CK25AR 1/12th car kit from Team CRC
#77
Tech Elite
iTrader: (16)
I thought it was obvious that the rear roll center is the pivot point on the rear pod. Do you have a diagram that shows that it is not? Just very curious about something I thought I've known over the years. It would certainly not be the first time or the last time I've been wrong!
#78
Tech Champion
iTrader: (4)
Just re reading the CRC post. -I was the last drivers for Leisure and Delta. Leisure also had the best charger at the time. Delta was an awesome company- some of the best guys in the industry (Especially Art Carbonel). Known Frank since the Class Charger days (still have onr but broken). CRC is the last American manufacturer and they make the best stuff for me to race. They always made quality and affordable stuff that wins races. Looking forward to racing the newest version CK25AR this weekend.I will be converting my F1 as soon as the parts can arrive. This is the best company- with the best Equipment for everyone to race pan car classes!
#80
Tech Elite
iTrader: (16)
From Post #23: "The metric hardware thing... well someday we will probably convert. It is tough being the last American company in the market. For the CK25AR, we almost included a SAE hex wrench /nut driver set in the kit. The reality is, you need maybe 4 extra wrenches; .050, 1/16, 3/32 and a 3/16 nut driver. But we do understand and we will work on it in the future."
Last edited by glennhl; 11-25-2021 at 09:44 AM.
#82
Tech Elite
iTrader: (3)
I thought it was obvious that the rear roll center is the pivot point on the rear pod. Do you have a diagram that shows that it is not? Just very curious about something I thought I've known over the years. It would certainly not be the first time or the last time I've been wrong!
#83
Tech Elite
iTrader: (16)
OK, are we talking about the rear? If we are, pretty sure the pivot point is the roll center. And if you raise the pivot, you raise the roll center. If you lower the pivot, you lower the roll center. Since it's a pod that has a single pivot point at the pivot, makes it pretty simple.
#85
Tech Elite
iTrader: (16)
EDIT: Even though this photo does have two shims under the Pivot Mechanism, the design of the horizontal versus the old vertical pivot ball lowers the ball down so that your adjustment range includes a much lower roll center than before. And the main point was that the statement "Higher roll center is lowering the pivot, sort of backwards of what it sounds like" is not correct when it comes to a pod design with a pivot point. Lower the pivot to lower the roll center. Now if you were talking about the standard suspension design that uses two A arms, you would be correct. On that design if you raise the inside pivot of the top arm you actually lower the roll center.
Final thing is I've attached a video from Alexander Hagberg on the X12. The X12 has a very similar pivot design as the new CK25AR. Go to the 5 minute mark and he says, we have a new rear pivot design which mounts a lot lower which lowers the roll center.
Last edited by glennhl; 11-26-2021 at 09:50 AM.
#86
Tech Master
iTrader: (41)
Directly from the Manual:
"Rear Roll Center: The rear roll center greatly affects the handling of the car. By raising the center pivot point, your decrease the amount of chassis roll making the car steer more. This keeps the inside tires planted, resulting in a more aggressive chassis. Conversely, when you lower the rear center pivot point, the chassis is more affected by weight transfer and exhibits greater chassis roll. This weight transfer, or roll, takes weight off the inside front which takes steering response away from the car. The AR center pivot makes adjusting the rear roll center very easy."
I am in full agreement with the description above regarding the rear roll center adjustment. It doesn't matter where the rear roll center actually is, tuning the car by adjusting this pivot will have the affect described. It is easy to see that in this case, the roll center is lower than the center of gravity (CG) of the rear. If the rear roll center was higher than the CG of the rear of the car, the affects would be opposite. My experience with all the 1/12 cars I have owned and raced supports my comments as I have made these adjustments in the past and those changes follow the description in the manual. Comment number 76 above is sort of confusing to me.
"Rear Roll Center: The rear roll center greatly affects the handling of the car. By raising the center pivot point, your decrease the amount of chassis roll making the car steer more. This keeps the inside tires planted, resulting in a more aggressive chassis. Conversely, when you lower the rear center pivot point, the chassis is more affected by weight transfer and exhibits greater chassis roll. This weight transfer, or roll, takes weight off the inside front which takes steering response away from the car. The AR center pivot makes adjusting the rear roll center very easy."
I am in full agreement with the description above regarding the rear roll center adjustment. It doesn't matter where the rear roll center actually is, tuning the car by adjusting this pivot will have the affect described. It is easy to see that in this case, the roll center is lower than the center of gravity (CG) of the rear. If the rear roll center was higher than the CG of the rear of the car, the affects would be opposite. My experience with all the 1/12 cars I have owned and raced supports my comments as I have made these adjustments in the past and those changes follow the description in the manual. Comment number 76 above is sort of confusing to me.
#87
Tech Elite
I've read several times in this thread that this is the last "American" made car but isn't Speedmerchant still producing cars?
#90
Looks to me that Frank lowered the pivot point and thus lowered the roll center which will give the rear tires more traction. If you want to raise the roll center, just put shims under the pivot assembly and that will give you less rear traction. Frank knows exactly what he's doing.
EDIT: Even though this photo does have two shims under the Pivot Mechanism, the design of the horizontal versus the old vertical pivot ball lowers the ball down so that your adjustment range includes a much lower roll center than before. And the main point was that the statement "Higher roll center is lowering the pivot, sort of backwards of what it sounds like" is not correct when it comes to a pod design with a pivot point. Lower the pivot to lower the roll center. Now if you were talking about the standard suspension design that uses two A arms, you would be correct. On that design if you raise the inside pivot of the top arm you actually lower the roll center.
Final thing is I've attached a video from Alexander Hagberg on the X12. The X12 has a very similar pivot design as the new CK25AR. Go to the 5 minute mark and he says, we have a new rear pivot design which mounts a lot lower which lowers the roll center. https://www.youtube.com/watch?v=_jC8UWJKgYk
EDIT: Even though this photo does have two shims under the Pivot Mechanism, the design of the horizontal versus the old vertical pivot ball lowers the ball down so that your adjustment range includes a much lower roll center than before. And the main point was that the statement "Higher roll center is lowering the pivot, sort of backwards of what it sounds like" is not correct when it comes to a pod design with a pivot point. Lower the pivot to lower the roll center. Now if you were talking about the standard suspension design that uses two A arms, you would be correct. On that design if you raise the inside pivot of the top arm you actually lower the roll center.
Final thing is I've attached a video from Alexander Hagberg on the X12. The X12 has a very similar pivot design as the new CK25AR. Go to the 5 minute mark and he says, we have a new rear pivot design which mounts a lot lower which lowers the roll center. https://www.youtube.com/watch?v=_jC8UWJKgYk
I was told by CRC that the new pivot is 2mm lower roll center than the previous car when the kit setup three .5mm shims are installed. So with no shims it would be 3.5mm lower.