Future of KOH 4400 chassis/car development?

After watching part of that video, I get the engineering advantages of being surrounded by the fuel, but I'm not sure I'd want to even start that truck without a firesuit on. And thats why I will never win a desert race. that and many millions of dollars. But then again, not many people bitch about flat fender and early CJ5s, driving around sitting on the unprotected and vented fuel tank, while wearing shorts and flip flops. Not trying to pretend its the same thing, but I bet that truck has a better saftey margin...
 
mobil1syn said:
ooh and i will add, mentally i can grasp how you can say youre safe being surrounded by fuel like that but man i am not sure i could do it. same could be said for the ufo single seaters
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The Campbell cars make me nervous, big cell right behind the seats. It’s within the rules but there’s an .060 aluminum firewall between the cell and the seats. The SXS’s are even worse. The fuel cell is directly under your ass
 
djljeep said:
After watching part of that video, I get the engineering advantages of being surrounded by the fuel, but I'm not sure I'd want to even start that truck without a firesuit on. And thats why I will never win a desert race. that and many millions of dollars. But then again, not many people bitch about flat fender and early CJ5s, driving around sitting on the unprotected and vented fuel tank, while wearing shorts and flip flops. Not trying to pretend its the same thing, but I bet that truck has a better saftey margin...
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once the big block is started, im sure all common sense goes out the window.
 
JR4X said:
The Campbell cars make me nervous, big cell right behind the seats. It’s within the rules but there’s an .060 aluminum firewall between the cell and the seats. The SXS’s are even worse. The fuel cell is directly under your ass
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Can-am is over the passengers legs. Which may be even worse. It makes me sorta uncomfortable even just duning the thing.
 
mobil1syn said:
ooh and i will add, mentally i can grasp how you can say youre safe being surrounded by fuel like that but man i am not sure i could do it. same could be said for the ufo single seaters
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Jimco 1 cars have had L shaped cells under the seats for 20 years. Zero issues. They only hold 90ish gallons though.
 
The cell in Ivan's TT the cell was right behind the seat and the can was a structural member in the frame.

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JR4X said:
The Campbell cars make me nervous, big cell right behind the seats. It’s within the rules but there’s an .060 aluminum firewall between the cell and the seats. The SXS’s are even worse. The fuel cell is directly under your ass
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The safety aspect has had consideration for many moons in our motorsport hobby. Im not close to the regs in these sorts of American race classes but typically it requies a safety bladder thats certified to motorsport standards which in turn is pretty much a copy of what the aerospace people do. The fuel bladder alone is really impressive with its properties in mechanical toughness and strength and fatigue heck even its ability to resist UV and ozone etcetc then ontop the external housing further protecting the internal bladder.

When you consider that some classes of race vehicles in say drag racing are loaded with 16 gallons of nitromethane which is super nasty compared to unleaded petrol and its fundamentally the same as anyone else with a fuel bladder + housing where those dragsters can and do have spectacular accidents - its really not a huge risk
 
mobil1syn said:
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occupants are surrounded by fuel

skip to 6:30
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Great post thanks for the info

Its not normal that this obsession with tube spaceframe chassis is sticking around in this particular class of motorsport unless the regs mandate it which I dont think they do

It was figured out ages ago like in 1950 that even lower tech aluminium monocoques can be lighter for equivalent outcomes strength and toughness and elastic modulus

Tube chassis spaceframe just isnt good for weight

That said impressive what this Team are doing elsewhere in this build
 
nullack said:
. The fuel bladder alone is really impressive with its properties in mechanical toughness and strength and fatigue heck even its ability to resist UV and ozone etcetc then ontop the external housing further protecting the internal bladder.
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Bet you could buy a LOT of trinkets for the cost of the bladder in the Campbell, MAson, and other cars......... Not a minor deal.

Maybe someone knows those budget numbers....and why a real BIG Decision to go that way.

I see that Morgan Clarke just broke the single tank into three tanks on the Range Rover. He said for installation and maintenance but wonder if cost was a consideration also.
 
Isdtbower said:
Bet you could buy a LOT of trinkets for the cost of the bladder in the Campbell, MAson, and other cars......... Not a minor deal.
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My country is a problem because everything tends to cost more - we call it the "Australia tax" haha. Pricing example a 14 gallon Radium brand bladder that fully meets both CAMS (confederation of Australian motorsport) and the international FIA rules, including it coming with certified expiry date etcetc for scrutineering approval is $AUD870 so $USD623. Id wager that actual local US prices are much better though.

Guys seem to do alright on tight budgets hobby style. Like Formula Ford open wheelers, pretty cheap to compete effectively. These bladders do have a marked expiry date and do have to be routinely replaced but it isnt a huge deal.
 
redneckK20s said:
Yeah I found that interesting, never really consider how the dynamics of a vehicle change as it burns fuel but with the amount they carry it obviously makes a big difference.
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It's one of the reasons that they invented the ****pit adjustable balance bars for brake systems. It can make a big difference even with a lot less fuel.
 
A flexible bladder costs a couple grand for a big rectangular tank (44gal). I'd wager a guess that the custom one for 140+gals and a wild shape would set you back around 5K, maybe a bit more.
 
mobil1syn said:
1776797064274.png


occupants are surrounded by fuel

skip to 6:30
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Watched the video thanks for that legend mate. Interesting.

Lower front control arms - he explained because of aluminium mechanical property shortcomings that all aluminium alloys universally suffer from and the packaging constraints in layout restrictions he cant do all one piece forging/forged billet then machined down in Aluminium alloys, hes forced into something else where he explains his design is 4340 chrome moly (bit strange he didn't step up to 300M but maybe hes being a bit coy and is using 4340M which is the same as 300M) with other sections of the assembly then in 7075-T6 for mass

This isn't "good" that it has multiple parts to the assembly in this sort of weight matters and high impact toughness and high strength type environment it really isn't good at all and needs to be one piece with section sizing respecting the flow of loads through the metal grains avoiding stress concentration much better

He seemed fairly open about trying to keep this "cost sensible" so I take it this is why it is not a one piece ***anium alloy single part that's the obvious direction for this application is a nice ***anium alloy. Ti alloys are way better than aluminium in just about everyway from specific gravity to toughness to strength to fatigue cycling etc etc

EDIT: hahaha the forum flags Ti tanium maybe mods can fix that up seems that material is a bit new in these circles

This is all pretty old school and not optimal which is hard for me to say because I truly admire the workmanship and thought of this race team. But, facts.

The mistake hes made is not just in not having already shifted to a monocoque chassis. Theres mistake here too. Like if it's budget stuff the Team should consider stepping up to say a powder metallurgy Aluminium matrix composite and making it from compacted mould in the "green" state then consolidating it all from green to a tangible part using say state of the art Spark Plasma Sintering and conduct ongoing finite element analysis studies until the right combination of matrix components is demonstrated. Its likely the AMC will overcome the constraints he faces in more traditional alloys that he mentions.

If they had more budget they could step up to ***anium metal matrix type compositions which rule as No 1 in this class of material. TMC would 100% do it and any FEA play around would just be for design optimisation over is this gunna work ok type questions.

I feel guilty a bit hahaha so something positive theyre spending good coin on good bolt choices I can tell by the video that those bolts are sound choices. Nice that he determined to use a combination of carbon fibre and Kevlar in the outer tank housing for the composite sandwich layout.
 
I just got pricing on a custom flexible bladder a few months ago and it was basically $100 per gallon. So a 44 gallon cell bladder was $4400. Adding a custom shell, pumps, pickups, etc. Could easily hit 10-15k.
 
nullack said:
Watched the video thanks for that legend mate. Interesting.

Lower front control arms - he explained because of aluminium mechanical property shortcomings that all aluminium alloys universally suffer from and the packaging constraints in layout restrictions he cant do all one piece forging/forged billet then machined down in Aluminium alloys, hes forced into something else where he explains his design is 4340 chrome moly (bit strange he didn't step up to 300M but maybe hes being a bit coy and is using 4340M which is the same as 300M) with other sections of the assembly then in 7075-T6 for mass

This isn't "good" that it has multiple parts to the assembly in this sort of weight matters and high impact toughness and high strength type environment it really isn't good at all and needs to be one piece with section sizing respecting the flow of loads through the metal grains avoiding stress concentration much better
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I don't think "the book" has been written yet on building a Top KOH Rig or Trophy Truck. There have been some minimum principles written for race safety tech, but a far cry from the challenges that include podium competition and finishing an event. The top classes intentionally have "no general rules" so mechanical, hydraulic, and electrical exploration is open for ....whatever you can dream up. If you are not a part of the community that designs and actively participates in new ideas and understanding what others are doing...it is easy to not "see the trees and rocks in the forest."

On the comments about front lower arms I have been hobby building with 7075. The arm sizing is physically exactly the same as a buddies winning IFS KOH car. That rigs bottom arm is 4340 cromo and heat treated and gets replaced regularly. Heat treating changes dimensions so gap adjustments at the frame pivots is always necessary. The process for making those arms is also labor intensive. So enter 7075 and CAD CAM. Everything is cool until you try to grip omni balls and etc with the necessary thickness to prevent cracking. Number one is the gap between the chassis and the inner arm pivot bushing. There is just no way with conventional tube chassis to allow for enough aluminum arm thickness at that pivot. The solution is usually a steel-ish bushing holder that is keyed and bolted into the 7075 arm. All this can be produced with more precision and "spare parts in pits can be real." In my hobby build case, the top and bottom center bulkheads are also 7075 so I can have more clearance in that inside pivot area. BUT.... It comes with a huge weight disadvantage...Especially in the chassis. Plus, I have never been able to beat the weight of the cro-mo welded arms. Ti might be a consideration but finding plates big enough was almost unobtanium...even when looking at Spooky salvage.

I DO like the thoughts on composite chassis frames. I think there is value there, but the race tech groups would have to learn up....... Right now, there is a pretty good on-board safety record in offroad racing. Think about the possibilities of laser cutting a 2.5" x 5' x 15' of 7075 and then bending for vertical clearances. if only you could bend............... But laying composite does seem more realistic in the future.

Don't expect anything quick. There have been some fairly good G-out seat ideas in the works but still written out because of old rules that seat belts must be attached to the floor....... Where new should be belted to a well structured seat that can give from the chassis but not break from it....multiple times. Composite seats are out there to do the job, but loose their value when the belts and seats have to go rigidly to the chassis, and the drivers loose that g-out cushion.

Keep thinking...............Identify the problem areas.........Keep throwing solution ideas out there. What makes offroad development fun....and low payback in $$$$.
 
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gt1guy said:
A flexible bladder costs a couple grand for a big rectangular tank (44gal). I'd wager a guess that the custom one for 140+gals and a wild shape would set you back around 5K, maybe a bit more.
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Its a little more than that if its a single one off. I talked to a few places at PRI a couple years ago. I think pyrotect was the most reasonable. The way he explained it to me, compared to one of their off the shelf bladder cells, you would pay 40-50% more for just the custom bladder of that size. So if a 32 gallon off the shelf cell is $2500, a custom 32 gallon bladder alone would be in the $35-3800 range. I think ATL, Fuel Safe and Harmon were more expensive, or either the people I talked to had no clue and just threw out some numbers. Ive also heard a builder on youtube comment on the price for a custom 100 gal radius can they built for a pre runner being like 8k just for the bladder from pyrotect.
 
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