Clearing up any misunderstandings about 7075 aluminum chassis

[Captain Bart]

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 .

 

[Tex Koder]

Thank you for sharing your knowledge & experience.

So would you say that you need to heat the entire chassis or can you go for "spot heating" with a butane torch (or heat gun) on the 'damaged' chassis section instead..?
Keeping it at a certain distance from the flame/heat source and using a thermometer -to monitor the heat applied.. for the amount of time necessary.

 

[Senton_Prime]

You gonna butane it for 4hrs straight and maintain that 840° all the while..

Thank you for sharing your knowledge & experience.

So would you say that you need to heat the entire chassis or can you go for "spot heating" with a butane torch (or heat gun) on the 'damaged' chassis section instead..?
Keeping it at a certain distance from the flame/heat source and using a thermometer -to monitor the heat applied.. for the amount of time necessary.

 

[slick2500]

This same concept applies to basically all metal parts they put on these cars, they should be heated up to a certain temperature before you try to straighten them be it 7075, 6065, titanium, stainless steel or hardened steel.

 

[Captain Bart]

Thank you for sharing your knowledge & experience.

So would you say that you need to heat the entire chassis or can you go for "spot heating" with a butane torch (or heat gun) on the 'damaged' chassis section instead..?
Keeping it at a certain distance from the flame/heat source and using a thermometer -to monitor the heat applied.. for the amount of time necessary.

It’s called solution heat treatment I wouldn’t recommend a blow torch 4 hours is a long time to heat up using a blow touch i would say from experience you should always heat up the whole thing as thermal expansion in the metal can cause distortion and internal stress of the none heated areas and the area heated would be weak for a long time until it fully aged hardened

 

[SrC]

Slightly Tweaked Chassis' and Towers I can deal with. With severely bent Towers, I may bend them back, (6061) and take my chances. They never get perfect, close enough, and still usuable. Buying some more time till I need a new one. 7075 is much too hard to even bother bending back straight. I tried and it can snap all too easily. I don't even bother with heat.
Bending back Ti doesn't work for me.. Will snap in a second. Bent Ti is junk once it happens.

 

[slick2500]

Slightly Tweaked Chassis' and Towers I can deal with. With severely bent Towers, I may bend them back, (6061) and take my chances. They never get perfect, close enough, and still usuable. Buying some more time till I need a new one. 7075 is much too hard to even bother bending back straight. I tried and it can snap all too easily. I don't even bother with heat.
Bending back Ti doesn't work for me.. Will snap in a second. Bent Ti is junk once it happens.

I managed to bend back my eBay titanium shock towers, they still aren't 100% flat but they are much flatter than they were before.

Well they were more like Chinesium than Titanium because these didn't even last a few bash sessions before they bent. I have had the same set of Scorched titanium shock towers on my Kraton for well over a year now and they are still as straight as they were when they were new. These weren't even straight when new.

 

[Dan B.]

A great deal of the final properties of 7075 aluminum is decided by the heat treating process. The best known, and most effective, is the process that results in ”T6” (as @Captain Bart pointed out) and it seems as though that’s what many people seem to automatically assume they have. As a final product, all 7075 is not created equally. The following is from the Speedy Metals website:
7075 may be solution annealed at 900°F for 2 hours at temperature, followed by a water quench. The alloy may then be given a precipation hardening (aging) heat treatment. Precipitation strengthening (aging) is done at 250°F for 24 hours and air cooled for T6.
There have been a number of people on this forum with angry posts accusing Arrma of lying about using 7075 aluminum on their EXB chassis and other components. I doubt that Arrma is lying, but I also doubt any of their aluminum is finished to T6 spec. If it was , their EXB chassis wouldn’t bend nearly as easily. The reason M2C’s high end aluminum chassis (and others) don’t bend is because they are actually produced from 7075-T6.
To reiterate, all 7075 aluminum is not created equally. This is from Wiki:
It is produced in many tempers, some of which are 7075-0, 7075-T6, 7075-T651. The first 7075 was developed in secret by a Japanese company, Sumitomo Metal, in 1935, but reverse engineered by Alcoa in 1943, after examining a captured Japanese aircraft. 7075 was standardized for aerospace use in 1945.

 

[Captain Bart]

A great deal of the final properties of 7075 aluminum is decided by the heat treating process. The best known, and most effective, is the process that results in ”T6” (as @Captain Bart pointed out) and it seems as though that’s what many people seem to automatically assume they have. As a final product, all 7075 is not created equally. The following is from the Speedy Metals website:
7075 may be solution annealed at 900°F for 2 hours at temperature, followed by a water quench. The alloy may then be given a precipation hardening (aging) heat treatment. Precipitation strengthening (aging) is done at 250°F for 24 hours and air cooled for T6.
There have been a number of people on this forum with angry posts accusing Arrma of lying about using 7075 aluminum on their EXB chassis and other components. I doubt that Arrma is lying, but I also doubt any of their aluminum is finished to T6 spec. If it was , their EXB chassis wouldn’t bend nearly as easily. The reason M2C’s high end aluminum chassis (and others) don’t bend is because they are actually produced from 7075-T6.
To reiterate, all 7075 aluminum is not created equally.

Thanks but even if it not t6 treated it will still weaken thr grainstructure when trying to bend back to shape if there is a metal handler near you you could get the 7075 arrma chassis heat treated straightened and then age hardend to t6 spec but i think it would cost more than it would to buy an m2c chassis also there are diffent types of 7075 with different alloying specs aircraft quality is very expensive one sheet depending on thickness can cost well over 600 dollars USand 7075 will age harden even if untreated sheets are made by heating billets of the aloy then hot rolled as they cool they harden and the hardness is not measurable as such ,that is why aluminum chassis are expensive the sheet you buy must be made to fit the oven you have access to

 

[Steve B in Vegas]

Chineseium galore.....

 

[MrTitanium]

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

Well said.

 

[minitt2015]

nicely explained. this just means Arrma isn’t using the right quality aluminum needed then. Adding more metal increases weight and increases damage potential. I feel like they should seriously consider non metal options. All these weight on kraton 8s/6s actually makes them very sluggish when compared to xrt.

 

[hobo]

nicely explained. this just means Arrma isn’t using the right quality aluminum needed then. Adding more metal increases weight and increases damage potential. I feel like they should seriously consider non metal options. All these weight on kraton 8s/6s actually makes them very sluggish when compared to xrt.

my kraton 6s full m2c upgraded is not sluggish at all and that's with stock motor esc its a bit harder to backflip than my stock kraton though

 

[Moirae]

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

 

[hobo]

the traxxas cars remind me of vacuum cleaner's although I've never had a traxxas car just don't like them at all they seem to look too toyish to me. when I see the xmaxx running on youtube it seems to be all over the place doesn't seem to handle well at all

 

[Radiocontrolsoul]

the traxxas cars remind me of vacuum cleaner's although I've never had a traxxas car just don't like them at all they seem to look too toyish to me. when I see the xmaxx running on youtube it seems to be all over the place doesn't seem to handle well at all

I enjoy driving it because it handles the way it does.
It’s different.

 

[Dan B.]

I’ve never to spoken to anyone who had an XMaxx who didn’t love it. I have no experience with them, but people really seem to love them.

 

[Moirae]

the traxxas cars remind me of vacuum cleaner's although I've never had a traxxas car just don't like them at all they seem to look too toyish to me. when I see the xmaxx running on youtube it seems to be all over the place doesn't seem to handle well at all

I have one and I will would hate it if it didn't have the m2c wide kit. Awesome with it though I'm more of a truggy guy personally

 

[Hector_Fisher]

Excellent material science discussion. I appreciate your expertise

Once a part has been (essentially) cold worked from a bad crash impact, the grain structures has already changed. While you could potentially argue that the bend from the impact has performed some sort of work hardening, and that now the part is stronger, you may have also caused too much plastic deformation. This would all depend on the extent of the bending. If the part was badly bent, further attempts to "cold work" by bending back would likely just break the grain structure and seriously weaken the part.

In some cases, with small bends or deformations in a high material quality part, I do think you can retain reasonable levels of strength after bending back. But I am constantly reminded that the part is likely to be more brittle than in stock form.

For minor bends, would you recommend attempting to re-align the part? Unless someone had the right equipment and lots of experience with materials sciences, I don't think I could recommend attempting any annealing at home.

 

[Captain Bart]

Excellent material science discussion. I appreciate your expertise

Once a part has been (essentially) cold worked from a bad crash impact, the grain structures has already changed. While you could potentially argue that the bend from the impact has performed some sort of work hardening, and that now the part is stronger, you may have also caused too much plastic deformation. This would all depend on the extent of the bending. If the part was badly bent, further attempts to "cold work" by bending back would likely just break the grain structure and seriously weaken the part.

In some cases, with small bends or deformations in a high material quality part, I do think you can retain reasonable levels of strength after bending back. But I am constantly reminded that the part is likely to be more brittle than in stock form.

For minor bends, would you recommend attempting to re-align the part? Unless someone had the right equipment and lots of experience with materials sciences, I don't think I could recommend attempting any annealing at home.

They problem is not the work hardening the bend will tear the grain structure apart bending it backe causes more grainstructure to part and curses at the least micro cracks that propagate with vibration and flexing if the metal shows dullling on bare metals it is best to throw in the trash as the metal dulling means the grain structure has beendestroyed bend it back and you have a two piece chassis