Torque twist...

[pitass]

hey guys, is there any way to fix the torque twist?

my crawler climbs always on three wheels and when i try to climb something steep it always flips me over.

like in this vid : http://www.youtube.com/watch?v=-COPFh3ph8k

Iv seen alot of crawlers that dont have torque twist (or atleast not that much) but i dont know what to do.

any help would be very welcome

[bob1961]

some pictures of your rig's links and some tech will help out more then what you just asked without any tech...............bob

....

[pitass]

I have a custom built super class crawler, using stock savage shocks and 3 link suspension (exactly like axial's) with 18" wb

dont have any pics of my crawler without the body :S

[bob1961]

from what i've read the 3 link is your biggest problem....try going to a 4 link and see how that works....little changes at a time so you know what works and what don't...............bob

....

[P1choco]

Switch to 4 link and try to get your links further away from each other on the axle, and closer together on the chassis.

Refer to the bottom drawing.

[mbmlcrawlers]

I had the same problem with my Axial! I rebuilt my Axial chassis and got rid of the upper 3-link and made new axle plates with longer links on top turn it into a 4-link set up. Drilled a new hole in the chassis for the new links due to being longer. Run a softer spring in front with stock Axial springs in rear. My crawler has ZERO torque twist with great flex!!!

[BrentH]

I would get rid of the 3-link and go with a 4 link setup. Make sure your links are setup as shown in the picture above... and add some heavier weight oil to your shocks. I eliminated about 90% of my torque twist by going to a 4 link, moving my lower links in close (on the chassis) so that the links have a reversed triangulated setup, and added 80wt shock oil with internal spring. I haven't had any problems with torque twist unless my front end is up in the air and my rear wheels get bound up.

[JeremyH]

What truck (axles) are we talking about here? TXTs?

[fernando]

Try doing the four link in the back. Works for me.

[VeryBumpy]

Climb steep enough and any shafty will have TT. Switch to MOA if you want easy driving.

[ultimate_monkey]

do the mirror tranny mod and it will help you HUGE!Mirror Imaged Transmission


and there is alot of playin with link geomitry to help aswell but you have to understand how a 4 link works if you want to do this with out waseting a hole lot of time

Originally Posted by VeryBumpy

Climb steep enough and any shafty will have TT. Switch to MOA if you want easy driving.

not true, if my shafty can climb up it with out just goin over back wards it will do it with absolute 0 TT

[Eritex Inc.]

Originally Posted by ultimate_monkey

do the mirror tranny mod and it will help you HUGE!Mirror Imaged Transmission


and there is alot of playin with link geomitry to help aswell but you have to understand how a 4 link works if you want to do this with out waseting a hole lot of time




not true, if my shafty can climb up it with out just goin over back wards it will do it with absolute 0 TT

If you are using drive shafts that transfer power from a suspended chassis to an axle, you will have TT.

Rock Forces suffer from TT less because of the axle ratio.

RF axle = 30:1

Axial axle = 2.92:1

If both trucks have a final drive ratio of 60:1, the RF will have a 2:1 transmission ratio. The Axial will need an axle ratio 20.55:1.

The Axial transmissions RPM out put is 10 times less, but that means the "torque" load is higher.

That is the reason an Axial TT's more then the RF.

[BMFOTP]

Originally Posted by mbmlcrawlers

I had the same problem with my Axial! I rebuilt my Axial chassis and got rid of the upper 3-link and made new axle plates with longer links on top turn it into a 4-link set up. Drilled a new hole in the chassis for the new links due to being longer. Run a softer spring in front with stock Axial springs in rear. My crawler has ZERO torque twist with great flex!!!

How long are the upper links for your Axial? Can you post a pic of the bottom of your crawler so I can see the placement of your lower links?

[ultimate_monkey]

yup the axial has TT no doubt about it but there is this stuff called tuneing you now, suspention geomitry, link lengths, shock set up, turning your squat / anti squat trans positioning, not runing the stock chassis things of that nature, if you take the time and know what mod will have what effect youd be suprised what u can do.

if you want i'll take time out of my actual crawling to set up a inclined ramp and take a video for you

point is even if there is TT properties at play iv taken the tme to set my rig up so that their effect is so minimal that the effect of them goes completly un noticed

[BMFOTP]

Originally Posted by ultimate_monkey

yup the axial has TT no doubt about it but there is this stuff called tuneing you now, suspention geomitry, link lengths, shock set up, turning your squat / anti squat trans positioning, not runing the stock chassis things of that nature, if you take the time and know what mod will have what effect youd be suprised what u can do.

if you want i'll take time out of my actual crawling to set up a inclined ramp and take a video for you

point is even if there is TT properties at play iv taken the tme to set my rig up so that their effect is so minimal that the effect of them goes completly un noticed

I would like to see what your crawler can do on a video. Give me some idea of what I shoud be shooting for in the future.

[soundcolor]

[quote=Eritex Inc.;1748719]If you are using drive shafts that transfer power from a suspended chassis to an axle, you will have TT. [quote]

[quote=Eritex Inc.;1748719]If you are using drive shafts that transfer power from a suspended chassis to an axle, you will have TT. [quote]

This is correct. It doesnt matter what you do to a shafty (meaning centrally mounted transmission with driveshafts exiting and going to the axles) A shafty will ALWAYS have torque twist. Believe it or not there are actual physics involved. Correcting suspension geometry and even the pinion angle (though pinion angle helps ever so slightly).

Torque is defined as
1: a force that produces or tends to produce rotation or torsion <an automobile engine delivers torque to the drive shaft> ; also : a measure of the effectiveness of such a force that consists of the product of the force and the perpendicular distance from the line of action of the force to the axis of rotation2: a turning or twisting force (sourced from meriam-websters dictionary)

Now that we know what torque is, lets figure out why no shafty can stop torque twist. 1st. The motor and trans are mounted directly to the chassis, 2nd. The axles are mounted to the chassis by linkages and shocks that are designed to allow articulation which can also be refered to as rotation. The way in which these shocks and linkage bars connect to the chassis and axles are by way of ball-end links which are balls that are pressed into an endlink by force.
And now we can discover why we must have some amount (no matter how large or small) in a shafty.
(here is a link to a webpage that will tell you everything you could want to know about the physics of torque twist)

Now our good friend Newton comes into play in two of his laws of motion

1st law.A body persists its state of rest or of uniform motion unless acted upon by an external unbalanced force.
How does this relate to torque twist in our shaft driven rock crawlers? If you consider that the chassis and motor/trans are two seperate entites that have been coupled together, we will call them "A", act as one unit and are then by default the item creating the force. Then you have to label the linkages/shocks/axles as "B", beings as they are coupled together and tied to "A". Now if item "A" is in anyway at rest or in a uniform motion (could be sitting still on the floor or slowly clawing its way up a rock face) then that item will stay in that state until acted upon by force. Which is the long way of saying it will keep doing what its doing until you apply more throttle.

3rd law. To every action there is an equal and opposite reaction.
Basically what this says is when object "A" exerts a force on object "B", then object "B" exerts and equal on opposite force back on object "A"
What this means to us is that when our "A" begins to apply force (torque), then our "B" must try to match it.

Now at low throttle, and provided nothing is acting on the crawler from the outside (i.e. we are rolling on a flat smooth surface) Then "B" has no problem countering "A". However as "A" begins to apply more and more force then "B" becomes temporarily overwhelmed and this is the moment that torque twist occurs. Now as the springs/linkages begin to compress and articulate they begin to "bind" a little (meaning that they are being compressed more and more, and are resisting that compression, which is why you truck doesnt stay flexed over to one side all the time). When they begin this "binding" they begin to apply more and more force back upon "A" and when the force of "B" matches the force of "A" the vehicle stops twisting, and stays at that point of flex until either more force is applied by "A" or the force from "A" is reduced. I could explain even further how outside forces also affect the physics involved but it gets really lengthy there.

Now heres why a 3 link allows more torque twist than a 4 link. In a 3 link, the upper link, or wishbone, is mounted to the top of the axle at one fixed point via a ball link of some sort. Now, this would allow the axle to spin indefinatly, and freely if it werent for the lower links and the shocks acting against the torque applied by the motor trans.

In a 4 link, the upper two links work in conjunction with lower two links to maintain a more controlled and defined motion. Now lets for example say that the rear axle of our car is climbing over an object known as "C". As the suspension begins to rotate (either by torque from motor, or outside force) the lower links begin motion first, followed by the upper links, and then the springs/shocks begin to apply force to stop this movement (see above). As the outside lower link begins to move, the inside upper link moves with it. Likewise the inside lower link, and outside upper link move to counter them. This movement, countermovement is what helps to manage torque twist.

I said all of that to say this. In a shafty, the only thing that will completly stop all torque twist is to solidly mount the axles to the chassis. You cannot defy physics. You may fiddle with the susp. geometry and that my well help, and you can play around with the springs/shocks and that may help. But you cannot stop ALL torque twist.

[rock addict]

[quote=soundcolor;1749364][quote=Eritex Inc.;1748719]If you are using drive shafts that transfer power from a suspended chassis to an axle, you will have TT. [quote]

[quote=Eritex Inc.;1748719]If you are using drive shafts that transfer power from a suspended chassis to an axle, you will have TT.

This is correct. It doesnt matter what you do to a shafty (meaning centrally mounted transmission with driveshafts exiting and going to the axles) A shafty will ALWAYS have torque twist. Believe it or not there are actual physics involved. Correcting suspension geometry and even the pinion angle (though pinion angle helps ever so slightly).

Torque is defined as
1: a force that produces or tends to produce rotation or torsion <an automobile engine delivers torque to the drive shaft> ; also : a measure of the effectiveness of such a force that consists of the product of the force and the perpendicular distance from the line of action of the force to the axis of rotation2: a turning or twisting force (sourced from meriam-websters dictionary)

Now that we know what torque is, lets figure out why no shafty can stop torque twist. 1st. The motor and trans are mounted directly to the chassis, 2nd. The axles are mounted to the chassis by linkages and shocks that are designed to allow articulation which can also be refered to as rotation. The way in which these shocks and linkage bars connect to the chassis and axles are by way of ball-end links which are balls that are pressed into an endlink by force.
And now we can discover why we must have some amount (no matter how large or small) in a shafty.
(here is a link to a webpage that will tell you everything you could want to know about the physics of torque twist)

Now our good friend Newton comes into play in two of his laws of motion

1st law.A body persists its state of rest or of uniform motion unless acted upon by an external unbalanced force.
How does this relate to torque twist in our shaft driven rock crawlers? If you consider that the chassis and motor/trans are two seperate entites that have been coupled together, we will call them "A", act as one unit and are then by default the item creating the force. Then you have to label the linkages/shocks/axles as "B", beings as they are coupled together and tied to "A". Now if item "A" is in anyway at rest or in a uniform motion (could be sitting still on the floor or slowly clawing its way up a rock face) then that item will stay in that state until acted upon by force. Which is the long way of saying it will keep doing what its doing until you apply more throttle.

3rd law. To every action there is an equal and opposite reaction.
Basically what this says is when object "A" exerts a force on object "B", then object "B" exerts and equal on opposite force back on object "A"
What this means to us is that when our "A" begins to apply force (torque), then our "B" must try to match it.

Now at low throttle, and provided nothing is acting on the crawler from the outside (i.e. we are rolling on a flat smooth surface) Then "B" has no problem countering "A". However as "A" begins to apply more and more force then "B" becomes temporarily overwhelmed and this is the moment that torque twist occurs. Now as the springs/linkages begin to compress and articulate they begin to "bind" a little (meaning that they are being compressed more and more, and are resisting that compression, which is why you truck doesnt stay flexed over to one side all the time). When they begin this "binding" they begin to apply more and more force back upon "A" and when the force of "B" matches the force of "A" the vehicle stops twisting, and stays at that point of flex until either more force is applied by "A" or the force from "A" is reduced. I could explain even further how outside forces also affect the physics involved but it gets really lengthy there.

Now heres why a 3 link allows more torque twist than a 4 link. In a 3 link, the upper link, or wishbone, is mounted to the top of the axle at one fixed point via a ball link of some sort. Now, this would allow the axle to spin indefinatly, and freely if it werent for the lower links and the shocks acting against the torque applied by the motor trans.

In a 4 link, the upper two links work in conjunction with lower two links to maintain a more controlled and defined motion. Now lets for example say that the rear axle of our car is climbing over an object known as "C". As the suspension begins to rotate (either by torque from motor, or outside force) the lower links begin motion first, followed by the upper links, and then the springs/shocks begin to apply force to stop this movement (see above). As the outside lower link begins to move, the inside upper link moves with it. Likewise the inside lower link, and outside upper link move to counter them. This movement, countermovement is what helps to manage torque twist.

I said all of that to say this. In a shafty, the only thing that will completly stop all torque twist is to solidly mount the axles to the chassis. You cannot defy physics. You may fiddle with the susp. geometry and that my well help, and you can play around with the springs/shocks and that may help. But you cannot stop ALL torque twist.

damn, got a little extra time^^^. When you do your four link in the rear on the axle's plate mount the left four link above the plate and the right link under the plate.this made all the difference when I setup my slingshot, now she climbs flat as can be

[soundcolor]

nope, i was avoiding changing a dirty diaper :-P

[rock addict]

in that case good work my friend

[ultimate_monkey]

Originally Posted by BMFOTP

I would like to see what your crawler can do on a video. Give me some idea of what I shoud be shooting for in the future.

sure i will try and grab some tonight, i went drinking last night so i am far to shakey to drive and take video lol, my set up is pretty ghetto cuz with the new chassis my massive stick pack ended up being on the back axle, so i can only climb 60* with out just goin over backwards.


soundcooler, thanks for phyiscs it was worth reading about 3 sentences of. i never denided that i had TT forces in play, i said that with proper tuneing you can make the effects so minimal that they dont effect any thing