Adding a Friction Brake to an Old Track

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FatSebastian
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Re: Adding a Friction Brake to an Old Track

Post by FatSebastian » Fri Feb 24, 2012 4:48 pm

Stan Pope wrote:This year I was tasked to fit 8 tracks, and only had 2 retired pillows. Time to subdivide those pillows!
We have yet to put it in action, but for $12 we recently picked up a memory-foam pillow at Walmart to replace our OEM foam braking barrier (or should I say breaking barrier, since that is what happened to cars sometimes). Easily wide enough for 4 lanes, probably not quite wide enough for 6. Relative to other expenditures related to derby, it was a relatively modest one.
Stan Pope wrote:We will see how well this stands up to a full day of racing tomorrow... pix and report, I hope.!
Looking forward to that!



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ciodude
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Re: Adding a Friction Brake to an Old Track

Post by ciodude » Fri Feb 24, 2012 5:48 pm

Stan Pope wrote:Here is what I did
Any photos Stan?



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Re: Adding a Friction Brake to an Old Track

Post by Speedster » Sat Feb 25, 2012 10:24 am

I originally built an 8' stop section and it remains that today. I don't like cars going very high in the air so the section was built to resemble the track (but painted red) and a guide strip is placed under the original guide strip to lift the cars off their wheels. That's as high as the car will go in the air. The second guide strip is placed back about 6" from the end of the track so the cars slide up a slight hill. The best thing I have found is the drawer liner you can buy at Walmart and it even comes in blue. The cars seldom travel more than 4 feet on the stop track due to the stopping power of the drawer liner. I have a soft pad at the end of the track (with a STOP sign, of course) but no car has ever reached the end. Just for "kicks" I put a caution sign at the 4 foot distance. This seems to make the parents smile.
Bill



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Re: Adding a Friction Brake to an Old Track

Post by Stan Pope » Mon Feb 27, 2012 1:48 am

ciodude wrote:
Stan Pope wrote:Here is what I did
Any photos Stan?
I took one, but for some reason, didn't show. I think that it was the focus delay got me!

Six of the eight tracks used these tempur-pedic stop bricks. After racing all day with no maintenance, the bricks were still working properly, i.e. cars came to a dead stop without damage or rebound with their noses against the brick. Since the bricks were pushed gently down against the center rails, there was some friction between brick and rail. At the end of racing, the bottom of the each brick had been compressed about 3/8".


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Shawn Stebleton
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Re: Adding a Friction Brake to an Old Track

Post by Shawn Stebleton » Mon Feb 27, 2012 12:30 pm

Stan Pope wrote:We have used full retired tempur-pedic pillows for some years successfully. This year I was tasked to fit 8 tracks, and only had 2 retired pillows. Time to subdivide those pillows!

Here is what I did:
1. form an "L-shaped" housing from 1/4" plywood (3-1/2 X 12") and 1X2" pine 12" long.
2. Chill the pillows so that they are stiff, then cut the pillows into 3"X2-1/2"X12" bricks with a freshly sharpened chef knife.
3. Attach the pillow bricks to the plywood with Gorilla Glue.
4. Duct tape along the center of the plywood and under each each side of the track with gentle compression of the brick against the end of the stop section rails.

Key design logic:
1. the plywood keeps the foam pressed down about evenly on all or the lanes. ... car's can't get under the foam.
2. 1X2 helps keep the plywood stiff and keeps the foam from being "pushed out the back."
3. Low profile (for visibility) and minimal incursion onto the braking surface.
I'm trying to visualize this. We have a 3-lane wooden Piantedosi track and I'm thinking of upgrading our stop section with something like this if I can get details worked out.

Are the two pieces joined along the 12" sides? Is that longitudinal with the track lane? I'm not sure how that would work.

Is the plywood piece horizontal and above the track surface, sandwiching the foam piece between it and the track surface, one per lane? Is the gorilla glue on the top of the foam or at the back end only?

Could you please provide a sketch? That would clear things up quite a bit.

For my project, I was thinking of something along the lines of having 4 lane dividers (2 between lanes and 2 outside of them) of 1/4" plywood, height to be determined, with a top piece of 1/4" or 3/8" plywood and an end piece of wood 2x4 or 4x4, with the 3 tempur-foam pieces boxed in, so to speak. Only the back end of the foam piece would be glued to the 2x4 or 4x4, allowing it to be compressed from the front by the cars. A width of 3" would allow for the foam to widen when squished from the end and still fit between the lane dividers (3-1/4" wide inside). The length of the lane dividers would be about 7" longer than the foam to prevent cars from deflecting upon first impact with the foam and interfering with cars in the other lanes or being sent off the track.

I just don't know how long the foam piece should be. I get a picture in my mind that you are using a 12" long section. Would that be enough to stop cars that are going full speed? I'm thinking of not rehabilitating the rubber stopping material (it ramps up and not the lane guide) and just using the tempur-foam as the stop. Is this idea not advisable?

What about longevity? How many races do you think your stops would last before needing to be replaced? At our Pack's annual Fun Day the track probably has 1000 to 1500 races during the day, and the actual Pinewood Derby is two weeks later. I would like to not have to replace the foam frequently....

What kinds of sources do you use for obtaining retired tempur-pedic pillows?

Thanks for any enlightenment you can provide!


Shawn

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Re: Adding a Friction Brake to an Old Track

Post by Stan Pope » Mon Feb 27, 2012 3:38 pm

Shawn,

My still did not turn out, but I'll snatch a still from my vids and also post the vids. Still have 10 or so hours of processing to get the vids ready to post, and then a day or so of transfer time to actually post them. Sure wish I had T-1 service to the house! :)

In the meantime, the plan was that the 1X2 is across all lanes with the 2X12 side facing uptrack. The plywood is fastened along its long edge to the 1X2 and ends up about 2 inches above the track, again, across all lanes. The brick of foam is glued to the plywood. I know of no reason other than my hurry to not glue it to the 1X2 also. The assembly is fastened to the very end of the track using 2" wide tape wrapping over the plywood and tucked under each side of the track. The tape should be centered a bit down-track from the plywood center.

One of the pillows had been retired about 2 years, the other for longer than that ... 4 or 5 years, maybe.

I saw no signs of wear on any of the foam from the day's racing. First race started 8 am, last race ended about 3:30 pm.

Shelf life is an open question at this time. In cutting the foam bricks, I have exposed interior material which had not been exposed to the air (directly) before. Will it lose any of its energy absorption quality while it sits in storage for a year? Dunno. If it does, I may regret having used gorilla glue to fasten 'em!

I'd like to find some really slick material to coat the underside of the foam so that when it is struck by the car, it returns easily to its original vertical orientation. As it is now, the slight downward pressure against the stop strips traps the foam. Each seemed to be indented at the bottom about 3/8" from their starting positions. That did not seem to affect their performance, though.


Stan
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Re: Adding a Friction Brake to an Old Track

Post by Shawn Stebleton » Tue Feb 28, 2012 12:21 pm

Stan Pope wrote:the plan was that the 1X2 is across all lanes with the 2X12 side facing uptrack
I understand now. I was picturing one foam piece per lane, not as one integral piece across all the lanes.

Getting back to my idea for a stop section with three separate compartments....
If I were to have the foam pieces not fit snugly inside each box, but rather have about 1/16" gap on the sides and top, and have the bottom either flush with the top of the lane guide or with a notch cut out so it could sit on the track surface, would it be able to spring back completely?

What depth of foam would stop a car going full speed, without damaging it?

To prevent cars from going underneath, would it make sense to have something like a thin piece of wood (tongue depressor/craft stick thickness) protrude from under the foam about 1/2" or so to prevent the foam from lifting and having the car go underneath?

Thanks,


Shawn

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Re: Adding a Friction Brake to an Old Track

Post by FatSebastian » Wed Feb 29, 2012 1:46 pm

Stan Pope wrote:2. Chill the pillows so that they are stiff, then cut the pillows
How much did freezing help stiffen the pillows and help make them cut-able? ( :thinking: If you froze memory foam compressed, would it stay compressed until thawed?)



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Re: Adding a Friction Brake to an Old Track

Post by Stan Pope » Wed Feb 29, 2012 2:46 pm

I have three brief videos of cars being stopped by these small blocks of memory foam here. (see the bottom of the page)

It is like they plunged into a mound of honey, except they don't come out sticky!

re freezing: I didn't actually freeze them ... just left them in my van while the outside temps were in the 30's. Little care was necessary to cut clean, well-shaped blocks. If they are frozen compressed and then cut, yes, they will expand at room temperature. That would not be a good plan for making well-shaped blocks. :)

re: Shawn: I'd not want the car to impact anything except the foam. Slight downward pressure on the top of the foam block was sufficient to keep the cars from diving under. That pressure was equalized on all lanes by the plywood above the block. Tape holding the ends of the block to the track sides provided sufficient pressure.


Stan
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Re: Adding a Friction Brake to an Old Track

Post by Shawn Stebleton » Thu Mar 01, 2012 12:15 pm

Stan Pope wrote:I have three brief videos of cars being stopped by these small blocks of memory foam here. (see the bottom of the page)
Thanks. That shows a lot.

On the first video, it looks like the stopping material on the lane guides isn't slowing the cars down very much, if at all. But there isn't any rebound. Is this due to the cars being off their wheels and sitting on the lane guide friction material? Or is it due to some downward pressure on the fronts of the cars, wedging them slightly and holding them in place?

I'm trying to determine the feasibility of forgoing replacing the friction material entirely. I'm not sure I have any authority to modify our pack's track and wouldn't want to make any permanent changes that would render it useless if what I try doesn't work. I really don't want to create an additional stopping section as our finish line is at the joint between the 4th and 5th sections, leaving 8' after the finish line (5' of plain track and 3' of used-up formerly-wedge-shaped friction foam) already. Having 12' after the finish line seems total overkill. Maybe an additional 3-4' of stopping surfaced center rail with lowered running surface ending in the foam blocks would be a good solution for our track.

Our finish line is electrical tape placed on the track at the joint and can be relocated to just before the old friction material, if our cub master approves. Personally, I like the idea of an extra 4-5' of racing length. We haven't had many issues with cars not making it to the finish line (maybe 1 per year) and don't think it would cause problems to lengthen it slightly.

Thanks drathbun for your PM. I'll look more closely at what you have posted and see how I might be able to incorporate it, if we go that route.


Shawn

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Re: Adding a Friction Brake to an Old Track

Post by Stan Pope » Thu Mar 01, 2012 12:53 pm

Shawn Stebleton wrote:On the first video, it looks like the stopping material on the lane guides isn't slowing the cars down very much, if at all. But there isn't any rebound. Is this due to the cars being off their wheels and sitting on the lane guide friction material? Or is it due to some downward pressure on the fronts of the cars, wedging them slightly and holding them in place?
Some substantial portion of each car's momentun is sunk in the skid area. The remainder is sunk in the memory foam. If the nose of the car and the direction of motion are in line with the car's CM, then the car comes to a "dead stop" over a distance of about 1/2" with no tendency to rotate. If they are out of line, then some tendency to rotate may be present, but probably not enough to raise the back end of the car.

The car does not "dive under" or "stick into" the foam. It just stops with its nose against the wall of foam.

I would not, for instance, place the stop pad close to the finish line ... too much momentum present for the stop pad to sink. Let the rubber skids sink a bunch first, then let the stop pad sink the rest.

Dividers create additional risks since they might be in the path of errant cars while the cars still have a lot of momentum..resulting in impressive flights and forces that are off line from the car's primary direction of motion. That means likely impact in nearby lanes.

So, keeping the laws of unintended consequences firmly in mind, draft ideas and analyze/evaluate them carefully!


Stan
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Re: Adding a Friction Brake to an Old Track

Post by Speedster » Thu Mar 01, 2012 3:37 pm

This is a picture of my skid track. It is 8' long, raises the cars off their wheels, and they come to a stop in about 4'. It has Walmart drawer liner on the center guide strip. It has been used for 7 years without being replaced. No problems so far. We do not allow weights to be screwed to the bottom of the car without being recessed. The CAUTION sign is set loosely in a hole with a 1/4" dowel and can easily be knocked out if a car should get into trouble. So far, so good.

Image



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Re: Adding a Friction Brake to an Old Track

Post by ciodude » Thu Mar 01, 2012 5:32 pm

Thanks for sharing the pic Speedster!



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Re: Adding a Friction Brake to an Old Track

Post by SlartyBartFast » Sat Mar 10, 2012 4:04 pm

Has no one thought about using gravity to slow the cars down?

If the track curved upwards in the stopping area, gravity would help stop the cars.



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Re: Adding a Friction Brake to an Old Track

Post by Speedster » Sat Mar 10, 2012 4:23 pm

I have seen this type of stop and I have been the victim of one. The cars shoot 2 feet up the hill, smash into the end, fall to the ground, break a wheel, and you're out of the race. A lot of hard work down the drain because of a lousy braking area.



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