Testing the new snorkel pipework – Wombat state forest

Dedman

Dedman

Forum Member
Joined
Dec 3, 2012
Messages
766
Location
Perth Western Australia
Car Year
1999
Car Model
Forester
Transmission
5MT
I decided to drive one of my favourite bog hole tracks in the wombat today to test out my changes to the snorkel. It had been a while since I had driven the track and it had been cut up by the big fourbys quite a bit.
The first hole I came to I checked the depth and decided I would need a little bit of momentum to get through the first section as the ruts were quite deep. Turns out I didn’t need quite that much momentum.

[ame="https://www.youtube.com/watch?v=5MjCzHpcpfM"]www.youtube.com/watch?v=5MjCzHpcpfM[/ame]

The good news is that my snorkel worked perfectly despite most likely getting some water down it. Also my carpet was perfectly dry when I got out as well which is great.

Took videos of a couple more holes which I took a bit more slowly than the first.

[ame="https://www.youtube.com/watch?v=-MpWuS7u4cg"]Subaru Forester Off Road - Wombat bog hole in winter - YouTube[/ame]

[ame="https://www.youtube.com/watch?v=ThWCsGXoGrg"]Subaru Forester Off Road - Wombat bog hole in winter 1 - YouTube[/ame]

All in all it was a fun little trip and the forester did surprisingly well considering the semi baled road tyres.
 
I just found a picture on facebook of a mate with a lifted 60series cruiser with muddies stuck (being snatched out) in that first bog hole. Subaru for the win!
 
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Interesting. The car pretty much stopped in the first part of that hole in the first video, so I think you are right about not needing so much momentum. Having a winch is surely a fair bit of peace of mind. I think it is these conditions where good diffs would be of most use. So, if you give me your snorkel and winch I should be looking half alright! The little Subaru trumps the big guys once again!
 
I saw that 60 series to, he looked like he'd taken the worse line possible.

Do you know if you search for subaru offroad videos on youtube most of the results are yours :rotfl:
 
Rally said:
Interesting. The car pretty much stopped in the first part of that hole in the first video, so I think you are right about not needing so much momentum
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Yeah as soon as the wave hit the wind screen I took my foot completely off the throttle in case some water got in the snorkel so that lost me some momentum. I think if I had gone slowly until the front was in the hole then given it a bit it would have gone much more smoothly.
Rally said:
Interesting. I think it is these conditions where good diffs would be of most use.
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With a good rear LSD getting out would have been a walk in the park combined with the rest of my mods
idw said:
I saw that 60 series to, he looked like he'd taken the worse line possible.
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Nah the one I saw had just gone straight in the ruts as I did. Probably not with as much momentum though. There was a patrol on a later hole that had taken a stupid line
idw said:
Do you know if you search for subaru offroad videos on youtube most of the results are yours :rotfl:
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I actually searched for just that this evening and only one of my videos came up :confused: Maybe its something to do with the fact that they are my videos....
 
Awesome! :biggrin:

That was a little too much momentum in the first one lol :rotfl:

With a plated rear diff you'll be hard core :lildevil:
 
A decent lsd would help heaps by the looks of those videos. If you have one wheel spinning at the front and the space to go either side of the exit try steering left to right repeatedly a lot of the time you'll manage to get enough grip to crawl forward until you find traction again.
 
Dedman said:
Have you tried your one out yet???
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Not yet, cant wait though, esp if I put the muddies on as well :lildevil:

idw said:
try steering left to right repeatedly a lot of the time you'll manage to get enough grip to crawl forward until you find traction again.
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Good tip, another is use your left foot on the brake to control wheelspin. You'll need more right foot to keep the revs up. This sends more engine torque to the wheels with grip :biggrin:
 
idw said:
If you have one wheel spinning at the front and the space to go either side of the exit try steering left to right repeatedly a lot of the time you'll manage to get enough grip to crawl forward until you find traction again.
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Normally I would have tried that but i was driving like a complete dud yesterday. Did you notice how in the first video I kept trying to get out with the wheels turned hard to the right. I meant to do that for one go then I could have sworn I had straightened up again. Took me quite a few goes of back and fourth to remember I had turned. Idiot...

NachaLuva said:
Good tip, another is use your left foot on the brake to control wheelspin. You'll need more right foot to keep the revs up. This sends more engine torque to the wheels with grip :biggrin:
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I have never got this to work at all and in terms of physics it makes absolutely no sense that it would work for open diffs. The reason for this is that the static coefficient of friction (stationary wheel) should theoretically be higher that the kinetic coefficient of friction (spinning wheel) This means that applying the brakes will apply more turning resistance to the stationary wheel than the spinning wheel. This combined with open diffs having to apply equal torque to both wheels means that applying brakes should hinder more than help. This is all theoretical of course so maybe it does work in reality.
Driving through the brakes should however work for a diff with a torque bias (such as a torsen) but not for a clutch style lsd for the same reasons as a open diff.
 
When are you down this way again dedman we can go exploring?

I've yet to try braking a little NachaLuva, i should next time
 
Great vids Dedman :)
I can kind of relate to having a touch too much momentum like you had in the first vid. I had a similar situation once :twisted:
I was on a trip a couple of years ago & was nominated as the test driver :p

lie.JPG


v82m.jpg


I made it across, but when it came time to come back (the others decided they didn't want to do it) I thought I'd better give it a bit in case my Forry decided to float.
And float it did :eek: Luckily I did make it back, thanks to the momentum :)

Sorry for the hijack, but I thought I'd share a similar experience I had.

Also, well done on making it through without needing to be assisted :)
The rocking back & forth worked well :raz:

Regards
Mr Turbo
 
Can't see that its a Foz on these pics...it could be a FIAT 500 :lol:
 
Crikey Mr.T, your car can barely be seen under all that water lol :lildevil:

Dedman, I understand what your saying about the friction. I think the way it works is with diagonal wheels lifted only minimal throttle is used before the revs rise too high, so the torque that is being developed by the engine is very low. So the torque each wheel receives is even lower.

With left foot braking, more throttle can be applied allowing the engine to develop more torque, so the torque each wheel sees is greater. Even if a high percentage of torque is then directed through the 2 wheels with less resistance (lifted), the 2 wheels with more resistance will still receive some torque, as opposed to none with no braking. This small difference is often all that is needed to keep forward momentum.

The more braking that is applied, the less the difference in resistance between the lifted wheels & the wheels with grip becomes, so this method becomes more effective. The only problem then is the lack of torque in our little EJ20Js.

My last trip, on a long steep clay climb with diagonal ruts (very slick, even Venom needed a few goes), I found myself a few times with my right foot almost flat to the floor & controlling the revs with my left foot on the brakes. I found this very effective, it just took some juggling of accelerator & brakes to keep the revs at ~4000rpm as the grip changed.

Anyway, I'm not sure if thats how it actually works in reality but I find thinking of it that way helps...
 
Nice work Mr T!!!!


NachaLuva said:
I think the way it works is with diagonal wheels lifted only minimal throttle is used before the revs rise too high, so the torque that is being developed by the engine is very low. So the torque each wheel receives is even lower.

With left foot braking, more throttle can be applied allowing the engine to develop more torque, so the torque each wheel sees is greater. Even if a high percentage of torque is then directed through the 2 wheels with less resistance (lifted), the 2 wheels with more resistance will still receive some torque, as opposed to none with no braking.
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Theoretically speaking though (assuming left and right brakes are equal) by definition, with an open diff any extra torque directed to the wheel with traction will be equal to the braking force on that wheel meaning no extra torque is reacted by the ground and thus no extra forward movement.
Yes the motor is producing more torque but it is being entirely reacted by the brakes and as such doing nothing

Again this is entirely theoretical but I cant for the life of me come up with a physics based reason why driving through the brakes would give any benefit with open diffs.

Edit: One possible explanation is that the faster a wheel spins generally will have less traction than a wheel spinning more slowly, so applying the brakes will reduce the engine rpm potentially gaining marginally more traction. The same result would be achieved from careful throttle use and Ive seen you drive so im not convinced this is the reason why driving through the brakes works for you....
 
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Awesome!

Can't wait to hook up a trip out there with you (or Cobaws) - just flat out for some time :(

Cheers

Bennie
 
Dedman said:
I have never got this to work at all and in terms of physics it makes absolutely no sense that it would work for open diffs. The reason for this is that the static coefficient of friction (stationary wheel) should theoretically be higher that the kinetic coefficient of friction (spinning wheel) This means that applying the brakes will apply more turning resistance to the stationary wheel than the spinning wheel. This combined with open diffs having to apply equal torque to both wheels means that applying brakes should hinder more than help. This is all theoretical of course so maybe it does work in reality.
Driving through the brakes should however work for a diff with a torque bias (such as a torsen) but not for a clutch style lsd for the same reasons as a open diff.
Click to expand...

I always assumed that this theory relied on ABS. It should work, given that ABS applies the brakes to the spinning wheels (or, to be more accurate, releases the brake on the stationary wheel). But ABS does weird stuff at very low speed, so I'm not sure what the practical answer is.
 
Im not sure mine has abs being the base model. I have locked up in a big cloud of smoke before....
 
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