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PART 7, March 9...'68 Harley Sportster: 1/8 scale Bronson bike resto and upgrade


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Anybody remember the one-season TV series Then Came Bronson ?

The bike in the show was a modified 1968 XLCH Sportster. MPC made a kit of it, released in 1970 and '71, and never again (as far as I'm currently aware).

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Most of the survivors are partial kits with missing and broken bits, or gluebombs...and usually pretty expensive.

"Bout a year ago, I picked up a semi-complete but poorly built and broken one.

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After a lot of research, collecting photos, info, and more parts, I'm ready to start the deconstruction and rebuilding process.

First thing is to split some of the glued parts that are out of register (due to incorrect pin locations and sloppy building). I've found that an X-Acto chisel tip blade and a small hammer work very well for this sometimes.

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In the photo above, the shock unit on the right has been split apart, the halves surfaced, and then re-glued with the parts in correct alignment. After drying overnight, files and sandpaper are used to clean up the seams.

Edited by Ace-Garageguy
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Great re-work on a very rare subject. Can't wait to see it rebuilt. At least you got the most important parts - the bedrolls!  (Kidding). 

Here's a 2015 thread on "ungluing" parts, just in case it helps. (You even participated in it.)  I wonder how that Freeze-Off stuff worked...
 

 

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Thanks to all for your interest and comments.   :D

PART 2

There are a lot of relatively minor things to fix on this old model, so I'll be taking them one at a time as she goes back together.

The handlebars were broken (and a previous repair at a different point seems to be strong enough to leave alone), so I drilled .025" holes in the broken ends to insert a length of steel pin for a reinforcement.

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The tires had both shrunk (badly warping the rear rim) and dissolved parts of the rims where the chrome had been scraped away for glue by the original builder. I was able to get the tires off the rims (with no additional damage) with the aid of a small, sharpened and bent screwdriver blade used like a tire-iron. The tires close to the rims are from this model. The ones on the left are repops from the same tooling, sourced from a fairly recent reissue of the old MPC Honda 750 race bike. Look closely, and you can see how badly the old ones have shrunk. The OD is almost 3/16" smaller on the originals.

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With some VERY careful sawing using a PE blade from MCG, I was able to split the heavily glued rims, again with very little additional damage. You have to work SLOWLY, with lotsa patience. The rims had also been assembled out-of-register, so the spokes didn't line up correctly. The new tire, a 19", fits the old front rim perfectly (but more on that later).

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The joining faces of the previously split jugs and engine cases were "milled" flat on a piece of 180 grit paper stuck to the bench.

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One jug, engine cases, and handlebars, glued back in correct register. Again, files and sandpaper will be used to address the seams after overnight drying. The engine cases are supposed to have a seam where the two halves are bolted together, and this will be re-scribed after the register problems are corrected. 

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Edited by Ace-Garageguy
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PART 3

Much of the frame was heavily glued together, again with the frame halves out of register, and several parts just stuck on where they didn't belong. The upper triple tree was also solidly glued to the frame, as was the shaft.

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After disassembly, the frame was carefully split, and the mating surfaces "machined" flat. The other cylinder has been done here too.

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When I split the frame halves, I had to saw through several heavily glued joints, and I lost about .010" of material due to the saw kerf. I replaced this prior to re-gluing, with dots of .010" styrene.

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A very handy tool to have for punching holes and making dots is made by Stanley.

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Frame halves back together, in correct alignment this time.

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Edited by Ace-Garageguy
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PART 4 

So...after the frame set up nice and hard, the seam on the upper tube was lightly dressed, and the location of the locating pin for the tank was drilled in and replaced with a piece of 1/16" styrene round stock. The bushing for the swing-arm pivot was also carefully drilled with a 1/16" bit, a little at a time from each side, to insure it was square with the frame. The frame head has also been carefully drilled out to 1/16".

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Checking the tank fit, and another view of the drilling for the swing-arm shaft. The spacer "dots" are apparent here, and have been shaved down to match the frame cross-tubes.

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The swing arm was also broken. I cut the poorly-aligned side arms apart, put in another .010" spacer dot to replace the thickness of the saw kerf, drilled the ends to 1/16", and assembled the whole mess with the arms parallel.

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To determine exactly where the rest of the broken arm would have to go, it was necessary to get all the parts together that have to go between the axle ends of the swing arm. The brake drum was among the missing parts, so I guestimated how thick it should be from photos of real bikes, and used the two white styrene discs as a stand-in. In this shot, the broken ends of the LH arm have also been drilled for a .025" steel reinforcing pin.

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With the axle ends of the swing arm drilled for a 1/16" brass axle, and all the parts assembled (with the axle held parallel with the swing-arm pivot shaft) it was possible to determine how thick of a spacer would be required to replace the filed-off jagged ends of the LH arm. A feeler gauge showed it to be .020".

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A .020" dot was drilled and inserted between the pinned broken ends, and the wheel and other parts used as a jig to hold the ends in position as the glue set up.

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Once again, thanks for the interest and comments.

PART 5

The forks and triple-trees were broken and damaged. Again, everything that could be glued was misaligned and slathered in goo, and not easily repairable to the standard I want this thing to come in at.

I made and recorded measurements of what was there, so the parts could be modified or replaced with scratch-built replicas.

The lower triple-clamp, shown still assembled to the forks, is two halves glued together around the fork tubes. It was split apart and the halves "machined" flat, as shown with other parts above, and re-glued in correct alignment. It also carries the headlight bracket, which was heavily glued in the wrong place. I just cut it off. We'll make a new one.

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The upper triple-clamp gets saved and re-worked too. The molded-in hex-heads will be replaced by brass fasteners.

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After all the bodged messes were removed and the upper triple-clamp was rebuilt, both clamps were fixtured together and drilled to get the holes to all line up straight and parallel...not including the steering shaft holes, which were molded slightly out of line when viewed from the side. I have to assume this was intentional on the part of the kit designer, to impart a little rake to the front forks.

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New fork legs were made up from brass tube, and aluminum telescoping sleeves of the same diameter as the OEM parts are being made to cover them. These can be highly polished to simulate chrome, and they'll hide the slightly elongated holes I ended up with in the lower clamp to get the fork tubes to assemble parallel. If I'd done this work on my mill, everything would have been dead-on, but the mill lives at one of the big-car shops now.

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Assembled and installed on the frame with a 1/16" brass steering shaft. I drilled the holes for the shaft in the same places on the clamps as were originally molded, so I have to assume that the rake of the front forks is the same as the original model represented. The white inserts in the upper triple-clamp are from where I drilled the holes for the fork tubes incorrectly...twice...and had to insert styrene fillers, let them dry, and re-drill to get everything aligned correctly. The fork tubes HAVE to be dead parallel in two planes.

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Now we can step back for a minute, and see something beginning to look like a motorcycle.

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Edited by Ace-Garageguy
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On 3/3/2018 at 8:00 AM, Marcin M. said:

You, Mister, are really an ACE!

:D Thank you, sir.

PART 6

More bits and pieces. The right hand engine case / gearbox cover had the shifter and kick-start levers heavily glued on, and again, not exactly in the right places.

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It took careful effort with the tools shown to get them off with minimal damage to everything. The ribs on the cover are largely obliterated where the shifter lever glue was globbed on.

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The lore surrounding the actual bike says the sissy bar, one of the notable custom touches on the Bronson bike, was made from a Schwinn bicycle part. The sissy bar was also among the broken kit parts, and there wasn't enough left to tell exactly what it was supposed to look like. I decided to replace the outer tube with styrene rod stock, and transfer the ring to the new part.

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The rod stock was bent cold around an X-Acto handle, just to make sure that I could get a 180 degree bend without cracking it...but I didn't get the shape quite right on the first try. I also didn't make one of the legs long enough, having no pattern to work from...which I realized after looking more carefully at photos of the real bike.

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The second try was better, and after getting the shape right, I taped it in position and "tempered" it, so it would HOLD the shape, by dipping in boiling water for 30 seconds. Styrene rod will spring back otherwise, if bent cold.

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In this shot, we see the first batch of parts to go in the chrome stripper, and the partially completed sissy bar. The stripped parts, as well as the tank, will also be scrubbed with hot water, a toothbrush, and Comet. I've chased the ribs on the side cover using the tip of a razor saw blade, and we'll see better exactly what we have to work with after the chrome is removed. I also repaired the broken off corner of the front fender.

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The mufflers were heavily glued, but not actually stuck together very well, or in register. They'll be "milled" flat on the mating faces, and re-glued, lined up correctly.

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The rear fender has heavy-handed holes and slots for mounting it to the frame, and for attaching the sissy bar. I'm filling the holes with .040" styrene stock. The frame details at the lower cross-tube don't match any of the online photos I've found so far, so that will be addressed shortly. The location of the kick stand is determined by this...and on this particular model, it was just heavily glued on under the frame, in an apparently random location. 

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On 3/8/2018 at 1:05 AM, Mr mopar said:

Bill this is so cool !........................ I love restoring glue bombs ,your on a roll keep it up.

Glad you're enjoying it.  :D

PART 7  

Time to get her up on her feet. I made up a temporary axle assembly from styrene tube that would telescope into the new brass fork tubes, and using them as a jig, cemented a cross-tube to serve as an axle. This insured the axle ends would be square with the forks. I then cut the cross-tube in half, so I could get it in the axle holes in the wheel.

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The REAL Bronson bike was customized somewhat, and one of the mods was a 21" front rim and tire. The model came with an incorrect 19" rim. I scrounged a 21 incher from another later-model Sportster gluebomb. The rear wheel on the Bronson bike is the stock 18 inch job, but I wanted a little different look there too, with a fatter tire. A 16" rim from another gluebomb, and a fatter, taller tire to fit it, and I got her mocked up looking pretty much as I had envisioned. The front brake disc is about the same diameter as the old brake drum center on the 19" kit wheel, so the proportions aren't really changed all that much. The tank has been shot with self-etching Duplicolor green primer, after sanding off the glue smudges and cleaning up the edges. The HOT primer didn't attack the 48 year-old plastic one tiny little bit, which is consistant with my constant harping about the poor quality of current kit plastic.

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With the forks, triple trees and front axle in place, this is how she'll look on the stand at this point.

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And with the handlebars and headlight mocked in final position...

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Now comes the tedious part...taking her apart again, and finishing up all the bits. I'll also have to come up with a hydraulic front brake master cylinder that isn't too bulky. I'll be staying with the stock style rear drum...and probably going to lower just a little...B)

Edited by Ace-Garageguy
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22 hours ago, Marcin M. said:

This kind of WIP is a honey for my eyes, as we say here in PL. You will do something with the rear spring? The one from the set does not look good. A thick wire maybe?

 

:D  The rear springs will be replaced with real wire-wound compression springs, yes. I was going to just detail them with paint, but after going to so much trouble fabricating new front forks, I need to do real rear springs too.

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3 minutes ago, Ace-Garageguy said:

:D  The rear springs will be replaced with real wire-wound compression springs, yes. I was going to just detail them with paint, but after going to so much trouble fabricating new front forks, I need to do real rear springs too.

That's a relief!

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