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Any of your work in there, Greg?


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#1 mariner

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Posted 21 November 2022 - 13:39

A very positive review in Uk of the Aussie developed Ford Ranger Raptor

 

https://www.autocar....d/ranger-raptor

 

 

Interestingly the dampers are Fox, not brand I think of as OEM

 

 

BTW what is the 0 60 mph ( or 0 - 100kph) time with the 400 bhp nor legal in Europe?



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#2 Greg Locock

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Posted 21 November 2022 - 20:30

I do a lot of work on the T6 platform, but had no particular involvement with the Raptor (at the time we had 6 of us on the team, it's rare to have more than 2 on a given model). Up until recently I was on Everest and Bronco. The shocks have position dependent valving which meant they had to write a custom model for them. Hey we won our class in Baja! In other news we were the only entrant in that class.



#3 mariner

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Posted 22 November 2022 - 07:56

Thanks Greg - turning the position sensitive shocks up side down  might be an interesting ride.



#4 Fat Boy

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Posted 23 November 2022 - 15:58

Hey we won our class in Baja! In other news we were the only entrant in that class.

It'll look just fine in the history books.



#5 gruntguru

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Posted 01 December 2022 - 08:34

A very positive review in Uk of the Aussie developed Ford Ranger Raptor

 

https://www.autocar....d/ranger-raptor

 

 

Interestingly the dampers are Fox, not brand I think of as OEM

 

 

BTW what is the 0 60 mph ( or 0 - 100kph) time with the 400 bhp nor legal in Europe?

0 - 100 kph in 5.5 seconds apparently.

 

0 - 60 mph would be a little less.



#6 Fat Boy

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Posted 01 December 2022 - 18:04

King Shock is close to me and they are big in the off-road world. Some of the dampers they produce are damned impressive. 4 or 5" diameter pistons and several bypass valvings. Interestingly, when talking to the owner he says that for them, piston area is huge. The bigger the piston, the better the control, even if the dampers are valved to equivalent forces. Apparently, reducing the working pressures (& hysteresis) is of massive importance to them when trying to control a big mass bouncing around a up to 1 M/s. I've never played with them, but they look cool.

In related news, F1 dampers have grown in size over the last decade or so. They used to be mountain bike sized, but they're getting a bit bigger, now.



#7 Greg Locock

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Posted 01 December 2022 - 20:36

Damper sizing is a big thing.  The diameter of the tube, length of the tube, and diameter of the rod, all get up someone's nose, and of course the program always wants to keep the cost down. The nice thing about these niche variants is that cost control more or less goes away. The problem with big pistons/rods is ride quality on smooth road, the stiction is more or less proportional to diameter. I vaguely remember that most of the stiction is in the rod seal, made worse by bending loads.. To get around that one of our retired engineers developed a rubber bushing that had very low coning rates but high radial rate to use at the shock to lower arm, I've been using that design ever since all over the place whenever I need a ball joint. Bronco/Everest has 6 of them.



#8 mariner

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Posted 08 December 2022 - 20:46

A nice vid of a test of teh Raptor off rad. I see it has a red ring on steering wheel to mark straight ahead!

 

https://www.autocar....breed-fast-ford



#9 Fat Boy

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Posted 20 December 2022 - 17:14

Damper sizing is a big thing.  The diameter of the tube, length of the tube, and diameter of the rod, all get up someone's nose, and of course the program always wants to keep the cost down. The nice thing about these niche variants is that cost control more or less goes away. The problem with big pistons/rods is ride quality on smooth road, the stiction is more or less proportional to diameter. I vaguely remember that most of the stiction is in the rod seal, made worse by bending loads.. To get around that one of our retired engineers developed a rubber bushing that had very low coning rates but high radial rate to use at the shock to lower arm, I've been using that design ever since all over the place whenever I need a ball joint. Bronco/Everest has 6 of them.

Some of your problems, I don't have to fight. First, bending loads are minimized, due to through shaft dampers and rockers. Rod size has shrunk significantly, since we're no longer using the displaced oil to alter damping. Those two things alone have reduced stiction. Also, our piston seals don't have to last forever. They have to seal up for ~50 hours of use and then they're in a trash can. Obviously, they need to seal well enough to produce the necessary low speed forces, but reducing damper stiction is fairly high on everyone's list. (I have heard of inducing stiction to produce very low shaft speed force, but I've never played that game myself.)

The pressure lag of small diameter dampers are a real thing, but I have no idea of how to characterize it. Many years ago, I was running the Ohlins TT44, which was a spectacular damper with a 44mm main piston diameter. They had introduced a smaller, lighter version called the TT40, which was the exact same architecture with a 40mm main piston. I was with a strong and well-funded team (at one point, they did exist!). We had an exclusive program with Ohlins to develop these things with all sorts of 7-poster and hydraulic dyno time. We put a ton of work and money into these things. At the time, the only other car on them was the Audi R8's. They had so many advantages on that car that the dampers were fine to them and it saved them a significant chunk of weight. For us, dampers were one of the defining characteristic of the performance of the car, so any shortcoming they had was magnified. The TT40 never saw widespread use and it wasn't long before they abandoned the entire architecture and shifted to their TTX-style damper. Regardless of the weight penalty, I'd have no issue running a TT44 on _anything_, even today.

After a year of working on these things, we ended the season back on the TT44. I don't know how much the piston size influenced the struggles we had making those things work, but I've always thought that there must me something in it. It was essentially the same damper produced by the same people using a lot of the same parts and all of the same philosophies. It would have the same curves on a crank dyno and it would produce better grip and control numbers on the 7-poster. In actual use, though, it never felt as good and it never gave the driver the same confidence or feel in the car. Our better driver was able to win races and contend for the championship, but he always said you had to just trust the grip would be there, because you couldn't feel it. The lesser driver, who was still pretty good, was absolutely lost on the new dampers and we converted him back over to the 44's earlier in the process.
 

Our damper program was an absolute failure in terms of performance, but it was an interesting and instructive failure, none the less.


Edited by Fat Boy, 20 December 2022 - 17:16.


#10 Greg Locock

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Posted 20 December 2022 - 21:42

" It would have the same curves on a crank dyno and it would produce better grip and control numbers on the 7-poster. In actual use, though, it never felt as good and it never gave the driver the same confidence or feel in the car. "

 

The man from the factory comes round for a tuning session for a few days a year. He spends a reasonable amount of time taking our  shim stacks and rebuilding them to give the same dyno curves but better manufacturability, durability and on-road feel.



#11 Fat Boy

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Posted 21 December 2022 - 16:50

I have a couple rules of thumb. The first is that any time you can introduce a bleed shim, it's a good thing. Even if it's just a tiny amount of bleed and only a part of the whole, it seems to always show up in terms of performance. It's not massive, but it's there. The other thing is in the shim stack itself. The more shims you can use to make a curve, the nicer it acts on track. You might be able to make a force curve with 4 thick shims, but if you use 10 thinner ones, you'll get better driver comments on it. 15 will be better yet. I have no explanation, I've just observed it too often for it to be a coincidence.

 

I have this book in paperback from when it was originally printed, but I think it's the best book on dampers that's been written and it's written about that damper I was talking about. It's not mathematical, but the practical information is priceless. An early racing shock guru named Bruce Burness, who did everything from Motocross to Baja to Indy, wrote it. Take it for a spin and see what you think. The price is right.

 

https://www.ohlinsus...4_Manual_p1.pdf

https://www.ohlinsus...4_Manual_p2.pdf

https://www.ohlinsus...4_Manual_p3.pdf

https://www.ohlinsus...4_Manual_p4.pdf


Edited by Fat Boy, 21 December 2022 - 16:54.