Reddback's first motored build



Finally settled on a new frame for my 50cc engine kit. Have a vertical alignment-jig holding the crank-tube, front and rear axles a dummy rear tyre cut-out and the suspension saddle off the previous chopper.

Pics are of the 1:20 scale draft of the frame layout which I'll use for reference on the fabrication table and jig. The second is a plan for a Steer-Tube alignment jig which I'm not using this time around but thought it may help someone else. The third image is a fantasy viewof what I'm looking to acheive . :cool:

Frame Fabrication
All tubing is el cheapo rolled mild-steel with 1.6mm wall, ex Bunnings. Top-Tube, Down-Tube and Bottom-Rail will be single lengths of 25mm OD. Upper and lower Chain-Stays will be twin rails of 19mm OD.


24" x 2" BMX rims from the '80s

Tyres front and rear are Maxxis 24" x 2.5" and 24" x 3" respectively. These tyres are high-profile and measure 26" OD.

Front-end is a hand-made Springer Triple-Tree with a 230mm Steer-Stem. Steering angle will be set at 30 degrees, but if all goes well this will be adjustable out to 45 degrees.

Front brake is a cable-op Textro 160mm Disc.

Rear is a V-brake assembly from a Huffy 24" freestyle donor bike.

Saddle is custom made 300mm long x 200mm wide with bound and rebound springs.

Crank set, Ring-Gears and middle hub sprocket are from the said Huffy donor.

Rear and idler sprockets from the '80s BMX unit.

Idler hub is a late '60's Shimano 3-speed with axle tube shifting rod.

Engine is a Chinese 48cc 2-stroke geared to a 28T on the Idler thru to a 36T final.

I've previously hand-made a metal coffin tank for a Trumpy, so may do so this time.

A 12V 7ah lead acid sealed battery will be located under the Top-Tube below the saddle mounts.

Head, tail & flasher lamps are from a Harley Pocket-bike. I have a micro-switch wired to the brake lever for a stop lamp.

Today I clean-up the workshop, which is mainly used for auto repairs/modifications and the build begins in the morning until finished.


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Adjustable Rake

Here's a couple of images showing the adjustable rake by way of a pivoting Steer-Tube plate inside two outer plates welded to the Top and Down Tubes.

You'll noticed that the handle-bar risers are also adjustable as is the front pivot on the saddle.

The previous chopper had a 45 degree steer angle and was a nice lazy ride on long, country road curves, but quite awkward around our skinny city road lanes. I've also tightened the wheelbase on this ride by raising my saddle from 500 to 600mm allowing for 1.5mtrs and 1.7mtrs in the two variations. The old bruiser was 1.8mtr.:rolleyes:


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I like the adjustable steering angle. I may have to blatantly steal that idea from you. :oops:

I like the adjustable steering angle. I may have to blatantly steal that idea from you. :oops:


Go for it bloke...let's consider it 'the borrowing of an idea!' However you can figure the plate and bolt holes out yerself, I reckon the rest of me hair's been pulled out on that one! :)

The only factor stopping me from building any facet of the plan will be lack of materials, equipment or skills. The first two are always my bug-bears, but I have three car wrecks around the place with lotsa steel in 'em & the MIG is still buggered, so its Arc Weld with 1.6mm & 2.0mm rods for the most of it. :D

Images below are a few 'ideas' I passed-over and are available to all and sundry.:rolleyes:


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rear suspension added

Been scratching my scone over this for a while now, but I reckon this'll be the duck's nuts for rear suspension and I can lose all the saddle hardware. Of course I'll need to fabricate a new saddle to suspend my butt in, but there'll be a rail wither side for a perimeter. :D

Also changing the front-end to a single coil-over damper to get rid of the current springer setup and save a few kilos in weight to boot.

I have a couple of ideas I've used on various autos for keeping the fuel cool and a shroud for directing air across the engine fins to cool it down as well.

Workshop's finally presentable and I'm into this project.:cool:

[edit] Using a front hub assembly from an old chopper for the swingarm pivot. After slowly grinding off the flanges this hub fitted snuggly inside a mild steel tube off-cut.It was located under the saddle atop the seat-tube in the 2nd pic. :D


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