Wheel weight Vs Axle weight.

[Simon.O.]

Pros and Cons
I can see the need for weight and have used wheel weights too. I have also used Nimh to power the rig and this gave me 11oz for a start. Above the axle is not ideal but it was a start.

I am now about to get my Lipos and have a few questions on weight placement.
I ran it up my test board that I use to check geometry changes and instead of the 6 Sub-C on the front axle I ran a long wire from a bench pack to the esc.
Yes it was pretty clear that I needed that weight back on the axle.
The (Nimh) weight was previously 1/2" above the axle and it crawled fine. Now I need to replace the Ni weight with lead that I have wads of.

Is there a big difference in placing that weight on the axle vs placing it in the rims.
I have done a few vector calculations and can see that any weight wrapped around the rim under the foam is similar to having all of that weight at the hub centre, or even on the axle housing.
This all applies well until we hit a serious off camber climb or a 45+ sidehill.
From there the maths gets tedious.

From a practical point of view I can see very little difference between on the axle and in the rim.
I can see it as being easier to adjust too.

Do some of you run the ballast weight on the axle housing ??

 

[run2jeepn]

How much weight do you have in your front wheels now?

 

[sweli]

Wow, has been a while since I have thought about vector diagrams!
When you draw them, do you draw one vector for what was the old batt mass or spread many across axle surface?
I can picture when you sidehill or off camber climb, how the batt weight vectors versus having he weight in the hub (at the four corners) would look.

I can believe that the (lets haul another blast from the past in) dynamics of having the weight around the hub is not good for crawling. Besides being hard on drivetrane components, centrifical force will keep you rolling further, when you want to stop versus axle weight.

But having the weight to the outside corners I thought was the key for all the off camber and sidehill moves.
I picture when you get one front wheel hooked over a ledge, but the rest of the rig is still on the climb. Where your vectors would be. In the hub, you would have 20% over the hump already.

Lots of nice scenery and rocks in NZ! Which island are you on?
My brother in law lives in Martinborough, outside Wellington.

 

[JeremyH]

From a practical point of view I can see very little difference between on the axle and in the rim.

The major difference between the two is that when you have the weight on the wheel, now it is part of the rotating axle shaft which will increase it's inertia when motion is stopped or started. This can cause an increase in the breakage of parts...specifically parts of the axle shafts.

When you remove the weight from the wheels and place it on the axles, you now make this weight static.

 

[irok]

Pros and Cons

Is there a big difference in placing that weight on the axle vs placing it in the rims.
From a practical point of view I can see very little difference between on the axle and in the rim.
I can see it as being easier to adjust too.

Do some of you run the ballast weight on the axle housing ??

Wheel weight is a better option then axle weight overall.
I played around with this about 2 years ago and also for the same reason as yourself.I went from heavy ni-cads on my front axle to lipo as well.
I did testing with adding and removing 1 oz lead weights in stacks of 1-6 on each side of the axle tubes in place of my saddle style battery's.
It did very little in terms of keeping the front down and adding almost 1/2lb total did not make a very noticable improvement in keeping the front end down on my home built indoor rock pile that had many steep climbs.

The biggest improvements can be made by suspension tuning of coarse,but i had good results from adding more front wheel weight.
It really helps hook into ledges and keeps the front end stable and planted,i used the same climbs for hours of testing and added wheel weights until i found what worked for me and my suspension.
also,alot of the 1:1 crawlers use water or lead inside the wheels for ballast.

 

[EvoKin]

In my opinion.
Esc, battery, rx are needed to run the rig and by placing these parts as low as possible will give a low cog. Adding weight in the wheel is for tuning and you can tune by spring rate and oil weight. In the end, I think the lighter the rig will perform better than a heavier rig. Is all test, tune and drive.

 

[Terranaut]

If you already know how much weight you like on the front end, it is better to put it equally spaced around the wheels, rather than above the axle tubes where the battery was. Weight in the wheel is centered on the axle shaft, weight above the axle housing tubes is centered above the axle shaft. So in the wheel gives a lower C of G which helps in both climbing and off camber. You can also benefit by the inertia of heavier wheels when you get high centred, bursts of throttle will rock the truck and maybe get you outa there.

Knuckle weights are now available too, which puts the added weight below the axle shaft, which is even better than in the wheels.

Cheers.

 

[JeremyH]

Knuckle weights are now available too, which puts the added weight below the axle shaft, which is even better than in the wheels.

Knuckle weights have been around since this hobby started. They allow you to position the weight out as far as possible and low while keeping the weight OFF the rotating axle shafts....which is important if you don't like breaking parts.

 

[Manning]

If you already know how much weight you like on the front end, it is better to put it equally spaced around the wheels, rather than above the axle tubes where the battery was. Weight in the wheel is centered on the axle shaft, weight above the axle housing tubes is centered above the axle shaft. So in the wheel gives a lower C of G which helps in both climbing and off camber. You can also benefit by the inertia of heavier wheels when you get high centred, bursts of throttle will rock the truck and maybe get you outa there........

The inertia of weighted wheels also can help flip the rig back over when it turns turtle. Bursts of throttle will rock the rig and if you have enough wheel speed, it can flip over.

 

[shelljeep]

Is there a big difference in placing that weight on the axle vs placing it in the rims.
I have done a few vector calculations and can see that any weight wrapped around the rim under the foam is similar to having all of that weight at the hub centre, or even on the axle housing.
This all applies well until we hit a serious off camber climb or a 45+ sidehill.
From there the maths gets tedious.

From a practical point of view I can see very little difference between on the axle and in the rim.
I can see it as being easier to adjust too.

We need brass axle housings.:idea:


Really glad you started this thread. I have just begun experimenting with axle housing weight vs wheel weight. Will be good to hear other's experienced opinions and input.
My take:
The extra inertia makes things unpredictable, as well as being harder on components. Say for instance, you are having to use major wheelspeed to get up a slick face. A heavy tire seems to amplify the reaction from a bounce or a skid, etc. Might be something oddly gyroscopic happening? I don't know, and I'm certainly no engineer. An unweighted tire seems to react less though.
I have shaped a lead weight that fills the gaps between tire and servo, and has a thin slice going over the top of the servo. I haven't been able to test yet, due to repairs being needed on my electronics. I will have that sorted out tomorrow I hope. Anyway, I was glad to hear that you found little difference in your analysis of saddle pack weight vs. wheel weight. I'll post up my thoughts after I get my rig running again.

 

[Simon.O.]

There are some very interesting and informed replies here.
I can see the whole arguement about rotating mass and inertia and now will consider that as a major factor.
I did some tests this morning on my vertical climb test board and can say that 8oz on the axle centre line has the same effect as 4 oz per wheel.
Yes that was a full mug of coffee and at least 1 fag to get all those rings undone and the tires weighted / unweighted. !

The axle weights will replace the old Ni cells but I do not need the whole 11oz of Nimh

Where I am at now is I have a Creeper that maxes out at 62deg vertical on the board and 55deg sidehill on my rock wall outside.

I have had the suspension all over the place and the shocks have had a lot of movement too.
I am happy to run axle weights for a while and see if I can get a little more out of the little bugger.

If you are bored and want to see it: http://www.rccrawler.com/forum/showthread.php?t=220164

 

[Irishchamp]

Interesting thread.

 

["N8"]

also,alot of the 1:1 crawlers use water or lead inside the wheels for ballast.

Nope, this is just flat out not true. Baring the occasional back yard stupid person, nobody does this.

Construction vehicles use liquid inside the tires for ballast, but these vehicles are not intended for serious offroad use, as they are for construction purposes.

But I have seen close to thousands of off road vehicles and none have had as you say water or lead inside the wheels. More notably I have never even heard of let alone seen a competition machine with such features.

The simple fact is that in 1:1 rigs axle shafts as large as they are become an inherently small part for the amounts of power they end up transmitting. (ive seen broken 2.5 rockwell axle shafts 8)) So adding any rotational mass to the driveline becomes a bad idea.

 

[shelljeep]

N8, you just made my ignore list you fawkin idiot. You don't know WTF you are talking about.

 

[XPLORx4]

N8: Please read this article (although since the article is 3 years old, the described techniques may have been made obsolete by the latest advancements in the [relatively new] sport of competition rock crawling).

 

[irok]

Nope, this is just flat out not true. Baring the occasional back yard stupid person, nobody does this.
But I have seen close to thousands of off road vehicles and none have had as you say water or lead inside the wheels. More notably I have never even heard of let alone seen a competition machine with such features.
QUOTE]

LOL...
i'll be sure to tell my buddy's w/ comp rigs,
{1 on the US circuit with sponsers} to stop cause you said nonbody does it :mrgreen:

 

[Bray D]

Just to further disprove N8 , I did a quick search on Pirate4x4 (largest online offroad community in existance). Here's 25 threads regarding using water in tires, most that say they run water in their comp buggies (with serious money dumped into their axles).

http://pirate4x4.com/forum/search.php?searchid=6251984

I guess Trail-Gear makes a water hose adapter so you can fill the tires, but I couldn't find it.

edit: aaaand you can't view it unless you're a member. I fail.

 

[Terranaut]

I am aware that Super class rigs have placed batteries under the knuckles for many years. but this is not feasable on 2.2 rigs. Knuckle weights do the same thing though for smaller rigs, and that's relatively new. It's a great (and obvious) idea. I think we'll see more of it.

Water, or lead, or ball bearings in the wheels or tires (live weights) can move around. When you point your rig uphill the weight moves backward and upward in relation to the truck, which somewhat negates the intended purpose. Your C of G goes higher and your weight distribution goes to the rear, both disadvantagious when climbing. A fixed weight under the knuckles stays in position and does it's job, regardless of how steep the climb. Also, knuckle weights are not rotating mass. So you get the best of both worlds.

I don't know if full scalers do this, but if you have a choice, knuckle weights are the way to go. "thumbsup"

Cheers.

 

["N8"]

Wow, just wow. I feel like I shouldn't even bother trying to defend my words against you people. Please by all means you people are welcome to ignore me.

Brayd i dono what you serched for, but it brought these results: http://i702.photobucket.com/albums/ww29/Gimpy_Nipple/Picture4.png

But for the record I will say I have not herd of any notable person running liquid filled tires from any of you. Irok your "friend" who is #1 on the US circut (as if there is one rock crawling type circit in the us) aperently has no name, and runs lead in the tires on his super crawler. xplorx4 was the only one who brought anything to the table. I read it btw, and I conseed that some people obviously do this, but honestly that azcrawlers site isnt particularly striking as a good place to source info for modifying your buggy. Like I said im sure this is something that people have done, but nobody searious into rock crawling or racing does this.

Shannon Campbell runs just a regular old air filled bfg krawler on his ifs moonbuggy. Casey Currie runs the same. I got to meet Lucas Murphy and Ian Johnson just a bit ago on a trail run where Lucas was running his KOH comp rig on a run that my buddys fab shop hosted. Funny... he didnt say anything about water filled tires when he was goin over his rig.

But then again im an idiot.
Feel free to keep up the notably polite conversation.




<table border="0" cellpadding="0" cellspacing="0"><tbody><tr height="19"><td align="left" bgcolor="#ffffff" width="68">
</td><td align="left" bgcolor="#ffffff" width="132">
</td></tr></tbody></table>

 

[Manning]

There was a TV show (something about trucks, pretty dumb show) on a while back with the Websters (as in Becca, you might have heard of her), and the host of the show couldn't hardly move the tires off the vehicle. They claimed each tire/wheel was well over 200 lbs each due to the addition of shot.