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Converting Existing Slot Cars to Arduino MagRacers

11259 Views 16 Replies 6 Participants Last post by  Drifter2
I decided to start a new topic away from Martin's Arduino + MagRacer thread (HERE) so things don't become confusing. The purpose of this thread is to discuss ways we can modify existing slot cars to work with Martin's Arduino system. The goal will be to create a fully integrated arduino system that fits into the car with little to no alterations to the stock chassis.

The reason behind this is simple. There are tons of amazing, highly detailed cars readily available. Some are truly works of art. Since a lot of you here may already have quite a few of these cars on hand, it would make sense to use them as a basis rather than investing in an entirely new system. It would be great if we could come up with a way to be able to switch back and forth from Mag and traditional slot car racing.

So what are some of the challenges? The biggest hurdle to overcome is space. There is little room underneath these bodies. An all-in-one small board that houses the arduino, motor drivers, and wireless transceiver will need to be created. The car will also need to house a 3.7v LiPo battery to power the system. The motor will also need to be converted from 12v to 3-3.7v. Lastly, a steering system will need to be devised.

All those items listed above have their own specific challenges to overcome in order to make the system work. So why not just swap out an existing body to a custom/universal chassis? Well there are a few issues
with that solution. 1) Every manufacturer's chassis design is different. 2) Ever car model's chassis is different. 3) Some of the body details are molded to or permanently attached to the chassis. So designing a universal part that can work with all cars is pretty difficult.

Even though all cars are different, I think a common solution can be reached that will work with a majority of the slot cars available. The ultimate goal would be to have a database of car parts and dimensional drawings that people can use to either scratch build or 3D print to change their cars over to MagRacing.

I have begun working on a solution for Carerra DTM cars since that's what I have. A lot of the designs I have could work in other models of Carerra cars. Over the next few days (weeks) I'm going to present
several different solutions for the slot to MagRacer conversion. I welcome anyone who wants to share their input or designs so feel free to join in the discussion!

Most of my work is done on lunch break, so I don't have access to my files now. Tomorrow I will post a few screen shots of what I have so far. Thanks !
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I think this is an excellent idea. I recently got to digital slotcar and one of key aspects was how nice the cars look these days compared to 20 years ago (or even longer than that). When I discovered MagRacing, I really liked the concept but clearly the cars are not on par in terms of details with the today slot cars. They remind me a lot of the old Polistil cars I used when I was a kid.

One question/suggestion: have you guys though about using the lipo batteries used in RC choppers? And how about brushless motors? A brushless motor should be more efficient than a brushed one such as the ones we have in slot cars.
I guess its time too reinvent the magracing concept cars!
WesR has done a wonderful job and good invention for us too take part of.
But ther should bee better possibility too use another bodys. Another kind of holding the body. Wheelbase adjustment and maybee another battery type.
I realy like the thinking from WesR to trye to make it easy and simple. But when wee chance the concept too ewen get reverse We lose some of the battery power save fiatures.

The hole concept with easy multiple racing is right. Lets make it better!

I lost many hours to try too change, before I now the concept. Just race its the key!
I spent about an hour so far converting an old broken scaley Ferrari to Mag. Still have to install electronics. Have two Ferrari's so plenty of spares.

heres a link to my MagRacing folder photos......;usp=sharing

Re brushless, it will happen, just a matter of time :) (cars will be faster and less battery drain)
I think brushless motors would be great also in slotcars...Cool conversion. Where do you plan to put the battery?
Does anyone know the gauge of the steering coil? I will be making my own. Probably will be getting a few different gauges just to see what works best. Mine will be similar to Wes' s but smaller. Figure starting a coil size close to his would be a good start. The smaller the coil the larger the wire diameter. Yes? That is. .... to get the same results.
The wire on the standard magracing coil is 0.2mm outside diameter. (This includes the enamel insulation)
Probably put the battery in the same place as a standard Mag Racer. Haven't had much time, I am back at work, holidays are over :-(
I have been having some thoughts for alternative steering mechanisms to replace the solenoid as this is quite a drain on battery power. I think the best alternative would be to use a micro servo, but there needs to be a way to connect the servo to the steering with a low force so it only operates the steering when off the guide wire or over a lane change plate.

What I think may work is to use silicone hose. You can get this in small diameters such as 2mm ID. There are two possible modes this could be used,

1) Bent in a U shape and used as a flexible spring. It would be easy to mount as the ends would just push over a pin at either end. You could tune the force transmitted from the servo by lengthening and shortening the silicon hose. Its a bit similar to my drawing as shown here but you replace the spring or wishbone with silicon tube.

steering concept

2) Transmit the force by torque. The servo horn has a pin sticking out the centre onto which pushes the silicone hose. The steering is operated by a vertical pin (at the centre of a pantograph setup so it turns the steering.

One major advantage is that the servo does not have to be above, but the silicone bends and the servo can be located anywhere in the vehicle. Again you can tune the force applied by shortening the silicon tube or alternatively inserting wire or small sections of toothpick into the tube to increase torsional stiffness.

I hope I have explained this OK.
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Sounds good Martin
Certainly worth investigating.

My idea was to disconnect the guide arm from the steering and connect the micro servo directly to the steering.

The guide arm position would be read with a ratiometric hall sensor and the servo moved accordingly via the Arduino.
The driver could then influence the position by say 10% to make LC.'s. The 10% would need to be adjusted by experimentation to find the right value.

When reverse is selected the driver would have full override control of the steering servo.
An extra button could be added to the controller for full override in fwd driving.
On my controller the wheel is connected to a pot, so mild steering inputs could select a LC or full steering on the controller would take full control of the servo.
just my 2cents worth.

If I understand you are going to measure the guide arm angle and in normal circumstances match the steering angle to it with the servo. Only on lane change do you override this. This sounds a neat idea.

How do you stop a driver turning the steering just before a lane change and driving off the wire. You need to somehow sense when you are off the wire or over a lane change plate.
Good question :)

under normal driving the driver can only influence the steering just like with the standard coil setup, so when a break in the track wire is encountered only then can the car change direction. If say in a straight line the driver steers L or R the car would only drive slightly offset to centre of wire and not continue off in a new direction. The lane changers would also need to be redesigned to catch cars inadvertently steering off in the wrong direction. To be totally honest I'm not sure that my idea would actually work.
On my test track the car can sometimes be steered wrong at an LC and leave the track. As I am only new to building mag tracks I put that down to "track builder learning curve"

It would take some testing and trial and error and a ton of patience. The more I think of it, the more I feel Wes's system is "simply brilliant, and brilliantly simple".

I guess the forum isn't sending me emails when people respond to my threads
. Had no idea there were responses here decided to check on a whim. Anyways lots of good ideas here. I really like the make your own mini magnetic coil around the tube. Something like that could easily be converted into a steering mechanism. Haven't had much time to mess with this project though. Hopefully I'll have some time Sunday to get back into things.
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Hopefully the above photo showing Brushless motor placed in a MagCar, with ESC

Interestingly the ESC has an ATMEL 168 processor!
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