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Old 02-19-2015, 07:12 AM   #481
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Now that I have watched the videos I see that the vehicle dynamics simulation is very useful in my setting of limited on-track testing. However, to get the benefit, it looks like I need the 4-corner scales.

Also, it seems that the information contained in the multitude of 'setups' available on the internet is only part of the overall package. Without knowing the 4-corner weights and CG of the car for which the setup pertains, one cannot expect equivalent performance.
true without the corner weights but you can still identify which direction or changes that might be usefull in given conditions
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Old 02-19-2015, 10:28 AM   #482
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Originally Posted by ic-racer View Post
Now that I have watched the videos I see that the vehicle dynamics simulation is very useful in my setting of limited on-track testing. However, to get the benefit, it looks like I need the 4-corner scales.

Also, it seems that the information contained in the multitude of 'setups' available on the internet is only part of the overall package. Without knowing the 4-corner weights and CG of the car for which the setup pertains, one cannot expect equivalent performance.
4 wheel scales are definitely helpful but not imperative. What you are looking for is the relative effect of setup changes. Normally weight transfer, camber gain, overall stiffness are all affected when you make a change. What's important to understand are which properties are affected, by how much and does it move the handling in the direction you want to go.

All RC3 models include at least an educated guess at the CG location by comparision to similar vehicles. The CG position is essentially a constant in the calculations, knowing it's correct location is great but not critical to understanding what your setup changes are doing.
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Old 02-19-2015, 02:29 PM   #483
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I'm importing CSV data to the motor dyno analysis.

I'm getting many errors.

Data is 0.2,7649,17.9, 8.4, etc
It looks ok as I assign the columns and rows.

First issue is the graph won't let me select. It won't 'take' the selection or update the little start and end boxes. If I fill in the values with start and end values for both time and rpm manually I get weird stuff.
When I click on Dyno Calc I get "Motor Form -Sub DataSmooth Object Variable or With block variable not set"

Re-doing the whole import then as soon as I click on the graph to select the values I get:
"Motor form- Sub SelectData
Index was outside the bounds of the array"

It won't let me select from 1.0 seconds to 0.2 (which is the dataset). It always selects all the way to zero. It never updates the Start KRPM box .
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Old 02-19-2015, 02:34 PM   #484
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Screen shot.
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Old 02-20-2015, 05:15 AM   #485
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I am actually in the process of revamping the entire Motor Manager Module which as you have discovered is not particularly robust. The Team Version of the program has been updated and is currently a work in progress. Once that version has been tested the General version will be updated to include these new features.

The issues you have encountered have all been fixed plus a new Motor Math Model has been developed that fits the test data much better.

To get around the data range selection issue just punch in the time range in the text boxes. That should solve the problem.
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Old 02-20-2015, 06:58 AM   #486
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I'm on day 4 of the trial, are those updates available when I purchase the activation code?

Still getting lots of errors. I manually entered the start and end time and start and end kRPM and click on "Dyno Calc" I get: "Motor Form - Sub SelectData Index was outside of the bounds of the array." When I click "OK" the "Selection Data Range" graph switches its axes so kRPM is on the x-axis.

When I select across the data range anywhere and release I always get : Motor Form -SubRPMRange Object variable or with Block variable not set
Then the visible data in the "Import Data" box near the bottom disappears; (the imported data that was under Time, Voltate, Current, RPM).

If I click on "Dyno Calc" I get "Motor Form - Sub DataSmooth Object variable or With block variable not set.

I did find a work-around. In the "Motor Model" screen I can adjust the settings and compare the model's graph to a graph of real data I have on another computer and match them up that way.

Last edited by ic-racer; 02-20-2015 at 07:16 AM.
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Old 02-20-2015, 07:29 AM   #487
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Quote:
Originally Posted by ic-racer View Post
I'm on day 4 of the trial, are those updates available when I purchase the activation code?

Still getting lots of errors. I manually entered the start and end time and start and end kRPM and click on "Dyno Calc" I get: "Motor Form - Sub SelectData Index was outside of the bounds of the array." When I click "OK" the "Selection Data Range" graph switches its axes so kRPM is on the x-axis.

When I select across the data range anywhere and release I always get : Motor Form -SubRPMRange Object variable or with Block variable not set
Then the visible data in the "Import Data" box near the bottom disappears; (the imported data that was under Time, Voltate, Current, RPM).

If I click on "Dyno Calc" I get "Motor Form - Sub DataSmooth Object variable or With block variable not set.

I did find a work-around. In the "Motor Model" screen I can adjust the settings and compare the model's graph to a graph of real data I have on another computer and match them up that way.
Once the updates to the Motor Manager are finished testing in the Team version they will be available to all users.

If you send me your Dyno Data file rwdesign@kingston.net. I will have a look to see what is happening. You don't seem to have many data points in the dyno file which may be causing some of the problem.
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Old 02-20-2015, 07:50 AM   #488
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Hi Bob,

When modelling a TC with pro dive/ anti squat on the lower arms, what point should I use, the higher one or lower? Or split the difference? I would assume the same answer would apply when reactive caster is used on the upper 'a' arm.
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Old 02-20-2015, 01:04 PM   #489
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Hi Bob,

When modelling a TC with pro dive/ anti squat on the lower arms, what point should I use, the higher one or lower? Or split the difference? I would assume the same answer would apply when reactive caster is used on the upper 'a' arm.
Split the difference and yes to the reactive caster.
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Old 02-23-2015, 04:56 AM   #490
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I'm working on models for my cars. I just finished the new TT02 S-Spec. Can I post the data here or would you rather all the chassis information exchange through the RC3 website?


Also, a suggestion. For high-turn motor classes, getting the low gear ratios can be a problem due to gear size. It would be nice to have chassis parameters for maximum total gear teeth and minimum total gear teeth that mesh. The gearing page could show red values when the pinion or spur are selected that won't fit on the car. Also, there could be a little bar graph that shows the relative motor location when a combination of gears is selected. That way one could select gears without changing the CG if so desired or select a spur that puts the motor in the middle of its adjustment range.
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Old 02-23-2015, 05:03 PM   #491
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Probably best to just send me the file. It will reach a bigger audience that way.

Thanks for the suggestion on pinion/gear combos. I'll keep it in mind.

Back to our earlier discussion on motor dynos. As you know the datafile you sent me didn't have enough data points to create a model. However the screenshot showed there may be quite a bit more data recorded at higher RPM. If you can provide the Diameter and weight of the flywheel and the entire data file I should be able to create a model using the additional data.
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Old 02-23-2015, 07:09 PM   #492
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After watching all the videos and working with the software I wanted to thank you for the graph of the F1 tire showing grip and loading. Everyone needs to understand that example to see why the firmer end of the car has less grip. So much of the balance is based on those principles, and the concept is not intuitive.

TT02 S-spec project. This Tamyia car is based on their lowest level tub touring car. What they did for the "S-Spec" was to tack-on the suspension arms from the TRF racing machines (419 etc). I thought this would be an interesting car to learn with.

First I created the model. I re-did the lower suspension point measurements a few times because it seemed as if even very small changes there made big changes in the roll center. Unlike the other TRF cars, this one does not have the adjustable hinge pin mounts. The hinge pins go right into holes in the tub chassis; only one location vertical or horizontal.

What I wanted to do, as an exercise, was to optimize the model with the software, using the parts that came with the kit.

First thing I noticed was that the roll centers are low and the camber gain is almost non-existent. Indeed eyeballing the car's front demonstrates an almost parallelogram front suspension and pressing 3mm keeps the camber meter the same.

There are very few adjustment points. Rather than drilling holes, buying hop-ups, and making stuff, the challenge was to get it the best it can be using the parts in the box and some shims.

I increased the height of the front outer camber arms, only to find the wheels don't fit. I had to compromise on 1.5mm. I did the same on the back, only to find the threads on the end of the ball will only hold about a 2mm shim.

Without changing springs from the kit springs, I used the model to adjust the shock positions to balance the car.

The suspension spring preload is set with those spring shims. With the 4-scales, I was actually able to get good side to side balance and equal cross-sums. Anyone can twist adjustable collars, but I wanted to see how close I could get with the shims. (very close indeed).

Camber gain is still low, so static camber of 2.5 was needed.

All, in all I think I got the numbers looking pretty good and I'm anticipating a easy-to-drive balanced car, realizing it will be a VTA and the chassis is pretty soft and has no roll bars. I may be able to try it out this weekend.

Last edited by ic-racer; 02-23-2015 at 07:28 PM.
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Old 02-25-2015, 01:00 PM   #493
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(question answered)

Last edited by ic-racer; 02-25-2015 at 05:37 PM.
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Old 02-25-2015, 01:47 PM   #494
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If you can provide the Diameter and weight of the flywheel .
That was not so easy, but I think I have it calculated. The issue is the 4 holes around the perimeter, so the disk is not of uniform mass.

I broke it down into a disk and a surrounding ring. Assuming aluminum at 2.7 g/ml.

The inner disk is 27.7mm radius and 8mm thick this yields a mass of 52.09g

The outer ring is 27.7 inner radius and 34.75 outer radius and 8mm thick. That yields a volume of 11065.25 mm3. The 4 holes work out to be exactly 1000 mm3. So the outer ring has a volume of 11065 - 1000 or 10065mm3. This gives a mass of 27g.

The total mass is 79g on a scale and the two calculated masses total 79g also, so the math seems good to this point.

So the outer ring calculates to 26,660.5 g*mm2 (I = 1/2 m ( Ri2 + Ro2 )) and the inner disk calculates to 19972.5 g*mm2( I = (1/2) m R2). So I presume the final answer would be the sum of the two:
46688 g*mm2

47698g*mm2 is the calculated inertia if one ignores the holes. This is an over-estimate of the true inertia of the flywheel by about 2 percent.

Last edited by ic-racer; 02-25-2015 at 08:28 PM.
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Old 02-25-2015, 06:09 PM   #495
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The way to factor in the holes is to subtract the inertia of the holes from the total disc inertia. The simple version for the inertia of the holes will be mass of hole times the radius from the centre of the disc to the centre of the holes squared. To be 100% accurate you should also include the actual inertia of the holes themselves about their centre but this is likely small compared to the above calculation.

If you provide all the diameter of the holes and the radius to the center can do a precise calc.
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