rti ramp- need help building one; specs please

[RydeFab]

need some help from you guys.......we're going to be starting our scale class this up coming season and i was thinking about making an RTI ramp for the comps. need some of your help with the specs on making the ramp. i understand the ramp is 30 degress but i need info on the scoring. i know that according to UTRCRC's rules that the rigs cannot score no more than 500 on the ramp. "500"............how does this score affiliate with how high you go up the ramp. any help on this matter is greatly appreciated, thanks alot .

[YoUnG_vErSiOn]

for 1:1 scale you take 3' and 30 degrees . Ryde i made one already.its kinda small though i'll give it to you, so you kinda have an idea.

[RydeFab]

shoots, thanks .................now just the scoring part is all i need to be explained to me .

[Grizzly4x4]

The "500" you refer to is the Ramp Tavel Index (RTI). A vehicle drives up the ramp, when a tire begins to lift off the ground it must stop.

From the center of the wheel (the one on the ramp) use a straight edge placed perpindicular to the ramp's surface to find the measurement point on the ramp. Then measure from the start of the ramp (where it meets the ground), up the surface of the ramp, to the point you found.

If a rig drives 7" up the ramp and it has a 12" wheelbase, the RTI is found by:

(7/12) x 1000 = 583

[1BadJeepBruiser]

May want to hit up colquittcustoms/DJ had a sick RTI ramp in MOAB, Im sure he can supply better pics for you to build your own His was awesome because it was adjustable, it was good for 1.9s and even bigger scale trucks like JIA ralph tuber

[Grizzly4x4]

Here's an illustration of how to measure.

[TunaMaxx]

Originally Posted by o5tacoma

how does this score affiliate with how high you go up the ramp.

The score is a ratio of distance traveled along the ramp divided by your wheelbase. Then multiply that by 1000.

I made this illustration of the rules as I understand them. Maybe it will help:

[TunaMaxx]

Oops... look like others responded bevore me while I was making the illustration.

[Grizzly4x4]

Tunamaxx, your measurement should be to the red circle, not the green circle.

[TunaMaxx]

Originally Posted by Grizzly4x4

Tunamaxx, your measurement should be to the red circle, not the green circle.

The illustration is based off my interpretation of the rules I found at UTRCRC that 05tacoma stated in his first post.

I've seen it measured both ways, as each has it's advantages. Measuring at the contact patch makes for higher RTI numbers, but leaves the exact measurement open to interpretation depending how much tire bulge their is, etc. Measuring at the axle center line results in lower numbers, but removes much of the fudge factor from the measurement.

Mind you, this is from back in the day with 1:1 rigs, but that was quite some time ago now and a more standard approach may have been accepted.

[RydeFab]

thanks alot guys, now i understand . i appreciate even the illustrations and photos that you guys took the time to post. HRCC and i really appreciate it ....................now it's off to the "shop", gots me a ramp to make . thanks again.

[Grizzly4x4]

Using that measurement system a vehicle can't score an RTI of 1000 without driving the rear tires up the ramp.

Using my illustration below and the other method, the distance traveled up the ramp is equal to the wheelbase when the rear tire is right at the bottom of the ramp. This is how the measurement was intended to be since it is a ratio of ramp travel to wheelbase.

The UTRCRC guys think only 1.9 wheels are scale so their judgement is suspect anyway.

[Grizzly4x4]

Originally Posted by o5tacoma

thanks alot guys, now i understand . i appreciate even the illustrations and photos that you guys took the time to post. HRCC and i really appreciate it ....................now it's off to the "shop", gots me a ramp to make . thanks again.

Post pics when it's done.

[TunaMaxx]

Originally Posted by Grizzly4x4

Using that measurement system a vehicle can't score an RTI of 1000 without driving the rear tires up the ramp.

Touché!

I don't ever remember anything other than attacking the ramp with the rear positioned beside it though, but you are right.

Now that I am thinking about it, I remember a ramp from years ago that had a slider built into the side of A 1:1 ramp. It allowed a bar (that was held perpendicular to the ramp surface) to be slid back and forth to find the center of the wheel.

I have redone the original illustration in my first post to show that it is UTRCRC rules. Then I created the following which should be more in line with yours:

The UTRCRC guys think only 1.9 wheels are scale so their judgement is suspect anyway.

I'd never heard of them until 05tacoma's first post!