Outer Limits 4x4 Board

we are goin to build a travel ramp between a couple of clubs down here to use for fun days etc and were wondering wat deg it is supposed to be???

thanks Ray

22 or 30 are the normal ramp angles I think.

Cheers
Steve

I thought it was 20 or 30.

Slunnie wrote:I thought it was 20 or 30.

x2

I thought it was 22.5 degrees - half of 45 degrees?

30deg is the go

i thought it can be anything.

your using a maths equation anyway to generate your RTI score.

stu wrote:i thought it can be anything.

your using a maths equation anyway to generate your RTI score.

Yep, that's what I thought too. I have seen everything between 20deg and 30 deg.

yer i did think it could be anything..

i reckon i'll go 30deg...

and for another question.. wat is the equation to work out ur RTI?

Ray, ive already got all the steel cutup for a ramp myself, and was told to go 30.

Ulises

udm wrote:Ray, ive already got all the steel cutup for a ramp myself, and was told to go 30.

Ulises

kewl.. u got any ideas wat the formula is to work out the rti??

If you are building the ramp for 'fun club stuff', I would go a lesser angle... say 20 or 23degrees. Much easier for novice or first timers... and they can actually make a reasonable amount of headway up the ramp.

If you are building a ramp to handle big built trucks, go 30 degrees... otherwise you will run out of ramp!

RTI is simply the distance up the ram divided by the wheelbase... and multiplied by 1000 usually. So if you go as far up the ram as your wheelbase, you score 1000. If you go less than your wheelbase up the ramp you score less than 100, etc.

It's a relative measure, but if you want to convert them you can. ie. measure on a 23 degree ramp, then convert to the equivalent of a 30 degree ramp.

S.

RTI = H/sin(A*pi/180)/W*1000
D = H/sin(A*pi/180)

H = height of tyre (on ramp) above ground
A = angle of ramp
D = distance travelled along ramp
W = wheelbase

Length units must be consistent (all " or all cm, etc)

ISUZUROVER wrote:RTI = H/sin(A*pi/180)/W*1000
D = H/sin(A*pi/180)

H = height of tyre (on ramp) above ground
A = angle of ramp
D = distance travelled along ramp
W = wheelbase

Length units must be consistent (all " or all cm, etc)

umm thanks..


can u put it in english now please

crankycruiser wrote:

ISUZUROVER wrote:RTI = H/sin(A*pi/180)/W*1000
D = H/sin(A*pi/180)

H = height of tyre (on ramp) above ground
A = angle of ramp
D = distance travelled along ramp
W = wheelbase

Length units must be consistent (all " or all cm, etc)

umm thanks..


can u put it in english now please

You wanted the formula - do you need a lesson on how to use a calculator?

crankycruiser wrote:
ISUZUROVER wrote:
RTI = H/sin(A*pi/180)/W*1000
D = H/sin(A*pi/180)

H = height of tyre (on ramp) above ground
A = angle of ramp
D = distance travelled along ramp
W = wheelbase

Length units must be consistent (all " or all cm, etc)


umm thanks..


can u put it in english now please


You wanted the formula - do you need a lesson on how to use a calculator?

im a dumb a$$ boiler maker and it works fine on my calculator.

...very complicated way of saying:

RTI = (distance up ramp / wheelbase)*1000

S.

FireTruck wrote:...very complicated way of saying:

RTI = (distance up ramp / wheelbase)*1000

S.

Yes but it corrects for different ramp angles. Your formula is fine if you want to compare vehicles on the same ramp.

um... no, it doesn't correct for the angle.

The formula D = H/sin(A*pi/180) is simply converting the height off the ground to the distance up the ramp... as in:

Sin (angle) = opposite / hypotenuse

So converting that to find the hypotenuse (or distance up the ramp), you have to take:

hypotenuse = opposite/sin(angle)

In your case the opposite is the distance off the ground, and the angle is the ramp angle. The angle has to be in radians though, so to convert to radians you have to multiply by pi/180

Soooo.... it does not correct for the angle, it simply uses the angle to calculate the distance up the ramp.

You can do the same thing by actually measuring the distance up the ramp... no calculator required.

S.

FireTruck wrote:um... no, it doesn't correct for the angle.

The formula D = H/sin(A*pi/180) is simply converting the height off the ground to the distance up the ramp... as in:

Sin (angle) = opposite / hypotenuse

So converting that to find the hypotenuse (or distance up the ramp), you have to take:

hypotenuse = opposite/sin(angle)

In your case the opposite is the distance off the ground, and the angle is the ramp angle. The angle has to be in radians though, so to convert to radians you have to multiply by pi/180

Soooo.... it does not correct for the angle, it simply uses the angle to calculate the distance up the ramp.

You can do the same thing by actually measuring the distance up the ramp... no calculator required.

S.

All of this just to be a farkin ramp queen

FARKKKKKK i didn't realize you had to have a whirlybird hat to work out the winner on a Travel RAMP i thought those equations were just to piss people off in school

You don't... that's what I'm trying to say.

You measure your wheelbase, and how far up the ramp you go, then divide one by the other.

If you measure the RTI on a 20 degree ramp, then want to see what it would be on a 30 degree ramp, THEN you have to use some math.

OR, if you lift your tire up with a fork lift you can measure how far off the ground it ends up and then convert that into an RTI at a given ramp angle... you need to do some math.

The RTI is depndant on the angle of the ramp... an RTI of 1000 on a 30 degree ramp is equivalent to an RTI of 1280 on a 23 degree ramp, and 1462 on a 20 degree ramp.

S.

IF maths is not your forte, than this may be easier:

http://www.snakeracing.com.au/2001/rticalculator.shtml

The FIRST formula I posted (you quoted the 2nd) does correct between ramp angles, and gives the same results as you posted.

FireTruck wrote:um... no, it doesn't correct for the angle.

The formula D = H/sin(A*pi/180) is simply converting the height off the ground to the distance up the ramp... as in:

FireTruck wrote:
The RTI is depndant on the angle of the ramp... an RTI of 1000 on a 30 degree ramp is equivalent to an RTI of 1280 on a 23 degree ramp, and 1462 on a 20 degree ramp.

S.

Dude - it doesn't correct for the ramp angle - it USES the ramp angle to calculate the distance up the ramp... which you can easily measure rather than using a complex calculation and confusing everyone (like I will now).

It is simple trig...

Sorry everyone - please change the channel now...

sin(angle) = opposite / hypotenuse

The angle is the ramp angle, the opposite is the distance of the tire from the ground, the hypotenuse is the distance up the ramp... if you were to complete the triangle, the 'adjacent' would be the distance along the ground to the point directly under the tire.

The only time you need to use this math is if you don't have a ramp at all... if you have a ramp you can just use a tape measure.

Here is your original formula...

RTI = H/sin(A*pi/180)/W*1000

H = height of tire off ground
A = ramp angle
D = distance travelled up ramp

and D = H/sin(A*pi/180)

soooo, you can either measure D with a tape measure (along the ramp), or calculate D by measuring H (the height of the tire off the ground) then using the (complicated) formula to calculate D... why bother? You have to measure once anyway, why not just measure D???

If you measure D with a tape measure, your formula becomes (by simply substituting your second formula):

RTI = D/W*1000

...look familiar??

To be clear(?), the math is correct... but overly complex and not needed for a simple ramp day kind of a thing. It doesn't correct for the ramp angle, it uses the ramp angle to calculate the distcnce up the ramp. The original question was about someone building a ramp, who wanted to know "what's the formula to measure the RTI"... you don't need to take the sin of angles etc to calculate an RTI on a given ramp - you just need a tape measure and you can do a simple calc on your phone to divide a couple of numbers.

When do you NEED to use this math?? If you don't have a ramp at all and you are just picking your tire up with a fork lift. Or, if you have a 23 degree ramp and you want to compare (not correct, compare) your score to the 30 degree ramp from Tuff Truck... then you use the math to calculate what your RTI would be on a different ramp angle.

Sorry all, I'm done now... too much high school math for 1 week.

S.

RTI should take the width of a rig into consideration aswell (wider track will go further up the ramp) Work that into the formula

Hey Professor, thats what we do. We take normal RTI as in distance up ramp/wheelbase, but we add another score which is basically the distance between the centres of the wheels across each other. Like in distance between front left and rear right and then divide this into distance up ramp. Makes some of the narrower vehicles look better compared to the really wide comp trucks.

Freakazoid wrote:Hey Professor, thats what we do. We take normal RTI as in distance up ramp/wheelbase, but we add another score which is basically the distance between the centres of the wheels across each other. Like in distance between front left and rear right and then divide this into distance up ramp. Makes some of the narrower vehicles look better compared to the really wide comp trucks.

Little more level playing field.

that would make the wheel base look longer for the wider trucks.

crankycruiser wrote:we are goin to build a travel ramp between a couple of clubs down here to use for fun days etc and were wondering wat deg it is supposed to be???

thanks Ray

If it's for a club, Id make it 23 degree's, if you have any standard 4wds in the club they will be lucky to drive a couple of feet up a 30 degree ramp, some new 4wds don't even have a 30 degree approach angle.

Well thanks 4 all the input guys..

im gunna make it 23deg and long enuf so the decent trucks dont drive off the end of it

Ray