Considering update of Shepherd Speedway

[slothead]

The current Shepherd Speedway was built in 2005 as a test track but once up and running hosted many thousands of laps of racing. I routed it into 1/4" hardboard with slots that went all the way through the surface to prevent anything from getting stick in the slots. This was possible because of a 1x3 lattice the surface was glued to before routing.

I love the track and over the years added a lot of 'short track' scenery with the help of my grandson to make it very realistic and so much fun to race on. But, it's 4' x 14' and was meant to be replaced by a bigger oval with wider turns years ago, and that time may have finally come.

As the weather warms up I should have room downstairs in the barn to build a larger oval, either 5' or 6' wide, and try it out before deciding if I want to dismantle the current one up in the loft. That means I can do this without touching the working oval for now.

Here's what I'd like some feedback on:

What sheeting to use for the track surface? I want something with decent grip (not as slick as hardboard) but that still has a smooth surface. I used MDF for the road course and am leaning toward using that again but am open to suggestions. Since I'll only need 3 sheets of whatever I end up using cost isn't an issue - I don't want to regret not spending more per sheet now for a better outcome.

What thickness of sheet to use? If I go with MDF I know it's quite heavy so the thinner that can be used safely the better. But, I might want to put a little banking in the corners so not too thin to risk cracking during shaping.

As a solo racer I only need one lane but am thinking about routing 2 lanes with a crossover so it actually takes going around twice to return to the dead strip for the timer/lap counter to complete a lap. I like longer lap times and think it will be challenging to run both the inside and outside grooves. I'm thinking of putting the crossover at the entrance to turn 1 so it will be within arms reach of the driver's station. I may put the crossover on a small section that could be swapped out to make it a normal 2 lane oval if desired.

Any other things I should be thinking about?

[mattb]

1/2 inch MDF works fine. ..and it is easy to bank. ..rout a 180 degree curve and cut off about 10-15 degrees and it will bend right up make a nice bank...I think yo better make it a 2 lane track though...
this stuff bends easy

[slothead]

Thanks for your comments and for including the picture. Is that a three lane track shown? Did you have to cut any grooves in the back of the sheeting to get it to bend?

[slothead]

I slept on Matt's comments and am more confident now I can do modestly banked turns on the oval, and have a plan for the layout of the lane(s).

My current oval was made in 6 wood sections that fit together like big pieces of plastic track. The straight sections ate 4 ft long and the 180 degree corners are 26" long by 4 ft wide. There are 6 joints in all held tight by screws through wood tabs.

I wanted the new oval to have as few joints as possible but will build a section of the start straight going into turn 1 that will be easily replaceable. One version will be a normal 2 lane section, and another version will be a crossover section. The tabs they attach to will be on the before and after sections so the start straight piece can lift out easily after removing the screws which will be contersunk to be flat with the track surface.

[mattb]

My track is 4 lanes... No undercuts,.. this stuff bends fine with no modifications. ..

I would suggest routing the curves and assembling the rest of the track,,,sanding the joints smooth ,... then rout the straights to connect the curves.... If you have access.. I would have a shop with a cnc router do 2 pieces of 4X8 - 1/2 mdf as 180 degree curves whatever number of lanes you want.,,you specify lane spacing.

Have a shop rout the two 180 curves ...Have them cut the straights also.....A 4X8 sheet will make you two 8 foot long pieces of straight track....Do 2 sheets as straights and two as curves and you have all you need to make a 24 X 8 banked oval......I have a local shop that could have done that, ...but they were too slow for me.....so I went ahead and did it myself...I would have liked to have had it all done perfectly on a cnc,,,,and the gains cut at the same time .

I have thought of having them rout the same thing for me and just storing it away for a future build,.... maybe 4 pieces of 180 curves and 4 pieces for 8 foot straights.... I could then cut it up and put it together as whatever design I would come up with....Here's the clincher, the local guy said he would rout the track for about $8 a sheet!.. He would have to get his guy to write the program and then have time to do it.....Maybe they would get it done in 2-3 years...

Jump in and you'll do fine..

[Eric P]

On the two tracks I've built, 1/2" MDF worked for me. I didn't need to bend it much since I didn't use NASCAR style corners. It did flex enough though for any elevation change and slight banking/camber in corners. I routed the first slot using flexible drywall trim and a straight edge for the fence. I think the grip comes from the paint put down. Unfortunately, you never know till it's taped and wired.

[mattb]

If you just want a uniform curve,,you can just make a compass arm to guide the router. ..Be sure the all attachment joints to the mdf and to the router have no play and that the arm cannot flex...Rout your lanes and out side edge...then cut off the inside of the corner...Banking is very easy.

There are expensive and fancy paints you can use,,but I've always had good luck with plain old latex wall paint..I have used gloss and semi gloss and flat...It seems the shinier the paint the better the grip with either silicone or urethane tires....If you run factory tires,,,I would paint with a gritty paint and not something smooth...I haven't seen any factory tires that will grip without magnetic false down force,,,but I have limited with 1/32 stuff the last 8-10 years.

[RichD]

I had a good article on making banked curves bookmarked, but the site is not responding. I did save several charts however. If you wanted a 180 degree banked turn the corner would have to be less than that.



To get a 20 degree bank you would have to make the corner about 170 degrees. If possible the section should include at least a short entry and exit straight section. When the legs of the corner are pulled together the width of the slots will be reduced a little. The radius of the corner will also be reduced. For a 25 degree bank the radius would be reduced by 10% . I also saved the chart for the radius reduction. If you make your banked sections first you can match the rest of the track to those. Because slot cars corner a lot faster to scale than 1:1 cars the banked corners do not need to be as steep. With a 30 inch radius 10-15 degrees might be enough for most cars to run flat out. You might make steeper corners just for looks.
If you use 3/8th MDF you will not need kerf cuts on the back.

[Scatman]

When I built an oval track and used the chart that RichD posted, I attached the straights and routed my lanes first. Gives you a smooth in and out transition.

[slothead]

What degree of banking did you end up with? I zoomed in on the photo of your painted track and it looks like what I have in mind.

[mattb]

1/2 inch bends very easy and allows a 3/8 deep slot. Slot may tighten up a bit when the bank is pulled, ,,but it is very minor and of no consequence unless it is an extreme bank,.More then 8-10 degrees is probably as much banking as you would want....15 is a lot.,,I have always sanded the slot before painting anyway and you can push a car thru to see if the slot is OK.

[slothead]

Thanks to everyone for their comments and feedback.

Matt - since I made my current oval to be like plastic track pieces made out of wood, I want this new version to be more 'organic', meaning the racing lanes will flow like actual racing grooves around a dirt track. I used a radius arm made from thin plywood to route the slots for the first oval but want changing radius slots this time. I like your idea of using a CNC machine for smooth cuts but don't know how freeform you can be in that case. I'm going to look up info on CNC programming to see what goes into the process.

Rich - thanks for the chart. I like the shallow banking on scatman's track and will try to duplicate something like that. I want to try banking but not to the point it makes getting around the corners too easy.

I want the final surface to be smooth and grippy just not as slick as hardboard. All my oval track cars have silicone tires on them which work best for me on a smooth surface so I want to replicate that. When I get closer to that stage I'll experiment with a few different paints to see what looks and works best. It may take some research into what's used for dioramas to learn how to get realistic dirt surface colors.

[Scatman]

Sorry, I don’t remember. This track was built back in 2002. Here’s some more photos. Hope it helps.

[mattb]

I think the only way to rout curves like you want is to use a flexible strip.

[Scatman]

Actually, I made a base for my router out of MDF. I mounted two 1/2 bearings so it can ride the edge of the MDF. The distance between the bit and the bearings was the distance I wanted for my gutter. After I cut the outside lane, I removed both bearings, and installed a piece a metal rod. The rod went inside the first slot and it was used as a guide to cut the next lane. I would post a picture, but I can’t find the part.

[HomeRacingWorld]

This is good to see a new plan coming together. Fun stuff to build a new track.

The post on banking are solid gold. I did it differently, but for a couple reasons:

The Show-Me Speedway Built Article Here

1. I had a very strong table/base already built.
2. Did not want a lot of banking. I was going for the local dirt/asphalt look.

The 1/2 MDF is more flexible than some might think. With a little pressure, it created the effect I was after.

2 lanes? I would almost suggest 3.

But please understand...that is just my old self trying to be a "planner"

Soon as you are 100% sure that is all you will ever need...someone is going to move close by and bring a friend

Of course if that is certain not to happen...I like your idea of the crossovers. It would make things rather interesting.

Good luck and look forward to your build progress.

[mattb]

It's easy to make a router guide that runs off track edge and the previously cut slot, ,,but that won't give you lanes with changing curve arcs.... for that you need a flexible strip,,,

I saw an article years ago that may have been from Popular Mechanics or an early model mag. It was a 2 lane oval with crossovers in the corners,,,like 2 overlapping circles..I always thought that would be great for circle track racing. ..I butchered up a pair of the Scalex sport track corner crossovers and mated them to some Monogram track and built a track like that a long time ago. ..I took it to Dolton one year and had it in the motel room. ... I had a wood case that was 3X3 and 3 inches thick...It opened into a 6X3 oval of Monogram track with the crossovers...It worked but not great. .. I believe today I could do better and would just rout it.

This is the router guide I made copying Steve Ogilvies guide that he built hundreds of commercial tracks with,,,one set of holes for a 6 inch gutter,,one set of holes for 4 inch spacing...and one set of holes for 5 inch spacing...All routing is guided by the outer track edge and then the previously cut slot.

[slothead]

I watched a couple of videos on how CNC's are programmed and think I'll end up routing the track myself. A really experienced machinist could come up with the program for a compound curve, but they are all going to be different. Once I get a definite plan designed on graph paper I'll transfer the grid to the mdf and trace the lanes out by hand. Then I'll draw a matching line the radius of the router base away from where the lane will be and firmly mount a flexible guide to the mdf. I like the idea of using a metal strip for drywall corners.

Does 1/2" mdf and 3/8" slot seem like a good math?

The banking will be slight, 10 degrees or less. I'll make some scale drawings and probably do a short practice piece to see if I like how it looks. A few of the dirt tracks I used to go to regularly had slightly banked turns and there was good action.

May have to scale back the width. The back straight will be against a wall and 6' will be hard to reach across even with a grabber. I'll play around with the table height and width to see what works best. Length will be what I get with 7' straights.

Yes, I'm going to do a ton of planning before I make any sawdust, except some practice pieces.