soap box racers.....gravity powered

[blink]

in atlanta every fall we have a soapbox derby.
only rules are it must have 4 wheels, weigh under 250 lbs and have a brake.

myself and a few friends are gonna build one.

i will keep everyone updated on the progress.
i am thinking a low stretched trike with a "wheelie" wheel on the back just to have 4 wheels.

it will definitely have a ratrod feel to it.
Mad Max comes to mind for some reason....

does anyone have any experience with these?

BLINK!

 

[aka_locojoe]

We're having a "gravity shoot out" here in a couple of weeks. It's being held at an old soapbox derby track. 2 wheels are allowed in our event though. I'm hoping to come up with something 4 wheeled but will go the 2 wheel route if I have to just to be able to participate.

Sorry no experience as this will be my first time with this.

 

[blink]

we went to the bike coop tonight and grabbed 3 20" wheels, 5 or so crappy steel bikes/frames, a couple rear triangles with shocks, and a front suspension fork, all for $20....sweet!

i am gonna chop up the bikes and use the tubing for the build.
i also have a relationship with a welding shop so i can grab whatever scrap i want from their dumpsters.

the rear triangles are gonna hold the rear wheels of the trike.
front suspension fork for the front wheel.

the design is still in the works, but its gonna be a low stretched trike, with a wheelie brace wheel hangin off the back for the "4th" wheel.

i will post the preliminary design soon...

cheers!

BLINK!

 

[aka_locojoe]

I threw this together for the Gravity Shoot-Out this coming Saturday. I know I won't be the fastest but I'm hoping there's an award for the best looking :lol:

 

[KOTA]

I don't know about "BEST" looking, Randy!.......But definitely "BEST" LOW buck engineering.

 

[CYRUS]

your a sick sick man, but we're glad its you instead of us, .......

 

[Markm]

Get video

 

[blink]

Joe,
that's Loco!

 

[aka_locojoe]

This could possibly be my last post as I'm heading out for a test run this morning. I'm bringing along someone to video and call 911 should the need arise.

 

[Markm]

just to be safe, have them dial 91....and wait for your cue :mrgreen: :mrgreen:
J/K...Hope all goes well!!

 

[user 135]

nice engineering. The steering is very creative. How did you attach the chain to the coaster brake?

 

[aka_locojoe]

nice engineering. The steering is very creative. How did you attach the chain to the coaster brake?

Thanks.
The rear sprocket I welded the chain to the sprocket. The front sprocket I just zip tied the chain to it so I could adjust it if needed. There's enough chain to teeth contact that all the the zip tie does is keep the end from falling off.

I could have just put the entire chain on as normal but I didn't want it to appear that I had a drive system or way to propel it.

 

[aka_locojoe]

It was a blast! Worked a lot better than I anticipated. My Dad and Daughter even rode it. Video doesn't do the speed justice though. Of course the most speed it as the bottom.

 

[Markm]

NEAT!!

 

[moparmayhem93]

paging kenny p.....

 

[hewey]

You guys need to check out the Aussie contingent we've got
http://aigrf.blogspot.com/

Make sure you watch the videos (links on the right)

 

[blink]

here is my preliminary design....

what does everybody think?

 

[MaddMatt]

through my experience, trike based gravity racers are extremely dangerous.

SFVISBF has the most lax rules out of everyone and the trike design was the first to get an official ban. The problem with trike designs is the handling. When your reach about 25-35 mph and try to turn the weight drastically shifts to one side or the other.

With a trike your weight is forced toward the front opposite your turn. In a normal 4 wheeled car that weight is taken by the front tire and gives you grip during the turn. In a trike however, that weight has no support and the most common result is the back tire lifting up, resulting in a pretty nasty roll. When we started our group in tucson one guy made a trike design was out of the race at the first turn.

The best designs have been the wider, 4 wheeled designs. When moving at that speed you get thrown around pretty good even during small steering adjustments. You really want all the stability you can get.

 

[fast eddie]

agreed, ive done some gravity racing and recreational riding at very high speeds, you could not pay enough to take a trike that fast. w/out the ability to lean into a turn the compensation is bigger contact patch (more rubber on the road) bike wheels just dont offer that. if you go trike, at least use go-kart slicks, theyre made for that.
fast eddie outt

 

[blink]

i am gonna use slick tires.....

and i know that turning with a trike sucks, but in this race, there is no turning.
its a 150ft long straight hill....probably get up to 25mph top speed by the bottom.

def gonna do some road tests first.