BigFoot hill climbing versus big ATV (SPortsman 700 or the like)

[BearFish]

I am still looking for my first Argo on the used bulletin boards up here in Ontario Canada and there is an interesting Bigfoot ...
ATVs seem to be rated by the manufacturer at about 25 degrees safe hill handling and the only reference I found for an Argo said 30 degrees.
I need to get back to small trout lakes in the steep and rocky hills. Sometimes those trails hit around 40 degrees I would say. Quads certainly get jittery even just crawling up or down. If you rolll it is all the way to the bottom. Trails often are straight down.
Will a BigFoot do better creeping up and going down those hills?
Is braking downhill an issue in a 2002 BigFoot?
I want safety, payload ability and do not need speed!

Any advice or observations would be appreciated!
Next I need to learn to drive an Argo ..

[mustangwagz]

Hey there bearfish, i know how ya feel, i got some area's here in the state of PA that are similar, very steep, rugged, and certainly off camber!! (side ways across hills) My old attex does awesome, although i have to go faster cuz of its drive-train setup and gearing ratio, it still does wanders. ive taken my attex into places that quads got a little tippy. The 6wheeler just kept on plugging along like a matured mountain goat that never even once double stepped. My advice to you, go test drive an argo..seriously. I can honestly say that if i buy NEW or used, it'll be an argo for me. i'd suggest tracks as well, from what ive seen and read, the tracks make a WORLD of difference also. and in all honesty, i myself will get tracks when i purchase an argo. lol..MY opinions though. i want something thats geared low, super stable, and virtually un-stoppable. and i think that MOST aatv's now a days fit that catagory, but i'd say in MY OPINION, argo is prolly the top of the line. Unless u wanna go ALLLLLLL OUT, and buy a mud ox but i aint got that kind of money. lol

ANYHOW, enough rambling..thats just my 2 pennies on ur dilema, i'd say go drive some to find out how ya like em, dont be scared.. My moto is "Dont hesitate,..... Accelerate!!" Besides, we only live our lives once buddy, and we cant take our money with us, so i say we go out N have some fun and take the paths less traveled...Do it in an AATV!!

-WagZ-

[BearFish]

After sleeping on it ....
I stayed up until 1:00 ( big deal when retired! ) and looked at lots of videos of ATV and AATVs on steep hills flipping out. I slept on it and here is what I see:
a) anything can flip or endo so having a roll cage is a plus for family and friends. Big ATV with two people and a roll cage??? Not feasible I think?;
b) I am sure my insurance would not pay up the $1M liability for an accident if I fabricated it myself, so need manufacturer's built or approved roll cage;
c) In any case, even with slow slow driving one can do an endo. The aim is to reduce that risk. Here is what I think goes on with AATVs ( just IMHO ). Let me know if any of this makes any sense:
1 - there is a centre of suspension and a centre of gravity on any vehicle. These change a lot on an ATV as it moves but less on an AATV;
2 - If the two centres are at the same place the unit is "balanced" as far as the rubber on the ground versus the gravity load centre. On an 8x8 I see the centre of suspension as being usually between the 2nd and 3rd set of whells while a 6x6 it is on the centre wheels of course. The centre of gravity depends on the machine's design.
3 - in ATVs the driver constantly moves his/her body to move that centre of gravity to keep stable. In AATVs we also rock forward and right and left for balance of the machine, but it is a much reduced effect. Meaning you can't always save yourself from a big endo on an AATV doing just that;
4 - AATVs with motor in front and people in front tend to have the centre of gravity ahead of the centre of suspension and tend to nose dive and could flip going down hill. This happens fast I am told when people's bodies lurch forward going downhill and a bump or brakes are hit. This super rapid "Weight Shift" can catch people by surprise and lead to a super fast endo;
5 - AATVs with motor in back and people in front may have these two centres closer together. They may not have such a bad lurch when going down hill or up hill and a bump is hit and people's or gear's weight shifts.

Does anyone have interesting endo video links that I could learn from ( of course only ones with happy endings )?

So, say an 8x8 has most of its weight in the front by design and has been known to flip more going down hill? It seems to me that you could load the back with well strapped down cargo and bring the centre of gravity backwards to get better "balance". Maybe you don't have cargo and maybe you want to go on water so no extra weight appreciated? What if you retrofitted that AATV for better balance by permanently moving some components as far back as possible? Maybe a battery? Maybe a gas tank? Otherwise just drive it backwards down the hills! ( lolx8 )

Any thought on the above "rant"? I realize lots of it may be obvious to seasoned AATV folks so bear with me as a newbie! y the way, I don't think I have read too much about this balancing of the centre of gravity and centre of suspension anywhere? Anyone got links?

Thanks

[spookum]

I have the same feeling that you do, the machines that have 8 wheels are more stable than the 6 wheelers. You should go and watch Utube videos of RockDock, he and his frineds will take an eight wheeled argo and run it up a 90 degree bank that looks uber tall. Some times it takes a few people pushing down on the front end to get it up over the ledge.

Another thing that you should consider in your search is just not only the 4 wheeled atvs but the 6 wheeled ones as well, such as the polaris big boss. They will climb a steeper slope than a max will... how ever, they WILL NOT side hill worth a darn.

It dosnet mater what im driving, but if i get in a super hairy situation, i make everyone else get out and walk.

now, to the bottom line. When i get into a situation like you do, i like math, you tube is great, but it also involves the human elament. I bet most people that flip an atv or aatv are showing off, being drunk and or stupid, or are driving beyond their capabiltes. If you dont mind me saying so, you are retired you need somthing that can go super slow, under any conditions, and go where it is pointed safely without a bunch of fan fair, and will not get stuck. Im not retired yet, but the super slow part is what i enjoy, without slipping a tire. Nothing is worse than taking a four wheeler wide open and hitting a hill trying to make it to the top, i prefer to start at a nice slow speed and keep it moderate on the way up. When you start bouncing, that is when you break stuff, i dont care what it is. Any way, im going to do some physics now.

To begin with, all objects have a center of mass, argos and atvs, you and me, ect.

If that is a totally foreign idea:

Center of Mass | Khan Academy Philosophy Lecture

moving right along. We are now going to take motion and the human element out of the equation. These two things will drastically change the results because humans and mass move around with motion and move the center of mass (hope you dont mind, im going to call it the COM)

so think about it like this: we are going to park an argo and an atv on a hill side, and make the hill steeper and steeper.

Please see my diagram:

hill question.jpg

so this is the maximum angle the machine will handle. If you rotate the macine up hill when the hypotenuse of the triangle hits 90 degrees from the horizontal, it is going to roll. If you can find better estimates for the center of mass, be my guest. Ill actualy run some numbers tonight if i get time.

oh, and some guys i see off roading in like jeeps and such, have a little critter mounted to the dash to see the angle of the hill.... lev o meter

like this

Lev-O Gauge - PRODUCT REVIEW



cheers!!!

[spookum]

ok, part two the calcualtions for hill stability. argo vs atv we will use a polaris sportsman 700 since you are from canada, i will be using the metric system... but it really dosnet matter degrees are degrees right???


the diagram:

hill question.jpg


Please remember we are simply picking arbatrary points on these machines and they are not moving. Aka, it dosent take into account leaning forward when going up hill in either an argo or a four wheeler. It is as if you sat on top of them and never moved, and did not have anything loaded.

for the polaris 700

Length/Width/Height 85.0/46.0/47.0 in. 2.54cm/inch = 215.9 cm long and 119 .38 cm tall.

both devided in half: 119.38/2= 59.69 cm tall and 215.9/2= 107.95 cm long.

So, the center of mas for the polaris 700 atv is at 59.69 cm tall and 107.95 cm long.

algebra time, the arc tangent of the rise divided by the run of a triangle yields the angle

so

arctan(59.69/107.95)= 28.94 degrees. So, subtracting from nintey degrees , you should have 61.06 degrees. Any steeper of a grade and the machine falls over on you, unless you get on it and change the center of mass with your weight forward, or power from the engine which will be a torsional force, i don't want to get into that. bet this sounds really odd... so i guess i will make this picture:

hill question2.jpg



same thing again for the avenger:

Argo ATV, 6x6, 8x8, Conquest, Bigfoot, Centaur, Vanguard, Response

length: 302 cm / 2 =151 cm

height: 108cm / 2 = 54 cm

arc tan of 54/151 = 19.68 degrees -90 degrees = 70.32 degrees

so, for the polaris 700 we get 61 degrees and for the argo, 70.32 degree slope. By my quick and dirty calculations, we have a clear winner.

Please remember that if you want, you can actually research the center of mass, but i believe that it will be really close to these machine numbers. After re reading this post, i screwed up and didn't actually use the wheel base (center of axel to center of axel) but you get the idea. You also need to know that argo puts the engines, trans and fuel tanks as low as they can get, so i bet you could even get a steeper slope than seventy degrees, how ever, i dont know if you could actually drive up it due to tire slippage any way.

my best advice is to go down to your nearest argo dealership and have someone who is good at driving one (just like you will be if you get one) and see what it will do and how stable it "feels".

i dont know if i could walk up a 70 degree slope... that is almost vertical.... wow....

[liflod]

If you are worried about going up and down steep hills, stay away from the 6x6 Argos and buy an 8x8. I have about 80 hours driving my 6x6 Conquest and climbing and descending hills scares the crap out of me. The extra length will keep you safer.

[liflod]

http://www.6x6world.com/forums/gener...hn-schwab.html

8x8 climbing video

[GreatWhite]

If you are worried about decending a hill could you not use a winch and repell backwards? You would need a good rope if it was some distance but it would be safe. I am no expert just thinking outloud.

[mudbug3]

GreatWhite

Great minds think alike. I sent BearFish a private message and I suggested the exact same thing as you did..

[BearFish]

First I , as a newby or a defector ( haven't bought a Polaris yet ... ) would like to thank all of you folks for the insights. FOr me, the knowledge that you folks have gained with experience is the big plus.

But, I can't help but be technical given my training before I retired ....

I have not verified Spookums' math, but I bet he is right in as much as all of your calcs, Spookums, work if the centre of gravity (AKA the Centre of Mass ) and the centre of suspension are at the same point. Be careful because in most machines, maybe worse in ATVs than AATVs, the mass is, in general, largelly concentrated ABOVE the axle height. That is why I guess they have the manufacturewr's specs as 30 degrees for some Argos and 25 degrees for a 2004 Polaris 700 Sportsman: Engines and stuff are above the wheels as are people. So I plan to be be very careful with big angles like you found, IMHO.

So, Spookums, buddy, you did an excellent job on one big part of the problem: the centre of suspension, but the ellusive centre of mass and how the 6x6 or 8x8 carrys that mass ( with dignity ) is really a bear of a problem.

My concern is that mass may be concentrated in front of your centre ( of suspension) in some AATVs, making downhill more risky, and behind in others, making uphill more dicey, as opposed to the centre of mass being just the way you show it on your geometric, frame-based diagrams.

Look at racing cars with big wheels where the centre of mass is actually below the axle height. When they go around a turn the centre of mass being below the axles (ie below the centre of suspension) actually makes the machine lean INTO the turn, not out of the turn like normal street cars. To see this, think of a cannonbal on a rod bolted exactly at the point you show in your diagrams but with the "cannonball" lower or higher depending on the machine. How would that cannoball tend to lean or roll in a race car? How would it pitch in our downhill or uphill AATVs? What would that force do to destabilize or stabilize the motion?

In the race car, as you swing around a turn that cannonbal ( as always) tries to zip out due to centrifugal force. It essentially tries to lift up because it is bolted lower than that centre of suspension rigidly. Basically it wants to be perpedicular to the centre of the turn, just like a ball you spin around on a string. That force , again, digs in the inside wheels and lifts the outer wheels, the opposite to a street auto.

If the AATV's motor and steel frame and drive trane etc rest lower than the centre of suspension then it behaves differently than if above. All AATVs I know have that centre of mass above your centre of suspension, I think, especially when people and cargo are loaded in since all cargo sit just above the axles and people are higher still on seats.

Now, that centre of mass compared to your centre of suspension, is it not only above it but in front of it? In some AATVs there is a motor etc and passengers in the front, out in the "pointy bow" so I think this just might shift the centre of mass in front of the centre of suspension you drew. Imagine that cannonball bolted on a rod that goes to your centre of suspension. But this rod leans a few feet in front of the centre line between the second and the third axle on an 8x8 , maybe even in front of the second axle a few inches in some machines.

Now going downhill that cannonball would "lean" down the hill ahead of the centre of suspension and tend to crank up the back end. That would destabilize the downhill run. If people are in the front ahead of the centre between the second and third axles ( your centre of suspension) Then they may move the centre of mass even more forward of the suspension. If they lurch forward they could make an endo that is just starting really happen fast. All AATvs have this type of tradeoff but some have the motor in the back and people in the front so they may balance the "teeter totter" more readily. For me 4 axles are more likely to resist this than 3 axles. In 3 axles the centre axle is a centre of suspension axle and is a teeter totter pivot point.

To easily see this, lets say a machne has a plough mounted in front and it starts down a hill. The plough has moved the centre of gravity ( i.e. mass ) way way ahead of the manufacturer's design and really far ahead of your centre of suspension. That big weight out front could almost flip an AATV sitting still!! Like a backhoe with its bucket loaded heavy at maximum extent.

This means that the hill angle a machine can safely handle is a complicated calculation ( I will leave the math to you once you find a centre of mass form the manufacturer for a given machine!!). I will say again as I did in my first post on this: for an ATV the person's body shifts around dynamically and the riders adjust the centre of gravity by leaning to try and maintain stability while for the much bigger AATVs we do shift, but with a lesser effect.

So, again, I guess I would want to put some cargo, battery, spare tire etc as far back as possible in a machine with the engine in front and for one with the engine in back make sure the front is not too light???

Hey, look at the excellent vidoes of AATVs in water. Some have the nose 6 or 8 inches lower than the stern with a big guy(s) in front. But don't let me mess up my mind even more with this idea because the centre of bouyancy ( i.e. the centre of suspension in water ) is different depending on the hull, but in my opinion the centre of mass of the AATV is the same in water as it is on land!

In otherwords, balancing an ATV in water about its centre of bouyancy does not guarantee it is balanced on land about its centre of suspension. You need to jack it up on land , probably at the second axle for a 6x6 and probably between 2 and 3 for an 8x8, and then balance it on land! Ideally you would suspend it exactly at Spookums' centre of suspension to do the balancing ...

Sorry again for the rant ...

This is a great forum with a lot of awesome support and comraderie. Lots of real knowledge based on experience. Many thanks again

Best regards

BearFish