Adding a Friction Brake to an Old Track

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VWAffe
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Re: Adding a Friction Brake to an Old Track

Post by VWAffe » Sat Jan 21, 2012 6:49 pm

I'm late to the party, but here's a picture of the new stop section I designed and built for an older track last year:

Image

The track used to have a ramp-style section with foam tape on it, but was entirely too short for today's cars. I removed the lift blocks from under the guide rails, gaining about 3' of useable track that way, and cut the new strips to match the width. The new section is 4' long (for a 30' track) and from what I've seen, is definitely overkill. It uses the McMaster-Carr natural foam rubber, and usually stops the cars within the first foot.

I'd add a small bottom plate to minimize the distance cars have to fall if something goes wrong, but otherwise I'd not change anything. 8)



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Re: Adding a Friction Brake to an Old Track

Post by rpcarpe » Thu Jan 26, 2012 11:25 am

That looks good.

Thank you all for the extra insight on sand paper between rear wheels. Won't do it this year.


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Re: Adding a Friction Brake to an Old Track

Post by rkniffin » Thu Jan 26, 2012 11:35 am

That picture is almost exactly what we did for our stop section. The missing piece was the right material on the stop section. I put the McMaster-Carr stuff on and will see how it works in two weeks at our derby.

McMaster-Carr was easy to deal with and the product was extremely easy to put on the stop section. Just cut to length and apply.



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Re: Adding a Friction Brake to an Old Track

Post by rkniffin » Sun Feb 12, 2012 7:08 pm

We had our race yesterday and the McMaster-Carr material performed great and held up pretty well. We had 120+ races and and no cars reached the end of the 3' stop section. Zero damage to any cars. Thanks so much for the recommendations.



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Re: Adding a Friction Brake to an Old Track

Post by Louie41 » Mon Feb 13, 2012 9:35 pm

ours looks like the first picture in the post but with side walls and a back stop. our skid stops use the tool drawer liner that looks like beads attached to each other. held onto strips with 3m adhesive spray. I don't like the foam backstop as it tends to cause the car to bounce back (I should have made section longer) so what we use are beanie baby animals that we use and call them roadkill. anyways I find the "bean bag" material cushions and absorbs without pushing the car back out if it make it that far.



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Re: Adding a Friction Brake to an Old Track

Post by ciodude » Mon Feb 13, 2012 10:40 pm

Louie41 wrote:we use are beanie baby animals that we use and call them roadkill.
Pretty smart idea (and clever naming!)!



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Re: Adding a Friction Brake to an Old Track

Post by drathbun » Fri Feb 17, 2012 10:27 am

I used the information in this topic (and some others) and built a new stop section for our older track last night. I ordered the stop foam from McMaster-Carr and it came in Wednesday night, so last night I cut my new stop section and the lanes for the track and got everything put together except for the foam. I added a coat of sealer / varnish last night, will do another tonight, and install the foam on Saturday. We're going to be using our track for our district derby (first one in a long time was last year, this will be our second) and I really want to have something besides pillows at the end of the track. :) I based the design on what I saw on a Best aluminum track that I've helped with on occasion, where the track surface drops away and the lanes continue on, leaving the wheels hanging as the cars slide to a stop on the rubber strips.

I'm going to test everything on Saturday. If it works, I'll post some pictures.

If it doesn't work, then I guess I'll go back to the drawing board...



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Re: Adding a Friction Brake to an Old Track

Post by MOFAST » Fri Feb 17, 2012 11:15 am

Does anyone find having the track fall away, that weights are knocked loose? I guess that is certainly easier than fixing a broken car.

I would say most of the kids in our pack have thier weights glued to the bottom, very few put them internally.



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Re: Adding a Friction Brake to an Old Track

Post by drathbun » Fri Feb 17, 2012 12:11 pm

I'll post a picture later, but maybe I can be more clear. Our wooden track has a flat base with four lanes; the lanes are the strips of wood that are attached to the flat base, and the wheels straddle that lane. For my stop section, the flat base drops but the lane continues. So the car doesn't really drop, but the track surface essentially drops out from under the wheels. There are really only two places to stop the car, from the bottom or the front. :) Having the car run into something (we've been using pillows) is probably far more dangerous to the car than having it slide to a stop on the bottom.

Bottom-mounted weights are probably more likely to do damage (over the longer term) to the stop foam strips than to the car, unless the weights are not attached very well. To that end my "lanes" on the stop section are tapered a bit so that the initial transition has the foam below the top level of the lanes on the track.



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Re: Adding a Friction Brake to an Old Track

Post by Darin McGrew » Fri Feb 17, 2012 12:45 pm

MOFAST wrote:Does anyone find having the track fall away, that weights are knocked loose?
It has only been a problem for us for some of the trim weights held on with tape or hot glue, but our kits come with a dovetail slot in the bottom for molten weight, so the primary weight is secure.



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Re: Adding a Friction Brake to an Old Track

Post by mebetree » Fri Feb 17, 2012 4:23 pm

We strongly encourage people not to put weight under the car but the few people who do used screws or a LOT of glue so it hasn't been a problem in our pack.

On my own car I had a last minute pinch of tungsten putty in a hole in the bottom of my car that was slightly lower than the wood and it didn't rip off either.



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Re: Adding a Friction Brake to an Old Track

Post by drathbun » Sat Feb 18, 2012 8:39 am

Here are some pictures of the nearly finished work. I have not added the black stop foam/tape yet.

First, an overall picture of the new stop section sitting on my kitchen counter:

Image

I have two cars sitting on the stop strips for sizing. One of them has standard weights on the bottom and as you can see the wheels are quite nicely lifted off of the running surface.

Image

The red car does not have any weights attached to the bottom. Without the stop tape on the lane the wheels are still touching the surface but there is only a millimeter or two of clearance between the bottom of the car and the top of the lane.

Image

I bought 1/16th thick stop tape. I think if I had built this first, I probably would have gone with 1/8" instead. But since the tape comes in 50' rolls I can always put down a double layer if testing shows that the red car is sliding off of the end.

Testing will happen either this afternoon or tomorrow, not sure which at this point.

I will show pictures of how the new stop section attaches to our existing track later on to show the transition between the running lanes and the stopping lanes. Have to wait until the track is assembled for that.

I used 5/8" birch plywood for the construction. I purchased a 2' x 4' section from one of the local big box hardware stores. It's more expensive per board foot to buy it that way, but I didn't need any more than that. I ripped the board to the width of the track and then ripped the four lanes from what was remaining. The stop section is 4' long with 6" designed to rest under our current track, leaving the stop lanes at 3.5' long. The lanes on the stop section are tapered slightly (using a bench sander) where they meet the lanes on the current track. The current track appears to be 3/8" thick with 3/8" lanes. The track sits on top of another 3/8" spacer to keep it off of the floor. 3/8 + 3/8 + 3/8 = 9/8 or 1 1/8" total height. My new board is 5/8 + 5/8 for a total of 1 1/4" of height. I used the bench sander to remove a bit over 1/8" of material from the stop lanes so that they start below the surface of the existing track lanes when it's all assembled. The math doesn't work out exactly right :) but when I was done the lanes on the stop section were far enough below the other that the stop tape should be below the top level of the current track lanes. Even if it's not, it will be even or perhaps only a tiny bit over, and the cars certainly have enough clearance to make that work.

The new stop section has two coats of Minwax varnish. The top of the lanes on the stop section is unfinished as I wanted a bare wood surface where I could attach the stop tape.



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Re: Adding a Friction Brake to an Old Track

Post by drathbun » Sat Feb 18, 2012 1:33 pm

Here's the final after installing the stop friction tape:

Image

The friction tape went on really smooth (with my wife helping) and it's really sticky! Not in an "eww" sort of way where it leaves a residue on your hand, but with a car on the tape I was able to pick the stop section up past a 45 degree angle and nothing moved. :O

As mentioned earlier I bought the 1/16" tape. Here's a picture of the wheel elevation from the track surface for a car with bottom weights:

Image

And one without:

Image

The red car has several millimeters of clearance from the surface of the track. If it turns out that some cars are too tall (have too much "ground clearance" for the stop section) then I will add a second layer of tape towards the end of the stop section. But for now I think it's going to work fine. I was really impressed with the stickiness of the tape. When I set cars on the stop section and slowly lifted one end up... here's a link to the video. I had my scout shirt on because we just go back from picking up bags for Scouting for Food this morning. :)

Friction Tape Incline Test



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Re: Adding a Friction Brake to an Old Track

Post by drathbun » Fri Feb 24, 2012 11:03 am

I put our track together on Sunday and tested it, and every car configuration I tested stopped at least a foot before the end of the stop tape. I am quite pleased, and confident that it will work for us at our district race. Total parts were probably about $40, but could be less if you didn't get a good grade of plywood. I reused the existing hardware (two hex-head bolts) to attach the stop section to our existing track. The most expensive item was the foam tape from McMaster (mentioned earlier in this topic) but I wanted to get the right stuff rather than mess around with something that "might" work.

Here's a video (mp4 format only) of one test. My boys and some of our neighbor friends were having fun racing the cars down the track. :)

The purple "geaux" car was going the fastest but stopped the quickest because it has weights screwed on to the bottom, so the tape really grabs it. The green car on the right was second fastest and went the furthest down the stop tape because there's very little area that contacts the tape due to the design of the car. The car on the far left has a standard flat bottom, and the other purple car had a hollow bottom, but still more contact area than the green car.



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Stan Pope
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Re: Adding a Friction Brake to an Old Track

Post by Stan Pope » Fri Feb 24, 2012 4:15 pm

rpcarpe wrote:Some tempur-pedic type foam for the end of a brake section makes a great absorber of all that energy.
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.

No problem seen during test runs of 3 of our fastest cars on a 4-section Freedom track and braking section. They just stopped with their noses still pressed against the foam! Each would have skittered well beyond the braking section otherwise.

I had intended to run parallel 1X2's over the stop and under the track and put carriage bolts / wing nuts on each end to "clamp" the stop in place, but I ran out of time and materials.

We will see how well this stands up to a full day of racing tomorrow... pix and report, I hope. Seven of the tracks will endure about 400 minutes of non-stop racing each. The eighth track will run Age Group Finals and the Race of Champions so it will be less stressed (but the scrutiny of any shortcomings will be much more intense.)


Stan
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