Automotive Race car suspension Class

[Blue Foxy]

What may work? Roll center construction method?

 

[OCR]

What. . .??

There is no such thing as weight transfer.

Well. . .!

...but drop that sledge hammer on your toe once.

It sure as hell feels like there is. . . . .Lol. . . . .

OK, carry on. . ✔

.

 

[Blue Foxy]

that may work good for left and right turn racing but not for left turn only round track racing in USA.

Strange answer, a straight line is a straight line, and a corner is a corner, whatever the country.
Physics laws are the same (Newtons laws) whatever you are place on earth.

I do not really understand what you mean? Can you clarify?

 

[Ranger Mike]

you did not understand because you obviously did not read the forum posts. page 28 post # 691. 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. And you are missing one huge factor not eve naddressed in the software..any guess as to what that may be??

 

[Blue Foxy]

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.

Honestly, do you think your reply is clever.
For your knowledge, I have an mechanical engineering degree, I have been working for 20 years in motorsport, I have been chief designer in company which produce single seaters (wich have produce more win than you expect).
I do not say I understand everything, I try to be open mind in a technical discussion on this thread.
The post is 59 pages, I tried to read most of them.

I open the discussion on roll center location, and I say it exist a geometric construction that allows to minimize his dispacement, you reply : Unless the race car is works built from the ground up, you will have roll center migration, you even not ask me: ok I m curious show me. I show a example of what is possible with this geometric constrcution (+-100mm suspension travel , 0.34 mm moving in height), that's just a example of what is possible. I do not say it is perfect, but it took 15 mn to achieve this.

You wrote: Weigh Jacking is a result of roll center location and tire contact patch. This a big approximation, as often you can find on books.

The jacking is a result of distribution in load in the suspension compenent (upper lower wishbone and spring), on certain construction more load go threw upper and lower wishbone, and less to the spring. To be convince to this, you should calculate every load on suspension component, if you are able to.

I though this thread was a open mid discussion and knowledge exchange, as a forum should be.

 

[Ranger Mike]

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.

 

[Hillbillyd]

Please bear with me as i try to explain my question reverse rotation of the drive shaft and using reverse rotation crown wheel and pinion to correct it so the car drives forward normally.
Now this is a purpose built race car to run a dirt oval with double A arm suspension and 3 link rear coil over suspension and i have researched this and read about Smokey reverse torque special https://macsmotorcitygarage.com/another-look-at-smokey-yunicks-reverse-torque-special/
What are your thoughts on the rear diff torque loading the right rear and unloading the left rear can this be over come by moving the 3rd link further to the left to load the left tire?
Have i just lifted the lid on the can of worms?

 

[Ranger Mike]

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.

 

[Hillbillyd]

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.

Thanks for the quick reply Ranger Mike could you please give a quick list of the advantages

 

[Ranger Mike]

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.

 

[Blue Foxy]

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.

811 is page 33 not 41, and 879 is page 36 not 44, seems like you are whistleing in the page.

I read all the post you mention, with attention, lot of approximation, I wil reply you via direct message.

 

[Hillbillyd]

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.

Ok what would be the suspension advantage of it?
I’ve read and understand what you’re saying about the engine but if the race car was in your hands how would you design and set up the suspension ?
I have chosen Double A arm front 3 link rear because it’s a simple design
Actually our suspension rules are free! build what you can

 

[Ranger Mike]

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.

 

[Hillbillyd]

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.

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.
How would you set up the suspension if this race car was in your shop?
Im here asking for advice because lots of people can not answer my questions which is understandable as most people have never even heard of it let alone thought about building it.

Write who Arans thanks for business award speech

 

[Ranger Mike]

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.

 

[Surdge]

Good afternoon I finally finished my four link race car I drove it for the first time past weekend whent well just one question we drive on clay oval track as soon as I exit the corner and I climb on throttle the rear starts to jump up and down any ideas where I went wrong

 

[Ranger Mike]

I assume you are NOT running stock rubber bushings. What are tire temperatures. what are the 4 link angles set at? are you running rear steer? if so how much? You have the classic wheel hop on acceleration it sounds like!

 

[Surdge]

Thanks for quick reply no I'm not running rubber bushes I'm not sure of Tyre temperature will check next event running rear steer it turns about 10 degrees. If ur behind car looking forward on left side top link 18 degrees bottom 12 degrees right side 22 degrees bottom 6 degrees

 

[Ranger Mike]

rear is too rigid causing pogo effect of wheel biting then bouncing up and spinning and dropping down .
18 ° should be MAXIMUM on upper links...14° minimum and left side should be less than right side.
both bottom links should be 5 ° starting out.
ball park settings
left top 13° rt top 18° up hill left and rt bottom 5° down hill

 

[Hillbillyd]

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.

Thanks for your reply one of my concerns is the lift of the left rear tyre under power.
Going off the Steve Smith book calculating the 3rd link mount location is based on your left side percentage weight to load the tyres evenly i.e. centre of the mass of the car, in my case I'm wondering if there is a calculation to determine where to mount my 3rd link for reverse torque?
So my understanding will be that i will be loading the right rear and left front under power?
How would this affect spring weights?

 

[Ranger Mike]

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.

 

[Hillbillyd]

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.

quote from Smokey
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 your not concerned about the torque is reverse and it will lift the left rear under power?

 

[Ranger Mike]

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.

 

[Hillbillyd]

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.

Ranger mike thank you for your patients I misunderstood what i was reading about lifting the rear under power
Quote from Smokey
The idea of reverse rotation is, when you accelerate hard the weight comes to the left front and left rear, and pulls weight off of the right front. This more evenly distributes weight across the chassis, increases your lateral traction on the front and back end. You go faster.”

 

[Hillbillyd]

quote from Smokey on a standard rotation torque
Torque reaction also 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. (Or, maybe why your vehicle’s right rear wheel spins helplessly when you’re stuck in the snow.) But for oval racing at least, this redistribution is in a nominally helpful direction—from the outside to the inside tire.
This i have seen at the drag strip many times of tuff street cars lifting the left front and burying the right rear up in the wheel well
So the way he explains it reversing the rotation of the drive shaft has the opposite effect on the rear axel lifting the left tire and planting the right tire.
Ranger Mike I'm happy to be proven wrong here as i will have learned something just getting under my car and rotating the pinion clockwise viewed from the rear it makes sense to me under load the right tire gets pushed down in the same direction of the rotation of the driveshaft.

 

[Ranger Mike]

rev rotation will lift right front tire and plant the left rear tire exactly opposite of current drag cars.

 

[Hillbillyd]

The last set of loads that the axle housing experiences comes from the reaction of the propshaft rotation against the wheels on the pavement through the axle gearing. As mentioned earlier, the propshaft is rotating in a counter-clockwise direction when viewed from the rear of the vehicle. This rotation and subsequent torque on the pin-ion is trying to rotate the axle housing. This rotation applies a downward force on the left wheel, and an upward force on the right wheel. So the load on the left wheel is increasing, and the load on the right wheel is decreasing. This is similar to the front-to-back weight transfer on the chassis during hard acceleration.

 

[Shorttracker93]

Hello Mike, I have read a large amount of your posts here and have a good understanding of most the suspension design concepts and roll centers for a asphalt oval car. Have you dealt with or seen the new " center pull" trailing arm setup everyone is going to on the rear 3 link? I kinda understand that it is accomplishing the same effect as a birdcage setup on a dirtcar but really don't understand what its doing geometry wise and what particular height adjustments change. The gentleman with Day motorsports that we spoke with at the Snowball Derby said that everyone's starting point is in the range of 6* up driver side and 12* up passenger side. i will attach a link for Port City Racecars design. It uses vertical screw adjusters but you will have to re adjust your square every time. Day motorsports carries a climber bracket that moves in an arc, I think it is produced by Wehers, I cannot find a link to it at the moment. I will be running the suspension on a Openwheel Modified and we are going to also install it on my fathers Outlaw latemodel.

Center pull kit Port city
https://www.portcityracecars.com/CENTER-PULL-REAR-SUSPENSION-KIT-1-3-4-ROUND-ADJUSTERS-DOUBLE-ADJUSTERS-FOR-J-HOOKS.htmlInstalled on chassis

https://gallery.mailchimp.com/3b755...ages/4261f5d6-3f5e-47e4-aae0-102ace3f8564.jpg

 

[Ranger Mike]

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]

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?

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.