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Establishing a Flat Patch

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My digital level is probably typical in that it has an resolution and repeatability of 0.05°, and an accuracy of ±0.2°. Over a 1500mm track width, a 0.2° error in level represents an out of level condition of a bit over 5mm. I have a 4 ft long builder's spirit level, and some experimentation with that shows that achieving ±0.2° of level accuracy with that is probably all that can be expected. There are some precision machinists levels available that are capable of considerably more accuracy at a substantial price. While I have one, I would not use it for the purpose of levelling a flat patch because there is a better way. Laser plumb bobs and levels that project vertical and horizontal lines are now widely available. Targets can be made with markings at the height of the laser, and the laser placed on one patch/scale with the target placed on the other. I made three of them from some aluminum T-extrusion. Any out of level is readily apparent, with ±1mm accuracy easily attainable which is better than ±0.05°. Corner balancing, in particular, needs this kind of accuracy with stiff springs installed, but alignment can benefit from it also.

The laser level can be checked for true level by checking with the laser on one pad, and then reversing the measurement from the other pad. My laser has proved to be very accurate (i.e. imperceptible difference) when checked this way.

Intercomp and others makes laser pad leveling kits, but something good can be put together from tools bought from the hardware store. My laser was made by Bosch. I am on my second, the first having gone wonky after a construction project, so they do need to be checked periodically and handled with care. Accordingly, making the two-way check part of your leveling process is a good idea.

Hi James,

In my experience 0.1 resolution is not ideal. for the purposes of leveling the flat patch the old school way (using a level) I have generally always used digital level with a resolution 0.01. They can be a bit pricey depending on the brands, but in my opinion, it's money well spent. I also tend to use the same level for the rest of the setup process: rake and wing angle etc. Of course, you need to be careful of the rest of the system, things like the "flat" bar you rest the digital level on to span the pads. I find these are very susceptible to damage, particularly when going back and forward between workshop and track. The best digital level in the world isn't going to help you in this case!

Here at RaceCraft, we have started to use a laser system to set the flat patch up, I've added an image of the Intercomp one we use below. The nice thing about this is it allows us to both level each individual scale pad and set the height of each with one tool and never needing to move the tools throughout the process. It's not a must-have, it just speeds things up for us when checking and setting up the patch.

I'm sure we will add a worked example of setting up the patch using this system in future.

Uh, you do realise that the level error is fixed between the bubble and the contact face - you can turn the level around and average the reading to get very close to true level?

Cheapest, simplest, and arguably most accurate method - especially over longer distances, would be to make up a water level with 4 inter-connected hoses. The water level will give a true level reference and 4 cheap hardware squares for the height comparisons from the level (use some ink or vegetable dye to see more easily - you can tape the hose ends to the vertical leg of the square. You could do it with a single length of hose and a single measuring tool, but there's a bit more mucking around.

Hi Gord,

You make good points! I guess it really comes down to practicality for me. In my experience with carting equipment around different race tracks and workshops, the frequency that things get damaged (some teams are a lot better than others!) makes a big difference in what I tend to use these days.

I find large levels and/or the reference bars we sit them on are susceptible to damage just because of how bulky they are to store. The water level idea is a nice tried and true approach but again it could be messy to use and store. The thing I like about using the laser level I posted above is I can use the same thing to set all the pad heights, level all the pads, and measure all my ride heights (by using the laser line as my fake ground level). It's a lot of capability packed into a small amount of gear.

Of course, not everyone has a budget to invest in something like this and each of the examples you list will also work well. In the end, they all need some care and attention to detail to work properly! 😁