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Hephaestus RC Tune Up Spreadsheets

Hephaestus RC Tune Up Spreadsheets

Old 11-25-2014, 03:51 PM
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Post Hephaestus RC Tune Up Spreadsheets

Disclaimer, I'm no world class pro but I want one thing with this thread, that every racer achieves a better setup. I'm no authority in Physics or whatever but I did a fair amount of research on the matter of suspension and most of the stuff that happens in our cars and translated that to a spreadsheet that helps understand what is happening mathematically.
Moderators, if this thread doesn't belong here please contact me.

About the service per se:
The suspension frequency spreadsheet is aimed at knowing your car's front to back balance regarding springs, shock pistons and roll stiffness. Every measurement is SI, millimeters and grams mostly.

Using the suspension frequency spreadsheet:
-I've included a sample of my personal JQ The Car setup. The input is the first sheet of the spreadsheet, you'll need a caliper to measure accurately and a scale (preferably 4 equal scales, the ones from e-bay that measure up to 1kg are sufficient up to 1/8th buggies). All measurements taken from center of screw or shaft.

Step 1 - lift the buggy (fig. 1) and drop it (fig. 2), try to not disturb the buggy when taking measurements, in the photo you see it sideways but that's because it doesn't fit in the bench facing me. Let's start front side first.
Step 2 - measure the distance between center of the upper shock mounting screws (fig. 3), input the number in the sheet.
Step 3 - measure the distance between center of the lower shock mounting screws (fig.4), input the number in the sheet.
Step 4 - measure shock length (fig. 5)
Then do the same for the rear end.

Now use an online spring K calculator like this, choose "ASTM 228 music wire" option and retrieve yours spring K using metric data (times 10 because it's not the correct unit used in the spreadsheet's equations).
The kickup is chassis kickup +/- A-B plate bushings, so let's say 10* of chassis kickup + +1 degree of bushings combo=11*. If 10* chassis kickup - -1 degree bushings combo=9*. Didn't make an anti squat ACF because it's of negligible effect on suspension frequency.
Weight each end of the car RTR, divide by two to have corner weight. Boom done.

Post your spreadsheet as a attachment or PM. I'll look at it and show how to improve your setup/driving



I'll update this post with all the spreadsheets I'll make. Stay tuned(no pun intended).

V2.1 - Now includes weight bias and track width and it's stored in google drive.
V2.2 - Added piston hole diameter recommendation!
V2.5a - A bunch of shock calculations and roll stiffness calculation, improved piston hole diameter starting recommendation. Corrected.
V2.6 - Added shock oil prediction for a balanced setup. Cleaned up the not so useful calculations and visuals.
V2.7 - Added Total tire load transfer equation. Tomorrow if I'm not at the track I'll break side to side load transfer in front and rear bias.
V2.8 - Removed the various line to input different shock tower hole and arm hole, now input your current setup and see if they are balanced. Gray areas are user input, green are results.
V2.81 - Corrected a mistake.
V2.9 - Expanded the load transfer equations and shuffled things a bit.
V3.0 - Visual tweaks and organization, place to enter tires used in the setup.
V3.2 - Roll stiffness and shock piston starting setup improved.
V3.3 - Added a roll angle estimation and discolouring for neatness.
V4.0 - Made weight transfer more visual and grouped on a new sheet, cleaned the layout and made it a little smaller. Important update.
V4.1 - Added a few pointers.
V4.2 - Cleaned up and changed shock angle measurement thanks to Morgoth.
V4.3 - Added spring recommendation!
V4.5 - Added graph to see your options regarding spring balance front to rear
V5.0 - Damping ratio graphs now available.
Lite v1.1 - A new condensed spreadsheet, some stuff was expanded and other corrected or deleted. Fixed suspension frequency error!
Lite V1.2 - Added spring converter from most manufacturers claims and improved CG height calc.
Lite v1.3 - Cleared some concepts and corrected some calculations.
Lite v1.4 - The return of roll angle. See if your car should be over or under steering.
Lite v1.7 - Sway bar equations added! Sorry for having sway bars with SAE units but will convert them visually if it causes trouble to you. Internally it's all good.
Lite V2 - That's it folks, has everything working properly and can't think of new features to add.
Lite V3! Cleaned up the weight transfer page and used the standard weight transfer bias layout. Shock hole diameter is more precise.

TODO:
-video of my cars running over ruts and uneven terrain, the track has no flood control so it gets very rutted, should be a great way to show how my cars work - done.


Sources:
Wikipedia
http://white-smoke.wikifoundry.com/ and it's sub links.
www.f1technical.net
http://www.rctech.net/forum/electric...t-results.html
Attached Thumbnails Hephaestus RC Tune Up Spreadsheets-1.jpg   Hephaestus RC Tune Up Spreadsheets-2.jpg   Hephaestus RC Tune Up Spreadsheets-3.jpg   Hephaestus RC Tune Up Spreadsheets-4.jpg   Hephaestus RC Tune Up Spreadsheets-5.jpg  


Last edited by 30Tooth; 11-11-2016 at 01:57 AM.
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Old 11-25-2014, 04:16 PM
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So you're using geometry and known equations to calculate the wheel rate, suspension rate, then overall corner rate and wheel frequency based on chassis setup parameters. I could see this being beneficial to those who can understand the concepts behind suspension geometry.
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Old 11-25-2014, 04:27 PM
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Originally Posted by AZRC4Me View Post
So you're using geometry and known equations to calculate the wheel rate, suspension rate, then overall corner rate and wheel frequency based on chassis setup parameters. I could see this being beneficial to those who can understand the concepts behind suspension geometry.
Hey Sean, thanks for stopping by.
I've been using this spreadsheet for personal use for some time and found some relations between the cars I have regarding suspension frequency. It was time to share the knowledge.
I don't know or drive as much as you but with this tool it's way easier to give better advice and know what your car is doing. This is a basic yet one of the most important spreadsheets you can have. Things like "my car doesn't fly level", "rear/front bucks going through bumps", "I can't get enough/more steering/traction" and so on are what this is trying to correct, this is shock tuning. The suspension geometry is still in the studying stage
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Old 11-28-2014, 02:32 AM
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New file update. Check first post
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Old 12-09-2014, 03:40 PM
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New feature added, shock piston hole diameter. Input the front piston hole diameter and the rear MR of the shock mounting on the arm and a size is given. Yes it's correct(and a well kept secret), you are supposed to run a bigger hole diameter in the rear shocks to maintain similar pack characteristics to front shocks. Go up in shock oil, I'm running 300cps on the front and 350 on the rear of my JQ, glides over bumps like they aren't there. Just try it if you are skeptic
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Old 12-15-2014, 02:11 PM
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Old 12-15-2014, 08:01 PM
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Originally Posted by 30Tooth View Post
New feature added, shock piston hole diameter. Input the front piston hole diameter and the rear MR of the shock mounting on the arm and a size is given. Yes it's correct(and a well kept secret), you are supposed to run a bigger hole diameter in the rear shocks to maintain similar pack characteristics to front shocks. Go up in shock oil, I'm running 300cps on the front and 350 on the rear of my JQ, glides over bumps like they aren't there. Just try it if you are skeptic
Subscribed. Great start! Keep it up.

Can you add the compensation for kickup/antisquat/shock angle in the formula the same way you did for suspension frequency? Currently the shock piston hole diameter recommendation is only using the ratio of arm length to shock mount location on the arm.
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Old 12-16-2014, 12:06 PM
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Originally Posted by razo125 View Post
Subscribed. Great start! Keep it up.

Can you add the compensation for kickup/antisquat/shock angle in the formula the same way you did for suspension frequency? Currently the shock piston hole diameter recommendation is only using the ratio of arm length to shock mount location on the arm.
Thank you, I'll do my best.

Yes I can do that, I'm researching the best way to calculate correctly because while the shocks are leaned over the same amount or a 5* gap, the rear shocks are longer and therefore the pistons has to travel faster. The way it is now is just a start, and as you see most start with the same pistons front and rear even before any corrections, or the setup sheet is a lie
Give me a couple of hours
*edit*
my research shows that kickup doesn't change piston choice enough to be noticeable, still figuring it out might have some math error.
On the bright side I figured out roll stiffness!

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Old 12-16-2014, 06:14 PM
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Old 12-18-2014, 05:18 PM
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Old 12-21-2014, 05:32 PM
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Tip - to eyeball CG height just use the ride height from ready to race and remove body, write new ride height. Now draw a vertically imaginary dot on the middle of wheels, diff cases, radiotray, fuel tank and engine. See where most of them are(normally on buggies is a little lower than the exhaust outlet) and holding a ruler vertically measure that point. Now input that measurement in the spreadsheet. Done.
The spreadsheet is approaching it's final version, once I add roll center height front and rear to determine roll axis and more roll calculations I don't know more to add, anything just ask.
Now that I'm thinking about it, clutch engagement calculator/ diff action calculator. Tomorrow, now it's bed time.

31/7/2015 - don't guess CG anymore! Lite version includes CG height calculator.

Last edited by 30Tooth; 07-31-2015 at 01:02 PM. Reason: news flash!
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Old 12-26-2014, 05:35 PM
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Hope everyone had a great Christmas.
Work on the spreadsheet has been slow, I've been beta testing the clutch force calculator and been researching a better differential, in the case of the clutch tool there's no real use as engines have different powerbands even with the same setup and so it's useless to determine theoretical friction. The ideas I'm pursuing are a better clutch and better differential.
I can talk about them, I'm open source:
- H.clutch is a clutch one can change shoes and springs without forcing anything or using special tools. The shoes also use a new spring that never make contact with the clutchbell so the shoes are used till they turn ~99% into dust(slight exaggeration). I can release it as a kit to use all the standard clutch parts except springs and clutch nut.
-H.diff is just a LSD diff, I'm still designing it. Also I'm aiming to be compatible with almost every diff on the 1/8th market and be different to the Kyosho LSD diff which is going to be very difficult as the Kyosho diff works theoretically.
-H.body, a line of bodies shells for certain cars(primarily to ugly cars, like Tekno lol), focused on durability and clean looks. No aero gimmicks even if that means mores sales.
-H.piston, as you see with the spreadsheet the gap between front piston hole diameter and rear shock piston hole diameter is big and most manufacturers don't have enough choice, that's when the H.piston enters.
The other stuff is about custom 2.4GHz receivers and transmitters.

Next days I'll share what I've learned with you, translated to simpler terms. First will be kick up and anti squat because it's a very gray area.

Last edited by 30Tooth; 12-27-2014 at 04:30 AM.
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Old 12-28-2014, 08:03 AM
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All right let's talk about anti dive (aka kick up) and anti squat.
First, they aren't the difference in angles between the hinge pins and chassis/ground. That's a common misconception. They are the difference between hinge pins and a parallel line crossing the center of gravity, designers measure the other way to be simpler. That means a buggy with a front ride height lower than the rear ride height has different anti dive and anti squat angles from a buggy with equal ride height front and rear and another with the front ride height higher than the rear.
Let's pick an example: Argentina 2012 World Champ Robert Batlle's Mugen MBX7 had a front ride height of 22mm and 26mm rear ride height on a very bumpy track. The rear is a little lower than most run but the front is very low, why?
At the speed the buggies were hitting the holes and ruts less anti dive worked best, he could have changed the suspension bushings but he didn't, I guess he wanted more weight in the front wheels. It made the suspension soak the bumps. He was running 1* of anti squat too, to also promote rear weight transfer on power.
Watching the first 7 minutes of the 2012 WC video it's easy to see that Batlle's MBX7 is more composed than Ty's D812 and Maifield's RC8.2, where the others have a tendency to lift the front wheels the MBX7 lift is lower and quickly regains grip.
So my recommendation when faced with a bumpy track is to start with the least amount of anti dive, anti squat, equal front and rear ride height then fine tune from there. I don't recommend changing springs\ride height after you found balance, changes too much.

Another quickie, tuning with weight. This a practice most seen in 1/10th Off and On Road.
My experience indicates that it's not used well, a "throw weight to make it better" approach. While it works in a certain extent the way it really works is by changing CoG location to where it works better with the current roll centers, roll stiffness and suspension frequency.
Let's say we have a 1/10th rear motor buggy and we will be driving on Astroturf. Most would start by adding weight to the front of the buggy and maybe some minor changes. It worked because you went the right direction, less front roll stiffness, lower front suspension frequency and a change in Cog.
Without adding weight the only thing we couldn't do would be changing CoG, but everything else is tunable. Buggies with the motor\engine inside the wheelbase don't really need weight bias change but change to ease weight transfer (like less anti squat).

So my recommendation regarding adding weight is:
- aim for a total weight that enables you to change weight bias without adding weight. I start between 50:50 - 45:55 for 4WD cars. That way I know what roll centers and shock packages work in that weight bias interval.

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Old 12-28-2014, 03:09 PM
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Old 12-29-2014, 03:44 PM
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