Shepherd Speedway V2 Take 2

[slothead]

A new version of Shepherd Speedway, a replica dirt oval, now has a new design and the MDF sheets will be CNC routed next weekend. The first take resulted in an error while being CNC routed 2 weeks ago that created a crack in one of the corner sections. That design also turned out to be faulty when testing showed the lane crossovers were too shallow and cars tended to depart a crossover in the outer lane even when that wasn't their intended path. This led to a new design as seen in the sketches below, and in the CNC routing file created by Brad Bowman.







The track is designed as a solo racing track with 3 lanes that a single car will traverse before completing an official counted and timed lap. The corners will be banked around 8 - 10 degrees when pulled in and the resulting track will be 6 feet wide and either 12 or 14 feet long depending on how many straight sections are used. I also have 4 additions straight sections from the prior routing so if space permits I could extend the track to be 20 feet long.

As I prepare to bank the corners for this new design I'm still concerned about how to achieve consistent banking. The 1/2" MDF with 5/16" deep slots had the inner 2 slots become compressed and the banking was slight or non existent inside of lane 1, slight between lane 1 & 2, slightly more between lane 2 & 3, and fully banked only outside of lane 3.

I'm looking for tips on how to prevent the inner lanes from being compressed to about half the routed width of 1/8" and how to get the corner to bank at a consistent degree from top to bottom as the ends of the section are pulled in to form a 180 degree turn.

[slothead]

Did some work on the old section this afternoon as a test bed for the take 2 section. I released the pressure on the track to let the banking relax, then attached strips of wood under the corner to flatten it out and put coffee stirring sticks in the slots to expand them to full width. Then I used a screw jack to push the ends in to form a 180 degree turn and recreate the banking.



In the above photo you can see the 3 pieces of wood under the track to keep the track from bending at the slots and the coffee sticks in the slots after banking. In the photo below you can see the coffee sticks seem to be working to keep the slots from closing under the pressure of banking.




I'm going to leave the sticks under the corner section and coffee sticks in the slots all week and hope the MDF settles in the current shape, then lock it in place with a framework underneath. I hope to use this same process to bank the new sections when the new design gets routed.

[4424ever]

When there’s a will there’s a way good work soon you’ll be a pro track builder

[slothead]

It's okay that the first design and CNC routing attempt didn't work out because now I have this corner and the one with the crack to experiment with and learn from. I'm still looking forward to slightly banked turns and now have experience implementing them and addressing associated issues.

[slothead]

Here's a question for track builders (or those with an interest in building a track) and woodworkers. Since this track is intended to replicate a dirt track I'm wondering if there's a way to seal it with something clear to preserve the MDF color? I bought a gallon of white primer & sealer to use, but will then have to recreate the brown color for the dirt look.

I'm not trying to be cheap or cut corners, just wondering if there are any clear options. FYI - all my dirt cars from my current oval have silicone tires. I plan to keep most of them that way, especially those with silicone over foam Pro Track tires. I like PG urethane tires (used on my road course) but don't intent to swap my 80+ dirt cars over at this time.

[32lbking]

Something to consider if using a clear over the mdf is that it will probably darken the color, so you might want to do a test spot first to be sure you like it.
Randy

[mattb]

Any type of clear polyurethane should seal your track and leave the brown color, probably want semi-gloss. Or just paint it varying shades of brown.

As to the slots narrowing when you add banking, that was no issue at all on my track. I routed a 180 degree 4 lane curve with on a 4 X8 sheet of 1/2 inch. Banked it about 20 degrees and the commercial guides run fine. Slots didn't close up enough to make any difference at all.

It just seems a shame you'll never be able race another driver on the track.

[Mickey thumbs]

For the dirt look in my infield I picked up a sample size of a dark beige at Lowe’s and added different amounts to three buckets of leftover primer from painting my trackbed and used a dabbing/swirling technique to do the infield.

[slothead]

I like your idea for creating different shades of brown, but also need to ensure it's flat and smooth. Sanding with a fine grade paper can make that happen.

[slothead]

I'll check out polyurethane sealer, thanks for the feedback.

My slots were pinched in quite a bit by the banking process but that might be due to unique factors. In my track design the corners are flattened, meaning the radius shrinks in the center of the corner. The inside radius is around 20" at entry, shrinks to 12" in the center, and then expands to 20" again at exit. Also, in 1/2" MDF my slots are 5/16" deep leaving only 3/16" as backing. Together these factors likely contributed to the reason that the section curved like the inside of a bowl during the original banking. I also had the 4 foot deep sections return to being flat on each side by screwing them down to the table top. Unlike your banked turn section on the right above with attached banked straights, my turn goes from dead flat to full 8-9 degree banking and back to being dead flat over the 6 foot wide by 4 foot deep area.

The good news is that when the pressure was released and the banking relaxed I was able to add the wood strips underneath and put coffee sticks in the slots so the initial banking issues didn't return when the ends of the section were pulled in a second time. The wood strips ensure the track stays flat at those places so it banks like a section of a cone and not like the inside of a bowl. This methodology should ensure the new sections come out as intended when I bank them next week.

I've been a purely solo racer for a number of years now. My younger grandson who lived next door was my prior racing buddy but he's a senior in college now and moving on. When he comes to visit he will run some cars on each track but we don't race anymore. I could use an AC2car or a digital setup to run 2 or 3 cars with each starting in a different lane and try to lap each other (see if any car can catch up to another car). As is I'll have a ton of fun doing extensive time trials with all my dirt cars and filling up a database with lap times to use for multicar simulated races. I use a modified version of the Barry Boor system to conduct simulated races for up to 20 cars.

[slothead]

Thanks to Mickey thumbs' post above I looked up images of dirt tracks and now have a good idea of the gradients of brown that will give the track surface a realistic look.





By using several shades I hope to create a realistic surface that mimics the way a dirt track looks after being prepped. The darker colors at the top and bottom indicate where the moisture is as it gets run in.

And, the photo showing late model cars all over the track, high to low, is why as a solo racer I'm going with a 1 lane 3 slot track so I have to learn to drive the whole track. It's going to be interesting to see how different cars run in the different grooves and how to adapt as a driver to different radius turns.

[slothead]

Backing up a little bit so I can show how I went about banking the corner section shown in post #2 above.

The section was laid flat on a 4'x8' table top and secured on the left side (corner exit) so it couldn't move as pressure was applied to the right side to pull the corner into 180 degrees. It was boxed in by a border made of 3/4" strips on the outside and front sides of the table. A small piece of 1/4" paneling is used to pin the inside of the corner section down so it can't lift during banking.



The photo below shows how the right side of the section was held down by a metal L clamp on the outside as it was pushed inward using the screw jack shown. The 1/4" piece of wood paneling holding the inside of corner entry down was secured once the section was pushed in to 180 degrees.



The screw jack worked very well. It took a lot of pressure to stress the section as needed and the biggest issue was giving the jack something secure to press against. The pieces of 2x4 behind the jack had to be secured with a large C clamp to prevent the screws going thru them into the table surface (MDF) from pulling out. This shows that while banking a corner is not the difficult, be prepared to apply a lot of pressure slowly to get it done and take the needed steps to secure the section. I didn't want the banking to continue into the straight sections so for me that meant securing the entry & exit edges to the table. This might not be what others choose to do.

[chris]

That's going to be a great track. I wanted a clay type colour for my oval so painted mine with paving paint called Texas Dust.
I added the non skid sprinkles for grip, added more for the two outer lanes, a light sand to get rid of the sharp edges, works a treat.
Good luck with the build, looking forward to the finished article.

Chris (in Canberra)

[slothead]

Today is routing day (again) and I'm excited. The weather looks good this morning and there's only a 7% chance of rain this afternoon. Just in case there is a shower on the way home I got a king size mattress moving bag to put the cut pieces of MDF in. The 2' and 4' straight sections will fit inside the car, but the 4' x 6' corner sections will be exposed on the open utility trailer. The plan is to put the corner sections together, slots on the inside, and clamp them together with small C clamps. Then the corner sections can go in the mattress bag as a single piece.

I hope to have one of the new corners banked within a day or two and have both banked, screw holes patched, and primed this week. Part of me wants to say I can get this all done tonight but I need to go slow and think things through as I go to eliminate (lessen) mistakes.

Then I'll get to start playing about with paints to try and get a realistic looking dirt surface. Since dirt track surfaces are really made from clay I'll be looking for some paint mixtures to match the reddish brown colors in the photos above.

[mattb]

I found it very easy to bank by just using a tie down strap to pull my straights parallel to each other. The routing was done flat with SCC bit. I just pulled the strap tight and the 1/2 inch MDF banked nicely. I screwed a 1 X 4 about 4 foot long to connect the ends of each straight together to hold them parallel. It bent very easy. MDF is easy to work with.

[slothead]

The CNC routing is done and the sections are all safely in the barn.



Here's a closeup of the new crossovers. In this design they are confined to turn 4 and the intersections have larger angles which should mean cars will follow the intended paths.



The slots are packed tight with sawdust which will take awhile to clean and vacuum out. I'll start prepping the corners for banking tomorrow. Banking is a little bit more difficult for me that for mattb because I'll be doing it without longer straights attached which would provide more leverage. My corners have about 1 foot long straights at either end that will be my pressure points.

[mattb]

That looks great, I bet you can pull that banking pretty easy. The new crossover should work fine.

[slothead]

Thanks for your comments, both now and throughout this build so far. I'll use a screw jack for cars and as long as I have something secure for the jack to press against it's easy, I can tighten the jack by hand without needing the handle provided.

I'm about to do another post about joining sections together asking for input on how to avoid issues if they are not exactly the same thickness.

[slothead]

The newly routed sections have had the slots cleaned out (packed in router dust removed), been lightly sanded to remove surface router fuzz, and been vacuumed. After a good going over with a tack cloth they will be ready for the next phase.

Question is - what should come next? Painting with primer and sealer, or banking of the corner sections? I was ready to start the banking process but now think the front, back, and sides of all the sections should be painted first.

Thoughts?