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by bartonmd » Tue Aug 10, 2010 3:56 pm

JamesDowning wrote:So what's the unit of this metric? If you're bringing tire diameter into it, your unit will be something like 1/inch. When you have units in the metric, it's no longer a ratio.

Essentially the number you're calling the crawl ratio works into this equation:

[Engine Torque (Ft-lb)] x ["Crawl Ratio" (1/inch)] x [12 (in/ft)] = Thrust (lb)

A drive ratio would be purely:

[Engine speed (RPM)] / [drive ratio] = Tire speed (RPM)

Someone correct me if I'm wrong.


[[Engine Torque (Ft-lb)] x ["Crawl Ratio" (1/inch)] x [12 (in/ft)]] / [ 1/2 tire diameter ] = Thrust (lb)

ETA: Wait. You started with a slightly different formula than I did... See my post a couple back.
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by Trail X » Tue Aug 10, 2010 4:01 pm

Right...

Drive Ratio / [ Tire Diameter (in) * 1/2 ] = "Crawl Ratio" ?
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by bartonmd » Tue Aug 10, 2010 4:08 pm

JamesDowning wrote:Right...

Drive Ratio / [ Tire Diameter (in) * 1/2 ] = "Crawl Ratio" ?


Where we're getting off track from "standard" terms is, if the standard linked too above takes tire size into account, it's really more of a "torque ratio" or "thrust ratio" than a "shaft speed ratio", and when people say "I've got a crawl ratio of 42:1", they're just talking about the gearing ratios, and disregarding the tire size. The calculators also call it "crawl ratio", but they take tire size into account.

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by KE7WOX » Wed Aug 11, 2010 2:16 am

JamesDowning wrote:So what's the unit of this metric? If you're bringing tire diameter into it, your unit will be something like 1/inch. When you have units in the metric, it's no longer a ratio.


If you use the same formula but with metric units it should still work (metric units since the beginning, no conversions in the middle)
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by bartonmd » Wed Aug 11, 2010 7:32 am

KE7WOX wrote:
JamesDowning wrote:So what's the unit of this metric? If you're bringing tire diameter into it, your unit will be something like 1/inch. When you have units in the metric, it's no longer a ratio.


If you use the same formula but with metric units it should still work (metric units since the beginning, no conversions in the middle)



There's a TON of other uses for the word "Metric" that don't involve the metric system of measurement. In this case, the metric he's talking about is a number that is a result of a calculation.... or more directly, a "calculation result."

JamesDowning wrote:So what's the unit of this calculation result? If you're bringing tire diameter into it, your unit will be something like 1/inch. When you have units in the calculation result, it's no longer a ratio.


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by glfredrick » Wed Aug 11, 2010 10:50 am

"Crawl ratio" is the standard term in the off-road industry. Better get used to it if you are going to play in the field. :lol:

I'm thinking that some of the bright minds here on the forum are over-thinking some of this stuff. Static, dynamic, crawl, torque ration, metric, etc. No one in the off-road industry would have a clue. :scratch:
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by Trail X » Wed Aug 11, 2010 11:01 am

Just trying to understand the numbers you're reporting. A number without comprehension is just a number.

My truck has a off-road maxion ratio of 520:1 - great, but what does it mean exactly!
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by bartonmd » Wed Aug 11, 2010 11:28 am

glfredrick wrote:"Crawl ratio" is the standard term in the off-road industry. Better get used to it if you are going to play in the field. :lol:

I'm thinking that some of the bright minds here on the forum are over-thinking some of this stuff. Static, dynamic, crawl, torque ration, metric, etc. No one in the off-road industry would have a clue. :scratch:


Guy,

I think where we're getting crossed up here is; the "crawl ratio" number apparently doesn't use tire size in the equation, as seen in the site you posted above. Tire size does matter, but is not in the "crawl ratio" number, according at least to the 4lo site, and everybody I've heard talk about their "crawl ratio."

http://www.4lo.com/calc/gearratio.htm
Image

I guess the metric having to do with the torque ratio dealing with larger tires is some different slang?

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by glfredrick » Wed Aug 11, 2010 12:01 pm

JamesDowning wrote:Just trying to understand the numbers you're reporting. A number without comprehension is just a number.

My truck has a off-road maxion ratio of 520:1 - great, but what does it mean exactly!


Nothing... :coffee2: It will still carry a tire over any off-road sized rock. :poke: :mrgreen:

If you check out the calculators on the grim jeeper site ( http://www.grimmjeeper.com/gears.html ) you will find that all your rpms and miles per hour are also calculated as you input numbers. That, and you can compare side-by-side two different builds, change tire size, gearing, add a doubler, etc., and see what changes in overall performance.

Some of you may be wondering why crawl ratios as low as 100:1 or lower are needed for off-road work. The reason is primarily technical trail or rock work. There are basically two ways to get up an obstacle, blast it and bounce over the top (if you don't first bounce back down or break something in the process) or apply your choice of correct wheel speed to slowly, with max power, place a tire on an obstacle and crawl it.

A T-case doubler (or a 3-speed case like a Stak) offers multiple choices of gearing, similar to a 10-speed bike. You can get higher or lower gearing with a selection, and in the case of a rock or step or other technical trail where side-slipping, spinning, etc., will eventually hurt something or someone, you select a gear that barely turns over the tires. At that extreme slow speed, it is possible to place a tire right against an obstacle and walk it directly up instead of bouncing off repeatedly until something bends or breaks. I've watched this process so many times it hurts... Also, when you get a tire on a big obstacle, you may be able to crawl up and over that obstacle if gearing is low enough. Tires grab best when you barely turn them over (spinning negates all forward motion). We commonly place a lug on a ridge of rock and let the tire go thump ... thump ...thump, until it grabs and pulls you up and over. We then watch the guys that didn't think that gearing and tire size mattered get on the same rock and spin and spin and spin and spin until, "Snap" and their day is over.

Most guys don't end up with doublers or crawl boxes, so they gear for the lowest possible wheel speed, but that eventually hinders some other aspect of the rig, like the time when you are on a clay hill when wheel speed is needed to clean the lugs, or a mud bog area where wheel speed is needed to get through the mud quicky before bogging down. One of my trucks built where mud and sand hills were the norm featured 38" tires with 3.73 gears. That gear ratio (crawl ratio) was stupid, except that in low range, with over 500hp on tap, I could cut loose and literally float on top of whatever I was trying to get through. I had an 85 mph top speed in low range and could "easily" outrun my brother's new 350 IROK Camaro. In my case, I geared the low range for the tallest possible ratio to have maximum tire speed. My max crawl ratio calculates to about 24:1. My Ranger truggy with a doubler (crawl box) calculates to 85:1 low-low, 31:1 in low, and 12:1 in high range. My maximum ground speed with the doubled Ranger will be 335 feet per minute @3000 rpm versus 1200fpm at the same speed from my mud truck.
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by KE7WOX » Wed Aug 11, 2010 12:04 pm

bartonmd wrote:There's a TON of other uses for the word "Metric" that don't involve the metric system of measurement. In this case, the metric he's talking about is a number that is a result of a calculation.... or more directly, a "calculation result."


Ohhhhh.... the metric. I should stop posting after 1AM
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by fishsticks » Wed Aug 11, 2010 5:04 pm

OregTrailBlazin wrote:
Image



If you can figure out a way to make my Trailblazer do this, and not break, you will be elevated to god status.
Last edited by Trail X on Wed Aug 11, 2010 8:11 pm, edited 1 time in total.
Reason: Split the thread hijack - merged it in where it belongs :)
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by OregTrailBlazin » Wed Aug 11, 2010 6:06 pm

fishsticks wrote:If you can figure out a way to make my Trailblazer do this, and not break, you will be elevated to god status.



It's all a matter of finances. I've been over SAS designs with a few different Fab guys. For me it needs to be small still, no more that 35's. And the hardest part we came up with is building a new oil pan either with a remote sump, or just a new shape to gain upward travel. And even that isn't that hard of an obstacle to get over. Its really just a matter of someone having the finances and nuts to just jump in and do it..... `calling hardtrailz :poke: `

As soon as my rig becomes mine, instead of my wife's kid carriage, I'm sure my ambitions towards it will increase quickly!
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by fishsticks » Wed Aug 11, 2010 6:25 pm

OregTrailBlazin wrote:
fishsticks wrote:If you can figure out a way to make my Trailblazer do this, and not break, you will be elevated to god status.



It's all a matter of finances. I've been over SAS designs with a few different Fab guys. For me it needs to be small still, no more that 35's. And the hardest part we came up with is building a new oil pan either with a remote sump, or just a new shape to gain upward travel. And even that isn't that hard of an obstacle to get over. Its really just a matter of someone having the finances and nuts to just jump in and do it..... `calling hardtrailz :poke: `

As soon as my rig becomes mine, instead of my wife's kid carriage, I'm sure my ambitions towards it will increase quickly!


It's just like cars... "How fast does your wallet want to go?"

How about a baffleless pan that's skinny up front with a deeper well in the rear and an extended sump tube? Seems like a simple enough thing to fab up out of sheetmetal. Extended hill descents might be interesting though.

Uh oh. :hijack:
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by Trail X » Wed Aug 11, 2010 8:15 pm

fishsticks wrote:...
How about a baffleless pan that's skinny up front with a deeper well in the rear and an extended sump tube? Seems like a simple enough thing to fab up out of sheetmetal. Extended hill descents might be interesting though.

Uh oh. :hijack:


Just gotta find someone that can TIG well. Then you can use a stock pan - cut off the bottom, keep the mounting bolts and the gasket area. Make sure you keep the same overall volume in the new design.
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by Diacom » Wed Aug 11, 2010 11:34 pm

Odd this hasn't been mentioned already... http://www.atlas-tc.com/

Designed to bolt right on to the transmission, options of 2 speed or 4 speed. Can be clocked to help with rear driveline angle. Can be used with any front output so either drivers or passengers.

Only issue I know of.... get out the $$$.

Seriously, if your going to do SAS and need a transfercase that will give you the gearing you need for your final ratio this is one of the best T-cases you can get.

There is an option for the NV231 and NV241 cases that eliminates the slip yolk on the rear to help with driveline angle also. Not sure if it would work with the T155 (NVG 226) case or not. http://www.offroaddesign.com/catalog/NP241SYEkits.htm
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by bartonmd » Thu Aug 12, 2010 7:29 am

Diacom wrote:Odd this hasn't been mentioned already... http://www.atlas-tc.com/

Designed to bolt right on to the transmission, options of 2 speed or 4 speed. Can be clocked to help with rear driveline angle. Can be used with any front output so either drivers or passengers.

Only issue I know of.... get out the $$$.

Seriously, if your going to do SAS and need a transfercase that will give you the gearing you need for your final ratio this is one of the best T-cases you can get.

There is an option for the NV231 and NV241 cases that eliminates the slip yolk on the rear to help with driveline angle also. Not sure if it would work with the T155 (NVG 226) case or not. http://www.offroaddesign.com/catalog/NP241SYEkits.htm


Clocking helps FRONT driveline angle... Rear driveline angle is in line with the transmission output shaft.

Atlas T-cases are good. My sister had a 4:1 in her krawlin' Jeep on 37x14.50's and 44's (and Detroits F&R)...

An NP205 is stronger, but it's hard to find one with anything more than a 2:1 4LO... A lot of people run a doubler to get a 4:1, but that only really works if you've got the space to run a doubler... If not, there are places who sell 3:1 gear kits for them. This is one I found by a quick Google search: http://www.jbconversions.com/index2.php?pc=3

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by The Roadie » Thu Aug 12, 2010 10:14 am

Years ago I asked Atlas tech support if they'd offer 4-to-1 gears for the NP226. They declined. Well, at least our 2.7-to-1 is better than the usual SUV 2.3-to-1. I always wondered why NP would throw us that bone. Such a small bone, but a bone nonetheless. The 2.7 tantalizingly marginal almost-enough-to-rock-crawl ratio.
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by glfredrick » Thu Aug 12, 2010 12:47 pm

There is a new doubler design that offers merit for the off-road crowd, the "Rubi-Crawler" box. It replaces the factory tailshaft housing on the transmission and offers a planetary gear set to double down without adding any additional length to the package. Same driveshafts, etc. GREAT concept and one that should be capable of duplication on our platform. Just some work to outfit a case with a planetary and a shifting mechanism.

http://advanceadapters.com/product/4341 ... awler.html

With all the 4L60E transmissions out there in 4x4 configuration, we may even talk Advance Adaptors into producing one for us! Should work on any Chevy transmission.
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by glfredrick » Thu Aug 12, 2010 1:24 pm

fishsticks wrote:If you can figure out a way to make my Trailblazer do this, and not break, you will be elevated to god status.


How much money you got for god? :coffee2:

All it takes is some creative welding and a duplication of a Trophy Truck setup. You have to build in about 18" suspension travel, hang a $1000 shock on all 4 corners, do a crossed A-arm front end, beef up EVERYTHING, gut the interier and add a full cage, and it would help to start with an SS platform so you have the required power.

Here are a few vids to wet your whistle:

http://www.youtube.com/watch?v=bQLDLc8M59c
http://www.youtube.com/watch?v=QJKLfRvL ... re=related

Ready for this? Amazing video footage! Imagine keeping up this pace for 12+ hours.
http://www.youtube.com/watch?v=8IpPVFkH ... re=related


Here is about what you can expect from a Trailbazer (with the mods that most of the off-road guys have now):
http://www.youtube.com/watch?v=wanzhebz ... re=related

But, us rock crawler types also like to play...
http://www.youtube.com/watch?v=m7ezoTEa ... feature=iv

A few friends of mine playing around at Disney, OK.
http://www.youtube.com/watch?v=IK1wA8TNcbA

BTW, I made the waterfall and lil blue. :mrgreen:

We've been talking about doublers and gears. Here's what gears will do for ya... :viking:
http://www.youtube.com/watch?v=JFk9yVwV ... re=related
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by bartonmd » Thu Aug 12, 2010 2:01 pm

glfredrick wrote:There is a new doubler design that offers merit for the off-road crowd, the "Rubi-Crawler" box. It replaces the factory tailshaft housing on the transmission and offers a planetary gear set to double down without adding any additional length to the package. Same driveshafts, etc. GREAT concept and one that should be capable of duplication on our platform. Just some work to outfit a case with a planetary and a shifting mechanism.

http://advanceadapters.com/product/4341 ... awler.html

With all the 4L60E transmissions out there in 4x4 configuration, we may even talk Advance Adaptors into producing one for us! Should work on any Chevy transmission.


THAT is AWESOME!

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