Corrosion resistant, light weight TJ frame

Good point! Kinda ties you in to one brand of lift, doesn't it? Which ever the frame is modelled after is the one it has to be.
Mostly, I'm wondering how the non-factory control arm mount locations are being determined. Longer arms for the sake of length (contrary to popular belief) is not correct. The reduced weight of the frame will change the dynamics of the suspension and necessarily the mount locations as compared to a well configured mid arm setup.
 
  • Like
Reactions: rowen01960
Mostly, I'm wondering how the non-factory control arm mount locations are being determined. Longer arms for the sake of length (contrary to popular belief) is not correct. The reduced weight of the frame will change the dynamics of the suspension and necessarily the mount locations as compared to a well configured mid arm setup.

Agreed ... lots of length options which should be based on a desired/known drive cycle/spectra ... any lift will raise the vertical CG, a mass reduction (frame) will exacerbate the Polar Moment further ... handling at speed will suffer ... travel or clearance increase effects need to be fully appreciated.

In general I try to extract and match the Flexural Response of the OE beam I am converting to composites. The correlation process defines a set of Moment/Forces required to achieve the material Limits/Allowables for each OE part at DSL/DLL/DLL. (Ref published min Tensile, min Yield and S-N working curves)

This set of Moments/Forces is then iteratively applied to the Composite Replacement Design to match flexural responses to the OE within 5%. At this point the 2 parts are equivalent, except the Composite part will be significantly stronger (higher tensile and compressive strength)

Once a Composite Beam has been flexurally “matched/correlated” to the OE beam, it is then tailored to a desired/improved response by decoupling Eix, Eiy (Bending) and GJ (Torsion) beam properties. Fortunately this is relatively straight forward with Anisotropic/Orthotropic laminates.

The reduced mass of the vehicle (-200# for the frame alone) will effect both the Polar Moment and NVH ... which will require geometry tweeking (>2kHz) to eliminate Drivetrain “Buzz”

All Laminated Parts (Frames and Suspension Arms/Rods, will be derived from market accepted Steel/Aluminum Part Geometry for HDPT locations ... all bushes/rod ends will be COTS, no need to reinvent the wheel.

I hope the above helps mitigate concerns for those that want to have a non-stock suspension (within a limits) ...

r/
 
Good point! Kinda ties you in to one brand of lift, doesn't it? Which ever the frame is modelled after is the one it has to be.

This would be correct if there were non-standard width Rod Ends/Bushings ... fortunately there are only 2 popular “std” widths and the bulk of the adjustable/dble adjustable standard arms are of 3 lengths with 1-1.5” adjustment per end ... so the brackets (2 widths) would have 9/16 - 3/4 dia Bearing Inserts for the thru bolts, and be positionable for bonding with a +/- 3” axial tolerance on the Rail CL ... Long arms would require Rail attachment closer to the mid WB location ... note ... bracket is fixture bonded to the rail ... it is an axial location specific to the arm length ...

As most Lower Rod HDPTs are on the CL (optimal) of the Frame Rail ... the procedure is Control Rod MFG independant ... I hope ... :)
 
I understand about 95% of the words, but follow about 50-75% of the sentences... Fairly sure you operate above my pay grade.

And you never know, I may need to do an 11m drop in ;)

Pressure points from rocks are also a serious concern, when you drop the full weight of the jeep onto the edge of a rock 1/8" wide that's a huge amount of psi. If the outside sheath can distribute that load then great. Keep in mind that there are guys looking for something stronger that solid aluminum stock sheathed on 3x.5 wall Dom tube... Because they bend it.


There must have been a time
when we could have said no.
 
I understand about 95% of the words, but follow about 50-75% of the sentences... Fairly sure you operate above my pay grade.

And you never know, I may need to do an 11m drop in ;)

Pressure points from rocks are also a serious concern, when you drop the full weight of the jeep onto the edge of a rock 1/8" wide that's a huge amount of psi. If the outside sheath can distribute that load then great. Keep in mind that there are guys looking for something stronger that solid aluminum stock sheathed on 3x.5 wall Dom tube... Because they bend it.


There must have been a time
when we could have said no.

Pay grades are of value only when they represent added value to the entity doing the paying ...:)

wow ... my communication skills must be getting better in my old age ... :) 10 years ago at least 50% of the Design Review teams were mumbling something about incoherency ... :) so we should meet up and have a beer (Guiness in my case).

Yea ... drop tests on tires are not that hard on suspended Frames ... the tires generally blow with the overload (150% rated load/pressure)

Point Loads ... yes ... all about contact area ... the more the better ... your 1/8” “guillotine” would have to be a very hard rock indeed ... more importantly a 3mm x 33mm “guillotine” style transverse contact edge (single rail) would statically support 3G (4500kg) within the elastic region of a Hybrid Carbon/Glass laminate 60x125mm Super Elliptical beam profile.

A 10m drop onto this “Guillotine” would put any metallic frame into non-transportable plastic deformation ... the composite frame would elastically deform/fracture and likely lose about 30% of its stiffness ... but you could get home ... to replace the frame.

A 10m drop capability is possible using common geometry with lower drop capability frames (Wall thickness increase) ... but only if all other components are verified drop capable ... you are talking Red Bull Games here or the the Dakar Rally ... but these have a forward velocity vector and will be easier to manage ... provided the Suspension stays on .. I like Rock Climbers and Time Trials as things happen slower and are more controllable ...

Realistically, vertical drops of less than 2.5m should allow the frame to stay within it’s fatigue life ... the trick will be to ensure all other “non-elastic” parts are not effected by the drop ... fasteners, wiring looms ... etc etc are not designed for this kind of shock loading... if the contact area increases

So the thickness of the UHMWPE Abrasion Cover really only functions as a flexible layer of “lubrication” during drops ... it prevents your “guillotine” from slicing/scoring the laminate ... I am pretty confident that there will be thicker aftermarket offerings from 3rd parties that will look pretty but add notthing to the structure in drops ... oh well, today’s marketplace .... :)

Of note ... there are six strength/yield grades of ASTM A513 Type 5 DOM tubing ... 1026 steel is in the lower half while 4130 is below ST52.3 ...
 
Pretty interesting concept, seems like there are a lot of pros and cons to consider. As someone who will not be subjecting his Jeep to the off-roading extremes of others, here are mine, for what they are worth.

I like the idea of no corrosion, obviously a weak point in the TJ design. This issue comes with a silver lining however- it forces me to look at my frame and suspension regularly, which I should be anyways. To me, the downside of the composite frame is my inability to quickly determine if there is an issue / pending failure. I can see bent rails, xmbrs, cracks, rust, etc. I cannot see pending failures or estimate the remaining life of a composite frame as readily.

As a non-rock crawler, my Jeep is sitting on an 18yr old frame. If I assume the average life of a frame is 15 yrs, I could expect to do the next replacement in the 2030s. Would the average consumer like me want to invest 20% more to have the composite frame? Will I even have the Jeep by then? I guess I am just not seeing the advantage, aside from the "cool" factor for the average weekend warrior.

For a "real" off-roader, I see the advantage of a low center of gravity so I do not see the advantage of a light-weight frame which would effectively raise the COG. Given that builders specifically design to lower COG, I would think composite items to reduce weight from the frame up would be more desired, but I openly admit that I have no direct experience.
 
  • Like
Reactions: rowen01960
Interesting thread. I understand the gist of most of what is being discussed, but not all the engineering terms. Looked some of those up and skimmed the others...I'm a Bio/Chem major/minor now working in software development LOL.

OP, sorry if I missed this somewhere. With the type of design you are looking at, and costs you are noodling over, how many frames would you estimate you would need to sell before you could make this a reality?

Pretty interesting concept, seems like there are a lot of pros and cons to consider. As someone who will not be subjecting his Jeep to the off-roading extremes of others, here are mine, for what they are worth.

I like the idea of no corrosion, obviously a weak point in the TJ design. This issue comes with a silver lining however- it forces me to look at my frame and suspension regularly, which I should be anyways. To me, the downside of the composite frame is my inability to quickly determine if there is an issue / pending failure. I can see bent rails, xmbrs, cracks, rust, etc. I cannot see pending failures or estimate the remaining life of a composite frame as readily.

As a non-rock crawler, my Jeep is sitting on an 18yr old frame. If I assume the average life of a frame is 15 yrs, I could expect to do the next replacement in the 2030s. Would the average consumer like me want to invest 20% more to have the composite frame? Will I even have the Jeep by then? I guess I am just not seeing the advantage, aside from the "cool" factor for the average weekend warrior.

For a "real" off-roader, I see the advantage of a low center of gravity so I do not see the advantage of a light-weight frame which would effectively raise the COG. Given that builders specifically design to lower COG, I would think composite items to reduce weight from the frame up would be more desired, but I openly admit that I have no direct experience.

I would think the weight would be an great advantage in some situations, like the Suzuki Samurai (less likely to sink into the mud or whatever type of soft terrain you may be on). But, a lower weight can cause traction issues on hills etc. Your point about COG is a good one (rollover potential etc.)...however I suppose this would be a good opportunity to have super beefy replaceable steel skid plates to add back some weight down low. You gain more armor, but still are at stock weight with a frame that won't rust (win/win). Perhaps a newly designed frame could come with some better options for attaching such armor.
 
  • Like
Reactions: rowen01960
Pretty interesting concept, seems like there are a lot of pros and cons to consider. As someone who will not be subjecting his Jeep to the off-roading extremes of others, here are mine, for what they are worth.

I like the idea of no corrosion, obviously a weak point in the TJ design. This issue comes with a silver lining however- it forces me to look at my frame and suspension regularly, which I should be anyways. To me, the downside of the composite frame is my inability to quickly determine if there is an issue / pending failure. I can see bent rails, xmbrs, cracks, rust, etc. I cannot see pending failures or estimate the remaining life of a composite frame as readily.

As a non-rock crawler, my Jeep is sitting on an 18yr old frame. If I assume the average life of a frame is 15 yrs, I could expect to do the next replacement in the 2030s. Would the average consumer like me want to invest 20% more to have the composite frame? Will I even have the Jeep by then? I guess I am just not seeing the advantage, aside from the "cool" factor for the average weekend warrior.

For a "real" off-roader, I see the advantage of a low center of gravity so I do not see the advantage of a light-weight frame which would effectively raise the COG. Given that builders specifically design to lower COG, I would think composite items to reduce weight from the frame up would be more desired, but I openly admit that I have no direct experience.


Steel could be protected for 15-20y service life ... but with a Material, Fab time and Weight penalty ... no free lunch here! :) Composites have a higher elastic regime ...then they begin to fracture(crack) ... no bending deformation (plasticity) ... so as delamination/fracturing onset is not visible a HUMS (Health Usage Monitoring System) needs to be included in the laminate ... plug in an OPD like reader into the frame fibergrate and you can read the accumulated % of fibre/matrix degradation in the frame laminate .. after/during the overload ... :) ... to determine fitness for follow-on use ..

I think a healthy dose of common sense will be able to determine if a “high performance” frame is appropriate for your build/rebuild ... your cost/benefit analysis is appropriate ...

VCG ... will always be dominated by the Power Plant/Drive Train mass ... while reduced overall vehicle mass (Frame/Suspension, Axles) is a good thing ... retaining mass at a specific vertical location in a lifted configuration is counter productive ... I am considering a frame with Inertia Moment mounts for the Power Plant/Drive Train ... creating an “effective” VCG which is lower than the OEM ... complicated Mult-Body Dynamics ... :-(
 
  • Like
Reactions: mots
Interesting thread. I understand the gist of most of what is being discussed, but not all the engineering terms. Looked some of those up and skimmed the others...I'm a Bio/Chem major/minor now working in software development LOL.

OP, sorry if I missed this somewhere. With the type of design you are looking at, and costs you are noodling over, how many frames would you estimate you would need to sell before you could make this a reality?



I would think the weight would be an great advantage in some situations, like the Suzuki Samurai (less likely to sink into the mud or whatever type of soft terrain you may be on). But, a lower weight can cause traction issues on hills etc. Your point about COG is a good one (rollover potential etc.)...however I suppose this would be a good opportunity to have super beefy replaceable steel skid plates to add back some weight down low. You gain more armor, but still are at stock weight with a frame that won't rust (win/win). Perhaps a newly designed frame could come with some better options for attaching such armor.

Well Bio/Chem Major/Minor ... I am interested in Inorganic Polymers as Matrices (Polysialates to be precise) and Inorganic Fibre reinforcements ... but don’t give up your day gig! ... just yet ...

Costing ... ya ... a real pain! ... steel products are, with the exception of casting/forging ... toolless ie no real NRC (Non-Recurring Costs) so minimal upfront costs ... purchase the stock profiles and tack them together ... perfect for test “mules” to determine functionality of the geometry ... not so for product performance where inertial properties dominate.

Composites require not only the application design (NRC) but also the “metallurgy” of the Laminate Constituent Materials (scheme), Frame Configuration dedicated Closed Form Tooling (Aluminum)(NRC) and shop infrastructure (CAPEX) ... etc etc

So after some research ... a “high performance” composite Jeep Frame family should have a 10-15 year production life of up to 250 frames a year in ~6 different Configurations (CJ, YJ, TJ, LJ, JK, JL) NRC and RC costs, CAPEX and OPEX with 20% EBIT will be met at 250 frames/year ... not realistic for the first 2-3 years but Y4/5/6 will cover at the curve peak.

This is of course only a moderate ROI and so other vehicle Ladder Frames need to be taken on ... this reduces the CAPEX/OPEX costs for all frame types with Jeep common materials and processes ....

Hope this explains things a little ... as far as realization time ... the VCG issue needs to be resolved and simulated in a Frame Design. If ignored the 10-15y production life is at risk ... not a good idea ...
 
Last edited:
  • Like
Reactions: mots
Well Bio/Chem Major ... I am interested in Inorganic Polymers as Matrices (Polysialtes to be precise) and Inorganic Fibre reinforcements ... but don’t give up your day gig! ... just yet ...

Costing ... ya ... a real pain! ... steel products are, with the exception of casting/forging ... toolless ie no real NRC (Non-Recurring Costs) so minimal upfront costs ... purchase the stock profiles and tack them together ... perfect for test “mules” to determine functionality of the geometry ... not so for product performance where inertial properties dominate.

Composites require not only the application design (NRC) but also the “metallurgy” of the Laminate Constituent Materials (scheme), Frame Configuration dedicated Closed Form Tooling (Aluminum)(NRC) and shop infrastructure (CAPEX) ... etc etc

So after some research ... a “high performance” composite Jeep Frame should have a 10-15 year production life of up to 250 frames a year in ~6 differrent Configurations (CJ, YJ, TJ, LJ, JK, JL) NRC and RC costs, CAPEX and OPEX with 20% EBIT will be met at 250 frames/year ... not realistic for the first 2-3 years but Y4/5/6 will cover at the curve peak.

This is of course only a moderate ROI and so other vehicle Ladder Frames need to be taken on ... this reduces the CAPEX/OPEX costs for all frame types with Jeep common materials and processes ....

Hope this explains things a little ... as far as realization time ... the VCG issue needs to be resolved and simulated in a Frame Design. If ignored the 10-15y production life is at risk ... not a good idea ...

Thanks for the reply. I guess I should have expected a detailed answer from you, haha! Mad respect for sharing your info here with us.

One reason I like my day job in software engineering is because I never have to produce anything physical that can be recalled or wasted. The output is always soft, so if I make a mistake, I fix the problem and run it down the hill again! Back in the early 90's, I used to run an experiment for a professor where we would remove and isolate DNA fragments from a soybean that coded for a protein (lipoxygenase enzyme). We would then then splice the DNA fragments into single cellular yeast organisms in a test tube using restriction/ligation enzymes. I would then grow massive batches of the altered yeast and harvest the cell contents. At the end of the day, it was my job to isolate the protein to prove the soybean protein was now being produced by the modified yeast using a spectrometer. This experiment would take a couple weeks, and if I made a mistake during week 2, I would have to do the whole experiment over again! Not with software though...LOL.

Good luck!
 
  • Like
Reactions: rowen01960
... the thing about getting old, is that, if you still have your wits, you learn what is shareable and what is your meal ticket ... I have aquired some special skills over the years ... namely decoupling of beam stiffness through flexural tailoring of anisotropic/orthotropic materials ... the rest is pure ME common sense (without material or process prejudice). I keep design methods for flex tailoring to myself ... my clients just want the product definition ... and proof that it works as stated ...

So far nobody has been injured or killed due to my negligence ... probably due to my scary description of what happens when they exceed my operating parameters ... :)

Your Protein Synthesis Study was/is real world stuff! ... Digital Simulations(FEA/CFD) for Stiffness/Strain/Flow are getting better but will never include all the mfg process variances that a human can introduce ... so the efficient development of a new product must have as much digital simulation as the schedule permits, Material Characterization (lean), physical test responses of critical components at the simulated LC/BC, adjustment of the simulated material properties to correlate at the Baseline LC/BC responses, expansion of the Simulated LC/BC spectra, and finally correlation of the full article/assy to Simulation of same. The idea is to define the expected responses using a digital/physical building block approach ... with no surprises during physical tests ... thats the plan ... :)
 
Last edited:
  • Like
Reactions: mots and Chris
So here is an idea for those with interest in low VCG (Vertical Center of Gravity) vehicles.

Given that the full suspension travel cannot be realized at the Vehicle CL ... one
could reduce the VCG on tilt/overturning moment sensitive vehicles ... install a subframe below the typical frame front, to which the Engine/Transmission mass is attached to the subframe .... theoretically a 4-6” lift would provide room for a subframe at the OEM VCG ... especially with Composite Axle Housings, Yokes ...

Too much “wacky tabbaky” or is this something to think about ... :)
 
So here is an idea for those with interest in low VCG (Vertical Center of Gravity) vehicles.

Given that the full suspension travel cannot be realized at the Vehicle CL ... one
could reduce the VCG on tilt/overturning moment sensitive vehicles ... install a subframe below the typical frame front, to which the Engine/Transmission mass is attached to the subframe .... theoretically a 4-6” lift would provide room for a subframe at the OEM VCG ... especially with Composite Axle Housings, Yokes ...

Too much “wacky tabbaky” or is this something to think about ... :)
A subframe would run counter to the goal of a lift...that is increased under body clearance. In fact, a lot of us using wranglers to off-road in actually move the transmission and engine higher in the frame to increase that clearance under vehicle.

Your idea would solve some driveline vibration issue though...similar to a T-case drop.
 
A subframe would run counter to the goal of a lift...that is increased under body clearance. In fact, a lot of us using wranglers to off-road in actually move the transmission and engine higher in the frame to increase that clearance under vehicle.

Your idea would solve some driveline vibration issue though...similar to a T-case drop.

Ok but is not Body Clearance separate from Differential Clearance? ... what I am envisioning is a Engine/Transmission SubFrame that is no longer than the OE Control Arm Rotation Axis (common hinge axis) and will terminate just slightly behind and above above the Front Differential ... effectively lowering the motor mounts 4-6” on a 4-6” lift ...

I will have a notional model ready later this week ... should help the discussion ...:)
 
Last edited:
There is differential clearance, which is achieved by using larger tires. Then, there is chassis clearance, which is what I refered to as under body clearance in my above post.

On a Wrangler, the common low point is the skid plate under the middle of the body. That defines the Breakover angle. The less vertical height that has, the lower your breakover angle. The skid plate also contains the transmission mount...which is important to driveline angles. Go too high with the skid or with the springs, without correcting the pinion angle, there are problems. A lot of guys will install a 3 inch lift, then need to drop the skid an inch to get the drive shaft to quit vibrating. Totally counter productive, unless your only goal is bigger tires.

So, I'm hesitant to suggest you design something to actually lower the drive train. I think you'll find it to not be popular. Not to say you can't come up with something clever, but you're fighting perception again
 
  • Like
Reactions: rowen01960
There is differential clearance, which is achieved by using larger tires. Then, there is chassis clearance, which is what I refered to as under body clearance in my above post.

On a Wrangler, the common low point is the skid plate under the middle of the body. That defines the Breakover angle. The less vertical height that has, the lower your breakover angle. The skid plate also contains the transmission mount...which is important to driveline angles. Go too high with the skid or with the springs, without correcting the pinion angle, there are problems. A lot of guys will install a 3 inch lift, then need to drop the skid an inch to get the drive shaft to quit vibrating. Totally counter productive, unless your only goal is bigger tires.

So, I'm hesitant to suggest you design something to actually lower the drive train. I think you'll find it to not be popular. Not to say you can't come up with something clever, but you're fighting perception again

So ... a SubFrame should stay above Fwd Control Rod Rear Attach Points (minimally) and ~ Pinion height of Diff at Max up travel position? under what condition would both front springs be under max compression? I am stumped to think of one, without adding weights?

Of course this means that the control rods are now defacto “sliders” but they will protect the Engine/Trans ... make sense? engine/trans width considerations/details aside ... :) TRANXMBR height should be adjustable/configurable to optimal shaft angles

Think of the subframe supporting only the engine/trans as a longitudinal extension of the side rails at their lowest height ... the old frame arch no longer has motor mounts just steering, suspension (springs/dampers), body, and bumper mounts ... the objective is to reduce the motor attach height (and therefore the MOI) to the minimum permitted by the short or long Control Arms ... irrespective of tire size .... comments/complaints?
 
3FAE1185-617B-4668-9864-A436F7AD2216.png
071E9B48-0A48-439A-88D2-1D3DC0D94A2D.png
B126592B-1293-49E1-B5FA-317746184144.png
6DDCE774-3B8C-4BA9-ABEB-19A280370CA4.png
7F5FDD54-2747-4A56-9488-C18996AED6D9.png
FC1BCC9C-2640-42F8-840E-077AFCF5486E.png
Hopefully these “connect the dot” images illustrate the concept ... the “subframe” (not shown) is actually 2 diagonal beams mounted to the Frame at the Control Rod Bracket and some point just forward of the Spring Perch Bracket ... a “landing” on the beam provides engine specific machined mount capability. A transverse XMBR will likely have to be fitted in somehow to mitigate roll moments in the Frame .... a pain but worth the -6” in VCG ...

The LS Engine was selected as a “worst case” volume/mass study scenario ...
 
  • Like
Reactions: mots
Jounce or compression stroke is currently limited to the OEM value ... increased jounce requires a reduction in the Engine/Trans “drop” and therefore a higher VCG ... trades to be done I guess ... help would be appreciated ...