THE COUNTDOWN IS ON - August 15, 2010
As the last few weeks of school were wrapping up, Cal and Eric were studying for their finals at Eureka High School and reviewing two years of machining curriculum here at South Technical High School preparing for their Precision Machining final test. While all of this was going on we are putting the final touches on the chopper so we can test ride, disassemble and apply a paint job.
8 Days left
The engine is now mounted in the frame and a chain and idler sprocket has been ordered. At this time we have not figured out how we are going to get brakes put on the chopper, so we are leaving this as a final task before painting. Cal, Eric and a student from our Motorcycle Mechanics Program are struggling to get the engine fired up today. They have a spark at the spark plug and fuel in the tank but for some reason the engine will not start. So, I call Mr. Prewitt who teaches our Motorcycle Mechanics Program over and he gives the engine a once over and says I'll be right back as he quickly walks out of our shop. We are all looking at each other and feel a sense of emptiness as we look at a year's worth of work in the chopper and it will not start. A couple of minutes pass by and Mr. Prewitt returns with a large box in his hands and drops it on the floor. In the box is a brand new 6.5 H.P. Briggs and Stratton engine and he instructs his student to pull off the old engine and give us the new one. Within minutes our sense of excitement returns as the sound of ratchets and wrenches are removing the old engine and installing the new. Eric pulls the oil cap and fills the crank case as Cal removes the fuel tank and works over the throttle linkage to hook up our cable. Some fresh fuel, a couple yanks on the pull start and the engine fires right up. The chopper comes alive and we sense we will soon be rolling when the chain and idler sprocket arrive. We end this day on a high note having heard the engine finally run.
7 Days left
The chain and idler sprocket arrive and we begin mocking up a bracket to mount the idler on the frame. Once Eric machines up the bracket, we roll the chopper once again over to the Welding and Fabrication Shop to get it welded into place. Minutes later the chopper rolls back into our shop; we measure and cut the chain and carefully mount the idler pulley to the new bracket because it is still hot from the fresh welding job. We attach the chain, set tension with the idler and roll the bike across the floor to see how the chain tracks on the sprockets. Sprockets all appear to be in alignment but we discover a new problem. The rear fender is a bit too wide which means the chain has only a fraction of an inch of clearance which creates a problem because the chain will vibrate when under a load and we are sure it will rub the fender and create major problems later. We mark the fender where clearance is needed and Eric and Cal remove it from the frame before heading home for the day. We are beginning to wonder if we are going to make the 6 day deadline.
6 Days left
When Cal and Eric arrive back to school, we quickly get the fender up on the bench and break out the 2" pneumatic cut off wheel and cut some clearance slots in the fender. We bolt the fender back into the frame it looks like the chain will clear, so we are ready to take it out for a test ride. We roll it out the back garage door and Cal jumps on it and gives it a couple of pulls. The engine starts, he cracks the throttle and the chopper starts pulling away as he grips the handle bars tighter so it won't run away on its own. Cal sits on the frame (where the seat will be once it is finished and upholstered) and pulls away racing down the driveway. He returns in a couple of minutes as he drags his boots on the ground (Fred Flintstone style) to bring it to a stop. As he steps off the chopper he says with a big grin on his face, "this is really cool....., your turn Eric." Eric quickly grabs onto the handle bars, jumps on and takes off. When he returns I direct him back into the shop and we shut it down to give an inspection to see how everything looks after its inaugural ride. We discover a couple of bolts that had worked loose and the guys talk about how much power it has. They talk about the sprocket tooth ratio and they are both in agreement that their rear sprocket size is very appropriate for quick take off and strong top end speed. Cal and Eric look at each other, then look at me and say, "We really need to figure out how to get brakes on this thing." So, we shut down the shop, lock thing up and head home for the day. We all feel a great sense of accomplishment thinking about how long it took to get the chopper running down the driveway. As we leave for the day I reassure them I will come up with some ideas for brakes and we will talk more about it tomorrow.
5 Days left
As soon as the guys arrive, we get on the internet and begin to research what type of braking systems is available for go karts and mini bikes. We find a "band" brake system that is used on go karts so we discuss how we could adapt it to the rear axle of the chopper. We have limited space on the rear axle and we don't want to install something too large that will cover the look of the rear rim. After looking over the chopper and the "band" braking system, we decide it is too large in diameter so we need another idea. We head up to our store room which has old bicycle parts and remnants of motorcycles and scooters. We find a disc brake and caliper system on a small pocket bike so we extract it and return down to the shop to take a closer look. After sliding the brake rotor over the rear axle we begin to position the brake caliper in various places to figure out the optimum location for mounting. At last we decide how it will mount and the guys begin turning a piece of stainless steel to act as a hub adapter between the axle shaft and rotor bolt pattern. Before we know it 2:20 pm is upon us so we clean up the tools and head home for the day.
4 Days left
Eric and Cal are starting to get to class earlier each day because they know the days are limited and they have 10 hours to finish the brake system, fabricate the exhaust, finish the kick stand, disassemble and paint. The last several days have been very productive so our confidence level is high as we plan our attack for the day. Our day begins with a tour of the campus scrap dumpsters to see if we can locate some bent tubing to use for an exhaust system. After visiting several shops and checking every dumpster, we end up outside the Welding and Fabrication shop checking their scrap metal. We locate several pieces of 1.0" diameter tubing with various bends that looks like it will work perfect for our exhaust. We drag the tubing back to the shop and size it up to see if it will work. It looks like it is going to be exactly what we needed. So the guys split up and take on different tasks that still need our attention. Eric will finish mounting the brakes and work on the kickstand, while Cal will begin mocking up the exhaust. Cal spends his afternoon cutting exhaust tubing in a band saw while running back and forth to the weld shop. Eric is moving between the chopper and the milling machines, while he finishes cutting the kickstand mount and fits it to the frame tubing. As the afternoon draws to a close, the brakes are in place, the kick stand is functioning and the exhaust is now welded, but the 1" diameter exhaust pipe seems too small. The chopper has a specific look... a stretched frame, a wide rear tire, a 45 degree fork rake so it needs to make a statement with the sound of the engine. So, on my way home from school I stopped at a local automotive parts store and pick up a 3.5" diameter chrome exhaust tip that should create the resonating thumping sound we are looking for.
3 Days left
Today, Cal arrives and quickly starts on a lathe turning a piece of stainless steel to adapt the 1" exhaust tube to the 3.5" chrome tip. After machining the adapter and getting it welded together we bolt the exhaust back onto the engine. Cal turns on the fuel and yanks the pull cord to hear the cackling roar of the engine that sounds like a descendent of a Harley Davidson with open pipes. I'm not saying it sounds just like a Harley, but I can tell you it is the meanest sounding Briggs and Stratton engine I have ever heard. Finally, the sound of the engine reflects the attitude of the choppers look. We shut down the shop as we talk about the seat and how we need to strip down the entire chopper tomorrow to prepare it for paint.
2 Days left
Today we finally feel we are on the downhill slide of this project as we begin to dismantle the entire chopper to prep it for paint. We apply heat resistant paint to the exhaust while we lay our base coat of gloss black pant on the frame and fork assembly. As soon as the paint begins to get tacky we apply our custom silver and blue spackle by touching the frame lightly with wrinkled up newspaper that has been sprayed with paint. This puts a cool industrial hammered effect on the black paint that carries our "Machinist" theme we designed by chopper around. As we leave the shop today the painted parts are drying and waiting for us to return tomorrow.
1 Day left
Today, we begin the pain staking task of assembling the chopper while trying not to chip or scratch the fresh paint. We drape a tarp over a work bench and begin to assemble it piece by piece for the next 2 hours. I think Cal and Eric found this to be one of the best days working on the project. All of their time and efforts are coming together into one of the coolest shop projects I have ever been a part of. We finish the project by taking many photos of the completed chopper then Eric and Cal taking turns going for rides out behind our shop.
I have been teaching machining students for 20 years and I think Cal and Eric have built one of the neatest shop projects I have ever been a part of that will become a marketing / recruiting tool for my Precision Machining Major here at South Technical High School. I am so proud of the creativity and artistic craftsmanship Cal and Eric put into this project and I am sure it was one of their most memorable experiences while here at South Technical High School.
If you have questions about the chopper project or The Precision Machining Major at South Technical High School, please contact me at: This e-mail address is being protected from spambots. You need JavaScript enabled to view it
I am Bob Arcipowski, the Instructor of our Precision Machining Program here at South Tech and I will be overseeing the project and providing guidance and assistance along the way. Periodically we will be posting new blogs to this website along with photos of our progress. So, after you read our blog and check out how the project got started, please come back later to watch it progress into one cool chopper.
April 22, 2010
Eric and Cal have been working diligently on the chopper for the last couple of months and are beginning to feel some pressure because the end of the school year is drawing near and we still have a lot of parts to design and machine. It is not on the ground rolling yet, but we are very close to getting this thing off the wood blocks and rolling on its two wheels.
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Eric moved on to machining the rear axle assembly while Cal concentrated his efforts on the front fork plates. Eric began by first measuring the wheel hub size and bolt locations for lug nuts and created a blueprint design for the rear hub and axle assembly. The rear axle is made out of a 1.0" diameter solid piece of steel and is supported by flange mount bearings that are bolted to the rear frame gussets Sam Littmann welded in earlier. Eric machined a cone shaped bushing that is welded to the rear axle and supports the rear wheel. The rear wheel is now mounted to the chopper and it feels great to see the back portion of the frame complete with a rotating wheel. (See photos 11 and 12)
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So as you can see, Cal and Eric are keeping up the "Machinist Theme" as they design and machine parts for our chopper that make it a unique and signature bike. Come back again to watch our progress.
Here is what we are working on next:
-Micrometer supports for the handlebars
-Dials for the dial caliper front drop outs
-Front wheel and axle mounts
-Rear sprocket
-Engine support plate
-Seat
-Custom paint
Mr. Arcipowski
Precision Machining Instructor
Let's Get Up to Speed - February 4, 2010
They started the project by deciding the overall size of the chopper, locating an engine and selecting rim and tire sizes so the bike will fit an adult and look proportional to a full size motorcycle. When designing a chopper not only are the overall proportions of the bike important but the shape and size of the frame can make or break the "cool" look of the bike. So, this step could be one the most important parts of the project, because you can manufacture precision parts with skilled technicians like Eric and Cal, but if the design is odd, the final result is a functionally ugly chopper that just isn't "cool" looking.
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Well, so long for now. We will keep designing, machining and assembling parts while taking photos along the way so you can follow along with our project.
Here is our hit list of the items we will be working on and you will see on our next blog.
- Front fork tubes and front drop-outs. (Wait until you see their drop-out design - "machinist theme".)
- Rear axle flange so we can get the frame rolling on the floor.
- Rear sprocket. (Cal is designed a sprocket to match the rear mag. wheel.)
- Foot pegs. (Eric is designing pegs made from large drill bits.)
Mr. Arcipowski
Precision Machining Instructor
