Clearing up any misunderstandings about 7075 aluminum chassis

[minitt2015]

I wish people would stop trying to turn the arrma 8s rigs into Traxxas rigs. They're different and both have pros and cons.

I do not own any RC cars from either Arrma or Traxxas but looking to get one in coming months. So doing some research on both brands. For 1/5 scale , Traxxas xmaxx and Xrt both have some obvious advantages over Arrma 1/5 scale cars due to lower weight. Which is why both have much better control in air. Arrma 1/5 is difficult to land at least for noobs such as myself. When you miss a landing with Arrma 1/5 cars it’s likely something will break or bent because of extra weight. Not making this up. This is the impression I got from YouTube and user posts.

 

[KnowAir]

Great info herein! My take, if it's still useable as is, leave alone, if not, nothing to loose by straightening since it's only scrap now anyway

 

[Captain Bart]

Great info herein! My take, if it's still useable as is, leave alone, if not, nothing to loose by straightening since it's only scrap now anyway

If its still useable leave as is that’s right when i was working with 7075 t6 in the aircraft industry we were only allowed to heat treat it 3 times then it was deemed as non structural aluminum only to be used in galleys and cabin nit this was as the 7075 we used was alclad that means it had a thin layer of pure aluminum rolled onto each side and each heat treatment the pure aluminum would be gradually adsorbed into the 7075 Weakening it and with no way of finding out how much it was weakened we practically scrapped it .but to be clear once the grain structure is torn apart the only way to fix it is to smelt it and form a new sheet. Anealing can only solve stressed grain structure but not tears or micro ,and stress cracks in the shops i worked in any thing bent or twisted was scrapped as soon as it come into the shop no exceptions if there was a dent in a skin panel any thing more than 2 square inches and 5 mm deep would be labled contact manufacturer for maintenance action which always meant replace whole skin panels very big job like 12 foot by 6 foot panels some were milled skins costing a few 100 thousand dollars drill one hole in wrong place scrap

 

[Dan B.]

If its still useable leave as is that’s right when i was working with 7075 t6 in the aircraft industry we were only allowed to heat treat it 3 times then it was deemed as non structural aluminum only to be used in galleys and cabin nit this was as the 7075 we used was alclad that means it had a thin layer of pure aluminum rolled onto each side and each heat treatment the pure aluminum would be gradually adsorbed into the 7075 Weakening it and with no way of finding out how much it was weakened we practically scrapped it .but to be clear once the grain structure is torn apart the only way to fix it is to smelt it and form a new sheet. Anealing can only solve stressed grain structure but not tears or micro ,and stress cracks in the shops i worked in any thing bent or twisted was scrapped as soon as it come into the shop no exceptions if there was a dent in a skin panel any thing more than 2 square inches and 5 mm deep would be labled contact manufacturer for maintenance action which always meant replace whole skin panels very big job like 12 foot by 6 foot panels some were milled skins costing a few 100 thousand dollars drill one hole in wrong place scrap

Well, crap. I guess I’ll fire up the old smelting pot…
Seriously though, thanks for some great info.

 

[Captain Bart]

Well, crap. I guess I’ll fire up the old smelting pot…
Seriously though, thanks for some great info.

Glad to of been of assistance i know there is a lot of bullshit been passed around about 7075 6061 7075 is stronger

 

[RC-Dude]

an aircraft engineer with over 40 years experience working with 7075 aluminum i can say that trying to straighten a bent chassis plate is the totally wrong thing to do and here is why 7075 alluminium is only malleable after it has been heated up to a certain temp in an oven for a set amount of time after it has cooled down you have 30 minutes to work with it after 30 minutes it will start to harden again reaching full hardness in around 3 weeks you can artificially age hard by heating to 120degrees C for 72 hours for peak tensile strength its called age hardening . I can tell you if it is bent slightly leave it as it is . When it bends it breaks the metal grain structure apart if you try to straighten it it pulls the grain structure even further apart weakening it even more and can cause micro cracking which will become worse and grow due to vibration and flexing. If it is a bend from landing on a metal railing trying to straighten it could cause it to break off at the bend line to straighten any 7075 chassis you must re heat treat it to reform the grain structure and straighten it within 30 minutes of reaching room temperature you can prolong this time by placing the part in a deep freeze at -18degrees C while frozen it stays malleable but at room temp starts to harden again . So if you slightly bend a chassis made of 7075 aluminum live with it or buy a new chassis .in aircraft it is used for structural parts that need to be very strong and not flex or bend very much . And no your kitchen oven will not get hot enough you Need around 450 degrees C for 4 hours you can leave it at 120 degrees for 3 days to harden it after working it , hope this is clear for you guys ask questions if you have any i will answer as best i can .

Mostly we are talking about very small angles when chassis are bent. So bending the chassis back will not be a problem. And it will not break if it bends at the same spot again - the angle it's bent at is just too small in most cases for anything to break. Of course the aluminium is not as strong in the bent area anymore. Structure damaged internally. But it's still strong enough for bashing. So bend it back without worries. Even a corrected 7075 chassis will probably outlast the rest of the model by years.

Aluminium chassis are just for weight benefits - no other benefit. 7075 is brittle compare to other aluminium alloys. Steel beats 7075 in pretty much every other way when it comes to bashing. Just weight - 7075 wins.

So it's a nice background. Good to know.

Scratches on aluminium are a pretty much an intended breaking point. If I look at the bottom of my M2C chassis .... . Just don't tell the aluminium and it will keep doing it's job. Bending back Arrma 3s motor mounts after hitting a curb. Works fine, strength still enough to handle a lot of bashing.

If you build an Arrma rig from scratch and use an alumium Mojave chassis - the first thing you notice how wobbly the chassis is. But once you have everything mounted it's very stiff. Same effect for a corrected aluminium chassis. Stiff enough to bash. Internal structure damage not really an issue. Still strong enough.

I am not even sure if the angle (kickup) at the front end of M2C chassis is bent or milled. Seems to me to be a lot of material wasted if the angle is achieved by milling. I think it's bent but I'm not sure. If milled it would mean about the same amount of material used to make the chassis is wasted away by milling. That would really drive up the cost for the cutters and machine costs.

 

[KnowAir]

Mostly we are talking about very small angles when chassis are bent. So bending the chassis back will not be a problem. And it will not break if it bends at the same spot again - the angle it's bent at is just too small in most cases for anything to break. Of course the aluminium is not as strong in the bent area anymore. Structure damaged internally. But it's still strong enough for bashing. So bend it back without worries. Even a corrected 7075 chassis will probably outlast the rest of the model by years.

Aluminium chassis are just for weight benefits - no other benefit. 7075 is brittle compare to other aluminium alloys. Steel beats 7075 in pretty much every other way when it comes to bashing. Just weight - 7075 wins.

So it's a nice background. Good to know.

Scratches on aluminium are a pretty much an intended breaking point. If I look at the bottom of my M2C chassis .... . Just don't tell the aluminium and it will keep doing it's job. Bending back Arrma 3s motor mounts after hitting a curb. Works fine, strength still enough to handle a lot of bashing.

If you build an Arrma rig from scratch and use an alumium Mojave chassis - the first thing you notice how wobbly the chassis is. But once you have everything mounted it's very stiff. Same effect for a corrected aluminium chassis. Stiff enough to bash. Internal structure damage not really an issue. Still strong enough.

I am not even sure if the angle (kickup) at the front end of M2C chassis is bent or milled. Seems to me to be a lot of material wasted if the angle is achieved by milling. I think it's bent but I'm not sure. If milled it would mean about the same amount of material used to make the chassis is wasted away by milling. That would really drive up the cost for the cutters and machine costs.

According to M2C, they're milled from solid billet. If you check out their video about the Xmaxx basher bar, it's milled, not bent to achieve the angles needed. Sounds like alot of waste but, if they're keeping the millings clean I'm sure it's prime material for recycling.

 

[Dan B.]

I am not even sure if the angle (kickup) at the front end of M2C chassis is bent or milled. Seems to me to be a lot of material wasted if the angle is achieved by milling. I think it's bent but I'm not sure. If milled it would mean about the same amount of material used to make the chassis is wasted away by milling. That would really drive up the cost for the cutters and machine costs.

Could be milled, then bent and annealed before the hardening process?

 

[Surchaufeur]

I have bent back my slightly tweaked exb chassis once. So far so good

 

[Hector_Fisher]

There are definitely some higher stakes when it comes to aviation than with RCs. I don't think the risks levelize nearly as high in this hobby, which is why the quality assurance and quality control is as lackluster as it is. You absolutely need assurance in the material condition to ensure correct operation of a plane. You don't need that in RC. Given the worst case scenario breakage on a chassis, for example, the greatest risk it will likely pose is to your wallet.

I think the material science portion is interesting to talk about, but I definitely think it's worth trying to re-align minor bends (OR assess leaving them as is). Particularly if you don't have a massive budget.

 

[RC-Dude]

According to M2C, they're milled from solid billet. If you check out their video about the Xmaxx basher bar, it's milled, not bent to achieve the angles needed. Sounds like alot of waste but, if they're keeping the millings clean I'm sure it's prime material for recycling.

Could be milled, then bent and annealed before the hardening process?

Both ways perfectly fine to me...

There are definitely some higher stakes when it comes to aviation than with RCs. I don't think the risks levelize nearly as high in this hobby, which is why the quality assurance and quality control is as lackluster as it is. You absolutely need assurance in the material condition to ensure correct operation of a plane. You don't need that in RC. Given the worst case scenario breakage on a chassis, for example, the greatest risk it will likely pose is to your wallet.

I think the material science portion is interesting to talk about, but I definitely think it's worth trying to re-align minor bends (OR assess leaving them as is). Particularly if you don't have a massive budget.

I'm not meaning to bash what you are saying. Absolutely valid what you are writing. Please don't stop giving your input - it's background worth knowing.

I just think many bash the rigs so hard - the internal structure damage of a chassis is a little issue compared to overheated ESCs, fans stopping to run while driving, bearings needing to be changed, dust getting into motor, shimming etc. Just a different kind of philosophy. I used to upgrade a lot. Now I do when stuff breaks. Just wobble the front two tires on a new Kraton and it's actually amazing it's able to drive straight.

 

[KnowAir]

Both ways perfectly fine to me...




I'm not meaning to bash what you are saying. Absolutely valid what you are writing. Please don't stop giving your input - it's background worth knowing.

I just think many bash the rigs so hard - the internal structure damage of a chassis is a little issue compared to overheated ESCs, fans stopping to run while driving, bearings needing to be changed, dust getting into motor, shimming etc. Just a different kind of philosophy. I used to upgrade a lot. Now I do when stuff breaks. Just wobble the front two tires on a new Kraton and it's actually amazing it's able to drive straight.

I do like my Arrma's but yeah, you're right. They get sloppy pretty quickly at the turnbuckles and hinge pins. I am always amazed how much freeplay they have and still drive as well as they do.

 

[Dan B.]

I do like my Arrma's but yeah, you're right. They get sloppy pretty quickly at the turnbuckles and hinge pins. I am always amazed how much freeplay they have and still drive as well as they do.

Agreed. If someone finally makes superior ball ends I’ll throw a freaking party. Many make “upgraded” center threaded shafts for them (titanium, hardened steel, why?) but nobody is making or addressing the root cause of some really goddamned crappy threaded ball ends. Word: they currently suck out loud in all iterations and, sadly, when the best ball ends are sourced from Traxxas then… Houston, we have a problem.
Can somebody please work on a solution to toe links, camber links, upper and lower links, etc. that don’t exhibit nearly as much play as a broke crack whore in Tampa? It must be possible…

 

[Hector_Fisher]

Both ways perfectly fine to me...




I'm not meaning to bash what you are saying. Absolutely valid what you are writing. Please don't stop giving your input - it's background worth knowing.

I just think many bash the rigs so hard - the internal structure damage of a chassis is a little issue compared to overheated ESCs, fans stopping to run while driving, bearings needing to be changed, dust getting into motor, shimming etc. Just a different kind of philosophy. I used to upgrade a lot. Now I do when stuff breaks. Just wobble the front two tires on a new Kraton and it's actually amazing it's able to drive straight.

No offense taken I'd personally correct minor bends (and have). Was just asking from a material science perspective regarding "cold working". I agree I would never do it purposefully, nor in case of major bends.

For scratches in the chassis from wear on the ground, those are different from micro cracking and hairline cracks. While the gouges or scratches do present a weakness on the surface, I believe you should be more concerned about cyclical loading and micro-cracking on a granular level within the part internals.

 

[Moirae]

I do not own any RC cars from either Arrma or Traxxas but looking to get one in coming months. So doing some research on both brands. For 1/5 scale , Traxxas xmaxx and Xrt both have some obvious advantages over Arrma 1/5 scale cars due to lower weight. Which is why both have much better control in air. Arrma 1/5 is difficult to land at least for noobs such as myself. When you miss a landing with Arrma 1/5 cars it’s likely something will break or bent because of extra weight. Not making this up. This is the impression I got from YouTube and user posts.

You say lower weight gives them advantages and I say arrma heavier rigs make them more fun to drive and jump. I have the XRT/Xmaxx and the Outcast/Kraton 8s and my arrma rigs definitely don't break more often. If anything I've had more problems with the xrt's than anything else and I still love them but being "lighter" really doesn't mean much imo.

Being lighter also means nothing for air control. The lighter XRT can't even backflip out of the box. What has a bigger affect on air control are the TIRES. Non belted tires give the best air control and the weight of the tires also plays a big role. You know which rig has the best air control? whichever rig I put proline trenchers on

This is my outcast 8s and air control is still perfectly fine even under the worst conditions of having belted tires.

Video of the wifey and I both jumping XRT's. You can clearly see numerous times in that video where she was barely able to correct out of some jumps and her XRT is a helluva lot lighter than my outcast 8s.

I would love to know what youtubers you were watching that gave you the wrong impressions because all of the serious bashers on youtube that I've seen have all made it pretty clear they prefer arrma 8s over traxxas 8s for serious bashing. Maybe the traxxas stuff is more durable if you don't bash very hard? I don't know of any even halfway serious bashers that prefer traxxas rigs. The people who send traxxas rigs on youtube are on a very very short list imo.

 

[Dan B.]

You say lower weight gives them advantages and I say arrma heavier rigs make them more fun to drive and jump. I have the XRT/Xmaxx and the Outcast/Kraton 8s and my arrma rigs definitely don't break more often. If anything I've had more problems with the xrt's than anything else and I still love them but being "lighter" really doesn't mean much imo.

Being lighter also means nothing for air control. The lighter XRT can't even backflip out of the box. What has a bigger affect on air control are the TIRES. Non belted tires give the best air control and the weight of the tires also plays a big role. You know which rig has the best air control? whichever rig I put proline trenchers on

This is my outcast 8s and air control is still perfectly fine even under the worst conditions of having belted tires.

Video of the wifey and I both jumping XRT's. You can clearly see numerous times in that video where she was barely able to correct out of some jumps and her XRT is a helluva lot lighter than my outcast 8s.

I would love to know what youtubers you were watching that gave you the wrong impressions because all of the serious bashers on youtube that I've seen have all made it pretty clear they prefer arrma 8s over traxxas 8s for serious bashing. Maybe the traxxas stuff is more durable if you don't bash very hard? I don't know of any even halfway serious bashers that prefer traxxas rigs. The people who send traxxas rigs on youtube are on a very very short list imo.

Dude, your vids just keep getting better. Kudos to you for some great production value and awesome drone work. Nice job, y’all!

 

[Moirae]

Dude, your vids just keep getting better. Kudos to you for some great production value and awesome drone work. Nice job, y’all!

All I do is drive the rc and toss in a good idea every other video! Well I guess I did come up with the smart idea to upgrade to a drone with a better camera after she got our old one lost in a tree! Maybe I do deserve a little credit.

Thank you bro

 

[minitt2015]

You say lower weight gives them advantages and I say arrma heavier rigs make them more fun to drive and jump. I have the XRT/Xmaxx and the Outcast/Kraton 8s and my arrma rigs definitely don't break more often. If anything I've had more problems with the xrt's than anything else and I still love them but being "lighter" really doesn't mean much imo.

Being lighter also means nothing for air control. The lighter XRT can't even backflip out of the box. What has a bigger affect on air control are the TIRES. Non belted tires give the best air control and the weight of the tires also plays a big role. You know which rig has the best air control? whichever rig I put proline trenchers on

This is my outcast 8s and air control is still perfectly fine even under the worst conditions of having belted tires.

Video of the wifey and I both jumping XRT's. You can clearly see numerous times in that video where she was barely able to correct out of some jumps and her XRT is a helluva lot lighter than my outcast 8s.

I would love to know what youtubers you were watching that gave you the wrong impressions because all of the serious bashers on youtube that I've seen have all made it pretty clear they prefer arrma 8s over traxxas 8s for serious bashing. Maybe the traxxas stuff is more durable if you don't bash very hard? I don't know of any even halfway serious bashers that prefer traxxas rigs. The people who send traxxas rigs on youtube are on a very very short list imo.

In your own outcast 8s video which you shared showed you upgraded the chassis. I am assuming you already bent your stock Arrma chassis or upgraded anyway because you knew it would bent. Lighter weight does make a big difference specially when you don't land on all 4. its just plain physics and inertia. Take Xmaxx for example. You take that and a kraton 8s to a skatepark and chances are xmaxx will outlive kraton 8s almost guranteed. Even if you break the chassis on xmaxx its like only 25-30 bucks to replace.

 

[KnowAir]

In your own outcast 8s video which you shared showed you upgraded the chassis. I am assuming you already bent your stock Arrma chassis or upgraded anyway because you knew it would bent. Lighter weight does make a big difference specially when you don't land on all 4. its just plain physics and inertia. Take Xmaxx for example. You take that and a kraton 8s to a skatepark and chances are xmaxx will outlive kraton 8s almost guranteed. Even if you break the chassis on xmaxx its like only 25-30 bucks to replace.

I see alot more of the "big air" YT guys prefer the aluminum chassis vs plastic. Mind you they all are running upgraded chassis of one brand or another. The M2C bash plate is a huge help for really airing out the Xmaxx it seems. Which I find interesting since it's just the rather flexible stock plastic skid plates that it attaches to.. seeing is believing tho so. It works.
There's more to it than just the chassis though, the TRX drivetrain doesn't seem as strong as Arrma's from my experience. The Arrma's seem to hold up much better long term to upgraded electronics than the TRX models, especially the diffs. Bulkheads/gearboxes are another area where I think TRX has a weaker design. Not knocking the TRX, I like my Xmaxx, just that I feel the Arrma's are better suited to big air, after upgrades of course..
Edit, I also don't think a Kraton 8s is a fair comparison to the Xmaxx, it has a considerably longer wheelbase than the Xmaxx and is inherently more prone to chassis damage from jumping because of it. The Outcast is much closer in dimensions to the Xmaxx, and the Outcast exb chassis does quite well as is for jumping at any rational levels.

 

[Moirae]

In your own outcast 8s video which you shared showed you upgraded the chassis. I am assuming you already bent your stock Arrma chassis or upgraded anyway because you knew it would bent. Lighter weight does make a big difference specially when you don't land on all 4. its just plain physics and inertia. Take Xmaxx for example. You take that and a kraton 8s to a skatepark and chances are xmaxx will outlive kraton 8s almost guranteed. Even if you break the chassis on xmaxx its like only 25-30 bucks to replace.

No bro, my chassis tweaked because I nose dived a sidewalk. If it would have been the xrt or Xmaxx I would have broke more than the chassis I'm sure. Traxxas chassis is cheaper for sure but time is also money and replacing cracked and broken plastic chassis all the time is not something that sounds fun or efficient. My stock chassis lasted me a year and would still be Gucci if I wasn't an idiot. You pay more up front for an m2c chassis but you never have to worry about it again. Funny enough I just nose dived my outcast 8s in the same way again yesterday and m2c chassis straight as an arrow while my motor mount snapped .

You also ignored 90% of my post. No hardcore bashers prefer Traxxas over arrma and there is a reason for that. Show me a youtuber who consistently bash Traxxas stuff hard besides kevin talbot? And even he doesn't really be sending them like duperbash, rcdude and Aldo to name 3 serious bashers who own both brands and prefer to bash harder with arrma because of durability.

I'm not even sure why you posted tbh. It sounds like you already have your mind made up and the opinions of people with actual experience don't matter to you.

I actually forgot to mention thunder rc as well. He was a big Xmaxx fan boy until he got the new outcast rtr. Even he has preferred the outcast now .

Let's not forget to mention the stock electronics either. Xmaxx esc, motor, and servo are garbage and all 3 fail in comparison to arrma 8s electronics by a large margin.