Go Back  R/C Tech Forums > General Forums > Electric Off-Road
How "Elastic" is a 7075 - T6 Chassis >

How "Elastic" is a 7075 - T6 Chassis

How "Elastic" is a 7075 - T6 Chassis

Old 03-14-2016, 08:59 AM
  #1  
Tech Fanatic
Thread Starter
iTrader: (15)
 
Join Date: Jan 2016
Location: Rhode Island
Posts: 783
Trader Rating: 15 (100%+)
Default How "Elastic" is a 7075 - T6 Chassis

I'm just wondering how elastic a 7075 - T6 alum chassis is, more specifically a TLR 22 3.0 chassis.

As in, can it bend and return to its original state quite well?

I ask this because i was popping on a ball cup yesterday, and I put the pliers in a bad spot (ontop of the rear camber block, and under the rear square part of the chassis where the hinge pins mount) and saw the rear camber block and rear part of the chassis flex into each other...not sure if this was the chassis bending, the camber block, the shock tower or all of them.

Because I'm OCD I then measured the chassis to camber link with my meter and the side i squeezed together in the wrong spot was about .2-.3mm closer (I know it's small). This could be coincidence I suppose...but it got me thinking...

How elastic are these chassis? Is it likely that I bent my chassis just a small amount? Or is it more likely it was already like this .2-.3mm off on one side, or perhaps the shock tower is the culprit and allowed the bending? Perhaps loosening surrounding screws and re tightening would bring it back to all square.

Last edited by lyons238; 03-14-2016 at 10:05 AM.
lyons238 is offline  
Old 03-14-2016, 09:28 AM
  #2  
Suspended
iTrader: (61)
 
Join Date: Jan 2011
Posts: 4,124
Trader Rating: 61 (100%+)
Default

Aluminum 7075-T6; 7075-T651

Subcategory: 7000 Series Aluminum Alloy; Aluminum Alloy; Metal; Nonferrous Metal

Close Analogs:

Composition Notes:
A Zr + Ti limit of 0.25 percent maximum may be used with this alloy designation for extruded and forged products only, but only when the supplier or producer and the purchaser have mutually so agreed. Agreement may be indicated, for example, by reference to a standard, by letter, by order note, or other means which allow the Zr + Ti limit.
Aluminum content reported is calculated as remainder.
Composition information provided by the Aluminum Association and is not for design.

Key Words: Aluminium 7075-T6; Aluminium 7075-T651, UNS A97075; ISO AlZn5.5MgCu; Aluminium 7075-T6; Aluminium 7075-T651; AA7075-T6

Component Wt. %

Al 87.1 - 91.4
Cr 0.18 - 0.28
Cu 1.2 - 2
Fe Max 0.5
Component Wt. %

Mg 2.1 - 2.9
Mn Max 0.3
Other, each Max 0.05
Other, total Max 0.15
Component Wt. %

Si Max 0.4
Ti Max 0.2
Zn 5.1 - 6.1
Material Notes:
General 7075 characteristics and uses (from Alcoa): Very high strength material used for highly stressed structural parts. The T7351 temper offers improved stress-corrosion cracking resistance.

Applications: Aircraft fittings, gears and shafts, fuse parts, meter shafts and gears, missile parts, regulating valve parts, worm gears, keys, aircraft, aerospace and defense applications; bike frames, all terrain vehicle (ATV) sprockets.

Data points with the AA note have been provided by the Aluminum Association, Inc. and are NOT FOR DESIGN.

Physical Properties Metric English Comments

Density 2.81 g/cc 0.102 lb/in AA; Typical

Mechanical Properties

Hardness, Brinell 150 150 AA; Typical; 500 g load; 10 mm ball
Hardness, Knoop 191 191 Converted from Brinell Hardness Value
Hardness, Rockwell A 53.5 53.5 Converted from Brinell Hardness Value
Hardness, Rockwell B 87 87 Converted from Brinell Hardness Value
Hardness, Vickers 175 175 Converted from Brinell Hardness Value
Ultimate Tensile Strength 572 MPa 83000 psi AA; Typical
Tensile Yield Strength 503 MPa 73000 psi AA; Typical
Elongation at Break 11 % 11 % AA; Typical; 1/16 in. (1.6 mm) Thickness
Elongation at Break 11 % 11 % AA; Typical; 1/2 in. (12.7 mm) Diameter
Modulus of Elasticity 71.7 GPa 10400 ksi AA; Typical; Average of tension and compression. Compression modulus is about 2% greater than tensile modulus.
Poisson's Ratio 0.33 0.33
Fatigue Strength 159 MPa 23000 psi AA; 500,000,000 cycles completely reversed stress; RR Moore machine/specimen
Fracture Toughness 20 MPa-m 18.2 ksi-in K(IC) in S-L Direction
Fracture Toughness 25 MPa-m 22.8 ksi-in K(IC) in T-L Direction
Fracture Toughness 29 MPa-m 26.4 ksi-in K(IC) in L-T Direction
Machinability 70 % 70 % 0-100 Scale of Aluminum Alloys
Shear Modulus 26.9 GPa 3900 ksi
Shear Strength 331 MPa 48000 psi AA; Typical

Cite: http://asm.matweb.com/search/Specifi...ssnum=MA7075T6
Socket is offline  
Old 03-14-2016, 10:02 AM
  #3  
Tech Fanatic
Thread Starter
iTrader: (15)
 
Join Date: Jan 2016
Location: Rhode Island
Posts: 783
Trader Rating: 15 (100%+)
Default

Thanks ^

I already looked at that though, I'm just wondering in lamens terms can a chassis like this take aq good squeeze from pliers when connected to all other bracing and flex a bit and return to original state.
lyons238 is offline  
Old 03-14-2016, 12:23 PM
  #4  
Tech Addict
iTrader: (27)
 
sacmiata's Avatar
 
Join Date: Jan 2015
Posts: 653
Trader Rating: 27 (100%+)
Default

To answer your question yes you can. alluminum is not nearly as elastic as steel and can permanently deform much easier. That being said even if you clamped down 15 lbs of force with a 1/2" length for a moment you would only have about 6k psi of stress so likely not enough for damage the chassis.....you would need closed to 50k or more before I would think that you could even start to deform it.

I guessed at the moment length and took some liberties with the moment of inertia about the axis but bussing this length of the chassis is at least 2" long.

I would back out the screws alittle and re-tighten

Also if you have a piece of glass or something very flat can you put under the chassis to see if it tweeked the chassis. Again I don't think you could of

Last edited by sacmiata; 03-14-2016 at 12:37 PM.
sacmiata is offline  
Old 03-14-2016, 12:55 PM
  #5  
Tech Fanatic
Thread Starter
iTrader: (15)
 
Join Date: Jan 2016
Location: Rhode Island
Posts: 783
Trader Rating: 15 (100%+)
Default

Originally Posted by sacmiata View Post
To answer your question yes you can. alluminum is not nearly as elastic as steel and can permanently deform much easier. That being said even if you clamped down 15 lbs of force with a 1/2" length for a moment you would only have about 6k psi of stress so likely not enough for damage the chassis.....you would need closed to 50k or more before I would think that you could even start to deform it.

I guessed at the moment length and took some liberties with the moment of inertia about the axis but bussing this length of the chassis is at least 2" long.

I would back out the screws alittle and re-tighten

Also if you have a piece of glass or something very flat can you put under the chassis to see if it tweeked the chassis. Again I don't think you could of
This is what I was looking for...thank you.

Basically I clamped with pliers to pop a ball cup on so i had the rear camber block on a TLR 22 3.0 and the bottom of the chassis in between the pliers. I squeezed about as hard as you need to pop a ball cup on, maybe a tad harder cuz the ball slipped to the side.

I saw the camber block flex toward the chassis and then back. I figure this is a combination of the chassis flexing up, the camber block flexing down, and the shock tower flexing as well. so not even all the force could have been applied to the chassis considering this, and the fact that its all braced with the trans, shock tower, and hinge pin mounts...

That got me thinking how elastic are these chassis....

Thank you for your advice, I will loosen, align, and re tighten. Also, good idea with the glass!
lyons238 is offline  
Old 03-14-2016, 03:09 PM
  #6  
Tech Elite
 
werner sline's Avatar
 
Join Date: Dec 2012
Posts: 2,987
Default

for my jumping and crashing style of driving (1/8 buggy ), I use the chassis flex as much as possible to avoid breaking parts
therefore I put a shorter or softer chassis brace
But if I put them away, I may bend the chassis. So aluminium has its limits
werner sline is offline  
Old 03-14-2016, 04:17 PM
  #7  
Tech Adept
 
avaldes's Avatar
 
Join Date: Oct 2015
Posts: 165
Default

Only you can tell if you bent your chassis. If it took a set then you bent it. You can likely bend it back if it is a small deflection. Do that too many times and it will break.
avaldes is offline  
Old 03-14-2016, 08:44 PM
  #8  
Tech Fanatic
Thread Starter
iTrader: (15)
 
Join Date: Jan 2016
Location: Rhode Island
Posts: 783
Trader Rating: 15 (100%+)
Default

i looseened the screws. retightened them mostly star pattern, but favored the opposite side just for a test and sure enough, now the otherside was .1-.2mm off. so i didnt bend the chassis.

should have done that test first but i was at work while thinking about it. But if anyone ever tweaks something a bit. measure it. Loosen all the surrounding fasteners, align and retighten.

this thread can be closed or ignored.

thanks
lyons238 is offline  
Old 03-14-2016, 10:03 PM
  #9  
Tech Adept
 
avaldes's Avatar
 
Join Date: Oct 2015
Posts: 165
Default

No it's a good one. The onroad guys deal with this "tweaking" the chassis all the time. Same in full scale racing.
avaldes is offline  
Old 03-14-2016, 11:58 PM
  #10  
Tech Addict
iTrader: (27)
 
sacmiata's Avatar
 
Join Date: Jan 2015
Posts: 653
Trader Rating: 27 (100%+)
Default

I agree good thread

When i did my b5m I spent a lot of time being careful and everything was perfect. A few laps and crashes later your perfection is ruined and I lost track of those fractions of a millimeter.

I often wonder of it makes a big difference off road like it does onroad. I race a Miata (no laughing) and corner balancing can make or break your lap times.

Build it right and you only have your driving skills to blame! To bad money can't fix that!
sacmiata is offline  
Old 03-15-2016, 01:44 AM
  #11  
Super Moderator
iTrader: (2)
 
Grizzbob's Avatar
 
Join Date: Feb 2002
Location: Sand Springs, OK
Posts: 3,073
Trader Rating: 2 (100%+)
Default

Originally Posted by avaldes View Post
No it's a good one. The onroad guys deal with this "tweaking" the chassis all the time. Same in full scale racing.
Yup, I also agree, & in fact that's why I think Tamiya changed from an aluminum chassis on their TRF201XMW to a new molded one on the TRF211XM. They had been getting a fair number of complaints from their sponsored drivers about the aluminum chassis tweaking, so they tried out the new plastic(it's white in color) & everyone seemed to really like it(& I can understand why, I'm really liking it myself).....
Grizzbob is offline  
Old 03-15-2016, 09:10 AM
  #12  
Tech Fanatic
Thread Starter
iTrader: (15)
 
Join Date: Jan 2016
Location: Rhode Island
Posts: 783
Trader Rating: 15 (100%+)
Default

Originally Posted by avaldes View Post
No it's a good one. The onroad guys deal with this "tweaking" the chassis all the time. Same in full scale racing.
thanks, i guess i was being hard on myself and thought i was the only OCD one worrying about fractions of a mm lol.

Originally Posted by sacmiata View Post
I agree good thread

When i did my b5m I spent a lot of time being careful and everything was perfect. A few laps and crashes later your perfection is ruined and I lost track of those fractions of a millimeter.

I often wonder of it makes a big difference off road like it does onroad. I race a Miata (no laughing) and corner balancing can make or break your lap times.

Build it right and you only have your driving skills to blame! To bad money can't fix that!
exactly. i track my sti and always am obsessing about alignment specs etc.

Originally Posted by Grizzbob View Post
Yup, I also agree, & in fact that's why I think Tamiya changed from an aluminum chassis on their TRF201XMW to a new molded one on the TRF211XM. They had been getting a fair number of complaints from their sponsored drivers about the aluminum chassis tweaking, so they tried out the new plastic(it's white in color) & everyone seemed to really like it(& I can understand why, I'm really liking it myself).....
yeah at first i didnt like it, but i heard its a very unique composite. i heard its extremely rigid and durable.

well see how this alum chassis holds up anyway. hopefully its good.
lyons238 is offline  

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.