135, but I don't think they'd really be as comfortable as the motorcycle seat would. The frame does not have the usual "bicycle seat post" mounting setup present, so I'd have to make a mount either way
Image below: tacked frame, quite a bit longer than the Worksman frame (now missing a couple parts):
Image below: basic frame with fork & wheels in place:
Image below: gas tank parts top to bottom - flat side, bent side, tank spine.
Image below: one side and two rear panels of the tank welded on. The tank is going to be VERY lumpy, but I'll just be happy if it holds liquid fuel. I didn't have any way to roll the sides to curve them so I heated them with a torch and bent them by hand, and in some spots the metal warped a bit. Also I did not think much of assembling the thing, in hindsight I should have pop-riveted the whole thing together and then welded it and grinding out the pop rivets as the torch got near them, but that didn't occur to me at the time.
I liked the way the Monark forks made by Crossbow Cycles looked, but still wanted a front brake. The way the Worksman brake is made, the brake's anchor needs to stay stationary relative to the axle (no twisting with suspension movement) because the axle nut would be twisted loose. The drum brake cannot be anchored to either blade, but the notch on the fork appeared to nearly straddle one of the fork bolts. In its original form the notch is cut too narrow to do that, but I have a grinder...
Image below: Worksman drum cover, before cutting. The long slot is present because on forks made specially for this drum brake, there is a tab on the left fork blade that engages the notch to prevent the drum brake from spinning when used. (The Worksman parts listing gives a number for drum-brake-specific forks, but for some reason the bike I ordered with a drum brake had regular forks, and anchored the drum brake with a P-clip mounted in the drilled hole)
Image below: Worksman cover, after cutting and reinstalled on drum hub...
The Monark forks are reproduction forks that originally were made during the 1930's to around the 1950's, and the wheels they are intended for are only about three and a half inches wide at the axle. The dropouts come mounted inside the fork blades. Current wheels are about a half-inch wider and the lower pivot bolts that come with the forks are an odd shouldered type so they cannot simply be reversed to allow mounting the dropouts on the outside of the fork blades. I had to buy new bolts and spacers to allow re-arranging the fork parts to be wide enough for a modern 4"/100mm wide 26-inch wheel.
Image below: With the front hub installed in the forks, the notch straddles the rear pivot bolt head. The notch is big enough that it will not turn the bolt head.
*Note #1: the dropout axle notches needed to be widened, from 5/16" to 3/8".
**Note #2: the fork's steerer tube lacks a lower cone shoulder, so you will need some shim stock to assemble the fork properly. I don't know at this point if this is how the original forks were or if Crossbow just left off this part for some reason, but it is critical.
Image below: frame with forks and engine mounted. The engine has its original angle mounting bracket rotated 90 degrees, that is bolted to a 1/8" steel plate, and the plate is bolted to a pair of brackets on the frame. This should make it fairly easy (in theory) to switch engines or even drive setups.
Image below: shelby-style bars, after slicing, hot bending, re-welding and a bit of grinding. To bend the tube it's necessary to make a series of cuts about halfway through, heat the tube with a torch and bend it, and then re-weld the cuts up. You get a bit of rippling this way but it's not real bad. Tubing bent cold tends to lose some of its stiffness, but tubing bent when heated orange-hot doesn't suffer that stiffness loss. If I had a way to heat the tube all-the-way-around without cutting it I would have, but so far I haven't got a torch setup that can do that.
The copper wire on the ground in front is a guide I made beforehand to get the sizing correct. These bars are about 18" wide and 26" long, standing over the bike they seem HUGE but the information I found says that's about right.
Image below, taken from an old bicycle catalog online here:
http://www.nostalgic.net/index.asp?S=arc/ScannedLit/catalog+%2D+1919+Harley+Davidson+accy+13%2Ejpg
There are a number of bars Shelby used through the years but this is what I was trying to copy.
Image below: aligning the bottom bracket for welding. Since the ends of the bottom-bracket shell are already cut square, you can "use" that for alignment. There's a long threaded rod held with nuts through the perforated square tube and bottom bracket shell, and the vise-grips are holding a small flat piece of metal to allow the horizontal tube to rest on the head tube. This way it's easy to eyeball the alignment and get it pretty straight.
Image below: idlers, in original and "finished" states. The bike frame will need to run one side of the chain up over the engine, and the other side below it. Since neither of these runs aligns with the sprocket, two idlers are needed. I looked around but couldn't find any idlers that I felt were built well. All of the recumbent-specfic ones I found online are plastic, and there's industrial idlers with roller bearings made of steel for roller chain in ANSI sizes, but there's no ANSI chain size that's identical to bicycle chain. Cruiser bicycle chain is 1/2"-pitch, 5/16" roller diameter and 3/16" roller width. The ANSI chain sizes that come closest are #40 (which has 5/16" wide rollers) and #41 (which uses 1/4" wide rollers that are also a very slightly smaller diameter).
Since these don't have a lot of engagement I chose a #41 ball-bearing idler and used an angle grinder to grind down the tooth width enough to accomodate bicycle chain. The bearings appear to be simply pressed in, but since I had no way to press the bearings out (or get them back in!) the grinding took a while to do. You can only grind for a few seconds before the sprocket gets VERY HOT, and I didn't want to risk melting the bearing dust covers, so I would grind for a few seconds and then hold the sprocket in a damp rag for a minute or so. It would only take about 5 minutes to do if I'd had way to temporarily remove those bearings, but it took about an hour and a half as it was.
