Banked turns vs Slanted turns

[slothead]

I have another thread going about an upgrade to Shepherd Speedway but thought this new post would be the best way to get feedback about options for the turns.

It looks like the track will be CNC routed using programs written by Brad Bowman. As the designs moves forward I'm debating whether to go with slightly banked turns for the oval, around 10 degrees, or just tilt the track upwards at each end to create slanted turns of the same degree. I've done the math for cutting the corner sections at less than 180 degrees so they can be banked while pulling the attached straight sections inward to be parallel, but am also considering slanting the turns as Harry did on the build thread he posted about his oval.

Slanting will be easier to do but will it provide the same effect as banking - allow cars to take the turns at slightly higher speeds without as much tail sliding? The current version of my oval is a flat track with a hardboard surface and some of my cars are very hard to control in the corners even at reduced voltage. The new track will use mdf but I think slightly banked or slanted turns will be valuable too.

For those who have built or raced on home track ovals with banked and/or slanted turns what are your thoughts?

[RichD]

If you go with slanted turns the angle will be greatest in the middle of the turns rather than being constant like banked turns. You would have to be more careful entering and exiting a slanted turn. You often see slanted turns with regular plastic track, if you try to bank regular flat sections the inside of the joints want to pull apart.
I have raced on tracks with banked and slanted turns, you quickly adapt to either type. With slot cars a little banking goes a long way, with as little as 10 degrees on an oval you might want to run more powerful motors or up the voltage a bit or you might find that you can run your cars flat out all around the track.

[mattb]

Bank it,, if you are using MDF. and just want a little bank..nothing could be easier.. It is as easy as just elevating and you'll be much happier with it. I have done regular banked turns with MDF and elevated corners with Carrera plastic and the banking is so much better.

[Pappy]

I agree with Rich on the slanting and banking. And he's right, a little banking goes a long way.

It's easy to bank a turn with MDF. When you pull in your banking the degree of turn will change, always cut the excess wood off of the turn section. Your straightaway sections should always have perfect 90 degree ends. When you make your joints just overlap the straight section on to the curved section and mark it with a pencil. The piece you have to cut off will be somewhat pie shaped. I wouldn't try to figure the turns with math, I'd fit them together and cut off the excess.

I'm building a new track. All my turns will be flat with just a hint of positive banking.

[ra7c7er]

I personally prefer slanted because you have to drive it a bit more. IMO a lot of people tend to overdo banking then you wind up making a boring section of track (IMO just holding the throttle down for a few seconds isn't all that fun). I'm not a track builder but I have been told Banked turns can be a bit easier to build but I have no direct experience.

If you have the spare MDF make that turn both ways and see what you like best. Or make it removable and switch them out whenever you want to.

[mattb]

The bank I showed is at the end of my long straight. .I would only do that much banking at that spot..The rest of the track has banking at no more than 5-8 degrees and it requires driving ability, , but you can still keep pretty good speed..A lot depends on the ability of the guys you race with.. I race with a bunch of blind old men and they overdrive most every corner. . banking is a requirement!.

You do a 2-3 lane track and raise the outer edge by as little as 2 inches and you'll be real happy with how it drives.

This pic is the other end of the track. It is about 5 degrees.

[HO RacePro]

Count me firmly on the side of banking curves instead of tilting them.

I have built many HO tracks with banked curves. The steepest banking I consider practical is 20 degrees. My tracks with 10 degree banking have been popular.

I have found it useful to model banked tracks in poster board. I make a 1/12th scale drawing on my computer, print it out, and paste the printout to the poster board. I cut out the track model and assemble it on a thin sheet of plywood. The model's banking accurately reproduces what the full-scale track will do. If it looks right it probably is right. If not, go back, tweak your design and build an updated model. Get it right before you start cutting MDF.

It is possible to use math to calculate the arc angle of the curve to produce a desired bank. But the model is a good way to check your math. It is also the best way to cope with complex geometry -- like a banked overpass.

When cutting out the curve I include 2-foot-long straight sections integral to each end of the curve. This gives me something to pull on when forming the bank. It also creates the ramps into and off of the bank.

Making banked curves isn't difficult. Like anything else you need to learn a couple of new skills. Once you've got your arms around them the actual work isn't hard.

Ed Bianchi

The 10-degree banked oval was built for Jeff Stillwell of Stillwell Racing Enterprises. The table and all of the scenery was created by Jeff.

The figure-8 track was built for Bob Beers. It has been on display at the "America On Wheels" museum in Allentown Pennsylvania.

[mattb]

I've always found this style figure 8 the most fun track to actually race on. You don't de-slot too much and lanes are pretty equal. I built a track like this back in the 80's and after lots of thought I built this last rack with nearly the same design

[slothead]

Thanks for the comments and photos which are most helpful. My track will be a 1:32 scale oval and I started working on the specs for a 50% sized model of a corner, but now I may even go smaller. I thought about using foam core poster board but thought it would crinkle so I was going to use a 2' x 4' handy panel of 1/2" mdf for the test section. Ed's comments have me thinking I should try a smaller model with poster board first before considering a larger size model in mdf. I've done calculations that suggest creating a corner section that is 177.5 degrees will result in 9.5 degrees of banking when the straights are pulled into alignment making the corner 180 degrees.

My next task is figuring out how to accurately measure 177.5 degrees for cutting the test section out. I guess I can draw a straight line thru the center point of the corner radius and then use trig functions to come up with the dimensions of a right triangle with a 2.5 degree angle located at the center point. The long side of the triangle would then become the end of corner line where the straight section coming off the corner on that side of the turn will begin.

I'm probably over thinking this 'cause I'm a math nerd. If there's a simpler way to measure things out please let me know.

[bdsharp]

It's old, but this is a good article about banked curves. About halfway down there's an accurate graph for what your U-angle should be to bring in the desired banking.

http://www.slotcarracing.org.uk/trackbuild/bking.htm

[RichD]

When you look over that article be sure to check the reduction in radius. For an oval that would not cause a problem, but if a banked section is included in a road course it might not connect to the rest of the track unless you compensated for the reduction. You can either make the original radius a little greater or do the banked section first and build the rest of the track to match that.

[Mitch58]

My track is cut out flat but I still banked every curve. The two big sweepers, 3'R & 4'R are banked 10 degrees and all of the others are banked 5 degrees. Once I had all of my elevations set I cut a wedge shaped support and slid it in next to the one already there. It seems to have worked well.

[mattb]

Easy way to figure your banked turn is to go ahead and rout a 180 degree curve...Either with a compass arm on the router of by a guide running around the outside edge of the curve. Cut the proper width so you basically have a 1/2 curve done. Screw a piece of flat mdf ,,most any dimension,, to make an extension of the curve, pull the extensions together until you have a bank that looks like what you want. Take a straight edge and lay it at one end of the curve and across to the other side of the curve and you will see how much of "pie" cut to make to have a 180 curve with the banking you desire.


Easy way to do this is to buy a piece of 1/2 mdf and experiment! It is very self explanatory,

[Pappy]

I never thought about doing it that way, Matt, but that would work for a 180 degree turn. You'd also need a flexible straightedge.

[HO RacePro]

If you really want to add a challenge to your track you can use the same methods to create an "off camber" corner -- a corner that is banked the wrong way! All you do is make the outside of the curve flex down instead of up.

I've never made a track with such a curve, although I have seen tracks where an off-camber curve was created -- I presume -- unintentionally. It doesn't take much of a reverse-bank to make an off-camber corner really tricky. At a guess I'd think a 5-degree reverse bank would be all you'd want.

One or more off-camber corners would be appropriate for a challenging hill-climb or rally track. And probably cause for many bursts of profane invective.

If anyone has photos of a track with an off-camber corner I think we'd all love to see them.

Ed Bianchi

[waaytoomuchintothis]

I want to underline a couple of things here that have been part of the meaning of what has been written above.

About banking... It isn't hard at all to make, in fact you will smile at yourself for not trying it before once you do it. More importantly, driving a banked turn mashes the chassis into the roadway, and when you come out of a banked turn at speed, the car feels like its floating by comparison and uncontrollable, unless the exit of the bank is nice and straight. And yes, a severely banked turn is just boring. Its the worst feature of the "King" or "Imperial" type track designs. Also, banking a long "sweeper" turn just ruins it.

About tilted curves... The spot on the track where the greatest "mash" takes place is much smaller on a tilted track, and its much easier to learn the track. You can be creative about it, and rout for a very small bank, then adjust the resulting track by tilting. It lets you try several treatments without routing MDF for a second hobby. It also lets you tilt the curve asymmetrically, higher at the point of curvature or at the point of tangency at the end. A lift at the point of tangency allows a much better exit from the turn, more fun in races. Good luck!