RRO INSANE A-ARMS: Updated w/ pics

Boiler · **Posted:** Sun Jul 19, 2009 9:43 pm

icarl wrote:

Ok, I think what you are saying is that the moment of inertia that you were talking about before takes into account not just area but also geometry. So then can we say that the metal that has a larger diameter has a kind of mechanical advantage because of the greater radius or distance from the center.

Surely. Consider three flat bars laying on top of each other. Try to bend them in the thin direction. Now weld those three flats into an I beam shape and try to bend them. The I beam is magnatudes "stronger", but has the same area. The reason is because the material is moved away from the centroid of the bend. Same goes for square or round tube of different sizes, or a rectangular tube being bent in the easy or hard direction.

Worth it or not, solid is stronger if the same OD, and that was the question. You don't need to ask a pirate, I'm right here

Apparently Green Renegade knows his stuff too. Nice to have someone to agree that I'm not making this crap up.

As far as equal deflection at max stress, I'm not sure how that is useful. When the solid reaches max stress, the tube has long since broken / bent permanently. The one with the higher section modulus bends less for a given load (like half the weight of the jeep, if the jeep were teetering between the left pair of tires and the right rock rail, whatever).

I don't plan on using much solid in my designs, as it is often just too darn heavy, but the question is answered now, and I think more than sufficiently.

tjkj2002 · **Posted:** Sun Jul 19, 2009 9:47 pm

Boiler wrote:

icarl wrote:

Ok, I think what you are saying is that the moment of inertia that you were talking about before takes into account not just area but also geometry. So then can we say that the metal that has a larger diameter has a kind of mechanical advantage because of the greater radius or distance from the center.

Surely. Consider three flat bars laying on top of each other. Try to bend them in the thin direction. Now weld those three flats into an I beam shape and try to bend them. The I beam is magnatudes "stronger", but has the same area. The reason is because the material is moved away from the centroid of the bend. Same goes for square or round tube of different sizes, or a rectangular tube being bent in the easy or hard direction.

Worth it or not, solid is stronger if the same OD, and that was the question. You don't need to ask a pirate, I'm right here

Apparently Green Renegade knows his stuff too. Nice to have someone to agree that I'm not making this crap up.

As far as equal deflection at max stress, I'm not sure how that is useful. When the solid reaches max stress, the tube has long since broken / bent permanently. The one with the higher section modulus bends less for a given load (like half the weight of the jeep, if the jeep were teetering between the left pair of tires and the right rock rail, whatever).

I don't plan on using much solid in my designs, as it is often just too darn heavy, but the question is answered now, and I think more than sufficiently.

18% more strength is not "long since" considering a 64% increase in weight.

Boiler · **Posted:** Mon Jul 20, 2009 3:48 am

tjkj2002 wrote:

18% more strength is not "long since" considering a 64% increase in weight.

Boiler wrote:

[I don't plan on using much solid in my designs, as it is often just too darn heavy....

I didn't mean to insinuate that "solid is better" anywhwere in here. It all depends on the application, size, shape, etc. As for these arms, by the numbers I gave yesterday I think that example was about 75% stronger, but the weight would have been about 300% heavier or something, assuming the diameter and thickness I guessed at were correct. There just isn't a one size fits all solution, you have to look at it case by case depending on geometry, applicable sizes, loads, cost, manufacturability, etc.

Ryan09 · **Posted:** Mon Jul 20, 2009 6:04 am

I hope you are happy with your purchase of your new upper control arms from that con artist company!
Best of luck!
I'll stick with my Al's Upper control arms.

tjkoen01 · **Posted:** Mon Jul 20, 2009 9:29 am

Boiler wrote:

There just isn't a one size fits all solution, you have to look at it case by case depending on geometry, applicable sizes, loads, cost, manufacturability, etc.

if there was a one size fits all, there'd be no need for engineers and some of us would be out of a job! :wink:

tommudd · **Posted:** Mon Jul 20, 2009 9:38 am

engineers and lawyers.................who needs them :roll:

tonycrd · **Posted:** Mon Jul 20, 2009 9:39 am

RRO needs some engineers.....I wouldn't even fit this to my KJ if they paid me.

jamangus · **Posted:** Mon Jul 20, 2009 9:48 am

tommudd wrote:

engineers and lawyers.................who needs them :roll:

i would say JBA :shock:

tommudd · **Posted:** Mon Jul 20, 2009 10:18 am

jamangus wrote:

tommudd wrote:

engineers and lawyers.................who needs them :roll:

i would say JBA :shock:

JBA ?????Why JeepinbyAl

Boiler · **Posted:** Mon Jul 20, 2009 12:03 pm

tommudd wrote:

engineers and lawyers.................who needs them :roll:

Anyone trying to size structural materials for purchase by consumers. I'd guess most engineers don't practice, they are basically techno managers.

Lawyers...I can understand the disdain people have for them.... But the disdain for engineers in this country makes me want to slap people.... Just about every invention and improvement in ANYTHING can be attributed to engineering. I guess we'd all rather live in log houses without power, AC, cars, phones, refridgeration, computers, washer/dryer, flood control, crop irrigation, guns, jeeps, tools, aerosol cans, safe food, condoms, golf clubs, trains, airplanes, space travel, television, radio, indoor plumbing...anything mass produced, pretty much anything...

Even settlers 400 years ago had tools and methods developed using early engineering.

<steps off soapbox>

tommudd · **Posted:** Mon Jul 20, 2009 12:28 pm

finally

but then I don't consider all the things mentioned above were first developed by "engineers", at least most of them did not need a title like that, they created something that worked for their purpose. Most of what I see is engineers over engineering things due to Lawyers wanting to sue everyone,

and yes I would rather live in a log cabin off the grid somewhere :wink:

Boiler · **Posted:** Mon Jul 20, 2009 1:21 pm

You don't have to be degree'd to invent something, but it usually helps to have a real understanding of the fundamentals of engineering. I'm willing to bet most of those inventions I mentioned were either done by engineers or had parts that were designed by engineers in them. Gears, etc.

tommudd wrote:

and yes I would rather live in a log cabin off the grid somewhere :wink:

I knew you would, and thats why I made the point that even log cabin dwellers have advancements due to engineering.

Think thatched roofs, spears, codpieces, and grinding corn on a stone....

nosnorb_808 · **Posted:** Mon Jul 20, 2009 1:50 pm

tonycrd wrote:

RRO needs some engineers.....I wouldn't even fit this to my KJ if they paid me.

What are you trying to point out? Have you looked at JBA arms with out the ball joints attached? JBA arms looks the same... :roll:

BjBnet · **Posted:** Mon Jul 20, 2009 4:01 pm

..and they are bolted on, I doubt there's any kind of excessive pressure on those points

JMSMN · **Posted:** Mon Jul 20, 2009 5:54 pm

They probably buy the plates from the same distributor.

STINGN · **Posted:** Mon Jul 20, 2009 5:56 pm

nosnorb_808 wrote:

tonycrd wrote:

RRO needs some engineers.....I wouldn't even fit this to my KJ if they paid me.

What are you trying to point out? Have you looked at JBA arms with out the ball joints attached? JBA arms looks the same... :roll:

how narrow the bridge is between both halfs

tommudd · **Posted:** Mon Jul 20, 2009 6:12 pm

JMSMN wrote:

They probably buy the plates from the same distributor.

So RRO is buying them from JBA? :shock:

nosnorb_808 · **Posted:** Mon Jul 20, 2009 6:42 pm

STINGN wrote:

nosnorb_808 wrote:

tonycrd wrote:

RRO needs some engineers.....I wouldn't even fit this to my KJ if they paid me.

What are you trying to point out? Have you looked at JBA arms with out the ball joints attached? JBA arms looks the same... :roll:

how narrow the bridge is between both halfs

So whats the point here? Like I said before RRO & JBA look exactly the same. If you have a set of JBA arms take a look at it.

JMSMN · **Posted:** Mon Jul 20, 2009 7:56 pm

I saw these balljoint plates for sale on line somewhere a little while back. So your telling me that JBA would take the time and money and cut all these pieces himself instead of ordering in bulk, cant hardly believe that. Dosent hardly seem cost effective.

Called and talked to marlin and he said they do laser cut some but when they get busy the buy them elsewhere.

PS He was a great guy to talk to. Anyone running the 3.5 arms. Am very interested in these.

Boiler · **Posted:** Mon Jul 20, 2009 8:12 pm

You could get those lasered or waterjetted pretty inexpensively, so yeah, he may cut his own parts if he has a CAD file. I get the feet for my rack waterjetted for $1.50 each (using my material & cad file) and the feet have probably 1.5 to 2x as long of a cut as those.

The problem is finding a shop that will bother with small quantities..

Edit: hey, no fair updating your post while I'm replying...

RRO INSANE A-ARMS: Updated w/ pics

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