Robert Thumper

[NEAT TIMES]

MR.B.

Both builds are awsum, waiting for finish of this build. Am inspired to asemble my stretch cruiser with 140cc Honda clone. Thanks much for sharing.

Ron

 

[dmb]

very nice. what rear hub are you using? and is that a freewheel next to the sprocket [pic's]?

 

[Mr.B.]

The hub is from a old Tomos moped, the 48t sprocket is off the shelf from a farm supply store.

Yes that is a BMX style freewheel- I simply cut the threaded side off of a bicycle cluster hub right at the spoke flange and welded it to the sprocket .

But first a recess was milled the depth and diameter of the flange on center to the sprocket to line things up.

-Kirk

 

[atombikes]

So you will use a jackshaft to get the engine drive chain to the bicycle side and run both chains on the bike chain side?

 

[Mr.B.]

Yes kind of, I’m using a bolt on CVT and extending it’s axle to the right side.

I also added a additional pillow block bearing on the right side to help support the now longer than stock axle...

-Kirk

 

[Mr.B.]

I finally finished Robert-T last weekend! (well kind of anyway...)

And I just now finished updating my Tumblr blog-

http://excalibur09.tumblr.com/

Here’s some excerpts from the blog to catch up all the progress...

-Kirk

 

[Mr.B.]

3-12-12 TANK & INTAKE…

Began the fab for Robert’s fuel tank and also a intake manifold made from a “street” style gas pipe elbow fitting.

 

[Mr.B.]

4-15-12 MOCK 3

I mocked up the Thumper again today, this time with the new exhaust & gas tank included. After just staring at it for a while I’m just not pleased with low slung “pregnant guppy” look of where the bottom bracket sits…

 

[Mr.B.]

4-22-12 PREGNANT GUPPY ERADICATION

Decided to take the plunge and try to tuck the sagging bottom bracket up a bit. The frame was cut and a wooden jig was made to straighten out the lower stays. With the help of my largest pipe wrench it went pretty fast!

 

[Mr.B.]

4-29-12 REFRAMED

Robert-T’s frame changes were welded today along with new tabs for the tank mounting and the rear brake stop.

 

[Mr.B.]

6-27-12 EXHAUSTED,

I painted the exhaust pipe with high temp paint today, I had to bake in the oven to cure it. Smelly stuff, I hope it works well!

I also drilled the baffle and turned a gas pipe connecter fitting that will fit into a section of chrome closet rod “tailpipe” purchased from the local home improvement center…

 

[Mr.B.]

7-6-12 MINI SHROUD

I started building a aluminum “mini-shroud” today. It has quite a personal connection as it was originally the saucepan from my bachelor days, and I’ve been married 25 years! Ha!
A wooden buck was made to shape the center hole roundover, then heavy to fine sanding to smooth things out.

 

[Mr.B.]

7-12-12 CHAIN GUARD

I scored a nice straight Schwinn “Bird wing” style chainguard. It will need to be stripped and re-painted though…

 

[Mr.B.]

7-15-12 SEAT PLANS!

Came up with this Robert Thumper seat design today…

 

[Mr.B.]

7-29-12 TTT

Begin the construction of Robert’s triple trees today, It’s just for looks as it doesn’t really add any actual strength.
Thick aluminum sheet and a vintage bmx stem used to create the top plate.
Left over chrome closet rod is a close size match and freshly turned wooden plugs with threaded rod ties everything together. Rubber o-rings clean up the connection point.

 

[Mr.B.]

8-8-12 BARRED

After trying several different handle bars on hand I ended up just buying a chunk of straight aluminum stock from the metal supply store. I think it gives it a nice aggressive drag bike look!

 

[Mr.B.]

8-28-12 FAB’N & WELD’N

This is the last of the fabbing and welding to be done for Robert-T.
Tabs for chain tensioners were added, the drive chain one came from a old automotive alternator bracket and is pretty damn heavy duty!
I added a toolbox similar to Excalibur’s “gaslight reservoir”. It’s a bit heavy walled for the job but I had the tube on hand and having a place to store tools & the rope pull will be worth the extra weight!
The original nut for the pull start and a 5/8” bolt were turned so they fit together tightly & perfectly centered for welding. Later I’ll tap and notch a hardware store pulley to attach here.

 

[Mr.B.]

8-29-12 PAINT ME!

Sandblasted, ground welds, and puttied seams, this guy is ready for paint! As is the gas tank, rear fender, and chain guard!

 

[Mr.B.]

8-30-12 OK
Painted stuff today!

 

[Mr.B.]

9-28-12 COVERED!

Worked on the seat today! I always envisioned a tooled leather seat cover for R-Thumper but had never actually tried carving it before.

I bought a inexpensive punch kit on Ebay but didn’t realize how important the missing swivel knife was going to be as I struggled with a old chisel I had quickly modified for the job.

I’m not 100% happy with the results but will keep it as a reminder of the learning curve, the next one will be better!
But I was happy with how well the wetted leather formed to the old children’s riding tractor seat pan!