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TTMax



Number of posts : 180
Registration date : 2006-11-06

PostSubject: RTI   Thu Nov 09, 2006 5:24 am

RTI - RAMP TRAVEL INDEX

ou

ÍNDICE DE PERCURSO EM RAMPA










O índice RTI é o único sistema reconhecido internacionalmente para avaliar o
curso de uma suspensão.
O conhecido "cruzamento de eixos" depende exculsivamente do curso
da suspensão.

Para calcular o RTI de uma viatura existem três processos:
- a rampa de 20º
- a rampa de 30º, ou
- um monta cargas para levantar uma das rodas.


A RAMPA DE 20º


Para calcular o RTI com uma rampa faremos o carro subir com uma das
rodas até que outra perca o contacto com o solo.
Este ponto deve ser confirmado introduzindo uma chapa fina entre a
roda que perdeu a aderência e o solo, recuar o veículo até que a chapa
não se possa mover manualmente.
Determinado este ponto mede-se o percurso da roda na rampa, divide-
se pela distância entre eixos e multiplica-se por 1000.

RTI = (L/D)x 1000

sendo
    L - distância percorrida pela roda na rampa
    D - distância entre eixos do veículo

Quanto mais o RTI se aproxima de 1000 melhor será o desempenho da
suspensão em situações extremas. O ideal seria 1000 e nenhum veículo
de série se aproxima deste valor.


A RAMPA DE 30º

Alguns veículos preparados superam os 1000 pontos de RTI.
Foi para estes veículos superdotados que se criou a medição em rampa
de 30º. Este tipo de medição só é usado para profissionais.





O MONTA CARGAS



Este sistema até pode ser mais prático no caso de não dispormos de
uma rampa.
Para fazermos o cálculo com um sistema elevatório precisamos de um
plano nivelado.
De seguida elevamos uma das rodas até que a outra perca contacto
com o solo que deve ser confirmado com o método descrito para a
rampa.
Para efectuar o cálculo medimos a distância da roda ao solo em
centrimetros, dividimos por 0,342. Divide-se o valor obtido pela distância
entre eixos e multiplica-se por 1000.

RTI = ((H/0,342)/D) x 1000

sendo H - altura da roda ao solo
D - distância entre eixos

A título de curiosidade aqui fica uma tabela com valores RTI de vários
veículos de série


Links sobre o tema:
RTI
http://www.bc4x4.com/features/1999/rti/rti.cfm#rti
http://www.erau4x4.com/TheRamp.html
Projecto de rampa
http://www.landroverclub.net/Club/HTML/RTI.htm
Calculador
http://www.4lo.com/calc/rticalc.htm
http://mark.legendz.com/ramp.html
Suzuki e RTI chalange
http://www.off-road.com/suzuki/tech/btire.htm
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zeca4x4



Number of posts : 422
Localisation : Lx
Registration date : 2006-11-09

PostSubject: Re: RTI   Tue Nov 14, 2006 9:37 am

Aqui ficam alguns valores retirados da Four Wheeler Magazine.
É pena que sejam de veículos Americanos mas também tem alguns dos nossos.
Atenção que o Sidekick é o Vitara.

'96 Acura SLX: 506
'93 AM General Hummer: 385
'92 Chevrolet S-10 w/Rugged Trail 3.5-inch lift: 351
'81 Chevrolet K-5 Blazer: 653
'81 Chevrolet K-5 Blazer w/Rugged Trail 2.5-inch lift: 695
'92 Chevrolet K-1500 Blazer: 453
'92 Chevrolet K-1500: 421
'92 Chevrolet K-2500HD turbo diesel: 365
'92 Chevrolet K-3500 Crew Cab dually: 303
'94 Chevy S-10 ZR2: 420
'94 Chevy K-2500 Suburban: 401
'95 Chevy ZR2 Extended Cab: 336
'95 Chevy Blazer 2-dr:. 405
'96 Chevy K-1500 extended-cab: 376
'96 Chevy Tahoe LS: 433
'92 Dodge Ramcharger: 613
'92 Dodge Dakota Club Cab: 393
'92 Dodge W150: 526
'92 Dodge W250 Cummins: 372
'92 Dodge W250 Cummins w/Natl. Spring 3-inch lift: 406
'94 Dodge Ram 1500: 556
'95 Dodge Ram BR2500 Club Cab: 431
'92 Ford Explorer 4-dr.: 460
'92 Ford Explorer 4-dr. w/Superlift 4-inch lift :492
'92 Ford Bronco: 516
'93 Ford Ranger SuperCab: 416
'92 Ford F-150 Flareside: 471
'92 Ford F-150: 484
'92 F-350 Crew Cab w/Mac's Spring Shop 2-inch lift: 405
'94 Ford Ranger SuperCab: 406
'94 Ford Explorer Limited 4-dr.: 443
'94 Ford F-250 SuperCab: 383
'95 Ford F-250 SuperCab: 406
'95 Ford Explorer 2-dr.: 391
'95 Ford Explorer 4-dr.: 352
'97 Ford F-150 SuperCab: 441
'92 GMC Sonoma: 354
'93 GMC Sonoma Club Coupe: 334
'92 GMC K-1500 Suburban: 342
'92 GMC K-3500 Crew Cab: 338
'95 GMC K-1500 Club Coupe: 387
'95 GMC Jimmy 4-dr.: 371
'93 Isuzu Rodeo LS: 435
'92 Isuzu Trooper LS 4-dr.: 497
'93 Isuzu Trooper LS 2-dr.: 508
'93 Isuzu Trooper RS 2-dr.: 529
'94 Isuzu Rodeo LS: 454
'96 Isuzu Rodeo: 464
'75 Jeep DJ-5D: 556
'92 Jeep Cherokee 4-dr.: 399
'92 Jeep Grand Cherokee: 458
'93 Jeep Grand Cherokee: 448
'93 Jeep Grand Cherokee: 439
'96 Jeep Grand Cherokee: 422
'96 Jeep Wrangler: 357
'96 Jeep Wrangler w/Pro-Comp 2.5-inch lift:532
'97 Jeep Wrangler:532
'96 Kia Sportage: 471
'94 Land Rover Defender 90: 580
'95 Land Rover DIscovery: 588
'94 Mazda B4000 Cab Plus: 409
'92 Mitsubishi Montero 4-dr.: 391
'92 Nissan Pathfinder: 511
'96 Nissan Pathfinder: 466
'92 Oldsmobile Bravada 4-dr.: 411
'92 Range Rover County: 670
'93 Range Rover County LWB: 588
'96 Range Rover 4.0SE: 600
'92 Suzuki Sidekick 4-dr.: 379
'96 Suzuki Sidekick Sport: 440
'96 Suzuki X-90: 441
'93 Toyota 4Runner:441
'93 Toyota Land Cruiser: 593
'93 Toyota T100: 407
'95 Toyota T100 XtraCab:369
'96 Toyota Tacoma: 435


Last edited by zeca4x4 on Tue Oct 28, 2008 6:31 am; edited 1 time in total
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TTMax



Number of posts : 180
Registration date : 2006-11-06

PostSubject: Re: RTI   Sun Feb 25, 2007 9:59 am

1º Evento RTI 2007 em Portugal



Graças às organizações André Simao http://www.rotasesistemas.com/andresimao/index.htm e à Rotas e Sistemas http://www.rotasesistemas.com/ temos nos próximos dias 2,3 e 4 de Março o primeiro evento RTI de 2007 na Expo Evasão em Oeiras.

A rampa patricinada pelas organizações André Simão está presente no evento e á disposição de todos os interessados graças à carolice do nosso amigo Rui Simão.

Encontra-se à disposição de todos os interessados podendo a sua utilização ser solicitada à organização do evento ou através do Fórum Suzuki. www.forumsuzuki.com

Participem e apareçam para testar as vossas máquinas ou simplesmente para assistir aos testes das viaturas que vão subir a rampa.
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zeca4x4



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PostSubject: Re: RTI   Wed Jun 13, 2007 5:40 pm




Tal como no evento anterior a rampa volta a marcar presença na grande festa do 4x4.

Montijo 22 a 24 de Junho
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zeca4x4



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PostSubject: Re: RTI   Mon Nov 03, 2008 7:20 pm

RTI Ramp Information and Calculations
By Steve Henderson

The information found in RTI history was borrowed from sources on the web, conversations, email, discussions and memory so I take no responsibility for it's accuracy. This is always open for revision or improvement so if you see anything wrong or would like to add anything please email the webmaster.


RTI Ramp History
It's believed that the RTI ramp was originally designed by Four Wheeler magazine, for what purpose I'm not sure, but all the information I can find seems to point to it's use to measure a rigs capability. RTI stands for Ramp Travel Index, which is basically a percentage of your wheelbase. The RTI ramp serves two basic purposes, bragging rights and testing. RTI scores have become a measure of how capable your rig is on the trail. The higher the RTI score the better your rig should be on the trail, in theory, and the more bragging rights you have. A RTI ramp is also a great way to max out your suspension to determine if new modifications made an improvement, how much of an improvement, check for binding, rubbing, make sure things, like brake hoses, aren't going to break on the trail, etc. I prefer it's use for the latter, but RTI ramp competitions can be alot of fun. The original ramp standard was a 20 degree ramp, but with the advances in suspension design and technology we are seeing an increase in ramps that are 23, 25, and 30 degrees. The Katy chapter ramp is a 25 degree ramp.

RTI Ramp Competition Rules
The rules here are to ensure fairness and equality for all rigs when competing for the Ramp King title!!!

Tire pressure must be equal in all four tires.

Shocks must be mounted.

No scoring on ramping in reverse.

No "riding the rail". You must travel up the center of the ramp.

RTI Ramp Measurements
There are several methods of taking RTI ramp measurements, but we prefer to measure from the bottom of the tire on the centerline of the hub to the ground.

RTI Scoring
As with measuring there are several methods of scoring. The method we chose can be applied with or without a RTI ramp. If you have access to a forklift, neighbors brick wall, or other method of lifting one tire off the ground then you can use the following formula to determine your RTI score on any degree ramp. You'll need two measurements to calculate your score, the wheelbase of vehicle from the center of the front axle to the center of the rear axle and the distance from bottom of tire raised off the ground to the ground.


in: http://katy.tx4wd.org/tech/rtirampinfo.htm

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zeca4x4



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PostSubject: Re: RTI   Mon Nov 03, 2008 7:51 pm

Ramp travel index
From Wikipedia, the free encyclopedia
Jump to: navigation, search

RTI ramp
Modified Jeep ramping an RTI rampRamp travel index or RTI, is a way of measuring a vehicle's ability to flex its suspension, a property also known as axle articulation. The RTI rating is used mainly in the off-roading industry to test and describe chassis limits of modified vehicles.

The ramps vary between 15-30 degrees of angle for the vehicle to ride up. "Ramping" a vehicle involves putting one tire on the ramp and driving up slowly until one of the other three tires (usually the rear one on the same side as the tire driving the ramp) begins to leave the ground. The measurement is only taken when the other three tires are still on the ground. The distance traveled up the ramp is then measured and is divided by the vehicles wheelbase and finally multiplied by 1000 to give a final RTI score[1]. Most stock SUVs have RTI values from 400 to 550[2]; vehicles modified for off-road competition have the ability to exceed 1000[3].

Contents [hide]
1 Significance of RTI and Axle Articulation
2 Calculating RTI
2.1 With a ramp
2.2 Without a ramp
3 See also
4 References



[edit] Significance of RTI and Axle Articulation
A high RTI or good axle articulation is essential for good off road performance on severe routes. A vehicle that has good axle articulation can keep all wheels in contact with the ground while traversing obstacles, which ensures that all wheels can deliver their torque to the surface with less risk of losing traction on any given wheel. All this can allow a very high level of off-road performance without the need for electronic chassis control systems that can be vulnerable and unreliable under extreme conditions.

Over a given obstacle, vehicles with simple AWD systems and chassis designs that restrict their RTI--i.e. that have poorer axle articulation--lift a wheel early which is then free to turn spinning away power unless differentials are able to be locked. A vehicle with high RTI tends to make uninterrupted (safer) progress as all wheels remain in contact with the ground during the maneuver. One chassis concept that often allows comparatively high RTI is the live axle (beam axle). Independent suspensions have tended to have reduced articulation while offering better on-road comfort, and are becoming increasingly popular in road-oriented SUVs.


[edit] Calculating RTI

[edit] With a ramp
The formula for calculating RTI using a ramp as pictured above is



Where b is the wheelbase of the vehicle, d is the distance travelled along a (usually 20 degree[4]) ramp before any wheels leave the ground and r is the calculated ramp travel index.


[edit] Without a ramp

"Ramping" a 2003 4Runner without a ramp.
RTI calculation diagram.It is possible to calculate RTI without a ramp using basic trigonometry, provided a safe method is available to lift one wheel, say, using a forklift. Using the diagram below, if h is the maximum distance from the bottom of the tire to the ground, then[5]



Although d is not an available measurement, we can use the relationship between h and d to express d in terms of h:



Substituting this into the RTI formula produces:



This yields a convenient formula for calculating a 20° RTI value when no ramp is available. If b is the vehicle's wheelbase and h is the maximum distance from the ground to the bottom of the wheel without allowing any other wheel to leave the ground, then

in: http://en.wikipedia.org/wiki/Ramp_travel_index

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zeca4x4



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PostSubject: Re: RTI   Mon Nov 03, 2008 7:56 pm

Offroaders

RAMP TRAVEL INDEX / RTI
The term RTI stands for Ramp Travel Index. Ramp Travel index is a measurement of a vehicles suspension, frame and tire compression and the resulting flexibility of all components of the vehicle to achieve a score. This standardized test uses a ramp to find the extreme flex point of the vehicle.

The RTI test is a good indicator of how well a vehicle will do in many situations offroad while traveling over an obstacle. Ideally a vehicle will do better if it is able to keep all wheels on the ground for maximum traction. If a vehicle's suspension is too stiff (less flex), it generally will lift a wheel or possibly two wheels while attempting to get over an object resulting in a loss of contact and traction at those lifted wheels. Loss of traction is especially apparent with vehicles equipped with open differentials. In situations requiring a lot of flex locking differentials and some limited slip differentials will help maintain momentum with the opposite wheel of the axle (front or rear), however good flexibility results in more wheels on the ground, better traction and better stability of the vehicle as the suspension conforms to the terrain.





At many shows and offroad events, you may have seen 4x4's taking a shot at the ramp. While the ramp itself is fun to challenge, it does have it's useful points as a valid test. The ramp can tell you a lot about your overall flex and is very useful in evaluating suspension, examining the length of your shocks and finding contact and interference points of components and other things all of which can give you insight into a vehicles capabilities on the trail under extreme flex. Several factors make up the score on the RTI ramp. These factors include the ramp itself, the length of the vehicle's wheelbase measured centerline of front axle to centerline of rear axle, and the distance traveled up the ramp without lifting a tire off the ground. In most cases the ramp used is a 20 degree ramp. Some events use a ramp with a more extreme angle such as a 23 degree ramp. The test proceeds as the vehicle attempts to climb the ramp as high as possible with a single front or rear tire without lifting a wheel off the ground. The distance the vehicle can travel up the ramp without loosing contact with the ground is measured from the leading edge of the ramp itself to the point on the ramp just below the center of the hub of the wheel on the ramp. The distance is measured up the ramp and on the ramp, not to the actual hub of the wheel. That number is the divided by the vehicles wheelbase and then multiplied by 1000 to calculate the average. For example if a vehicle with a 81 inch wheelbase traveled 59 inches up a 20 degree ramp then the RTI would be calculated as: 59 divided by 81 x 1000 = 728 (rounded down). This method of multiplying by the vehicle's wheelbase allows vehicles of different wheelbases to compete with each other on the same ramp.

Although you can't "cheat" on the ramp, you can optimize your score on the ramp and in the process improve your vehicles ability to flex and maximize traction over terrain. One of the easiest things that you can to do to improve your score somewhat, which translates into improved traction offroad, is to air down your tires. Airing down means to reduce the air pressure in the tires to the point where the tire is more likely to conform to the terrain. Airing down to approximately half the recommended maximum PSI of the tire will allow a small gain on the ramp. More noticeably, "airing down" will improve offroad driving in the form of better traction, a smoother ride over harsh bumps and allowing the tires to conform over obstacles resulting in better grip. How much you air down may depend of several factors. Some people air down as low as into the single digits however this can result in bead separation. As a result bead locks are sometimes used to secure the tire bead to the rim. Also smaller tires with a short profile aired down too low can suffer damage to the tire and rim such as tire pinch on the rim or a bent wheel rim. Generally speaking extreme low pressures are usually reserved for large tires equipped with bead locks and in many cases bias ply tires are the preferred tire as they are more durable at low pressures. Another factor for how low you go is whether you are equipped to air back up when you leave the trail ... or the ramp. Obviously if you are not able air up, don't air down. It is important to always bring your tire pressure back up to the recommended PSI for highway driving to avoid damage to the tire or loss of control while driving.

Another factor that can improve your ramp score and improve the offroad ride with leaf sprung suspensions is to grease between the leafs in the leaf spring pack. Without grease leaf springs in the pack tend to bind together and resist flexing. Vehicles equipped with sway bars can greatly improve ramp travel by disconnecting the swaybar from the axle or suspension. The swaybar is designed to limit wheel travel from one side to the other. Most vehicles have a front swaybar, some have one in the front and in the back. Many aftermarket vendors sell swaybar quick disconnects. Disconnecting the swaybar will again, not only improve your ramp travel index score but also improve your articulation off-road resulting in better traction and a better ride offroad. Always be sure to re-connect your swaybar(s) before hitting the road again. With leaf sprung suspension, another aftermarket product designed to improve articulation is compound shackles such as the Revolver Shackles and obviously better suspension all together will improve RTI as well as off-road performance.


Measuring your RTI Score
Without a Ramp

If you want to find out your RTI score but you don't have a ramp, you can find out what your RTI would be if you were on the ramp. Given that the RTI score is simply mathematics it can therefore be measured and calculated without a ramp. At it's core the RTI score is a measurement of how high a tire can travel vertically before another tire is lifted off the ground. The challenge is to safely raise one of the tires until one of the other tires almost comes off the ground but still has contact with the ground. How the tire is safely raised depends on your resources but some people use a forklift with the tire resting on a strong pallet or they use a floor jack with the tire resting on a flat surface on the jack. Be sure to do this safely. Placing jack stands under the vehicle as it is jacked is one way people secure the raised vehicle. The main objective is to raise one wheel as high as possible before lifting a tire off the ground. Once the vehicle is raised to that point, measure the distance between the bottom of the tire and the ground.

If using a fork lift you would measure where the tire meets the pallet to the floor. With this measurement you calculate the score like this: Since a 20 degree ramp rises at .345 inches per inch of travel, divide the height of the lifted tire by .345 (for 20 degrees). Then divide that number by your vehicles wheelbase. Multiply that number by 1000. The result is your RTI score on a 20 degree ramp. While the ramp is a true measurement of your RTI this calculated method is pretty close. The calculator below does the math for you and allows for different ramp angles

in: http://www.offroaders.com/info/tech-corner/rti.htm

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zeca4x4



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PostSubject: Re: RTI   Mon Nov 03, 2008 8:02 pm



Ramp Calculations:

Finding RTI score from tire height
If you do not have a 20 degree ramp, but have some other way to get a wheel up in the air (such as a forklift).

(1/sin(20) * Wheel height) / Wheelbase * 1000

for example, If I get a wheel 23 inches high:

1/sin(20) = 2.924

(2.924 * 23) = 67.247

67.247 / 92in * 1000 = 730 RTI Score



Converting a score from a 20 degree ramp
to a 30 degree RTI score

20deg score * sin(20) / sin(30)

and

sin(20) / sin(30) = 0.781

Therefore:

20 deg score * 0.684 = 30 deg score

For Example, If my 20 deg RTI score is 1000

1000 * 0.684 = 684 RTI score on a 30 deg ramp



Converting a score from a 30 degree ramp
to a 20 degree RTI score

20deg score * sin(30) / sin(20)

and

sin(30) / sin(20) = 1.462

Therefore:

30 deg score * 1.462 = 30 deg score

For Example, If my 30 deg RTI score is 1000

1000 * 1.462 = 1462 RTI score on a 20 deg ramp


in: http://4wheeldrive.about.com/gi/dynamic/offsite.htm?zi=1/XJ/Ya&sdn=4wheeldrive&cdn=autos&tm=67&gps=110_680_1020_621&f=00&tt=14&bt=1&bts=1&zu=http%3A//www.broncohio.com/tech/calculations.html

http://4wheeldrive.about.com/od/calculators/Online_Auto_Calculators_How_To_Do_Off_Road_4x4_Vehicle_Calculations.htm

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