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Blue Foxy
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What may work? Roll center construction method?
Well. . .!Ranger Mike said:There is no such thing as weight transfer.
It sure as hell feels like there is. . . . .Lol. . . . .Ranger Mike said:...but drop that sledge hammer on your toe once.
Ranger Mike said:that may work good for left and right turn racing but not for left turn only round track racing in USA.
Ranger Mike said:you did not understand because you obviously did not read the forum posts. it is all there and all you need do is read. A corner is a corner but how you traverse it properly is the difference in left turn only racing and road course racing. Unless you understand this all the software in the world will not get you a win.
Thanks for the quick reply Ranger Mike could you please give a quick list of the advantagesRanger Mike said:Hill
i love smokey yunick! he was the best! I am all for the rev rotation. Yes 3rd link offset can assist. I would have gone rev rotation if it were not so expensive. doomed by production design from get go i guess. i am for anything that adds down force to the lazy left side tires.
811 is page 33 not 41, and 879 is page 36 not 44, seems like you are whistleing in the page.Ranger Mike said:I did not think it was clever as i revised it after reflection. this is not my forum and the administrators are the best you can find. And i can understand you not reading the entire long 59 pages of posts. I do get bothered when i have addressed this RC issue many times, page 10 post 229 pg 11 post 251, pg 28 post 691 pg 41 post 811 pg 44 post 879. Seems like i am whistleing in the wind sometimes.
Ranger Mike said:Engine - driveline torque produces an equal and opposite reaction upon the chassis, lifting the left side of the body, pushing down on the right side, and redistributing the load to the outside of the corner in a left-hand turn. This is exactly what we want thru body roll. So if we reduce the body roll and can put the same amount of down force on the right front tire, we can keep the nose down and seal up the aero just like the big bar soft spring set up. But on the rear end, Torque reaction lifts the right end of the rear live axle and pushes down on the left, with the axle housing forming a sort of lever. On a typical car developing oh, 300 lb-ft of crankshaft torque, there might be 75-120 lbs. of force loading one end of the axle and unloading the other. For oval racing at least, this redistribution is in a nominally helpful direction—from the outside to the inside tire. And note that reversing the engine’s rotation does not cancel the reaction forces in any event. It simply reverses them. And in the case of the forces acting on the axle housing, it’s in the wrong direction for oval racing. So reverse rotation is a help to the front but bad for the rear end set up. Drivers who have raced the rev rotation set up also state it works great but you had to stay on the gas pedal in the turns or it wants to make right turns if you lift.
Engine specific changes are - is the fact that the coolant flow is reversed. The engine doesn't cool as efficiently with flow entering the top and exiting the bottom.
Some engines have the cranks knurled for that rotation only. Running them backwards they will leak oil at the front & rear seals. The wrist pin was slightly offset in the piston ( they do that to make sure there is no piston slap...), so you had to turn the pistons 180 deg in the bores.The engine needs a different cam, and the little driveshaft that goes between the oil pump and the distributor. ( the gear on it meshed with a gear on the cam ). Water pump & alt or generator need reverse rotation models from marine application that ran the right way ( alt might work either way, but the cooling fins next to the pulley will be pointed the wrong way.) Need starter that runs backwards too. Clutch and transmission should be ok but pinion gear has to go on right side in differential.I don’t think it is worth the hassle and I look at track side repairs. You cannot win ifin you don’t finish and you are super screwed at the track when you have many special order items. You are at the track and suddenly a starter, water pump goes out on you. Reverse flow – neat trick but not worth it.
Ranger mike I am not sure if you think I'm wasting your time here? I have already got the reverse rotation crown wheel and pinion rear done and also the reverse rotation of the drive shaft.Ranger Mike said:like i said i do not think it is worth it. if you wish to go rev rotation, keep us updated. Your Double A arm front 3 link rear is a good foundation. now find a rev rotation rear end. the rest is simple.
Write who Arans thanks for business award speech |
Thanks for your reply one of my concerns is the lift of the left rear tyre under power.Ranger Mike said:By no means do i think i am wasting time. this is a forum for racers. Any question is ok as long as it is in compliance with the administrators who are THE BEST. I am not doing this to sell software or books. Just passing on what limited knowledge i have as long as the person reads what i already wrote and does not ignore it and then continues to dog the issue.
Hill, you are most welcome to ask, no problem.
Once you have all the working pieces of rev rotation i would back off the front roll center off set since the engine torque will provide down load. All yo ucan do is use tire temperature to see how much down force you are getting and tune from that. Otgher than the Rc set it up as you have before. You need to get the car to handle going then work on center out.
quote from SmokeyRanger Mike said:Use same mount location. it is for % left side weight. Your rear wheels will still be rotating forward regardless of the rotation of engine since your rear end has also been chage to right side pinion gear.
Ranger mike thank you for your patients I misunderstood what i was reading about lifting the rear under powerRanger Mike said:the torque is not reversed relative to tire rotation. This stays the same since you now have reverse rotation differential.
You have the engine torque now twisting to driver side ( vs traditional way of twisting to the right front) and the rear twist it going to the left rear vs traditional twist to the right rear.
This is what happens when you go rev rotation.
Just by watching the cars running it at the Derby that won and have it figured out already it was essentially moving like a dirt car, the left rear tire was traveling into the fender well, the rear of the car was rising and the left ear tire was just being pounded into the pavement. We all know modifieds with 8" tires are an animal at the end of the race but mot anymore with this setup. same thing with the super Late models. I will add they are running the rear calipers on the bottom of the axle tube also. Yet again this is things I've seen on dirt but am not familiar with dirt as we've always ran pavement.Ranger Mike said:Couple of quick observations. This Center pull suspension with J bar links combines the best of 4 link and 3 link suspensions. The 4 link is the best set up for dirt as you need maximum traction tuning. This center pull set up eliminates the lower links of the 3 and 4 link suspension. Less weight hanging below the axel and less garbage to get snagged up on a bad track. Everything is above the rear axel tube out of harms way.
Look at the Instant center angle. I do not have the hard numbers but it sure looks like the intersection of the two J bars and the pull bar is way out in front of the axle. Like 10 foot in front of the car! We want the angles of the rear suspension linkage to form an Instant Center (IC) as far forward as possible. This longer lever cushions the acceleration when the tires hook up. This set up does not have a shock damper on the top link. Too short an IC distance means we have a lot of angle change on both sides and the car will be real darty when you nail it. Longer is better and gives the driver more control because you don't have a lot of angle change as the shorter IC has. The top link angle can be zero to 5 degrees down hill for traction.See attached forces on rear axle -
It is easier to pull a chain than push it. Race cars love forces that directly pull versus forcers that push and this set up is strictly a PULL. All links are pulling on the chassis. We have more initial static angle on the driver side of 6 ° and the right side angle of 12 ° . This means the car in chassis roll will grow more angle in chassis ROLL as the right side angle reduces as the right side springs compress. This is a feature that 3 link has but to a much lesser degree due to the limitations of the lower links. About the only thing you could to bias the rear wheel loading was to off set the top link mount. With the J bar design you can dial in rear wheel load directly to each wheel.
This is HUGE!
Question for you to ponder- What happens when the rear end is in Roll? What happens to wheel base on left and right side?
Shorttracker93 said:Just by watching the cars running it at the Derby that won and have it figured out already it was essentially moving like a dirt car, the left rear tire was traveling into the fender well, the rear of the car was rising and the left ear tire was just being pounded into the pavement. We all know modifieds with 8" tires are an animal at the end of the race but mot anymore with this setup. same thing with the super Late models. I will add they are running the rear calipers on the bottom of the axle tube also. Yet again this is things I've seen on dirt but am not familiar with dirt as we've always ran pavement.
RM, I've been watching this center-pull setup with keen interest since it first started winning (lots of aero on outlaw bodied cars). Firstly trying to figure out how to model it to understand if it's actually better in force management and location or just a shiny object (winners win, builders sell cars). On the modeling since it appears to give another element of freedom in the linkage. Also, one spring/shock assembly is mounted in front of the axle which helps on the off-throttle torques. So far, the best way can understand the IC effect is to model it like IRS, from the center of the axle tube and not from the tire patch. A second reason I lean toward that understanding is that the spring rates used in the competitive cars are very stiff. Another reason is that the actually-running setup I tried to model would up having the linkage intersection point looking like that of a Viper or modern Corvette, really high. Racers are using bumpstops in both rears with very high rates. Also, very low rear roll centers. Panhards under the driveshaft, 6"-7" RC height. So with the steep upward angles you get a lot of desired roll steer, but the bad potential for wheel hop checked by more freedom and dampening than traditional. I'm guessing, but my real question is how to appropriately model the forces.Ranger Mike said:Couple of quick observations. This Center pull suspension with J bar links combines the best of 4 link and 3 link suspensions. The 4 link is the best set up for dirt as you need maximum traction tuning. This center pull set up eliminates the lower links of the 3 and 4 link suspension. Less weight hanging below the axel and less garbage to get snagged up on a bad track. Everything is above the rear axel tube out of harms way.
Look at the Instant center angle. I do not have the hard numbers but it sure looks like the intersection of the two J bars and the pull bar is way out in front of the axle. Like 10 foot in front of the car! We want the angles of the rear suspension linkage to form an Instant Center (IC) as far forward as possible. This longer lever cushions the acceleration when the tires hook up. This set up does not have a shock damper on the top link. Too short an IC distance means we have a lot of angle change on both sides and the car will be real darty when you nail it. Longer is better and gives the driver more control because you don't have a lot of angle change as the shorter IC has. The top link angle can be zero to 5 degrees down hill for traction.See attached forces on rear axle -
It is easier to pull a chain than push it. Race cars love forces that directly pull versus forcers that push and this set up is strictly a PULL. All links are pulling on the chassis. We have more initial static angle on the driver side of 6 ° and the right side angle of 12 ° . This means the car in chassis roll will grow more angle in chassis ROLL as the right side angle reduces as the right side springs compress. This is a feature that 3 link has but to a much lesser degree due to the limitations of the lower links. About the only thing you could to bias the rear wheel loading was to off set the top link mount. With the J bar design you can dial in rear wheel load directly to each wheel.
This is HUGE!
Question for you to ponder- What happens when the rear end is in Roll? What happens to wheel base on left and right side?