Help! How do you "Bend" the First Track Section

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jackstrat
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Help! How do you "Bend" the First Track Section

Post by jackstrat »

I built the standard 3 lane cub scout derby track. I tried to assemble the first section and fasten the long brace to the long legs but had great difficulty "bending" the track. Any tips or suggestions?

I made the track using 1/2" Birch veneer core plywood with 1/4 masonite for the track guides.

Thanks,
jack
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Stan Pope
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Re: Help! How do you "Bend" the First Track Sectio

Post by Stan Pope »

That sounds like a very sturdy track!

Most of the "bend" in a traditional track (built to specs in the Cub Scout Leader's HowTo Book) occurs between about 4 and 12 feet from the starting line. So a secure linkage between the first two sections is necessary for that design. Piantedosi wood tracks use that profile, but are constructed from (last time I measured one) 5/16" birch solid core, which is somewhat less of a challenge to bend, and is locked in solid with either a 10 or 20 pound weight near the first joint.

I think you must rely on more than gravity and weights to get the curve that you want! A method used with success is to add tension cables between the bottom of the support (near floor level) and the underside of the track. Track setup with tension cables is two-person job ... one to press the track down and one to hook the cables in place.

Some added weight near the first joint or slightly beyond will still be necessary to "lock the track to the floor".

Good luck!
Stan
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jackstrat
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Re: Help! How do you "Bend" the First Track Sectio

Post by jackstrat »

Stan,

Thanks...

As far as sturdy, 1/2" plywood is recommended in the Cub Scout plans, but it is very stiff.

Jack
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Re: Help! How do you "Bend" the First Track Sectio

Post by Stan Pope »

Yup! My old pack's track (from 20 years ago) was built to those plans. A pair of cables ran from about 4' down-track to the low end of the support under the starting line. This gave enough curvature that a couple of sandbags at 12' down-track would hold that point on the floor. (I like Piantedosi's use of free-weights better... less sand getting loose on the gymnasium floor!)

The cables need to pull on each side of the track, and they should be separately adjustable. You might approach it with a common turnbuckle and a turnbuckle in one cable. The lower (common) turnbuckle could have a hook instead of an eye at the lower end to facilitate track setup!

If this isn't clear, drop me an email and I'll sketch it on paper and email it back to you.
Stan
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gpraceman
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Re: Help! How do you "Bend" the First Track Sectio

Post by gpraceman »

I don't know about doing cables. As others have suggested (on Derby Talk and the timer forum), you can use weights to help give the curve. Some weights on the front legs is probably all you need. You can also check out the Piantedosi weight configuration at http://pinewoodderbytrack.com/specs.html to see how they do it.

As I mentioned on the other forum, it does help the section curve easier if you do perpendicular saw cuts every few inches along the lane strips.
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Re: Help! How do you "Bend" the First Track Sectio

Post by Teeeman »

our Pack track bend was made by cutting slots or kerfs on the inside of the board and gluing (hold until dry with weights or bricks or some way, I was not involved in the actual build).

The kerfs were about 2/3 through the thickness of the board, spaced about 1" apart I think...

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Stan Pope
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Re: Help! How do you "Bend" the First Track Sectio

Post by Stan Pope »

gpraceman wrote:... you can use weights to help give the curve. Some weights on the front legs is probably all you need.
This is very similar to my old pack's track. Reasonable amount of weight (less than 80 pounds) was not sufficient ... and it had the "saw cuts" across the center rails. I'm hesitant to recommend the saw cuts on masonite rails, though.
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Re: Help! How do you "Bend" the First Track Sectio

Post by Pinewood Daddy »

I also built the 3 lane 1/2" birch plywood track with 1/4" plywood lane guides. I used 10 lbs of weight hung on the lower leg.
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Re: Help! How do you "Bend" the First Track Sectio

Post by jackstrat »

Thanks for all of your comments. I don't have enough space in my crowded woodshop to attach the sections, but I was able to attach the brace to the long leg using a combo of 20 lbs of free weights and a stretcher/stringer placed between the two legs.

Thanks very much for all of your comments and help.

Jack
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Re: Help! How do you "Bend" the First Track Sectio

Post by gpraceman »

jackstrat wrote:Ran out of time for timer though--guess we will be judging by eye.
Depending on how close your race is, you may want to check out the Fast Track K1 Cheap Kit by Micro Wizard. For $50 you solder together the electronics and build an enclosure. For $15 more, they will do the soldering for you. It is a good option if you are in a time crunch and you end up with a good timer complete with computer interface. It is a 4 lane kit, but that doesn't mean that you can't use it on a 3 lane track. IMO it is a better option than building a parallel port system.
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Re: Help! How do you "Bend" the First Track Sectio

Post by obs4 »

I built one of the standard 32ft three lane tracks also and use a 40lb lead weight on the brace to hold it down. Also, if I remember correctly, the plans show a 1x3 brace attached flat under all three sections of plywood. This should really only be under the two flat sections. If you remove it from the ramp section, it will curve much more gracefully.
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Re: Help! How do you "Bend" the First Track Sectio

Post by Pinewood Daddy »

obs4 wrote:I built one of the standard 32ft three lane tracks also and use a 40lb lead weight on the brace to hold it down. Also, if I remember correctly, the plans show a 1x3 brace attached flat under all three sections of plywood. This should really only be under the two flat sections. If you remove it from the ramp section, it will curve much more gracefully.
I built it to those plans also and had to cut out part of the first brace to get it to bend easily.
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Re: Help! How do you "Bend" the First Track Sectio

Post by Stan Pope »

obs4 wrote:I built one of the standard 32ft three lane tracks also and use a 40lb lead weight on the brace to hold it down.
Good data point! Thank you for posting that!

A 4-lane track is about 30% wider, so about 30% stiffer ... Would you need a 54 pound weight for one of those? :)
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Re: Help! How do you "Bend" the First Track Sectio

Post by Pinewood Daddy »

Stan Pope wrote:
obs4 wrote:I built one of the standard 32ft three lane tracks also and use a 40lb lead weight on the brace to hold it down.
Good data point! Thank you for posting that!

A 4-lane track is about 30% wider, so about 30% stiffer ... Would you need a 54 pound weight for one of those? :)
Or just remove the brace and a 10 lb weight will work.
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