Fuel cell placement [Archive]

Griffin

11-11-2006, 09:12 PM

I still have the stock gas tank in my truck and am planning on finishing my cage and putting a fuel cell in it this winter. Anyways, I dont know where i want to put the cell at, in front of the axle or behind it?? Anyone know the advantages of either location?

SantaCruzRC

11-11-2006, 11:12 PM

I would get it as close to the center of gravity as possible so it is neutral with respect to your truck handling, ie. front and rear wheels will have the same fraction of weight with or without a full tank. That way you don't have to adjust your driving as you run down your fuel, and your truck will handle more predictably. If you put it behind your axle the weight of it is gonna want to both pull your rear wheels to the outside of the turn and push your front wheels into the turn, which will tend to send you into a spin.

YoTRacer158

11-12-2006, 12:25 AM

Most people tuck them as close to the cab as possible. If you have it too far back, it will affect suspension as it will be softer with a full tank and stiffer as you get closer to empty.

AllJumpStyle

11-12-2006, 02:23 PM

I think I have to disagree. You can actually place the fuel cell lower if you place it behind the axle. Placing more weight towards the rear seems to be a bigger plus for me than trying to put it in the center. Your truck doesn't have a 50/50 weight distribution to begin with, and trucks always drive better with more weight in the rear. And I usually see more trucks with the cell behind the axle.

SantaCruzRC

11-12-2006, 03:44 PM

Put non-consumables in the back to balance out weight. Consumables should always be close to the center of gravity to keep handling consistant. When I'm pulling into a corner I have enough on my mind, I don't need to be calculating moment arms for my burnt fuel.

Also behind the axle has the roughest ride by a wide margin. A good fuel cell can handle the abuse, but as a personal preference I prefer to keep my fuel as safe as possible.

AllJumpStyle

11-12-2006, 07:21 PM

Let's play "find the fuel cell"
http://www.chaosfab.com/12.05/vance12_06.jpg

AllJumpStyle

11-12-2006, 07:22 PM

Also behind the axle has the roughest ride by a wide margin. A good fuel cell can handle the abuse, but as a personal preference I prefer to keep my fuel as safe as possible.
It's called valving, you do it to your shocks.

SantaCruzRC

11-12-2006, 08:05 PM

It's called valving, you do it to your shocks.

It's called 360 pounds of fuel with a mechanical advantage so figure about 420-430 extra weight on your rear wheels at full tank and about 60-70 pounds less weight on your front end, that makes properly valving your shocks for the full fuel range impossible.

Compare with a fuel cell mounted at the center of gravity, 180 pounds weight difference front and 180 pounds for the rear in a full fuel burn.

Factor

11-12-2006, 08:57 PM

DGAF :rolleyes:

lol nice edit. :saw:

Oh and mine will be mounted to the rear behind the axle.

Tweeter

11-12-2006, 10:07 PM

I agree with Factor. To each their own. There's pros and cons to everything. Your truck, weigh it out, do what you want.

Baja Belk

11-12-2006, 10:27 PM

I think another consideration is that for a linked truck, in order to mount the cell tucked up against the cab you have to mount it higher up to account for the up-travel of the center link, thus negatively affecting the center of gravity. Mount it behind the axle, and you can mount it lower.

For a leaf-sprung truck, you can mount it lower behind the cab.

SantaCruzRC

11-12-2006, 11:17 PM

YoTRacer158

11-12-2006, 11:43 PM

Chris...i completely agree with you about the lower COG and the weight over the rear end...but the weight wont always be there. If you valve the shocks for a full tank, it will be a lot stiffer with an empty tank...if you valve it for an empty tank it'll be softer with a full tank. If you valved it for a half tank the extremes wouldnt be as bad, but the suspension would still be affected more than it would with the cell mounted closer to the center of the truck.

BLOWNYOTA

11-13-2006, 01:41 PM

Sorry to everyone. I get a little hot headed when physics comes up, being a physicist and all (most of my friends have given up going to movies with me). Sometimes I ignore practical aspects in favor of just arguing over the physical results.

apology accepted. You really pissed me off (J/K).

I personaly think that it is more important to build your truck strong and reliable with the correct spring rates (wet) and valving than to worry about how your fuel cell will effect your handling. We all know that dezert racing is not a test of how well each vehicle corners. If you are building a short course truck that may be a different story, but the dezert is a harsh environment, and I would rather have my truck push a little than have it oversteer, especialy in the hoopdees.

DesertTRD

11-14-2006, 12:39 PM

It's called 360 pounds of fuel with a mechanical advantage so figure about 420-430 extra weight on your rear wheels at full tank and about 60-70 pounds less weight on your front end, that makes properly valving your shocks for the full fuel range impossible.

Compare with a fuel cell mounted at the center of gravity, 180 pounds weight difference front and 180 pounds for the rear in a full fuel burn.
got news for you, ive ridden in dans truck with both a full tank and empty (ran a few races with him) and his truck both ways rides smooth in the rear, the weight change doesnt do anything to the truck...

SantaCruzRC

11-14-2006, 01:56 PM

his truck both ways rides smooth in the rear

Smooth and smoothest are two very different things, there would have to be something seriously wrong with your suspension design, shock valving, or shock body, to not get a smooth ride in a LT racing rig. But to eek out the very best out of each and every one of your components is the difference between an awesome rig and a superior rig (toyotas should never be anything less then awesome).

the weight change doesnt do anything to the truck...

Nothing much to say here, this is simply wrong, and shows a gross misunderstanding of how damped harmonic oscillators function.

I'll concede that from a CG, and practical standpoint a rear of axle fuel cell is the better choice. But I'll defend to the death that a CG mounted fuel cell offers more consistant handling, and better suspension characteristics.

Half Baked Taco

11-14-2006, 03:26 PM

IMO, you'll have more fun on http://race-dezert.com lol For starters, here's something that will keep you entertained on that forum (http://www.race-dezert.com/forum/showthread.php?t=18207&highlight=center+of+gravity)

I remember this same discussion about fuel cell placement on DR, but I can't find it at the moment.

BTW, my vote gets behind the axle :D

Tweeter

11-14-2006, 03:48 PM

I vote for on top of the cab for maximum weight displacement ratio to the non-linear function of xyz, thus stating the inertia to impact relative to the distance created will subject center of gravity to be totally absurd, but at least your muffler bearings and flux core capacitators will be well out of harms way :D

...it's not that I don't care, I just don't give a shit :xsmokin1:

Half Baked Taco

11-14-2006, 03:52 PM

LMAO! Tweeter for President....or at least Govenator. Carry on.....

miguelitro

11-14-2006, 04:56 PM

it looks to me that matt helton's truck has the fuel cell mounted aft of the axle AND its a leaf sprung truck. However I would assume that he doesnt know shit from shinola as he only won 1450 class this year and overall points in MDR. that kind of real world example however has no strength in an arguement against theoretical physics.
Mike

Tweeter

11-14-2006, 04:59 PM

Word. Not to mention his truck is made of MILD steel with the ultimate dead tubes junctions as well...and not to be a dick but I'm pretty sure it was MDR :missingto, sorry Mike

miguelitro

11-14-2006, 05:23 PM

right right thanks for the correction tweeter...see its not too hard to admit it when you are wrong:D

LOL mild steel and dead tubes, bolt on suspension, can you say 90% driver!

Factor

11-14-2006, 05:45 PM

Real simple. Fuel Cell placement will not make you a better driver!!!

I guess we could always put it in the cab for ultimate center of gravity. waj.

miguelitro

11-14-2006, 05:51 PM

or you could put the motor out back and the fuel up front...orrr you could oh never mind

DesertTRD

11-14-2006, 06:30 PM

Smooth and smoothest are two very different things, there would have to be something seriously wrong with your suspension design, shock valving, or shock body, to not get a smooth ride in a LT racing rig. But to eek out the very best out of each and every one of your components is the difference between an awesome rig and a superior rig (toyotas should never be anything less then awesome).

Nothing much to say here, this is simply wrong, and shows a gross misunderstanding of how damped harmonic oscillators function.

I'll concede that from a CG, and practical standpoint a rear of axle fuel cell is the better choice. But I'll defend to the death that a CG mounted fuel cell offers more consistant handling, and better suspension characteristics.
why is it always an engineer who has to say we are doing everything ass backwards, yet said engineers have never actually delt with real world stuff 99% of the time, explain your engineering background in racing and how it applys.

Obvoiusly CG is important, now understand that the fuel cell in Kung Fu hangs almost lower than the CG of the truck, at full bump it has about 3" off the ground, which is as low as the motor is.. and kung fu must be doing something right, i mean hell its not often you see a toyota truck overalling a race...

SantaCruzRC

11-14-2006, 09:14 PM

why is it always an engineer who has to say we are doing everything ass backwards, yet said engineers have never actually delt with real world stuff 99% of the time, explain your engineering background in racing and how it applys.

Those darned engineers, like the ones who built your truck. Pfft, what would they know. An engineer who's never dealt with real world stuff has never had a job, cause that's what engineers do, real world stuff.

That said, what have I done? I designed and built a SAE formula and Baja race car from the ground up, nothing real world there. I'm in the process of designing a suspension system for my truck since I couldn't find one that did what I wanted, but I couldn't see how that would apply. Oh and I'm building a datsun 240 up from the rusted out remains of a frame, into a high performance race car.

Granted two of those are road vehicles, and have different most desirable characteristics, maybe the desert racing community could take some pointers from the road racing community seeing as how they tend to get alot more money dumped into it and have been refining their systems for many, many more years.

Oh and while this really doesn't apply I'm also designing and building an airplane. Which, while mechanically is not related to an offroad race truck, should illustrate how much confidence I have in my engineering.

As far as real world examples go. You could give a truck with the fuel cell mounted on the roof of the cab, "maximizing weight displacement ratio to the non-linear function of xyz," to an excellent driver, and he could win. Or you could give the best technology class 1 purpose built buggy to a nit-wit, and laugh as he crashes into everything in sight. As was pointed out by Factor fuel cell placement will not make you a better driver, nor will shock quality/valving, suspension design, engine size, brake systems or anything else. But that doesn't mean that they don't make a difference.

OOwballer

11-14-2006, 09:45 PM

Those darned engineers, like the ones who built your truck. Pfft, what would they know. An engineer who's never dealt with real world stuff has never had a job, cause that's what engineers do, real world stuff.

That said, what have I done? I designed and built a SAE formula and Baja race car from the ground up, nothing real world there. I'm in the process of designing a suspension system for my truck since I couldn't find one that did what I wanted, but I couldn't see how that would apply. Oh and I'm building a datsun 240 up from the rusted out remains of a frame, into a high performance race car.

Granted two of those are road vehicles, and have different most desirable characteristics, maybe the desert racing community could take some pointers from the road racing community seeing as how they tend to get alot more money dumped into it and have been refining their systems for many, many more years.

Oh and while this really doesn't apply I'm also designing and building an airplane. Which, while mechanically is not related to an offroad race truck, should illustrate how much confidence I have in my engineering.

As far as real world examples go. You could give a truck with the fuel cell mounted on the roof of the cab, "maximizing weight displacement ratio to the non-linear function of xyz," to an excellent driver, and he could win. Or you could give the best technology class 1 purpose built buggy to a nit-wit, and laugh as he crashes into everything in sight. As was pointed out by Factor fuel cell placement will not make you a better driver, nor will shock quality/valving, suspension design, engine size, brake systems or anything else. But that doesn't mean that they don't make a difference.

So by your own admission you have no real world experience as it pertains to trucks. Yes your mini baja is a solid experience, although not what i would use as my only leverage in a discussion like this.

...now don't get me wrong im not trying to cut you down, I actually agree with you. But i am bothered by "engineers" who use big words and fancy language to try to talk down on people with ALOT of experience. To me it just shows that you are still wet behind the ears.

and just so we can get this out there i am just some lowly internet fabricator.

Half Baked Taco

11-15-2006, 08:43 AM

Half Baked Taco

11-15-2006, 08:54 AM

Granted two of those are road vehicles, and have different most desirable characteristics, maybe the desert racing community could take some pointers from the road racing community seeing as how they tend to get alot more money dumped into it and have been refining their systems for many, many more years.

Pflueger is doing this now with his new TT. I actually can't wait to see how it does.

So by your own admission you have no real world experience as it pertains to trucks. Yes your mini baja is a solid experience, although not what i would use as my only leverage in a discussion like this.

...now don't get me wrong im not trying to cut you down, I actually agree with you. But i am bothered by "engineers" who use big words and fancy language to try to talk down on people with ALOT of experience. To me it just shows that you are still wet behind the ears.

and just so we can get this out there i am just some lowly internet fabricator.

I heart you (in the most non ghey way) lol

TimF

11-15-2006, 09:21 AM

I heart you (in the most non ghey way) lol

You are a :supergay: I knew it!

You don't need to worry about the cell placement just get some of these dudes to balance out the truck.

http://www.ahajokes.com/cartoon/car01.jpg

miguelitro

11-15-2006, 09:54 AM

^truck see more off road miles than 90% here on ttora.

SantaCruzRC

11-15-2006, 11:58 AM

Sorry if this is a newbie question but, who's Pflueger, and what is he doing exactly?

TimF

11-15-2006, 12:04 PM

Sorry if this is a newbie question but, who's Pflueger, and what is he doing exactly?

click and learn (http://www.popsci.com/popsci/automotivetech/d5f67cdd8d83e010vgnvcm1000004eecbccdrcrd.html)

BLOWNYOTA

11-15-2006, 12:05 PM

Sorry if this is a newbie question but, who's Pflueger, and what is he doing exactly?

WAJ

Factor

11-15-2006, 12:37 PM

Problem Solved! =D

AllJumpStyle

11-15-2006, 03:41 PM

When in the desert, especially in Mexico, even when you're in control, you're not.
I concur... :eek:

SantaCruzRC

11-15-2006, 03:50 PM

I'm racing next year so I guess we'll see. Alot of you guys will get the chance to put me in my place like I'm sure you've been wanting too.

Or maybe not :D

OOwballer

11-15-2006, 05:12 PM

I'm embarrassed to say I'll be racing class 11, bone stock bug. But I'll have a chance to go fast when I'm prerunning in my custom LT tacoma, and if I have time, I should be pulling about half trophy truck hp. I have plans to entirely tear apart my engine's top end, and cooling, plus some hefty boost in the 16-18 PSI range.

another "lowly internet fabricator."

don't be embarrassed...those class 11 guys have some of the biggest stones and the most heart of anybody racing. I would be proud to race with them.

edit: forgot to mention that i would be very interested in what you come up with for a front end.

BLOWNYOTA

11-16-2006, 10:08 AM

Lets see your titanium lug nuts....

Tweeter

11-16-2006, 10:50 AM

Lets see your titanium lug nuts....

Seriously...I should probably go lock that thread now anyways...

Tweeter

11-16-2006, 10:52 AM

I hope this doesn't put me permanently into the ignore list of the other members on the board.

:rolleyes: you probably should've kept that part to yourself...I'm just sayin...

Baja Belk

11-16-2006, 11:38 AM

Lets see your titanium lug nuts....

Damn - you beat me to it...

Tweeter

11-16-2006, 11:59 AM

Damn - you beat me to it...

What would be a good size for behind the cab gallon wise? I was thinking 22-26 or so. I've heard of people using the stock senders and components on the cells. I'd probably need a new fuel pump and what else?

YoTRacer158

11-16-2006, 02:53 PM

Seriously...I should probably go lock that thread now anyways...

Dont even think about it...:D

Baja Belk

11-27-2006, 10:38 PM

Alright, enough is enough. I could let this guy go on forever making a presumptuous ass of himself, but let's get back on track, this is a good topic. Argue all you want about CoG and where a fuel cell should be, but let's keep the "Adrenaline is for Baja pussies" bullshit - and retorts (sorry guys) - off the boards. - Fin

Tweeter

11-28-2006, 01:23 AM

Way to go Mr Mod :) Woulda stepped in earlier but I was myspacin it. I agree with Mike though, PM if you want to argue about Baja adrenaline and the laws of physics we don't need that crap in here.

str8xedge

11-28-2006, 09:54 AM

What would be a good size for behind the cab gallon wise? I was thinking 22-26 or so. I've heard of people using the stock senders and components on the cells. I'd probably need a new fuel pump and what else?

For a desert truck I wouldn't run anything less than a 32 which is what I have now. It's not like a stock tank that you can run till it's just about empty with no problems. As it starts to get empty you could start having problems with your engine cutting out.

DezertTacoma

11-28-2006, 11:44 PM

I'm also running a 32 gal cell and wouldn't put anything smaller then that. Remember your MPG goes to crap in the desert so the more you can hold the better. Whenever I redesign the back half of my truck i'll most likely put a 40 gallon tank in.

My cell is behind the axle and I can notice a SMALL difference in performance when the tank is full, and when the tank is below half empty. When the tank is full the back end feels more planted over large sections.