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Piste Martini

11934 Views 33 Replies 13 Participants Last post by  a Bill
When I posted this shot in the Scratchbuilding forum as an excuse for my current relative silence, Swiss asked me to amplify a bit.

It is a 61', 4 lane routed track using 3/16" Magnabraid recessed about 0.007". On the right side you can see the dead strips for the timer/lap counter. I use a PC based system by SRT in California. It is a bit of overkill for a home track being designed for commercial use but it has a lot of nice features and has proven to be absolutely reliable (this track replaced a 4 lane Scalextric track that was dismantled and sold last March)

I promise to add some more shots as the work goes forward but right now I am concentrating on getting ready for the "Grand Opening" in about ten days time.

The material for my Armco barriers has just arrived and I will photograph and describe that part of the project (caveat - I have an idea but have never done it before!)

The track is routed in 1/2" MDF with a 1/8" slot. The track surface is three coats of flat alkyd enamel and is almost velvety to the touch.

Hidden from view at the far upper end are the "esses" that connect the starting straight on the right with the main straight angling down from the upper left. The hairpin at the end of the main straight is the only constant radius corner on the track - all of the others open or close.

I have done only a few laps on it but my initial impression (and the design goals) is that the apparent simplcity is deceptive!

To be continued......


PS - one last note - this is the first routed track that i have done. I assure you that the process is more tedious than difficult!
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QUOTE (BEEJAY7 @ 3 Nov 2004, 18:47)Excellent, and it could not have come at a better time, as I'm now committed, (more or less) to building one and I know JP is wavering.

Could you describe in more detail the "dead" strips and how you will include timing, as this is one area, (among many others!), that I haven't got a clue about.



The "dead strip" is essentially a switch. It is a 4" length of braided track with 1" gaps in the braid at each end. The power braids are jumpered across this 6" gap (I also use this connection as one of my power feed points) One side of each of the dead strip braids are connected, in common, to the ground return on the lap counting/timing system. A separate wire runs from the other side of each of the lanes to the timing inputs on the system. As a car passes over the dead strip, it effectively shorts that input to ground and triggers the counting/timing function. This is a common type of input for most computer based systems. Any other trigger, such as a light bridge/photodiode combination will accomplish the same end. The only really critical dimension is the gap. It must be long enough so that the braid on the car cannot close the gap and feed power into the computer input. One inch is long enough. The length of the dead strip needs to be long enough to fit the response time of the computer input board. None of the systems that I have seen needs more than 4". The calculation looks something like this (imagine the back of an envelope or a slightly soiled napkin) A fast lap might be 60' in 5 seconds - that's 12'/second - assume that the straigtaway speed is 2X the lap average or 24'/ second. A 4" strip will close the contact for 14 milliseconds - pretty long time in the computer world! I see no apparent "lurch" or hesistation as the cars cross the dead strip - just don't stop on it!

Jim Butt (Subdude 01) and I built our tracks as a joint project. We have both made the same singular observation - to achieve the same apparent speeds that we saw on our Scalextric tracks, we have turned the power down. This may be an illusion due to the very smooth operation or it could be that the braid/braid interface is a more efficient power transfer system than braid/rail or that the hefty cross section of the braid and the lack of joints avoids some power loss.

My overall reaction - Why didn't I do this years ago? - There is simply no comparison. BTW - mindful of the vagaries of life, my track is designed to come apart into 5 pieces, the largest of which is 5' X 8' - the size of a full sheet of MDF.

Happy routing!


PS - If one has the manual dexterity to erect the top on a Healey, one can rout a track!
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QUOTE (Fergy @ 3 Nov 2004, 19:03)I posted on the original thread, but it looks great EM! Fast and smooth.....
I'll appreciate any info on exactly how you did the braid relief routing and installation because that's exactly what I'll be using too!

The track was routed using 2 bits: - a 1/8" bit to cut the slot and a 1/2" bit with a 1/8" pilot to cut the braid recess. I had the latter made (and it was a bit expensive) but they show up on eBay frequently. You could also buy a 1/2" bit and have a machine shop driill the center and braze a short piece of 1/8" rod into it to act as a pilot. Don't consider using anything but carbide bits. MDF machines beautifully but it is quite abrasive. Between Jim's track (80') and mine (61') or a total of 564' of slot, we went through 2 bits.

The process is simplicity itself. I used a combination of geometric lay-out of the track and Luff Linkerd's guide method. A single lane was routed using a home built compass ( a length of masonite with the router bolted to one end and a series of hole at appropriate points drilled down the length to take a 1/8" pivot) and a long straight edge - an 8' length of 1" X 1" X 1/8" aluminum angle. The latter had a series of holes at about 12" intervals and was loosely screwed to the track to keep it straight (just don't put any screws in places that subsequent lanes will cross) After the first lane was routed (slot only) a piece of 1/8" X 1/2" nylon, 12' long was pressed into the slot and the router, filtted with an acrylic base whose diameter matched the desired lane spacing. was run along this guide to cut a second slot. the nylon strip was moved around the track until a complete second lane was cut and then moved into the new slot to do another etc. etc. (BTW, if you geometrically cut one of the inner lanes (assuming that you are building a 4 lane track, you need only move the strip twice since you can cut 2 lanes with the same guide - one on each side)

After the slots are cut, the guide recess is cut by simply tracing the slot with the router and the recess bit.

We used solvent-based contact cement to fis the braid. Two coats of the standard formulation on the MDF and a single coat of the gel type on the braid. At the joints in the MDF, the ends of the braid are fed down through holes, very slightly offset away from the slot, and wire-nutted together underneath. this makes it possible to dismantle the track and also allows for replacement of only a section of briad should it become damaged.

The most difficult part of the project was the overpass. Because the tracks cross at an obtuse angle. the overpass is very long (over 6') and support became an issue. I could have build "girders" underneath but that would mean raising the level of the overpass, exacerbating an already compromised sight line issue at the far end of the track.

After careful consideration, I decided to revive the remmnants of an old experiment. Some time ago, whilst preparing a car for the second "Daytona West" proxy race, I tried using small solid-state anti-gravity modules running with reversed polarity to provide downforce akin to magnetic attraction on a track with copper braid. The system did not work because the response time of the modules could not cope with minor irregularities in the track and the handling was unpredictable. This, however, was a stationary application. Three modules, fixed to the underside of the fly-over, provide adequate support without compromising the clearance (they are only about 0.105" thick) It is, however, necessary to allow them about 10 minutes of warm-up for the current to stabilize.

Who said "Go to your room"?

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QUOTE (Fergy @ 4 Nov 2004, 17:03)BTW, EM, forgot to ask....

Exactly how do you pronounce "Piste Martini"?


Depends on how many I have had!

Closest that I can suggest is: "Peest Martini"

(to avoid distress, I always carefully chew my olive)

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QUOTE (GRAH1 @ 4 Nov 2004, 19:14)alan does this new track mean 3 US world proxy rounds next year,hope so

Actually, if the Salt Lake City rounds are completed in a reasonable time, Jim and I would be happy to host a pair of races for the cars here on their way back (for most of them) across the pond. Our two tracks are quite different. Jim's is modelled fairly closely on his former Scalextric track - tighter corners than mine - but is also longer. His is on a 20' table whereas mine is at max, 16' and his front straight is probably about 16.5' long. The surfaces are also different, his having been painted with a latex paint and mine with an alkyd. Although both are matte finish, there are differences which I expect will grow with the passage of time as alkyd paints are much less resistance to burnishing than the latex variety.

In any event, now or in the future, I'd be happy to host an event. We would probably follow the format used last year for a leg of the "Race Across America" with four really good drivers*, each assigned to one of the four lanes and the cars rotated through all the lanes and all the drivers.


* entrant or no, I am not one of them!
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QUOTE I believe they warm up faster with a proper bi-polar, phase-shifted AC supply, assuming of course that you have a zero-threshold inverter in the circuit. rolleyes.gif

True, but if the inverter deviates at all from a true zero-crossing point in the AC supply, you can get a low level coriolis effect and the cars may unexpected spin.

QUOTE (Russell Sheldon @ 13 Nov 2004, 09:06)I really have to plan a visit, EM!

Kind regards,


A wonderful idea - the welcome mat is always out for any of my friends on the forum - but I think that you would be particulary amused to see how a couple of 30's Alfa monopostos come sliding down the big sweeper.

Race here tomorrow - Armco installed (pix later as soon as I push the construction debris to one side)

And thanks to aBill for his comments - often interspersed with his claims to be new to 1/32 - a disclaimer belied by his driving!

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