35cc Honda 4-Stroke= 30mph!

[noiseguy]

Pull rope's readily available from a bunch of places. You could splice a piece but winding on a completely new rope and cutting to longer size would be a more sturdy option and only a 15 minute job. Use polished screw eyes (stainless steel are good) or better still simply pulleys to route the rope to a point where the driver can easily reach it.

I think your time would be better spent on other issues than building in electric start. Like addressing that flimsy front end

[Petrock's 1984 Spree]

Yeah I just want to get this thing runnin with the competition less than a month off.

Well see if I really want to tug on that rope 70-80 times or not lol.
I think the front end might be okay. We welded in a steering post between the two wheel arms so now we have the option to tie it all in with a top bar if we see fit. I honestly think it'll be okay

[Petrock's 1984 Spree]

Alright well we made some more headway. We proto-typed a starter gears out of masonite on tuesday. It looked good so we went forward and constructed it out of .290'' thick aluminum (some odd scrap). It'll be driven by a plastic drive gear from the starter.

The bolt is 5/16'' threaded through the gear and 1/2 way into the small steel spacer behind it. The other 1/2 of the steel spacer is threaded for the small 10mm rod coming out of the engine case (part of the crank).

Testing better start soon with the race on May 13th
Pics

0420111334 by jpetrak, on Flickr

0420111720 by jpetrak, on Flickr

0420111720a by jpetrak, on Flickr

0420111720b by jpetrak, on Flickr

The rear wheel should be mounted on friday if everything goes smoothly *knock on wood*

[noiseguy]

How does the starter disengage? Is it on a Bendix?

[Petrock's 1984 Spree]

Yeah pretty much. My shop teacher calls it a solonoid but i dunno if thats what it really is or not.

[noiseguy]

That's auto speak for the same area (different part.)

[Petrock's 1984 Spree]

Ah okay. He pulled out the solonoid, now realize its not directly connected to the starter

Anyways, we got one of the electric start systems hooked up and tested (were trying to take two vehicles to the competition)
And it looks as though we need to change the pressure angle on the teeth from 14 to 20 because it is chewing into the plastic driver on the starter a bit. Easy fix, just another 2 hours of machining.

And on the new vehicle, we are about 15min of cutting away from mounting the rear tire, and probably an hour away from mounting the engine. Ready for another 8 hour day in the shop again tomoro

[Petrock's 1984 Spree]

Alright were a lot farther along now.
-Rear tire mounted
-Engine Mounted
-Electric Start Mounted
-Fuel system mounted
-Steering wheel mounted( kinda looks like bull horns upside down)
-Brakes and wheels mounted (for good)

And the newest addition-- electric throttle
Servo operated, controlled by a micro controller

0510111557 by jpetrak, on Flickr

0510111557a by jpetrak, on Flickr

More pics of the entire vehicle tomoro, cant wait for the first test drive

[noiseguy]

Why electronic throttle?

And our of curiosity, where did you get that engine? I've never seen one sold separately; they are always attached to a piece of equipment.

[Trafficjamz]

Why electronic throttle?

Petrock has a Rube Goldberg approach to problems.

[spree-rider]

Why electronic throttle?

And our of curiosity, where did you get that engine? I've never seen one sold separately; they are always attached to a piece of equipment.

he likes to make things as complicated and heavy as possible

[mousewheels]

Servo control, and a uC providing position input has advantages for testing/tuning as well an economy run.

What might a microcontroller bring to the table?

• Selectable multiple max throttle opening limits.
• Experiment with limits on throttle ramp up/down rate vs economy
• Add a wheel sensor and automate economy protocols - accelerate to xx mph, kill engine, coast, trigger electric restart at xx mph
• Cruise control - make driving easy at the most efficient ground speed.
• Easily log operator control inputs.
• Students with uC experience can enforce a throttle policy with electronics easier than mechanically.

If the team has the interest and ability - go for it!

There's some really bitty servos out there. It does not take much to control the carb on that engine. Chances are a servo/uC system can be found which weighs less than a std cable and housing. Cost wise anyone can get started in uC's for well under $10 - circuit board, compilers and all. It would be capable of accepting user throttle intput, running the servo, log some data and more.

[Petrock's 1984 Spree]

Just like mousewheels said it'll let us precisely control how fast we are going at any given time. The controller is connected to 2 buttons on the steering wheel. Throttle up and throttle down. It's very precise and we have set the limits on the micro controller to have the servo exploit the full range of the throttle. Plus you don't have to hold down a pedal the entire time.

The engine we got online, it can be had from a number of places for around $250.

As heavy as possible? Only when my neck is on the chopping block for motorized death.

We tested the entire thing today and have a slight problem which we can hopefully remedy asap. The electric start whips the starter gear on the motor over very fast, however the engine won't fire. We have spark, and air, and fuel. So it's the starter holding it back. We do not have a bendix type thing, only what is attached to the starter motor which is supposed to act the same way. We'll see what happens tomoro and hopefully we can get this resolved in time for the race

[mousewheels]

Nice project Petrock

Talent always recognizes talent, I think your engine controls effort will be recognized. Good luck with your project, the fun and learning which goes along with it. As a school project, am confident no matter what the outcome your team is a winner and others in the competition will take note.

[Petrock's 1984 Spree]

Thanks a ton man
Here are some pics of the entire car
http://m.flickr.com/photos/58369736@N06 ... 1/sizes/m/
http://m.flickr.com/photos/58369736@N06 ... 5/sizes/m/
The micro controller throttle circuit. It actually deceptively simple
http://m.flickr.com/photos/58369736@N06 ... 5/sizes/m/