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derikson@wi.rr.com
Starting Member

USA
4 Posts

Posted - 07/20/2017 :  15:08:02  Show Profile  Reply with Quote
Starting to gather info on a crazy project my son and I are going to start soon. Any of you build and race pine car derby with your kids in the past?? Well, we've found the adult version in adult soap box derby! Yep, ride it down the hill! All gravity power with low wind resistance and cutting friction to a minimum as our only opportunities to beat the clock. Shortest elapsed time wins. 40 sec is the time to beat. Anyway, I need a crash coarse in what you guys use for your recumbent trikes. Our plan is for 4 tires on straight axles with no forks. I have machinist friends who can assist with prepping the end of the axles. Guessing we'll need the largest hub I.D. because of the lack of support by a fork. We also think the largest rim diameter will be an advantage as well. Maximum weight
of our machine can be 500# Pine car taught us to go for maximum weight
to start and see if your speed increases by shedding some pounds.
Penny for your thoughts guy's! Hope you guy's can get us headed in the right direction!

Dan and Devin

purplepeopledesign
recumbent guru

Canada
673 Posts

Posted - 07/20/2017 :  20:51:39  Show Profile  Reply with Quote
What are the rules?

:)ensen.

Those who claim to be making history are often the same ones repeating it.

Video of my trike
http://www.youtube.com/watch?v=MdSLRD_2vzc
Photos of my trike
http://www.flickr.com/photos/purplepeople/
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jjackstone
recumbent enthusiast

USA
231 Posts

Posted - 07/21/2017 :  06:29:34  Show Profile  Reply with Quote
https://www.youtube.com/watch?v=vhj58mGyGQ0

Guy Martin gravity racing

JJ
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derikson@wi.rr.com
Starting Member

USA
4 Posts

Posted - 07/21/2017 :  08:20:32  Show Profile  Reply with Quote

Not many rules!
500# max weight
$500 budget (Honor System)
Max size 12'x5'
Must be able to turn in a 10' radius

Previous winner uses a plastic car top carrier as the body.
4 wheels with Schwalbe Run Rights as tires (Wheelchair tires?)
Also has plastic wheel covers to keep the breeze out of the spokes.

We're hoping to stay at $100 a corner for rims & large hubs
2 of the hubs must accommodate disc brakes.
No rules on brakes other than no Flinstoneing it or dragging any thing on the street. Brakes are not included in the build buget rules.
What's going to get us down the hill quickest?
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warren
human power expert

USA
6050 Posts

Posted - 07/21/2017 :  10:18:02  Show Profile  Visit warren's Homepage  Reply with Quote
Do you have a link to the event site? That will tell us things like slope, Length, corners. You need to optimise for those things. If it's got a bunch of corners you need to make it handle well, if it's just straight down a hill it's all aero.
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derikson@wi.rr.com
Starting Member

USA
4 Posts

Posted - 07/21/2017 :  11:50:06  Show Profile  Reply with Quote
Straight as an arrow! If we're turning we're done LOL!!!
We still have to make it turn by rule, in a 10' radius. (turning it around at the top of the hill).

We've got a pretty good handle on the aero.
Love the work the trike guy's here have done with steering design!!! We're going to save some cash and just go with a straight pivoting axle. If we screw up the spindle/steering we're scrubbing speed. Our primary focus is best bearings, skinniest tires, and a hub/axle dia.to carry the load.

I don't have specifics on slope or distance. The coarse is set up covering 3-4 city blocks. All cross streets are flat spots as you come down the slope. My son drove a car last year and thought the track was pretty smooth. Search "Muscatine Adult Soap Box Derby"

I'll see if I can post a drawing or 2 of our body concept in the next day or 2.
D & D

Edited by - derikson@wi.rr.com on 07/21/2017 11:57:16
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Speedbiker
human power expert

USA
3703 Posts

Posted - 07/21/2017 :  14:11:06  Show Profile  Reply with Quote
Would someone please post pictures of the Gareth Hanks/Trisled BM trikes. Thats where he should start. Cut it down due to not needing a foot flail envelope and he'd have a winner. If you think you know aerodynamics, but your vehicle doesn't look like that, you DON'T know aerodynamics.
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derikson@wi.rr.com
Starting Member

USA
4 Posts

Posted - 07/22/2017 :  06:25:48  Show Profile  Reply with Quote
I'm with you speedbiker on the Gareth Hanks aero. Don't think we can get quite that extreme on the $100 left in our frame/body budget. We are by no means Aeronautical Engineers but think well be OK on aero for the money we'll be allowed to spend.

Our main focus here is gathering thoughts about rolling as free as possible down hill with gravity as our only source of energy.
Our wheel budget is $100 ea x 4 Forkless so we're looking for the best Trike wheels we can get for our $400 budget! Also contemplating Wheel Chair wheels.

Got more track info as well. .25 mile with a 65ft elevation change from top to bottom.

D&D

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Speedbiker
human power expert

USA
3703 Posts

Posted - 07/22/2017 :  09:03:12  Show Profile  Reply with Quote
Look into bmx wheels with 14mm axles, which are plenty strong to mount from one side. And you can mount some very fast trike tires to them. No matter your budget or build method, try to shape it as closely to top streamliner shapes as possible. Make all joining surfaces go parallel to the airflow. See the velomobile page for Jerry's coroplast velombile for ideas. Coro could easily be fashioned into a cheap, effective shell. Since it has no drivetrain the frame could be anything, even wood. A $500 budget is kinda silly.
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