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Old 10-07-2011, 08:36 PM   #41
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Here is the example that best suits CTBM's theory.....

1# weight under a slinky on an incline, in any direction.

And,

A 1# weight on top of a slinky in the same circumstance.

What will go over first.
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Old 10-07-2011, 08:37 PM   #42
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Actually a 20lbs scx10 and a 1lbs scx10 would fall at the same pace because the only thing that mater is the aero dynamics, so if they have the same aeros then the will fall the same.
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Old 10-07-2011, 08:39 PM   #43
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Originally Posted by krawlfreak View Post
Here is the example that best suits CTBM's theory.....

1# weight under a slinky on an incline, in any direction.

And,

A 1# weight on top of a slinky in the same circumstance.

What will go over first.

That's center of gravity, and I don't think that's where he's going. I believe he's wanting to test the upper limits of weight, though obviously he's going to keep it as low as possible and place it strategically. Otherwise he'd duct tape a 20lb barbell to the roof and hit the rocks and this thread would be over.
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Old 10-07-2011, 08:42 PM   #44
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Actually a 20lbs scx10 and a 1lbs scx10 would fall at the same pace because the only thing that mater is the aero dynamics, so if they have the same aeros then the will fall the same.
Or do it in a vacuum where aerodynamics wouldn't matter.
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Old 10-07-2011, 08:50 PM   #45
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That's center of gravity, and I don't think that's where he's going. I believe he's wanting to test the upper limits of weight, though obviously he's going to keep it as low as possible and place it strategically. Otherwise he'd duct tape a 20lb barbell to the roof and hit the rocks and this thread would be over.
O.k.

Your right

Why don't you all just take a little trip back in the ol' time machine to when every one was running 22-3300 mah batteries in the belly and a dig switch plate.

It has all been done already and the fact is we have found that the more you remove from the sprung side of things the better the trucks have started performing.

Like I stated earlier there is a reason every one has been putting weight in or around the wheels.

Last edited by krawlfreak; 10-07-2011 at 08:59 PM.
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Old 10-07-2011, 09:17 PM   #46
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I look at traction as a potential with upper and lower limits. Somewhere in the middle is the place where the most potential lies. Not all tires are the same, not all offer the same amount of potential traction, and they certainly don't all work equally well on vehicles of different weight. Too little or too much weight can yield poor results from even the best of tires.

A heavy truck doesn't "make" less traction, its weight has simply exceeded the amount of traction available from the tires it has and the surface they are on. The same truck on the same surface but with different tires may do just fine.
And another thing... Would it be the tire or foam failing? Assuming the same tires at work with properly supporting foams, I wonder if its the actual rubber failing to support the weight? Reason I ask is I've been liking stiffer foams recently, 2lbs/cu ft or so for a 6-7lb I think.

The weight down low is always a good thing and have been considering adding weight.

Good thread guys, lots of ideas being thrown and considered.
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Old 10-07-2011, 10:14 PM   #47
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O.k.

Your right

Why don't you all just take a little trip back in the ol' time machine to when every one was running 22-3300 mah batteries in the belly and a dig switch plate.

It has all been done already and the fact is we have found that the more you remove from the sprung side of things the better the trucks have started performing.

Like I stated earlier there is a reason every one has been putting weight in or around the wheels.
The bad thing about nickel batteries is that they are big and bulky and optimal mounting positions are limited, if not impossible. It could very well be that their weight was a plus but their size is what killed them. Since a lipo is relatively light, you can get away with mounting them a bit higher.

Its not always about how much weight you have, but where you put it.

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And another thing... Would it be the tire or foam failing? Assuming the same tires at work with properly supporting foams, I wonder if its the actual rubber failing to support the weight? Reason I ask is I've been liking stiffer foams recently, 2lbs/cu ft or so for a 6-7lb I think.
Certainly, heavier rigs require denser foam. But on the same hand, some tires (Cougars come to mind) work extremely well with dense foam, even on a 5-6lb rig. At some point you could either remove or add too much weight for the tire to work as well as it could. A super stiff foam that holds the weight of a heavy rig may not allow the tire to conform to the terrain, which would reduce its contact patch.

Why do 1:1's deflate their tires when they do serious offroading? To gain more grip by expanding the contact patch.
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Old 10-07-2011, 10:29 PM   #48
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...Certainly, heavier rigs require denser foam. But on the same hand, some tires (Cougars come to mind) work extremely well with dense foam, even on a 5-6lb rig. At some point you could either remove or add too much weight for the tire to work as well as it could. A super stiff foam that holds the weight of a heavy rig may not allow the tire to conform to the terrain, which would reduce its contact patch.

Why do 1:1's deflate their tires when they do serious offroading? To gain more grip by expanding the contact patch.
Sorta getting away from the chassis weight theory... Maybe I was feeling the lugs folding under with a softer foam vs. a stiffer foam to support the carcass + a lil more bounce. Just proves everything is experimentation, trade-offs and driving preference.
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Old 10-07-2011, 10:37 PM   #49
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Its not always about how much weight you have, but where you put it.

That is the most quoted phrase on this board and it seems to be getting by you.

I was talking about lipos....

And your right about the weight, and putting it in the chassis is a bad move.
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Old 10-07-2011, 11:17 PM   #50
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Man, all I know is the more weight I add the better my mantis is...it still hops, and I'd like that to stop...I never thought of adding weight to the chassis itself, but I'm going to change that....not so comfortable with all the added weight to the wheels and rotating mass...I think it's a great idea Chris....could be that you could take all the weight of the wheels, add it to the chassis by half, and still achieve the same results....just by COG
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Old 10-07-2011, 11:33 PM   #51
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Man, all I know is the more weight I add the better my mantis is...it still hops, and I'd like that to stop...I never thought of adding weight to the chassis itself, but I'm going to change that....not so comfortable with all the added weight to the wheels and rotating mass...I think it's a great idea Chris....could be that you could take all the weight of the wheels, add it to the chassis by half, and still achieve the same results....just by COG
You need to add weight because it is a torsion chassis. It will probobly always hop.

And why is every one so worried about rotating mass with the upgrade products we have these days. Is it so you can jump the one gate of 70 at a comp?

How many 300's or xr cvd's have been broken by rotating mass. I know some.parts have been broken but that is more than likely from something other that weight.


And no you can't take all the weight out of the wheels and add it to the chassis and get the same result.

I am really trying to help you guys ....
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Old 10-08-2011, 12:14 AM   #52
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Really, always hop ? I hope you're wrong...as for the rest, I'm still trying stuff. Just seemed to make sense...the only thing that bothers me is the height of the mantis chassis to begin with....a bit high.
I'll try it nonetheless ....thanks for the input Krawlfreak
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Old 10-08-2011, 10:02 AM   #53
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The civic vs semi argument would be valid only if we did not run a drag brake. It's like locking the brakes every time we stop hence like leaving the ebrake on. Leave the civics ebrake on and the semi's parking brake on and use an outside force to push them backwards down the hill, the civic will move with far less force upon it. The semi is also capable of pulling far more weight up the hill than the civic, largely because of the HP difference but also because of the weight difference.

Semi is more weight and more contact points to the ground, hence a heavier crawler with more contact would work better in theory. And rovers are wider and usually a softer compound than stock axial rock lizzards so they grip the rocks better.

There are so many things that come into play when talking about traction. Weight is only one of them. Really we have two civics, one with f1 tires weighing 5k lbs and one with stock 14" tires weighing 2k lbs. the lighter is still easier to push down the hill with the brakes engaged.

I have actually been messing with the weighted links thing for a little bit now, and it actually seems to make quite a bit of difference. Running an aluminum steering link vs a solid carbon steel one, I now run the carbon steel one. The only issue is you create a disadvantage for the rod ends because they are automatically under more stress from the added weight, so break more often than when using a lighter link. That's my two cents anyway...
The Semi VS Civic comparison is very valid. A lot of people are assuming that Chris is talking about crawling on high traction surfaces. Which we don't have a lot of over here in Oregon. Especially now with the rainy season starting. Trying to climb a slick hill with a heavy truck, you can't go anywhere. But a light truck, lots of wheel speed, and if you happen to get a tiny glimpse of traction, you can shoot up a climb. So weight is a HUGE variable in how a truck performs on the slick Oregon rocks.

Being able to have a light truck (under 5lbs) that can drive predictably would be awesome over here in Oregon. But the lighter you go with the truck, its seems like every change you make to the the truck is a "give/take". It's not like any change you make to the suspension, tires, balance, gives a 100% improvement all around. Unless your switching your tires from rock lizards to boss claws of course ...

TOM

Last edited by sourdojack; 10-08-2011 at 10:06 AM.
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Old 10-08-2011, 10:11 PM   #54
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I guess I'd like to try a "slick rock" scenario , I'm sure there would be some difference. I tend to crawl in high traction settings. A trip to the big O could be in my agenda soon, get some slippery experience . I really strive to be a well rounded crawler
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Old 10-08-2011, 10:36 PM   #55
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...A trip to the big O could be in my agenda soon, get some slippery experience .
That's what she said...
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Old 10-10-2011, 02:13 AM   #56
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Especially now with the rainy season starting.
as opposed to the sunny season?
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Old 10-10-2011, 04:53 AM   #57
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Chris I think that a plate hanging off of the rear with weights will give too much traction in the rear thus flipping the rig. I think we need a heavy front maybe heavy links in the front. The rear needs enough weight so it doesnt hop but not so much that it flips the truck. maybe different tire combos in the front/rear. A tire in the rear that gets better traction with less weight and a tire in the front that does well with more weight. Maybe rover in the front and boss claw in the rear. Just an idea
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Old 10-11-2011, 09:27 PM   #58
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Engineering stuff here. Don't read if easily bored. Very likely best climbing will come from nearly equal weights on all four tires. This because tire efficiency, grip vs normal force (force straight into the surface) is slightly non-linear and shifting weight from one tire to another hurts the now heavier tire just slightly more than it helps the now lighter tire. Bottom line -- keep all four tires equally weighted.

That's very hard to do when on a steep climb. Weight will naturally transfer from the front tires to the rear tires unless the CG is at ground level (ain't happinin'). That's why we run front-heavy rigs, to give the front tires a head start. Even so at a very steep angle, those heavy fronts start coming off the ground proving there's no weight on them.

So where do you add weight to improve climbing? Not in the chassis. All of that weight will transfer to the rear tires. Best added weight will be nearest the ground and very far forward. Gee...kinda like knuckle or front wheel weights. But we knew that all along, right? Even without the science. A little keg of solid tungsten cantilevered in front of the axle just above the ground would make for a great climber. Not so good on approach angle tho.
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Old 10-12-2011, 12:11 PM   #59
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I think it's kind of funny how some of you are talking to me like I am a noob even though I have been around since 06'.


Perhaps I am not making myself clear as to the goal here. Take a losi or axial ax10. They cant pull some of the crazy lines an MOA can by nature. But they can still drive really well, and handle nicely. My sportsman was such a fun truck to drive, and I was able to out drive many MOA trucks with it... with no dig, and only about 5oz on the front. Yhe tranny, motor, and electronics in the belly all weighed about 10oz. So in this case, I had MUCH less axle weight, and much more chassis weight.

Now does that mean that it will drive better than an MOA? No. But I was able to do 95% of the lines anyone locally could do. I am not saying that some sprung weight will not in some fashion effect the truck negatively. The CG will suffer some, and it will transfer weight to the rear tires more. But I truly believe that these draw backs aren't enough to really notice a huge difference.

My sportsman always felt more planted than any MOA I have driven. I have even out drove people with very little sprung weight, when I had the battery and electronics in the belly. Tanis has kicked our asses for years with anything from a honcho, to a spare parts axial, to a nice axial with a DNA dig. So does some sprung weight really effect someone just being a good driver? I am not claiming that I am that guy. But that some chassis weight, to help tune a truck to your desired handling may not be the worse thing. I know that sometimes my ideas get shot down. Like running a light truck a couple years back by superdave and Lars who now run trucks under 5 lbs. Or that putting XR goodies on a berg but that certainly wont defer me from my ideas


Now some of you are getting off topic here. This thread isnt about light trucks, or front weight bias. ONLY about chassis weight on an MOA truck, and the effects it has on the handling. My current XR has the electronics in the belly, and the battery. My berg had only the electronics in the belly, and the battery on the front axle. My xr handles night and day better. Probably somewhat due to the link geo, and shocks being tuned better. But I still have more chassis weight, and the truck is extremely capable.

So this weekend is our ORCRC comp, and I am just going to be a guinea pig and try it.... We will see how it goes. Maybe I will get some video too.
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Old 10-12-2011, 02:14 PM   #60
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The only way to make youre comparison fair, and educational, would probably be to actually move youre battery up to youre front axle, and do the same line`s over again..

And if it handles worse, you should try to move some weight back on the rear axle as well, to find out if the problem was changing the chassie weight, or just weight distribution..

I know, i just talked n00b to you But it`s a semi-basic subject, so we gotta talk semi-n00b

But it`s an interesting subject for sure
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