Crawl speed and rocks

[Wooky]

Suppose this is a "how long is a piece of string" type question..... but here goes.

If we take the crawl ratio out of the discussion and look purely at crawl speed as this takes tyre diameter into account.
What would be a reasonable crawl speed for Carnage Canyon type terrain?

Currently I can chug alone up almost anything at ~1.8km/h in Low 1st and ~750rpm but get the feeling that slower would still be better.

Cheers

W

[Mike Nel]

What would the speed of a winch be? It’s relatively slow and I would use it’s speed as a minimum.

Do we know what speeds those operate at?

[Wooky]

Winch line speed is dependant on load but would be somewhere around an average of 5m/min under load.
That will be 300m/hr.... that's a unimog with double low crawler gears.
Would love that but to be honest would be a bit of overkill in a lightweight SJ410

[Mike Nel]

1.8km per hour is pretty slow

The Crawl Control on the Cruiser runs from 1-5. One being the slowest at 1.6km per hour. It’s pretty damn slow.

What would you want the speed to be?

Maybe increase the tire size one size bigger?

[Wooky]

1.8km/h is pretty slow and she does "walk " through most obstacles quite nicely with the current gearing.
At this speed the motor is only at ~750rpm which means you can't back off on the pedal at all and she will stall.
The places I have felt slower would have been better it would have given just a small measure of better control and made better use of available traction.

I have quite a bit of offroad experience but only recently decided to build up a crawler as a toy, so still figuring out what works and what doesn't.
Not really sure what the speed should be at this point. Obviously as slow as possible but at what point does it become overkill.

Increasing tyre size would have the opposite effect. The larger tyre would have a greater circumference and would give a greater ground speed for the same rotational RPM

[Wooky]

The question of comparing crawl ratios appears to be a problematic one on most forums and so far the best way I thought would be to compare crawl speed, maybe not. After some more googling the net I found this over on an USA ford site.....

They divide crawl ratio by tyre height in inches. This gives a meaningful ratio and allows the comparison of relative "crawl-ability" taking tyre size into account. A crawl-ability ratio of between 1 and 2 is good for general offroading. A ratio of between 2 and 3 is the beginning of good crawl-ability and greater than 3 is true crawler territory.

With this in mind I made up the table below comparing tyre height and crawl ratios worked back from the crawl-ability ratio.... Might be useful to someone. This would be for a manual gearbox.

[Saxj]

The question of comparing crawl ratios appears to be a problematic one on most forums and so far the best way I thought would be to compare crawl speed, maybe not. After some more googling the net I found this over on an USA ford site.....

They divide crawl ratio by tyre height in inches. This gives a meaningful ratio and allows the comparison of relative "crawl-ability" taking tyre size into account. A crawl-ability ratio of between 1 and 2 is good for general offroading. A ratio of between 2 and 3 is the beginning of good crawl-ability and greater than 3 is true crawler territory.

With this in mind I made up the table below comparing tyre height and crawl ratios worked back from the crawl-ability ratio.... Might be useful to someone. This would be for a manual gearbox.

Where does Charlie Brown feature in the table?

[Wooky]

Currently have a crawl ratio of 64:1 on 31" tyres.
That works out to a crawl-ability ratio of 2.06...... so in the bottom end of the intro crawler category.

Would like to go lower

[dawidloubser]

I'd say 1.8km/h is plenty slow for pretty much anything!

I imagine that "no speed is too slow" for a rock crawler, of course, but - to be honest - when it get's *so* slow that people are watching you inch along in slow motion, it also takes some of the fun out of it. There are very few places that *needs* much slower than that, including Carnage Canyon I'd say.

When are we going?

[Wooky]

For 95% of trails around the gearing I have now is perfect.
In the few places I have found some larger rocks to play on I have had to work the clutch a bit to climb the bigger steps but not to badly.
Ultimately would like to go lower still but for now it is working well.

At the moment the SJ is off the road. I have the gearbox stripped to replace the bearings.
How is the Mog repairs / mods going?

[dawidloubser]

For 95% of trails around the gearing I have now is perfect.
In the few places I have found some larger rocks to play on I have had to work the clutch a bit to climb the bigger steps but not to badly.
Ultimately would like to go lower still but for now it is working well.

At the moment the SJ is off the road. I have the gearbox stripped to replace the bearings.
How is the Mog repairs / mods going?

Very well! My mog should be ready for an outing in 2 weeks from now at the most.

Very much on the topic of this thread: No matter how low your gearing, there will be some obstacles in which you have to work the clutch.
Wit the "fast" axles and gearbox in my mog, I've had to work the clutch a great deal, in fact. On a lighter 4x4, this is usually not a problem, and even part of the fun. On a 3.5+ tonne beast like the Unimog, not always fun, and harsh on the clutch.

I managed to find an absolute rarity - a hydraulic torque converter gearbox used in the Unimogs that shunt trains and jumbo jets. Initial tests have been amazing, it's superb for extreme off-road obstacles, because one can have infinitely fine control between 0 and 1 kph. I now understand why people enjoy the torque converter aspect of driving an automatic 4x4 off-road (but mine is a manual, of course - which makes for a slightly strange driving procedure).

Really looking forward to another jol together!

[Wooky]

WOW... that was a good find.
Best of both worlds. Torque converter with a manual box.

I have been toying with going Auto at some point for the extra control you get just off idle.

SAXJ (Vic) will be getting his new Jimny in about 2 weeks so we will need to take it out for a "test"
Will keep you posted if you keen to join in the fun?

[dawidloubser]

WOW... that was a good find.
Best of both worlds. Torque converter with a manual box.

I have been toying with going Auto at some point for the extra control you get just off idle.

SAXJ (Vic) will be getting his new Jimny in about 2 weeks so we will need to take it out for a "test"
Will keep you posted if you keen to join in the fun?

"New" new Jimny? If so, very cool!!
Yes please, do let me know.

[Wooky]

Cool... will let you know once he has confirmation on a delivery date.
It will be at hennops for historical reasons.

[Estee]

This speed seems about right

https://www.youtube.com/watch?v=PB-3M6kV0kA