Hephaestus RC Tune Up Spreadsheets
02-11-2015, 11:27 AM
#31
I really enjoy your thread very impressive information. I have thrown together a couple sets of "Different" shock piston/oil setup to test Friday. I'm excited and will report back with my findings.
02-13-2015, 04:23 PM
#34
Toe angle.
To not be confused with another adjustment that produces a similar result, arm sweep. Toe angle can be convergent, neutral and divergent (also known as toe out, zero toe and toe in depending if you are talking about front or rear end), it primarily changes the slip angle ratio between opposite wheels. Let's break into possible scenarios:
-Toe in in the front is rarely used because of the much increased steering response, starting to turn in the wheels are converging so one of them is already helping the car entering the turn. As the wheels keep turning the outside wheel will have more and more load 'till it reaches the intended steering angle, the outside wheel is lightly loaded so it doesn't affect much. Most of the time this increased steering response is too much in Off Road racing and because of the angle any increase in tire load produces a steering response;
-Toe out in the front is pretty much the norm in Off Road racing, they do the opposite of toe in which is decreased steering response because as the car starts to turn the outside wheel is fighting against the steering input, the outside wheel angle is greater but remember the load it has is way smaller than the outside wheel.
-Toe in in the rear is the only way to do it, no toe out ever. Works the same as the front out, the outside wheel is fighting the rear from sliding, keeping the car going straight.
To conclude, toe is a minor change in the grand scheme of things but help a great deal in consistency. Always strive to run the least amount of toe front and rear. I've found front toe to be relative to how much tight is the track layout, toe in or neutral when it's more tight and toe out when it's more open and high speed. Simple tuning option to test so I urge you all to test it.
Bonus bit, arm sweep.
-Technically in the rear we are running arm sweep(and I know the Tekno can run at the front, only one at that I think). The JQ White Edition/D812 and a few others can run outboard toe in the rear which is a more correct way of doing things. At zero angle of toe at the rear inner hingepin, the car has more consistency in grip and landings.
To not be confused with another adjustment that produces a similar result, arm sweep. Toe angle can be convergent, neutral and divergent (also known as toe out, zero toe and toe in depending if you are talking about front or rear end), it primarily changes the slip angle ratio between opposite wheels. Let's break into possible scenarios:
-Toe in in the front is rarely used because of the much increased steering response, starting to turn in the wheels are converging so one of them is already helping the car entering the turn. As the wheels keep turning the outside wheel will have more and more load 'till it reaches the intended steering angle, the outside wheel is lightly loaded so it doesn't affect much. Most of the time this increased steering response is too much in Off Road racing and because of the angle any increase in tire load produces a steering response;
-Toe out in the front is pretty much the norm in Off Road racing, they do the opposite of toe in which is decreased steering response because as the car starts to turn the outside wheel is fighting against the steering input, the outside wheel angle is greater but remember the load it has is way smaller than the outside wheel.
-Toe in in the rear is the only way to do it, no toe out ever. Works the same as the front out, the outside wheel is fighting the rear from sliding, keeping the car going straight.
To conclude, toe is a minor change in the grand scheme of things but help a great deal in consistency. Always strive to run the least amount of toe front and rear. I've found front toe to be relative to how much tight is the track layout, toe in or neutral when it's more tight and toe out when it's more open and high speed. Simple tuning option to test so I urge you all to test it.
Bonus bit, arm sweep.
-Technically in the rear we are running arm sweep(and I know the Tekno can run at the front, only one at that I think). The JQ White Edition/D812 and a few others can run outboard toe in the rear which is a more correct way of doing things. At zero angle of toe at the rear inner hingepin, the car has more consistency in grip and landings.
02-16-2015, 04:08 AM
#35
Well yesterday tried less toe in on my JQ. Very responsive and has steering and rotation to place the car where I want it, I'm more in command of the car.
The added rotation id good, never had a car with so much rotation, like in most of the turns if I keep the throttle pinned and the steering locked the car continues to steer until it does a 180, not because the rear is loose but because the front pulls immensely. Going to try longer wheelbase to tame it down but I like it. Also need to remove the anti-roll bars to test something.
The added rotation id good, never had a car with so much rotation, like in most of the turns if I keep the throttle pinned and the steering locked the car continues to steer until it does a 180, not because the rear is loose but because the front pulls immensely. Going to try longer wheelbase to tame it down but I like it. Also need to remove the anti-roll bars to test something.
02-19-2015, 03:31 PM
#36
Today was a brainstorming afternoon.
Went to vsusp.com and input the THE Car rear suspension dimensions doubled because the site doesn't scale well. Between my changes and the 2013 starting setup, my changes lower the roll center and keep it lower when the buggy rolls. It also lowers roll center height by 5mm... Tomorrow I want to be at the track to test this to see if I can learn something from it. Jacking forces primarily.
For comparison sake, Maifield's RC8.2 at the 2012 Nats had the roll center at the ground, more or less 12mm lower than my setup.
Went to vsusp.com and input the THE Car rear suspension dimensions doubled because the site doesn't scale well. Between my changes and the 2013 starting setup, my changes lower the roll center and keep it lower when the buggy rolls. It also lowers roll center height by 5mm... Tomorrow I want to be at the track to test this to see if I can learn something from it. Jacking forces primarily.
For comparison sake, Maifield's RC8.2 at the 2012 Nats had the roll center at the ground, more or less 12mm lower than my setup.
02-20-2015, 06:35 AM
#37
Todays test session went somewhat good. Rain cut it short but the track performance is very good still, going to try less camber gain and long wheelbase next time to see what is better to tame the rotation and have to change springs back to stock ones as the K light blue are too long.
Will have an important race mid March so if I don't have a better setup just need to dial back steering D/R
*edit* less camber gain was a failure as predicted, less on power traction and less responsive. The car will bite you back when you need it. I'm reluctant of trying longer wheelbase because on power traction is at premium. On the bright side, the front pulls the buggy nicely, maybe if I change rear diff oil to 5k and see what happens.
Will have an important race mid March so if I don't have a better setup just need to dial back steering D/R
*edit* less camber gain was a failure as predicted, less on power traction and less responsive. The car will bite you back when you need it. I'm reluctant of trying longer wheelbase because on power traction is at premium. On the bright side, the front pulls the buggy nicely, maybe if I change rear diff oil to 5k and see what happens.
Last edited by 30Tooth; 03-01-2015 at 05:32 PM.
02-24-2015, 04:45 PM
#38
Have you seen both A main races from DNC? It looks so hard to do the woops section, both truggies and buggies look inconsistent and sketchy going through. That's a race where all the tricks and some a driver knows have to be tested and put to good use.
Most cars seemed upset by the "track monster", riding on the sidewall of the tires or having a corner easily thrown up, I had that problem before and still have sometimes as it is very difficult to eliminate that trait with current shock technology, what we need is variable speed damping or at least two stage damping. In the mean time, shock pistons with two big holes work very well, like 1.5mm rear and 1.4 front ( that's a setup I have in the mbx5r so with big bore shocks something in the lines or 1.5f and 1.6r).
Having the roll axis balanced (meaning not much difference between front and rear roll center height) would help a unsettled car as do lower roll centers. Lowering roll centers have detrimental performance in the conditions you might find but balancing roll centers and shock packages front and rear will definitely help in the grand scheme of things because your car will become less unsettled, easier to drive and have neutral reactions. Unfortunately you can't do both in my spreadsheets ( haven't figured out roll center height in a manner I can use) but you can use www.vsusp.com to have a slight idea of where are the roll centers.
Now, The Car gained a reputation of lacking on power traction and not being totally planted, I can relate to that because mine is sort of like that and after plugging the data in the spreadsheet and comparing to my other 1/8th buggies I see big differences in roll stiffness front and rear. The rear roll center is higher than any other buggy I have or have the measures. Believe it or not, the same changes done to the rear of the RC8.2 during the parts mod era applies to the JQ, and I want to test both as they are easy to do.
Most cars seemed upset by the "track monster", riding on the sidewall of the tires or having a corner easily thrown up, I had that problem before and still have sometimes as it is very difficult to eliminate that trait with current shock technology, what we need is variable speed damping or at least two stage damping. In the mean time, shock pistons with two big holes work very well, like 1.5mm rear and 1.4 front ( that's a setup I have in the mbx5r so with big bore shocks something in the lines or 1.5f and 1.6r).
Having the roll axis balanced (meaning not much difference between front and rear roll center height) would help a unsettled car as do lower roll centers. Lowering roll centers have detrimental performance in the conditions you might find but balancing roll centers and shock packages front and rear will definitely help in the grand scheme of things because your car will become less unsettled, easier to drive and have neutral reactions. Unfortunately you can't do both in my spreadsheets ( haven't figured out roll center height in a manner I can use) but you can use www.vsusp.com to have a slight idea of where are the roll centers.
Now, The Car gained a reputation of lacking on power traction and not being totally planted, I can relate to that because mine is sort of like that and after plugging the data in the spreadsheet and comparing to my other 1/8th buggies I see big differences in roll stiffness front and rear. The rear roll center is higher than any other buggy I have or have the measures. Believe it or not, the same changes done to the rear of the RC8.2 during the parts mod era applies to the JQ, and I want to test both as they are easy to do.
02-26-2015, 05:05 PM
#39
Hephaestus RC How-To Droop Measurement:
Step 1 - start by measuring the wheel we will use (can use two) fig.1
Step 2 - place the wheel in a hard and level surface.
Step 3 - take wheels of the car, place it on top of the wheel(s) previously you put on the hard and level surface.
Step 4 - for each axle, measure with a caliper the distance between the surface and the top of the axle fig.2-3,subtract the wheel measurement.
Step 5 -??????????
For consistency in your measurements one should always use the same wheel even across different platforms like truggy or 1/10th 2wd buggy provided the arms don't touch the hard and level surface.
Step 1 - start by measuring the wheel we will use (can use two) fig.1
Step 2 - place the wheel in a hard and level surface.
Step 3 - take wheels of the car, place it on top of the wheel(s) previously you put on the hard and level surface.
Step 4 - for each axle, measure with a caliper the distance between the surface and the top of the axle fig.2-3,subtract the wheel measurement.
Step 5 -??????????
For consistency in your measurements one should always use the same wheel even across different platforms like truggy or 1/10th 2wd buggy provided the arms don't touch the hard and level surface.
03-01-2015, 05:25 PM
#40
A great person has just shared shock dyno graphs http://www.rctech.net/forum/13878386-post1.html. I will try my best to explain it:
First, RC shocks have linear response even for tapered pistons as I said before, if they work for you great but I didn't find anywhere that they work and now there's proof that they don't work as advertised. With that said, until 2 stage pistons arrive at the 1/8th market we will have to tune to the majority of the track sacrificing low or high speed damping. If anyone knows of 5wt or less silicone oil say so (my 2 stage shock piston design needs it).
Something I've learned recently, it's good practice to have higher ride frequency in the rear - or vice versa - to account for the front tires passing first through surface irregularities. How much, that depends on the type of irregularities you find at a particular track.
Please check the pdf on that link, any question just ask here I will do my best to explain.
I've been researching the best possible RC shocks, if I scale down the racing shocks used in MTB and other motorsports there's one that stands out, GMade XD. I want to try them with dual stage pistons. They have the bladder out of the piston way, proper bladder design and available in different shock length and type. On the other hand, if I stay with linear RC shocks (current gen) doing every trick in the book (foam behind the bladder+unvented cap+x-rings) will certainly not be enough performance wise. You can't tune compression separated from rebound and that hurts immensely. Even if I further develop my piston shim stack design it would be difficult to find a range of oils and piston holes to make it work, right now I'm looking at 4mm x 4 holes to use something around 200cps oil.
Other thing I found to help lots when tuning shock package is to see the track surface making the suspension work and not the car making the suspension work, also each tire of the car carries around one quarter of a car's total weight, that's spring related not damper related. Stiffer springs than most drivers would use and pistons that are balanced front to back would improve lots on bump handling. Once again I will say that it doesn't make sense using smaller piston hole size in the rear end, nor using shock oil to change the rate at weight transfers side to side, that's why most cars have roll bars.
Quick list of what to change setup wise.
Use this list only after your car is maintained properly, corner weights are balanced L-R and chassis de-tweaked.
Intended adjustment ----------------------------------------- What to change/address
Change side to side rate of weight transfer(WT)-------------Roll bar thickness/pre-load
Change rate of front to rear or rear to front WT--------------Kickup and Anti Squat
Change bump handling-----------------------------------------Piston hole total area/ shock oil
Change grip -----------------------------------------------------Increase tire load by using stiffer springs or roll center change
Loss of grip/gain of grip through track temperature----------Change tire compound
Prevent traction Roll--------------------------------------------Lower suspension frequency
Unbalanced flight attitude--------------------------------------Chassis has wear marks?yes - higher ride height on affected side; No - balance springs
Front tires balloon and wear on the middle-------------------Increase diff oil thickness front and center, smoother throttle finger
Increase stability: acceleration--------------------------------Increase rear toe-in in; rear diff oil change
Increase stability: straight line/bumps------------------------Decrease front/rear toe-in; increase rear droop; front roll bar too stiff
Increase stability: braking-------------------------------------Increase rear droop; balance rear roll resistance; more rear camber
Increase response----------------------------------------------Firmer inserts; check for too low springs/roll bars; too much rear wing
Decrease response---------------------------------------------Softer inserts; too stiff springs/roll bars; excessive front/rear toe-in
Dealing with understeer
Decrease understeer: steering fades at corner entry--------Less toe angles; more front droop; check if the front suspension dumps - increase front roll stiffness; roll axis not balanced.
Decrease understeer: no steering at corner entry-----------Coming too hot to turn; too narrow front track width compared to rear; too stiff wheel/insert combo; too stiff front roll bar/springs; too much bump stops; lack of front toe-in/out; unsuitable Ackermann angle; front RC too high or too low; more front droop; wrong weigh bias.
Decrease understeer: mid corner-----------------------------Too firm wheel/insert combo; excessive relative front roll stiffness; excessive front toe-in/out; wrong Ackermann angle; lack of camber gain; front track width narrow relative to rear; might be bottoming shock(s); lack of droop.
Decrease understeer: coming out of slow corners-----------Too much WT front to back - less kickup/more anti squat; less front droop.
Decrease understeer: coming out of fast corners------------Front track width narrow relative to rear; thinner rear diff oil.
Dealing with oversteer
Decreasing oversteer: corner entry---------------------------Too much rear brake bias/drag brake; roll stiffness imbalance; rear roll center too high; too little rear droop.
Decrease oversteer: mid corner------------------------------Rear wheel/insert combo too stiff; excessive rear roll stiffness; rear suspension might be bottoming; lack of rear droop; very loose rear roll bar.
Decrease oversteer: corner exit------------------------------Rear diff oil too thin; too much anti squat angle; excessive rear roll stiffness; rear shocks bottoming out; too much negative camber; too little rear toe-in angle.
If the car snaps suddenly exiting corners the usual culprits are: rear shocks bottoming out; lack of droop/wrong droop setup; sudden change in rear camber, particularly the outside wheel; getting on the throttle too soon ("Too soon junior...").
If the car can't put the power down smoothly check for: diffing out, particularly the rear diff; excessive roll resistance; excessive anti squat angle; rear wheel/insert combo too stiff; rear shock damping too stiff; too much camber change in outside wheel.
Transitions
Understeer starting to transition then snap oversteer on power: usually caused by too little roll resistance, suspension bottoms out and jerks the car. Stiffening the front ARB will load the inside rear tire on acceleration (win-win), increase front roll resistance by means of roll center or CG.
If the suggestion above cures the understeer but the car still snaps then the car falls on the outside rear wheel, same fix as the front - increase roll resistance. Loose ARB might behave like this too!
First, RC shocks have linear response even for tapered pistons as I said before, if they work for you great but I didn't find anywhere that they work and now there's proof that they don't work as advertised. With that said, until 2 stage pistons arrive at the 1/8th market we will have to tune to the majority of the track sacrificing low or high speed damping. If anyone knows of 5wt or less silicone oil say so (my 2 stage shock piston design needs it).
Something I've learned recently, it's good practice to have higher ride frequency in the rear - or vice versa - to account for the front tires passing first through surface irregularities. How much, that depends on the type of irregularities you find at a particular track.
Please check the pdf on that link, any question just ask here I will do my best to explain.
I've been researching the best possible RC shocks, if I scale down the racing shocks used in MTB and other motorsports there's one that stands out, GMade XD. I want to try them with dual stage pistons. They have the bladder out of the piston way, proper bladder design and available in different shock length and type. On the other hand, if I stay with linear RC shocks (current gen) doing every trick in the book (foam behind the bladder+unvented cap+x-rings) will certainly not be enough performance wise. You can't tune compression separated from rebound and that hurts immensely. Even if I further develop my piston shim stack design it would be difficult to find a range of oils and piston holes to make it work, right now I'm looking at 4mm x 4 holes to use something around 200cps oil.
Other thing I found to help lots when tuning shock package is to see the track surface making the suspension work and not the car making the suspension work, also each tire of the car carries around one quarter of a car's total weight, that's spring related not damper related. Stiffer springs than most drivers would use and pistons that are balanced front to back would improve lots on bump handling. Once again I will say that it doesn't make sense using smaller piston hole size in the rear end, nor using shock oil to change the rate at weight transfers side to side, that's why most cars have roll bars.
Quick list of what to change setup wise.
Use this list only after your car is maintained properly, corner weights are balanced L-R and chassis de-tweaked.
Intended adjustment ----------------------------------------- What to change/address
Change side to side rate of weight transfer(WT)-------------Roll bar thickness/pre-load
Change rate of front to rear or rear to front WT--------------Kickup and Anti Squat
Change bump handling-----------------------------------------Piston hole total area/ shock oil
Change grip -----------------------------------------------------Increase tire load by using stiffer springs or roll center change
Loss of grip/gain of grip through track temperature----------Change tire compound
Prevent traction Roll--------------------------------------------Lower suspension frequency
Unbalanced flight attitude--------------------------------------Chassis has wear marks?yes - higher ride height on affected side; No - balance springs
Front tires balloon and wear on the middle-------------------Increase diff oil thickness front and center, smoother throttle finger
Increase stability: acceleration--------------------------------Increase rear toe-in in; rear diff oil change
Increase stability: straight line/bumps------------------------Decrease front/rear toe-in; increase rear droop; front roll bar too stiff
Increase stability: braking-------------------------------------Increase rear droop; balance rear roll resistance; more rear camber
Increase response----------------------------------------------Firmer inserts; check for too low springs/roll bars; too much rear wing
Decrease response---------------------------------------------Softer inserts; too stiff springs/roll bars; excessive front/rear toe-in
Dealing with understeer
Decrease understeer: steering fades at corner entry--------Less toe angles; more front droop; check if the front suspension dumps - increase front roll stiffness; roll axis not balanced.
Decrease understeer: no steering at corner entry-----------Coming too hot to turn; too narrow front track width compared to rear; too stiff wheel/insert combo; too stiff front roll bar/springs; too much bump stops; lack of front toe-in/out; unsuitable Ackermann angle; front RC too high or too low; more front droop; wrong weigh bias.
Decrease understeer: mid corner-----------------------------Too firm wheel/insert combo; excessive relative front roll stiffness; excessive front toe-in/out; wrong Ackermann angle; lack of camber gain; front track width narrow relative to rear; might be bottoming shock(s); lack of droop.
Decrease understeer: coming out of slow corners-----------Too much WT front to back - less kickup/more anti squat; less front droop.
Decrease understeer: coming out of fast corners------------Front track width narrow relative to rear; thinner rear diff oil.
Dealing with oversteer
Decreasing oversteer: corner entry---------------------------Too much rear brake bias/drag brake; roll stiffness imbalance; rear roll center too high; too little rear droop.
Decrease oversteer: mid corner------------------------------Rear wheel/insert combo too stiff; excessive rear roll stiffness; rear suspension might be bottoming; lack of rear droop; very loose rear roll bar.
Decrease oversteer: corner exit------------------------------Rear diff oil too thin; too much anti squat angle; excessive rear roll stiffness; rear shocks bottoming out; too much negative camber; too little rear toe-in angle.
If the car snaps suddenly exiting corners the usual culprits are: rear shocks bottoming out; lack of droop/wrong droop setup; sudden change in rear camber, particularly the outside wheel; getting on the throttle too soon ("Too soon junior...").
If the car can't put the power down smoothly check for: diffing out, particularly the rear diff; excessive roll resistance; excessive anti squat angle; rear wheel/insert combo too stiff; rear shock damping too stiff; too much camber change in outside wheel.
Transitions
Understeer starting to transition then snap oversteer on power: usually caused by too little roll resistance, suspension bottoms out and jerks the car. Stiffening the front ARB will load the inside rear tire on acceleration (win-win), increase front roll resistance by means of roll center or CG.
If the suggestion above cures the understeer but the car still snaps then the car falls on the outside rear wheel, same fix as the front - increase roll resistance. Loose ARB might behave like this too!
Last edited by 30Tooth; 04-30-2015 at 02:58 PM. Reason: Done!
03-13-2015, 12:56 PM
#42
Tech Adept
Fantastic thread! Just like tuning real cars 
03-13-2015, 02:12 PM
#43
Thank you.
Indeed, both obey the same laws of Physics but our cars have certain key aspects. Once you figure them and develop your own setup methodology it's like you can squeeze more performance out of your old setup to reach performance levels you thought impossible. Most important of all I would say is a open mind, there's so much misinformation out there it isn't even funny. This week while I was at the track helping new drivers and practising for the Sunday race one of the new drivers commented that my car's rear end wasn't soaking the bumps and told me I should lower the shock collars to lower the ride height and make the suspension stiffer
must learned that on a LHS... He was the only one with a pro car/engine/tires, I have high hopes he can learn and drive better. If not, there's at least 5 RTR 1/8th buggies (all of them designs date from 2000-2003, some earlier) that can give him a run for his money 
Indeed, both obey the same laws of Physics but our cars have certain key aspects. Once you figure them and develop your own setup methodology it's like you can squeeze more performance out of your old setup to reach performance levels you thought impossible. Most important of all I would say is a open mind, there's so much misinformation out there it isn't even funny. This week while I was at the track helping new drivers and practising for the Sunday race one of the new drivers commented that my car's rear end wasn't soaking the bumps and told me I should lower the shock collars to lower the ride height and make the suspension stiffer
must learned that on a LHS... He was the only one with a pro car/engine/tires, I have high hopes he can learn and drive better. If not, there's at least 5 RTR 1/8th buggies (all of them designs date from 2000-2003, some earlier) that can give him a run for his money
03-16-2015, 05:42 AM
#44
I'm looking at the Excel sheets and that's some nice work!
Just 1 question about the shocks. The sheet gives advice on the size of the piston holes, but not the number of holes. And I guess it's also depends if the shocks are 15mm or 16mm in bore size.
Just 1 question about the shocks. The sheet gives advice on the size of the piston holes, but not the number of holes. And I guess it's also depends if the shocks are 15mm or 16mm in bore size.
03-16-2015, 10:18 AM
#45
That's one thing I have to add, captions to explain what is going on and a different approach to hole size calculation, for a clearer result maintaining number of holes is the way to go and you just have to stock on 3-5 different pistons.
According to shock dynos, for pistons with the same hole area, the one with the smaller holes provides more damping. Dyno sheet shows a 1.7mm x 2 holes being equivalent to a 1.3mm x 4 holes.
Funny you post today, yesterday I won the club race with THE Car but I can't add more stability (still one thing to try) so I'm going back to the Mugen Mafia
In fact I'm headed to the track right now! edit/ with a RTR based engine and old DLD tires it felt and went better than the JQ... who knew? /editAny question regarding setup just ask.
Last edited by 30Tooth; 03-16-2015 at 01:44 PM.