I've looked a bit closer at the sheet and I'm going to input to input my car tonight or tomorrow when I have some time.

I have a question about the shock angle. Do meassure it with the A arm level (parallel with a setup board) or at rideheight? I ask because the angle of the shock is changing during when the suspension is working.

And instead of using a protractor, you could also measure the distances between mounting location on the tower, the hingepin of the A arm and the mounting location in the A arm.
Then input the distance on this website http://ostermiller.org/calc/triangle.html and you'll get the angles. I think that could be more accurate than eyeballing it with a protractor in front of the car.

Thanks for the link, will add that to the spreadsheet.
Measure at ride height. One thing I've learned is that all the cars I have except the Kyosho MP7.5 have shock angles in 5º increments. Each hole in the shock tower is 5º apart and the same with the arm holes. Typically 20-25-30 and so on.

I did this way, measure distance between right and left upper shock mounting screws in the shock tower and then between lower shock mounting screws in the arms at ride height, subtract the first measurement from the distance between lower shock screws and input that in the page (it's our lower side), then measure shock length at ride height and input that (the triangle's side), then from 90º subtract the result from the side angle et voilà.

With the protractor I would lay it with the 0 facing the left upper shock mounting point and the center reticle on top of the left shock lower mounting screw, then eyeballed the measurement. While the accuracy was low, the repeatability was good.

That's also possible, but you should divide the result by 2 before doing the input. Am I correct?

Yes you can do that way and it's the way I did in the v4.2. New version is up




Still want to see what's going on with the front roll rate prediction.

Great! Another question and suggestion.

The unit for springconstant k is N/m right?

I converted my Serpent springs from pounds per inch to Newton per meter and I'm getting values between 700 and 1000N/m which seems correct to me. My Mugen spring are also in the 700-950N/m range and they are labeled in Newton/meter.

When I look at you preentered data from the JQ, I'm seeing values around 60 which seems don't seem right to me (very very soft spring). Could you check that?

I used this website to convert from pounds per inch to Newton meter by the way: http://www.convertunits.com/from/pou...o/newton/metre

Mugen spring chart: http://cl.ly/aFrV
Serpent spring chart: http://cl.ly/aG6L

No problem, and keep the suggestions coming!
The unit is gr/mm, you can convert your spring charts by dividing by 10 (except the Serpent one)
I did the first equation with lbs/inch but because the site for calculating springs k used N/cm I converted the equation to use SI units.
By the way, I don't trust manufacturers ratings that's why I recommend the spring calculator site, it's easy to calculate and just need a caliper and one spring of each.

SI units are the way to go for calculations or everything will be a mess
Go to know that it's N/cm and not N/m :-)

I'll try the website, but I don't know which material to choose from the list. Do you have a suggestion? And is it the same for all RC springs?

For consistency sake yes it should be the same throughout all your measurements. That way my measurements will be the same as yours and everyone else. Select Music Wire ASTM A228.
For example, my Kyosho Ligh Blue springs measure the same as the Yellow ones in the Kyosho chart (527N/cm).

Thanks for all the help, I will update the first post to better explain the new procedures. If you find something to add say so, I'm trying to add a roll bar roll force calculator to know total roll rate.

Allright, thank you for explaining.
I have a Mugen mbx7 and Serpent Cobra 2.1 at home, so I'm going to input the 2 cars. I'd like to see the differences.

I'll share the results if you're interested in them.

You're welcome, glad to help really.
PBS cars are present a difficulty in measuring arm length accurately, looking at the bottom of the upright and turning the steering both sides consecutively, it should be apparent that there's a point which seems to not move. There's the point where one should measure to get arm length.

Yes I am very interested in the results

Here is the filled in sheet from my Serpent Cobra 2.1
https://docs.google.com/spreadsheets...it?usp=sharing

The difference in roll rate between the front and rear is quite big

The mbx7 on my shelve have not servo's and motor on it. So I don't know the corner weight. If someone could give me that, I can fill in a sheet for the mbx7.

Thank you very much! Indeed there's a massive difference between front and rear roll rate, I see that's because the rear suspension is stiffer than the front, look at Suspension Frequency you want those numbers to be close. Try a most inner arm shock hole and keep the same shock angle, also pay attention to shock piston hole and oil starting recommendation, those are the very base of the entire process.
I saw some numbers outside the usual cells, would it be better if I made changes to the layout to improve something?

MBX7 corner weights - FR 815gr and RR 875gr.

Thanks. I'm going to measure again with the rear shocks in the inner holes.

The numbers outside the other cells was to calculate my oil viscosity if I'd use the same pistons in the rear. So I have a few combo's to test :-)

No problem, usually there's 5mm hole center to hole center in arm holes, I change those values to account for a rear shock moved in and the balance between shock piston holes and oil was good. The change in suspension frequency was not immense but a good move, maybe a stiffer front to help?
*edit* OK did the front and rear lower shock hole change, .46 SF at the front and .48 at the rear. Seems pretty good to me, a 50cps increase in rear shock oil and a .1 increase in piston hole size. 29 degrees of front roll rate vs 21 degrees rear roll rate, now that's nice!

Thanks! Going to test some things next time I'm at the track :-)
Are you going to expand the spread sheet with upper link positions? Or would that be too complex?