2017 - Entry #1 - Micro Chopper - DNF

[OzFab]

I'm actually glad the build-off has started so early, I've been itching to cut into this thing for weeks... now I can

Below is the required pic of the parts pile with the sign...

 

[Joe-405]

I'm glad also. Which means my 2 will qualify also. Nice to see you back sir.

 

[OzFab]

"Back"?

I've been slowly whittling away at this thing (it's difficult to make any real progress with limited time, extreme heat (35°C+ almost every day for the past few weeks) & no welding wire but, I have managed to do enough cutting to mock up most of the frame mods...

Stretching the height at the rear of the frame was simple enough, I simply cut the frame & inserted the necessary extensions... done; the only issue here is that the swing arm is now at the wrong angle so, shock mounts need to be moved...

The front was a little more difficult; first, to obtain the correct angle for the seat, I cut the welds holding the rear of the upper frame from the front bar & bent to the desired angle, making sure the engine now had enough clearance; once that was done, I then had to fabricate the front of the frame...

Originally, there was a single tube joining the lower section to the upper support, which also held the rather retro looking framework which held the foot rests; at that point I decided I wasn't going to use that piece so, & used two of the bends to create the inner supports for the front of the frame. I then cut slots in the outer tube to allow for the bends & pieced it all together...

Next step, rake the frame & stretch the forks...

 

[OzFab]

The first step to stretching the forks was to make a triple tree which was done using 5mm flat bar, lots of drilling & a lot more filing...

I then discovered some threaded square tube inserts my buddy gave me (I knew they'd eventually come in handy) & modified them to fit round tube...

At the same time, I cut 3/4 of the head tube from the main frame bar (sides & bottom) to set the rake angle, which is now around 50°, & calculated the correct length of the forks, mocking up the whole bike in the process...

 

[Kartorbust]

I've always had a soft spot for these older chopper styles.

 

[TheCollector]

Looking good!! I'm follow this one.

 

[chancer]

I like the way it looks.
I really like the old schools "Sissy Bar" but it still looks a little big compared to the "Micro Chopper" theme you have goin on.
Anyway still nice work.

 

[TheCollector]

I Agee. it is a little to big

 

[courts94s]

I like the way it looks.

I really like the old schools "Sissy Bar" but it still looks a little big compared to the "Micro Chopper" theme you have goin on.

Anyway still nice work.

I think it looks proportional to the handle bars. We really need to see a picture or video of him riding it.


Sent from my iPhone using Tapatalk

 

[OzFab]

Ok, let's see if this adds a little context...

- That's a Metre rule in the pics; as you can, hopefully, see, the top of the tank sits 2' from the floor
- the handlebars account for 1/3 of the total height, currently sitting 37" from the ground at their highest point
- the wheels are 10" tyres on 4" rims
- without the forks, handlebars, tank, seat & sissy bar, it's actually quite small...

Now, that may not be "micro" by some standards but, the bike was originally built on pocket bike standards, I'm making things larger not only to improve the look but also to make it easier to ride...

At the end of the day, I couldn't call it a "mini" bike because it's smaller than that...

 

[OzFab]

Been busy welding & grinding & welding & grinding &... you get the idea...

The majority of the frame is welded & finished, with the exception of the front as I still need to set the rake once the forks are completed...

I am quite proud of the finish on the front tubes; considering there were 4 weld lines, I think they came out quite good... not perfect but, close enough considering...

 

[OzFab]

My most trying dilemma to date is figuring out how to reassemble the shocks on the front forks after I stretch them; see, originally, a bolt was inserted from the top of the inner fork which attaches at the bottom of the outer tube with a spring in between; once I extend & seal the inner tubes, there's no way of accessing this bolt so, I had to come up with an effective solution...

As you can see in pic #1, when the shocks recoil, the bolt travels up inside the inner tube as it's fixed to the outer tube; a rubber bush is fitted to reduce metal on metal damage...

If I simply drilled out the outer tube & placed a nut on the end of the bolt, the bolt would fall through the bottom of the outer tube when the shock recoiled, creating a potentially dangerous situation; I then realised if I added a lighter expansion spring under tension on the bolt in the inner tube, when the shock recoiled, the smaller spring would pull the bolt up inside the inner tube, eliminating any metal on metal fatigue & the bolts wouldn't protrude out the bottom of the outer tube (see pic #2)...

As you may also see in pic #2, a nut is fitted between the inner & outer tubes; this is to prevent the bolt from springing up into the inner tube if/when the need arises to disassemble the shocks...

 

[landuse]

That looks like a good way to go with the shocks

 

[OzFab]

Rolling frame done; now for the hard part, EVERYTHING ELSE!

Here's my grandson trying it on for size...

 

[Kartorbust]

Scaling looks about right with the ape hangers on it, with him riding it lol.

 

[landuse]

That is looking awesome Tony!! You can really see the size with your grandson on it

 

[OzFab]

Picked up some parts the other day, namely, sprockets...

Now, remember, items like this are not as accessible over here...

The two jackshaft sprockets are ok but, the wheel sprocket (#35 60t) seems a bit overkill to me; pic 1 shows the weight; note that's grams, which is equivalent to 2.5 pounds & it's 5.2mm thick (1/4" = 6.4mm)...

Think I may be doing some machining...

 

[landuse]

You could cut some holes out of that sprocket plate to lighten it

 

[OzFab]

That I will be doing; for starters, I need to cut a 55mm hole in the centre to fit it to the hub & I will figure out a design & cut other holes in the body...

The width of the teeth is only 4mm, meaning I can safely cut up to 1.2mm from the thickness of the plate; that's 23% or 270g, just over half a pound...

With just those mods, it should end up AT LEAST a pound lighter...

 

[OzFab]

I'm officially throwing in the towel on this build; it will be finished, just not this year; my priority is the twin karts which ABSOLUTELY NEED to be done for Christmas plus I also have the black kart I need to get going in the same time frame...