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Old 07-16-2009, 12:28 PM   #1456
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I got to pet Josh's Photon last night....



Seriously, You TOP guys have a very cool car to run, excellent design Josh
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Old 07-16-2009, 12:29 PM   #1457
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Old 07-16-2009, 01:06 PM   #1458
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Josh-

Had a quick question for you...I have noticed that on the bench the front dampening/spring rebound feels alot softer in the front then the rear of the car. No matter what I do with piston, oil, spring I feel the same thing. At this point I am running 60wt oil, HPI Yellows, and HB 1.2 3 hole pistons in the front and it is now finally starting to feel a little harder then the rear (40wt, HPI blues, HB1.2 3 hole pistons in the rear). I have also tried all of the arm holes and it does not seem to change all that much. I was analyzing the overall shock positions on the tower is it would seem that by design the rear would be in fact softer just based on natural angles.

This has indeed translated on the track, I have been doing a lot of testing with the car and I am finding that the stiffer the front (and softer the rear gets) gets the better the car seems to feel, but at this point I am concerned that I might be going a bit to far.

Is the rubber tire car naturally softer/ more flexible then other rubber tire cars by design?

As for the car feeling softer up front is this an excepted phenomena?

This is a medium sized high bite carpet track.

Thanks...
Honestly, I'm not 100% on how are chassis flex compares to the others out there. I know the prototype car was a ton stiffer and at the HK Charity race I felt ours vs. a 416 - Ours was stiffer with the top deck off!! After that, we changed the material and changed the shapes to induce more flex.

At the Reedy Race, a well traveled and experienced European checked out the flex and made a comment that it was good but still not as soft as Tamiya's or the HB that his driver used to run (3 guesses on who said it..lol). He said it was similar to the Yokomo thought. I don't think the car is a lot different when it comes to the overall feel/stiffness in your hands. BUT - This car does flex a lot differently than other cars on the market due to the bulkhead and chassis configuration.

From what I have felt in the past, usually the cars are similar or softer in the front when you actually compress the car on the bench. I think though that with so much different with the Photon we really are on a different path than the other cars out there so it's just going to take some time/experience to break the ideas and set-up thinking that everyone has previously done. I know at the Reedy Race, EJ and everyone thought I was nuts for going up as hard as I did on springs. I then went down a little but went to the outside hole on the arm which I really liked. Again though, I wanted to go more but was afraid of going too far as at that point we were into the heads up racing.

Last night, I did run at MSI and while I only made a few small changes as I was really just trying to get some motor testing in - I thought the same thing that I really needed to get back up there and test with some more set-ups for the shocks as the car would be a little lazy initially until the front end set into the corner but then it would sometimes break loose if I pushed it too hard. I think you are on the right track but I think it's just going to take time and testing to figure it out.
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Old 07-16-2009, 02:50 PM   #1459
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Darn !! I missed my chance to see a completed Photon. Any idea when you'll be back to MSI (even if for testing) ?
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Old 07-16-2009, 06:54 PM   #1460
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Originally Posted by Josh Cyrul View Post
Honestly, I'm not 100% on how are chassis flex compares to the others out there. I know the prototype car was a ton stiffer and at the HK Charity race I felt ours vs. a 416 - Ours was stiffer with the top deck off!! After that, we changed the material and changed the shapes to induce more flex.

I then went down a little but went to the outside hole on the arm which I really liked. Again though, I wanted to go more but was afraid of going too far as at that point we were into the heads up racing
The 416 is a 2.25mm bottom deck, so you'd expect the TOP to be a little stiffer but I can barely tell the difference when I bend them by hand. I also heard a rumour there is a "super flex" 2mm bottom deck for Photon in the works???

Question, is changing the shock mounting position on the arm the same as doing it on the tower, or does the movement of the arm effect the net result?

I've been running hole 1 on the front arm and 2 at the back and it felt better right away than 2 on both. I think the front shocks are a little too angled at the moment so I'm going 1 hole more upright on the tower for Sunday
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Old 07-16-2009, 06:58 PM   #1461
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I can't imagine needed a more flexible chassis than the one that comes on the rubber car.

Flex isn't the only way to get your car dialed in guys.
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Old 07-16-2009, 08:10 PM   #1462
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jag88 - Not sure when....

CraigM - Our chassis is 2.5mm as well like the 416. I was told that they do have a 2.25mm chassis with the batteries further forward that they like to run a lot. At the moment, we have a 2.0mm chassis for the Photon but there are no battery slots in it (for Lipo) so I think the flex is similar to our 2.5mm chassis. Changing the shock postion on the arm is a lot different than on the tower - On the arm, you effect the shock travel - Further out = more actual shock travel per wheel movement. This makes the shock work more thus stiffer. Keep in mind though, it's stiffer on oil, pack, pressure, spring and slower on rebound (because more travel means it has to change direction through more movement which again is more pack, etc). From my testing, usually with changing the shock package to generate a simlar feel on the bench, it will have slightly less steering/roll into the corner but the front end will stay more in the corner from center-out generating more on-throttle steering. Changing the position on the shock tower will make a difference in stiffness but moving to an outer hole on the tower will generally release the car faster from the exit of the corner generating on-throttle push.... It's quite a bit different so that's why it's going to take a little time to learn the Photon and how to set it up correctly.
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Old 07-16-2009, 08:25 PM   #1463
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jag88 - Not sure when....

CraigM - Our chassis is 2.5mm as well like the 416. I was told that they do have a 2.25mm chassis with the batteries further forward that they like to run a lot. At the moment, we have a 2.0mm chassis for the Photon but there are no battery slots in it (for Lipo) so I think the flex is similar to our 2.5mm chassis. Changing the shock postion on the arm is a lot different than on the tower - On the arm, you effect the shock travel - Further out = more actual shock travel per wheel movement. This makes the shock work more thus stiffer. Keep in mind though, it's stiffer on oil, pack, pressure, spring and slower on rebound (because more travel means it has to change direction through more movement which again is more pack, etc). From my testing, usually with changing the shock package to generate a simlar feel on the bench, it will have slightly less steering/roll into the corner but the front end will stay more in the corner from center-out generating more on-throttle steering. Changing the position on the shock tower will make a difference in stiffness but moving to an outer hole on the tower will generally release the car faster from the exit of the corner generating on-throttle push.... It's quite a bit different so that's why it's going to take a little time to learn the Photon and how to set it up correctly.
Great info

fyi both 416 kits (normal and WE) came with 2.25mm chassis, the latter with the more forward battery position. 2.5mm was the optional carpet deck
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Old 07-17-2009, 12:06 AM   #1464
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Josh's comment on hard springs: Just as a mater of interest Mi4 runners here in the UK are starting to favor "stupidly" hard springs even on tight technical asphalt tracks. Also a club mate who has resently gone from a 416 to the worlds eddition is finding he prefers a harder spring than what he normaly used "food for thought"??

I must admit spring for spring the Photon does "feel" and drive slightly softer than other chassis's,very stable but will get out of shape when pushed that bit harder on kit springs,too soft,too flexi ?? maybe, Dunno?.......getting the best out of a new car can be fun but fustrating too,especialy when your on your own.
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Old 07-17-2009, 08:26 AM   #1465
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CraigM - Thanks for the info, I think that just proves what I know about the 416 is only from people talking and not having one in my hands with calipers. (Just for those that think I copied anything..lol).

lesbaldry - I would say too soft. Try the outer holes on the front and rear suspension arms for the shock positions. Also try the 324 springs in the rear with the 347 or 367 springs in the front.

Also, everyone be careful with your camber adjustments - I don't think it's quite as sensitive on asphalt but at the indoor carpet track I ran at the car was really sensitive to the front camber. A little too much in the front made it very loose and hard to drive (we are talking like .25 degree). Sounds rediculos but it made a huge difference with my car on Wednesday.
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Old 07-17-2009, 08:27 AM   #1466
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I sorta of figured if the chassis was stiffer the shock and suspension changes would make more of a difference. It would be difficult to determine how much a chassis actually flexes during normal operation. Granted changing decks may help but I believe stiffer tub means better tune ability. Unless you are on some crazy surface that has absolutely no bite , or so much of it... hmmm
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Old 07-17-2009, 08:32 AM   #1467
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John - Usually, a stiffer chassis has a better oppertunity to be faster on the track IF the car is set-up correctly. A more flexi car has a larger set-up window and can allow you to tune within that window easier. I think that we will be able to learn a lot about the car and when we get really dialed in on set-ups then we will probably be able to stiffen up the chassis and go quicker but really it's going to depend on the traction level/tires that are being run at the time.
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Old 07-17-2009, 08:42 AM   #1468
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John - Usually, a stiffer chassis has a better oppertunity to be faster on the track IF the car is set-up correctly. A more flexi car has a larger set-up window and can allow you to tune within that window easier. I think that we will be able to learn a lot about the car and when we get really dialed in on set-ups then we will probably be able to stiffen up the chassis and go quicker but really it's going to depend on the traction level/tires that are being run at the time.
Sounds good . Bite there @ MSI is good but not consistent. Kinda makes for an interesting evening at the track. This fall will be big there. I love racing there but.... whats with the oval ? zzzzz
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Old 07-17-2009, 10:20 AM   #1469
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Originally Posted by Josh Cyrul View Post
John - Usually, a stiffer chassis has a better oppertunity to be faster on the track IF the car is set-up correctly. A more flexi car has a larger set-up window and can allow you to tune within that window easier. I think that we will be able to learn a lot about the car and when we get really dialed in on set-ups then we will probably be able to stiffen up the chassis and go quicker but really it's going to depend on the traction level/tires that are being run at the time.
Racecar chassis design suggests your chassis should be infinitely stiff compared with the difference in your roll stiffnesses. Since this would also require infinite weight, a compromise must be made. A sound guideline is to design your chassis to be 10x stiffer than the difference between your front and rear roll stiffnesses. Realistically we should all be running 3-3.5 mm chassis to achieve the appropriate stiffness, but Josh is absolutely correct that a flexible chassis opens the window that the car performs well. A stiff chassis narrows the window but increases its performance potential greatly. Compliance in the suspension/chassis system is evil . Josh, do you have any design parameters that you could share? I'm talking the vehicle dynamics figures more than anything else (motion ratios, wheel rate, roll center nominal heights, camber gain per deg of roll etc).
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Old 07-17-2009, 10:27 AM   #1470
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Racecar chassis design suggests your chassis should be infinitely stiff compared with the difference in your roll stiffnesses. Since this would also require infinite weight, a compromise must be made. A sound guideline is to design your chassis to be 10x stiffer than the difference between your front and rear roll stiffnesses. Realistically we should all be running 3-3.5 mm chassis to achieve the appropriate stiffness, but Josh is absolutely correct that a flexible chassis opens the window that the car performs well. A stiff chassis narrows the window but increases its performance potential greatly. Compliance in the suspension/chassis system is evil . Josh, do you have any design parameters that you could share? I'm talking the vehicle dynamics figures more than anything else (motion ratios, wheel rate, roll center nominal heights, camber gain per deg of roll etc).
LOL I wish ! One day some rich bloke will buy some super computer crunch time and fill in all the blanks.
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