For those wit SFBD frame size Q's

ConnecticutX · 10-23-2003, 12:17 PM

mkay...i quick made this up to stop all the rumors about what size box tubing to go with for frame rails.....its kinda self explanitory, ignore the stuff in the middle, just pay attn to the hieght, width, thickness, deflection and weight. The deflection is in inches and the weight is in lbs.

BTW...this is assuming stock dimensions, a 5 foot length, and 1000lbs of force on the beam....

BYONDSIC · 10-23-2003, 12:19 PM

Where did you find that chart?

ConnecticutX · 10-23-2003, 12:22 PM

This chart is only for bending in the vertical direction....But If the beam is square it will bend the same in all directions...If u plan on usin 3" height by 2" width, the beam will bend much more in the horizontal than in the vertical....If thats the plan and u want horizontal bending just look at 2" height by 3" width and that will give u horizontal displacement....

BTW...displacement just means how far in inches the beam will bend.....here is what I mean by 3x2 and 2x3

ConnecticutX · 10-23-2003, 12:24 PM

Quote:

Where did you find that chart?

Quote:

mkay...i quick made this up

damn u quick.......as u guys can see 2x2 even with 1/2 inch wall still has about 2" of bend in it...I wouldnt want that under me....I personaly went with 3"x3"x1/4" wall

if anyone wants it in its excel for just shoot me a pm and I'll email it to ya...

Dragginblazer · 10-23-2003, 01:26 PM

Thank you for proving most these fools wrong!

ConnecticutX · 10-23-2003, 02:27 PM

Quote:

Thank you for proving most these fools wrong!

well, I try.....lol....It just helps when u can look at numbers and actualy see what is goin on.....

Dragginblazer · 10-23-2003, 03:14 PM

Yeah, I'm glad slammy used 3x3x.25" inside the stock frame on mine now.

lol

BYONDSIC · 10-23-2003, 03:42 PM

Now do you have one for round tubing

acrofobia · 10-23-2003, 03:54 PM

Yeah but S-10 frames are C-channeled frames not square. Does this throw off the chart?

BYONDSIC · 10-23-2003, 04:51 PM

He's not talking about deflection on the frame he is talking about deflection on the new tubing you are going to be using to make the sfbd possible.

acrofobia · 10-23-2003, 05:03 PM

He has a "stock" frame size in the chart, that's why I was questioning it.

ConnecticutX · 10-23-2003, 05:10 PM

Quote:

Yeah but S-10 frames are C-channeled frames not square. Does this throw off the chart?

2nd gens are boxed in from the radiator support to the back wall of the cab.....not sure about 1st gens......and since under the cab is the only place u would need to use small stuff it works out perfect.....

Slammy · 10-23-2003, 06:05 PM

Nice chart man, ive been telling people forever that 3x3 1/4 wall is the smallest youd ever want to use for frame rails.They dont seem to understand the concept, or maybe they do but are being blinded cause they think they HAVE to have a stock floor cause its the "cool" thing right now.Stock floor body drops work great on fullsizes cause it requires almost no cutting on the floor and you can get a decent size frame under the truck easily.A mini is WAY smaller , requires a bigger bodydrop usually and you will have to chop the shit out of the floor to be able to get a strong enough frame under it. I see what people are doing with these 2x2 and smaller frame as dangerous or trucks that dont need to be daily driven at all.Trailer queens would be ok i guess but i still wouldnt do it on anything i worked on.The frame is the back bone of the truck, the body isnt meant to hold the truck together and if you try and make it you will start breaking the spot welds on the cab cause the stress from too much frame flex.Oh well i guess actually knowing about structural intergrity is one of the things that separates being a professional from the rest of the ummmm what should i call them? Hacks i guess?Not trying to be a ass but damn it gets old.

ConnecticutX · 10-23-2003, 06:35 PM

Quote:

Nice chart man

Thanks man....The biggest misconception is that thicker the wall wall the stronger, no matter the size....3x3x1/4 is much stronger than 2x2x1/2. And 3x3 still isnt as strong as factory verticly, but it is stronger horizontaly...so if u use crossmembers correctly u can get a super stiff frame side to side....and close to as srong verticaly.... I see no reason to use 3x2 rather than 3x3 because the stock frame is about 4.5" wide near the firewall and about 2.5-3 inches wide behind the cab.....horizontal space isnt an issue so use 3" wide .....later, Jon

dragginbalz · 10-23-2003, 11:38 PM

can you do me a favor?

compare a 2x4 .188 wall box tube with a 2x8 .125 wall channel frame

just curious

thanks!
t

ilovesparks · 10-24-2003, 09:06 AM

thanks for posting that chart. it helped me out alot to see some actual numbers. im sure everybody else appreciates it too. good work, batman!

ConnecticutX · 10-24-2003, 08:42 PM

Quote:

compare a 2x4 .188 wall box tube with a 2x8 .125 wall channel frame

yea, no prob....im not on my pc right now tho...i'll have it done for ya on tuesday......and is that 2" tall x 4" wide? or the other way around....

dragginbalz · 10-25-2003, 12:24 AM

4 " tall 2" wide 3/16 rect box tubing

i am just curious as to how it compares, ( for my NON s10 truck)

)

thanks, I really appreciate it

t

blazentrout · 10-29-2003, 06:38 AM

i would like to know were this info was dug up at. if you look at the deflection #'s 3x2 and 3x3 1/4 wall, you will notice that the #s are not the same,but differ by.255. what this is telling me is that something is not quite right with your formula. your vertical height stated the same, the thickness of the wall stock is the same. it should not matter how wide the piece is do to the fact that we are not measuring a horizontal deflection. last ? why doesn't my Reese hitch bend big time when it put my car trailer on it with a tongue weight of 900lbs. it is only made of 1/4 wall
2 1/2x2 1/2. thanks
ps i have a machinist hand book at work if you have a page # for the formulas.

Dragginblazer · 10-29-2003, 10:12 AM

Your trailer hitch is less than a foot long compared to a 5 foot section that was put into the formula. I also have a Rierson book at my work that I'll lookup & see if they have a similar chart.

alteredimage · 10-29-2003, 12:35 PM

This would make a good sticky!

blazentrout · 10-29-2003, 03:19 PM

Quote:

Originally posted by Dragginblazer
Your trailer hitch is less than a foot long compared to a 5 foot section that was put into the formula. I also have a Rierson book at my work that I'll lookup & see if they have a similar chart.

opps sorry i meant the receiver that mounts to the frame and it about 36" to 40" long(its raining up here so i am not going to get wet to measure it). i have looked in my machinist hand book and did not find the chart. if its a beam formula, i would like to know were you add the second vertical in at. sorry to be a pain but inquiring minds would like to know.

Dragginblazer · 10-29-2003, 06:41 PM

Bah. The book I have dosen't show it either.

ConnecticutX · 10-30-2003, 09:05 AM

Quote:

i would like to know were this info was dug up at. if you look at the deflection #'s 3x2 and 3x3 1/4 wall, you will notice that the #s are not the same,but differ by.255. what this is telling me is that something is not quite right with your formula. your vertical height stated the same, the thickness of the wall stock is the same. it should not matter how wide the piece is do to the fact that we are not measuring a horizontal deflection.

let me learn you.....the vertical section of the beam is called the "web"...the horizontal section is called the "flange"....the 1000 pounds, that I estimated, is exerted on on the flange....and from the flange to the web in the form of pressure (psi)... the equation for pressure is P=F/A, where P is pressure, F is force, and A is area of the flange cross section......now I will use your example....

for the 2" wide.....P=1000/(2*.25) which =2000psi exerted on the web

for 3" wide......P=1000/(3*.25) which =1333.33psi exerted on the web

less pressure on the vertical sections (web) means less overall deflection......

Quote:

last ? why doesn't my Reese hitch bend big time when it put my car trailer on it with a tongue weight of 900lbs. it is only made of 1/4 wall

because the beam (hitch) is only like 6" long.....the beam on that chart is 5 feet long...

ConnecticutX · 10-30-2003, 09:27 AM

Quote:

i would like to know were this info was dug up at.

Quote:

ps i have a machinist hand book at work if you have a page # for the formulas.

well, I guess that info was dug up from the past 5 years ive spent at Central Ct State U. Engineering dept. as for the mec. handbook...what edition do you have?....I have one at home but not with me right now....but here are the equations....

Moment of inertia (I, in^4) =[(1/12) x base x (height^3)] - [(1/12) x (base - (2 x thickness)) x (height - (2 x thickness)^3]

Deflection (in.) = [force x (length^3)] / (3 x modulous of elasticity x moment of inertia)

Modulous of elasticity for steel = 30 x 10^6

all these equations are in any edition mech. handbook...

so as you can see thru the equations, if you increase the width you increase the moment of inertia, which decreases the deflection.....

ConnecticutX · 10-30-2003, 09:36 AM

Quote:

can you do me a favor?compare a 2x4 .188 wall box tube with a 2x8 .125 wall channel frame

mkay....4x2x3/16 deflects .569 inches and will weigh 36lbs
..........8x2x1/8 "C channel" deflects .19 inches and will weigh 25lbs

lemme know if you need to know why....lol

ConnecticutX · 10-30-2003, 09:48 AM

Quote:

opps sorry i meant the receiver that mounts to the frame and it about 36" to 40" long(its raining up here so i am not going to get wet to measure it). i have looked in my machinist hand book and did not find the chart. if its a beam formula, i would like to know were you add the second vertical in at. sorry to be a pain but inquiring minds would like to know.

okay so ur talkin about the part of the hitch that goes from one frame rail to the other? if so, it is because that beam is under way more torsion (twisting) than bending.....it works out to be the force on the tounge x the length from the tounge to the beam......if you are talkin about the part of the hitch that sticks out, pointing at the trailer...my answer stands as b4..too damn short to noticably bend...

As for where you add in the second vertical....the equation that is used for moment of inertia in that chart is for a rectangular beam...the second vertical is inherent of the equation...If you want the deflection for a c channel frame you can just double the width and then double the deflection.....and divide the weight by 2...

btw...no pain, when I post somthin like this I fully expect to have to defend it....

alteredimage · 10-31-2003, 05:00 AM

Your a smart man:thumbup:

blazentrout · 11-04-2003, 03:08 AM

Quote:

Originally posted by ConnecticutX
okay so ur talkin about the part of the hitch that goes from one frame rail to the other? if so, it is because that beam is under way more torsion (twisting) than bending.....it works out to be the force on the tounge x the length from the tounge to the beam......if you are talkin about the part of the hitch that sticks out, pointing at the trailer...my answer stands as b4..too damn short to noticably bend...
btw...no pain, when I post somthin like this I fully expect to have to defend it....

thanks for pointing out that it would be torsional instead of deflection,i was not thinking of it in that way. i see what you mean.

blazentrout · 11-04-2003, 04:04 AM

Quote:

Originally posted by ConnecticutX
[B
Moment of inertia (I, in^4) =[(1/12) x base x (height^3)] - [(1/12) x (base - (2 x thickness)) x (height - (2 x thickness)^3]
[/b]

i was wondering a couple of more ? i did some more digging and found the formulas that you post and see now how to use them. while i was digging i found this formula(pg 224 of the 25th edition of the machinery's hand book) and i was wondering if this would be a better one to use
bd^3-hk^3/12 (with x height^3- inside with x inside height^3 divided by 12) or is it the same thing but by different means. you have a lot more knowledge on this than i do that is why i am asking that way i can have a better idea of what to use for what project i am working on.

clean n low · 11-04-2003, 04:44 AM

real men raise the floor and take it like a man.

blazentrout · 11-04-2003, 04:50 AM

Quote:

Originally posted by ConnecticutX

Deflection (in.) = [force x (length^3)] / (3 x modulous of elasticity x moment of inertia)

Modulous of elasticity for steel = 30 x 10^6

one of the guys at work gave me this formula for figuring out deflection wl^3/48EI have you heard of this one?
last question in my hand book it said the modulus of elasticity was 29,000,000(pg193) for steel. is this a misprint?i hope to get a chance tonight to play with the formulas at work with my calculator. i thank you for your time in answering these ? i am a machinist and welder by trade if you are wondering. sorry to whore your thread.
to any one else that is reading this stuff just remember when in doubt go thicker/heaver duty than not.

blazentrout · 11-04-2003, 04:55 AM

Quote:

Originally posted by clean n low
real men raise the floor and take it like a man.

been there done that. i need to gain as much room on the next truck as possible do to the fact i want to go to the doors, chop the top 4" and section the body 2 1/2" all on a gen 1 blazer. you tend to run out of room quick.

ConnecticutX · 11-04-2003, 09:08 AM

Quote:

(with x height^3- inside with x inside height^3 divided by 12)

thats the same formula....but where you have the inside dimensions, I have the outside dimensions - 2x the thickness....and 1/12 is applied to both equations in mine so its fine to divide the whole thing by 12

Quote:

wl^3/48EI

Im gunna say no way will that work....basically because force is not in the equation...that would mean the beam would deflect the same amount with 10lbs on it as it would with 1000lbs

Quote:

modulus of elasticity was 29,000,000(pg193) for steel.

true, sometimes....its not really a good number to think of as exact....talk to 10 different people you will get 10 different numbers...the fact is that there are so many steel alloys now that just saying that the modulus is 29,000,000 is kinda ridiculous...i mean come on...does any thing ever work out that perfect? Its an approximated number and it is so large that the difference is too small to mater....heres an example

3.00x3.00x3/16 modulus=30000000 deflection=0.859
3.00x3.00x3/16 modulus=29000000 deflection=0.889

kinda tuff to measure .030 of an inch.....thats like the width of mig wire, lol...so for sake of memorization and factor of safety, I always round up to 30000000....but 29000000 is certainly acceptable.....But then agian if you are trying to compare deflections of stock size and a diff size, the modulus wont even make a difference as long as you use the same number for both...later, Jon

ConnecticutX · 11-04-2003, 09:12 AM

Quote:

real men raise the floor and take it like a man.

real men take off the skirt....and the cab....

ConnecticutX · 11-04-2003, 09:28 AM

see....

clean n low · 11-04-2003, 02:22 PM

Quote:

Originally posted by blazentrout
been there done that. i need to gain as much room on the next truck as possible do to the fact i want to go to the doors, chop the top 4" and section the body 2 1/2" all on a gen 1 blazer. you tend to run out of room quick.

holy mad man, you started this yet? You aren't going to cut up that sick blazer you already built are you?

blazentrout · 11-04-2003, 03:01 PM

Quote:

Originally posted by clean n low
holy mad man, you started this yet? You aren't going to cut up that sick blazer you already built are you?

yes and no to that ? . what i do have so far is the rendering showing the mods, an 89 4x4 blazer for a body,an 86 extended cab frame for the front suspension,350/350 combo for power, and a ford 9" for a rear end(i would love an IRS but need to do more research before i by one). if i had a scanner,i would post the rendering. the goal is to start the frame in the spring/early summer of '04. ill try to keep you guys updated when i start to build. any ? just feel free to ask.

blazentrout · 11-04-2003, 03:11 PM

thanks for you time ConnecticutX. i under stand now whats going on a Little better. to most people 30 grand is a small amount, but at work we like to split hairs example i need this wall moved over 1 grand- reply thanks my night going to suck. now ill quite bugging you for info. Trout

ConnecticutX · 11-04-2003, 04:40 PM

I know exactly what ur talkin about trout.....my buddy runs a wire edm and .030 is huge...lol he was burnin a hole the other night wit a tolerance of -0.0000 and +.0002.....but its all relative.... cuz .030 spread out over a 5 foot length is nuthin....any more q's just lemme know...later, Jon

BYONDSIC · 11-04-2003, 07:17 PM

hey blazentrout where can I find some pics of the blazer thats already built. I had some ones from before but they were unfinished after paint.

blazentrout · 11-05-2003, 02:20 AM

Quote:

Originally posted by BYONDSIC
hey blazentrout where can I find some pics of the blazer thats already built. I had some ones from before but they were unfinished after paint.

i have a gallery here under gen 1 blazers. ill post some current ones of it tonight to the gallery. pm to let me know what you think, i like all feed back.

clean n low · 12-01-2003, 12:28 AM

someone help these guys out, they are tryin to say that 2x3 1/8" is strong enough for a stockfloor. crazy assholes, need a little help here.

http://www.blazinlow.com/forum/showt...957#post253957

ConnecticutX · 12-02-2003, 11:37 AM

Quote:

someone help these guys out, they are tryin to say that 2x3 1/8" is strong enough for a stockfloor

Bwaahhhahahahahhahahhahahhahahhahaha....breath.... Bwaaahahhahahahahhahaha.....thats funny....you could stand on that and bend it, lol....later, Jon

XonAir · 12-10-2003, 01:01 AM

see your formula is great .. but when it comes down to it.I think when the "hack shacks" do sfbd's They do not care about the customers quality as long as they get paid.they only think of how to be the "lowest" and they look at 2x3 and 3x3 and think to them selves.You know what i could be 1" lower with 2x3.. so don't blame them for being blind its not there fault.

alteredimage · 12-10-2003, 07:18 AM

How would 2x3 be lower You use tubing with the longest side parralel to the greatest force.

ConnecticutX · 12-10-2003, 11:28 AM

Quote:

see your formula is great ..

tanks...

Quote:

How would 2x3 be lower You use tubing with the longest side parralel to the greatest force.

Im prety sure hes talkin about layin it on its side....

I dunno, Imo if you build a sfbd frame that is weaker than the stock frame, it was a waste of time....Low should NOT mean you need to compramise quality, or strength...I dont think I ever said it was imposable to build a strong frame out of small stuff, you just need more of it and a actual design....I could go on for hours about guys who build stuff by thinking that it will work and just throwin stuff togather with no overall plan...but I'll spare you, lol...later, Jon

12-10-2003, 01:19 PM

with 3x3 could you do a stock floor, i mean not raise the floor any besides the tranny hump?

Southern · 12-10-2003, 08:08 PM

XonAir · 12-11-2003, 12:08 AM

just curious with 3x3 would that do a 2 1/2 sfbd? and if so what would be the steps to make it 3 1/2 lower with 3x3. without chopping the floor?

10-23-2003, 12:19 PM	#2
BYONDSIC Hell Yeah I Drag!! Age: 30 Join Date: Feb 2003 Posts: 864 Location: ontario canada User is: OffLine	Where did you find that chart?
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10-23-2003, 12:24 PM	#4
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: Where did you find that chart? Quote: mkay...i quick made this up damn u quick.......as u guys can see 2x2 even with 1/2 inch wall still has about 2" of bend in it...I wouldnt want that under me....I personaly went with 3"x3"x1/4" wall if anyone wants it in its excel for just shoot me a pm and I'll email it to ya... Last edited by ConnecticutX : 10-23-2003 at 12:32 PM.
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10-23-2003, 01:26 PM	#5
Dragginblazer DFWminis.com Age: 30 Join Date: Sep 2002 Posts: 154 Location: Ft. Worth, Tx User is: OffLine	Thank you for proving most these fools wrong!
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10-23-2003, 02:27 PM	#6
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: Thank you for proving most these fools wrong! well, I try.....lol....It just helps when u can look at numbers and actualy see what is goin on..... Last edited by ConnecticutX : 10-23-2003 at 02:29 PM.
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10-23-2003, 03:14 PM	#7
Dragginblazer DFWminis.com Age: 30 Join Date: Sep 2002 Posts: 154 Location: Ft. Worth, Tx User is: OffLine	Yeah, I'm glad slammy used 3x3x.25" inside the stock frame on mine now. lol
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10-23-2003, 03:42 PM	#8
BYONDSIC Hell Yeah I Drag!! Age: 30 Join Date: Feb 2003 Posts: 864 Location: ontario canada User is: OffLine	Now do you have one for round tubing
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10-23-2003, 03:54 PM	#9
acrofobia I hate you Age: 32 Join Date: Aug 2001 Posts: 2,237 Location: Castle Rock, Colorado User is: OffLine	Yeah but S-10 frames are C-channeled frames not square. Does this throw off the chart?
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10-23-2003, 04:51 PM	#10
BYONDSIC Hell Yeah I Drag!! Age: 30 Join Date: Feb 2003 Posts: 864 Location: ontario canada User is: OffLine	He's not talking about deflection on the frame he is talking about deflection on the new tubing you are going to be using to make the sfbd possible.
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10-23-2003, 05:03 PM	#11
acrofobia I hate you Age: 32 Join Date: Aug 2001 Posts: 2,237 Location: Castle Rock, Colorado User is: OffLine	He has a "stock" frame size in the chart, that's why I was questioning it.
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10-23-2003, 05:10 PM	#12
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: Yeah but S-10 frames are C-channeled frames not square. Does this throw off the chart? 2nd gens are boxed in from the radiator support to the back wall of the cab.....not sure about 1st gens......and since under the cab is the only place u would need to use small stuff it works out perfect.....
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10-23-2003, 06:05 PM	#13
Slammy circa 1996 Age: 32 Join Date: Aug 2003 Posts: 424 Location: Ft Worthless , TX User is: Online	Nice chart man, ive been telling people forever that 3x3 1/4 wall is the smallest youd ever want to use for frame rails.They dont seem to understand the concept, or maybe they do but are being blinded cause they think they HAVE to have a stock floor cause its the "cool" thing right now.Stock floor body drops work great on fullsizes cause it requires almost no cutting on the floor and you can get a decent size frame under the truck easily.A mini is WAY smaller , requires a bigger bodydrop usually and you will have to chop the shit out of the floor to be able to get a strong enough frame under it. I see what people are doing with these 2x2 and smaller frame as dangerous or trucks that dont need to be daily driven at all.Trailer queens would be ok i guess but i still wouldnt do it on anything i worked on.The frame is the back bone of the truck, the body isnt meant to hold the truck together and if you try and make it you will start breaking the spot welds on the cab cause the stress from too much frame flex.Oh well i guess actually knowing about structural intergrity is one of the things that separates being a professional from the rest of the ummmm what should i call them? Hacks i guess?Not trying to be a ass but damn it gets old.
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10-23-2003, 06:35 PM	#14
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: Nice chart man Thanks man....The biggest misconception is that thicker the wall wall the stronger, no matter the size....3x3x1/4 is much stronger than 2x2x1/2. And 3x3 still isnt as strong as factory verticly, but it is stronger horizontaly...so if u use crossmembers correctly u can get a super stiff frame side to side....and close to as srong verticaly.... I see no reason to use 3x2 rather than 3x3 because the stock frame is about 4.5" wide near the firewall and about 2.5-3 inches wide behind the cab.....horizontal space isnt an issue so use 3" wide .....later, Jon
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10-23-2003, 11:38 PM	#15
dragginbalz lame-o Age: 32 Join Date: Sep 2002 Posts: 784 Location: illinois User is: OffLine	can you do me a favor? compare a 2x4 .188 wall box tube with a 2x8 .125 wall channel frame just curious thanks! t
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10-24-2003, 09:06 AM	#16
ilovesparks Registered User Join Date: Sep 2003 Posts: 8 Location: User is: OffLine	thanks for posting that chart. it helped me out alot to see some actual numbers. im sure everybody else appreciates it too. good work, batman!
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10-24-2003, 08:42 PM	#17
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: compare a 2x4 .188 wall box tube with a 2x8 .125 wall channel frame yea, no prob....im not on my pc right now tho...i'll have it done for ya on tuesday......and is that 2" tall x 4" wide? or the other way around....
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10-25-2003, 12:24 AM	#18
dragginbalz lame-o Age: 32 Join Date: Sep 2002 Posts: 784 Location: illinois User is: OffLine	4 " tall 2" wide 3/16 rect box tubing i am just curious as to how it compares, ( for my NON s10 truck) ) thanks, I really appreciate it t
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10-29-2003, 06:38 AM	#19
blazentrout Mad man from michigan Age: 35 Join Date: May 2003 Posts: 264 Location: grand rapids michigan User is: OffLine	i would like to know were this info was dug up at. if you look at the deflection #'s 3x2 and 3x3 1/4 wall, you will notice that the #s are not the same,but differ by.255. what this is telling me is that something is not quite right with your formula. your vertical height stated the same, the thickness of the wall stock is the same. it should not matter how wide the piece is do to the fact that we are not measuring a horizontal deflection. last ? why doesn't my Reese hitch bend big time when it put my car trailer on it with a tongue weight of 900lbs. it is only made of 1/4 wall 2 1/2x2 1/2. thanks ps i have a machinist hand book at work if you have a page # for the formulas.
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10-29-2003, 10:12 AM	#20
Dragginblazer DFWminis.com Age: 30 Join Date: Sep 2002 Posts: 154 Location: Ft. Worth, Tx User is: OffLine	Your trailer hitch is less than a foot long compared to a 5 foot section that was put into the formula. I also have a Rierson book at my work that I'll lookup & see if they have a similar chart.
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10-29-2003, 12:35 PM	#21
alteredimage Registered User Age: 32 Join Date: Sep 2003 Posts: 1,458 Location: Plainfield CT User is: OffLine	This would make a good sticky!
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10-29-2003, 03:19 PM	#22
blazentrout Mad man from michigan Age: 35 Join Date: May 2003 Posts: 264 Location: grand rapids michigan User is: OffLine	Quote: Originally posted by Dragginblazer Your trailer hitch is less than a foot long compared to a 5 foot section that was put into the formula. I also have a Rierson book at my work that I'll lookup & see if they have a similar chart. opps sorry i meant the receiver that mounts to the frame and it about 36" to 40" long(its raining up here so i am not going to get wet to measure it). i have looked in my machinist hand book and did not find the chart. if its a beam formula, i would like to know were you add the second vertical in at. sorry to be a pain but inquiring minds would like to know.
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10-29-2003, 06:41 PM	#23
Dragginblazer DFWminis.com Age: 30 Join Date: Sep 2002 Posts: 154 Location: Ft. Worth, Tx User is: OffLine	Bah. The book I have dosen't show it either.
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10-30-2003, 09:05 AM	#24
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: i would like to know were this info was dug up at. if you look at the deflection #'s 3x2 and 3x3 1/4 wall, you will notice that the #s are not the same,but differ by.255. what this is telling me is that something is not quite right with your formula. your vertical height stated the same, the thickness of the wall stock is the same. it should not matter how wide the piece is do to the fact that we are not measuring a horizontal deflection. let me learn you.....the vertical section of the beam is called the "web"...the horizontal section is called the "flange"....the 1000 pounds, that I estimated, is exerted on on the flange....and from the flange to the web in the form of pressure (psi)... the equation for pressure is P=F/A, where P is pressure, F is force, and A is area of the flange cross section......now I will use your example.... for the 2" wide.....P=1000/(2.25) which =2000psi exerted on the web for 3" wide......P=1000/(3.25) which =1333.33psi exerted on the web less pressure on the vertical sections (web) means less overall deflection...... Quote: last ? why doesn't my Reese hitch bend big time when it put my car trailer on it with a tongue weight of 900lbs. it is only made of 1/4 wall because the beam (hitch) is only like 6" long.....the beam on that chart is 5 feet long... Last edited by ConnecticutX : 10-30-2003 at 09:12 AM.
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10-30-2003, 09:27 AM	#25
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: i would like to know were this info was dug up at. Quote: ps i have a machinist hand book at work if you have a page # for the formulas. well, I guess that info was dug up from the past 5 years ive spent at Central Ct State U. Engineering dept. as for the mec. handbook...what edition do you have?....I have one at home but not with me right now....but here are the equations.... Moment of inertia (I, in^4) =[(1/12) x base x (height^3)] - [(1/12) x (base - (2 x thickness)) x (height - (2 x thickness)^3] Deflection (in.) = [force x (length^3)] / (3 x modulous of elasticity x moment of inertia) Modulous of elasticity for steel = 30 x 10^6 all these equations are in any edition mech. handbook... so as you can see thru the equations, if you increase the width you increase the moment of inertia, which decreases the deflection..... Last edited by ConnecticutX : 10-30-2003 at 09:59 AM.
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10-30-2003, 09:36 AM	#26
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: can you do me a favor?compare a 2x4 .188 wall box tube with a 2x8 .125 wall channel frame mkay....4x2x3/16 deflects .569 inches and will weigh 36lbs ..........8x2x1/8 "C channel" deflects .19 inches and will weigh 25lbs lemme know if you need to know why....lol Last edited by ConnecticutX : 10-30-2003 at 10:24 AM.
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10-30-2003, 09:48 AM	#27
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: opps sorry i meant the receiver that mounts to the frame and it about 36" to 40" long(its raining up here so i am not going to get wet to measure it). i have looked in my machinist hand book and did not find the chart. if its a beam formula, i would like to know were you add the second vertical in at. sorry to be a pain but inquiring minds would like to know. okay so ur talkin about the part of the hitch that goes from one frame rail to the other? if so, it is because that beam is under way more torsion (twisting) than bending.....it works out to be the force on the tounge x the length from the tounge to the beam......if you are talkin about the part of the hitch that sticks out, pointing at the trailer...my answer stands as b4..too damn short to noticably bend... As for where you add in the second vertical....the equation that is used for moment of inertia in that chart is for a rectangular beam...the second vertical is inherent of the equation...If you want the deflection for a c channel frame you can just double the width and then double the deflection.....and divide the weight by 2... btw...no pain, when I post somthin like this I fully expect to have to defend it.... Last edited by ConnecticutX : 10-30-2003 at 10:28 AM.
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10-31-2003, 05:00 AM	#28
alteredimage Registered User Age: 32 Join Date: Sep 2003 Posts: 1,458 Location: Plainfield CT User is: OffLine	Your a smart man:thumbup:
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11-04-2003, 03:08 AM	#29
blazentrout Mad man from michigan Age: 35 Join Date: May 2003 Posts: 264 Location: grand rapids michigan User is: OffLine	Quote: Originally posted by ConnecticutX okay so ur talkin about the part of the hitch that goes from one frame rail to the other? if so, it is because that beam is under way more torsion (twisting) than bending.....it works out to be the force on the tounge x the length from the tounge to the beam......if you are talkin about the part of the hitch that sticks out, pointing at the trailer...my answer stands as b4..too damn short to noticably bend... btw...no pain, when I post somthin like this I fully expect to have to defend it.... thanks for pointing out that it would be torsional instead of deflection,i was not thinking of it in that way. i see what you mean.
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11-04-2003, 04:04 AM	#30
blazentrout Mad man from michigan Age: 35 Join Date: May 2003 Posts: 264 Location: grand rapids michigan User is: OffLine	Quote: Originally posted by ConnecticutX [B Moment of inertia (I, in^4) =[(1/12) x base x (height^3)] - [(1/12) x (base - (2 x thickness)) x (height - (2 x thickness)^3] [/b] i was wondering a couple of more ? i did some more digging and found the formulas that you post and see now how to use them. while i was digging i found this formula(pg 224 of the 25th edition of the machinery's hand book) and i was wondering if this would be a better one to use bd^3-hk^3/12 (with x height^3- inside with x inside height^3 divided by 12) or is it the same thing but by different means. you have a lot more knowledge on this than i do that is why i am asking that way i can have a better idea of what to use for what project i am working on.
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11-04-2003, 04:44 AM	#31
clean n low can i video tape you? Age: 25 Join Date: Mar 2002 Posts: 2,319 Location: on the ****in ground in Oregon User is: OffLine	real men raise the floor and take it like a man.
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11-04-2003, 04:50 AM	#32
blazentrout Mad man from michigan Age: 35 Join Date: May 2003 Posts: 264 Location: grand rapids michigan User is: OffLine	Quote: Originally posted by ConnecticutX Deflection (in.) = [force x (length^3)] / (3 x modulous of elasticity x moment of inertia) Modulous of elasticity for steel = 30 x 10^6 one of the guys at work gave me this formula for figuring out deflection wl^3/48EI have you heard of this one? last question in my hand book it said the modulus of elasticity was 29,000,000(pg193) for steel. is this a misprint?i hope to get a chance tonight to play with the formulas at work with my calculator. i thank you for your time in answering these ? i am a machinist and welder by trade if you are wondering. sorry to whore your thread. to any one else that is reading this stuff just remember when in doubt go thicker/heaver duty than not.
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11-04-2003, 04:55 AM	#33
blazentrout Mad man from michigan Age: 35 Join Date: May 2003 Posts: 264 Location: grand rapids michigan User is: OffLine	Quote: Originally posted by clean n low real men raise the floor and take it like a man. been there done that. i need to gain as much room on the next truck as possible do to the fact i want to go to the doors, chop the top 4" and section the body 2 1/2" all on a gen 1 blazer. you tend to run out of room quick.
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11-04-2003, 09:08 AM	#34
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: (with x height^3- inside with x inside height^3 divided by 12) thats the same formula....but where you have the inside dimensions, I have the outside dimensions - 2x the thickness....and 1/12 is applied to both equations in mine so its fine to divide the whole thing by 12 Quote: wl^3/48EI Im gunna say no way will that work....basically because force is not in the equation...that would mean the beam would deflect the same amount with 10lbs on it as it would with 1000lbs Quote: modulus of elasticity was 29,000,000(pg193) for steel. true, sometimes....its not really a good number to think of as exact....talk to 10 different people you will get 10 different numbers...the fact is that there are so many steel alloys now that just saying that the modulus is 29,000,000 is kinda ridiculous...i mean come on...does any thing ever work out that perfect? Its an approximated number and it is so large that the difference is too small to mater....heres an example 3.00x3.00x3/16 modulus=30000000 deflection=0.859 3.00x3.00x3/16 modulus=29000000 deflection=0.889 kinda tuff to measure .030 of an inch.....thats like the width of mig wire, lol...so for sake of memorization and factor of safety, I always round up to 30000000....but 29000000 is certainly acceptable.....But then agian if you are trying to compare deflections of stock size and a diff size, the modulus wont even make a difference as long as you use the same number for both...later, Jon
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11-04-2003, 09:12 AM	#35
ConnecticutX Still plays with sparks Age: 29 Join Date: Aug 2001 Posts: 488 Location: Where do you think? User is: OffLine	Quote: real men raise the floor and take it like a man. real men take off the skirt....and the cab.... Last edited by ConnecticutX : 11-04-2003 at 09:21 AM.
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11-04-2003, 02:22 PM	#37
clean n low can i video tape you? Age: 25 Join Date: Mar 2002 Posts: 2,319 Location: on the ****in ground in Oregon User is: OffLine	Quote: Originally posted by blazentrout been there done that. i need to gain as much room on the next truck as possible do to the fact i want to go to the doors, chop the top 4" and section the body 2 1/2" all on a gen 1 blazer. you tend to run out of room quick. holy mad man, you started this yet? You aren't going to cut up that sick blazer you already built are you?
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11-04-2003, 03:01 PM	#38
blazentrout Mad man from michigan Age: 35 Join Date: May 2003 Posts: 264 Location: grand rapids michigan User is: OffLine	Quote: Originally posted by clean n low holy mad man, you started this yet? You aren't going to cut up that sick blazer you already built are you? yes and no to that ? . what i do have so far is the rendering showing the mods, an 89 4x4 blazer for a body,an 86 extended cab frame for the front suspension,350/350 combo for power, and a ford 9" for a rear end(i would love an IRS but need to do more research before i by one). if i had a scanner,i would post the rendering. the goal is to start the frame in the spring/early summer of '04. ill try to keep you guys updated when i start to build. any ? just feel free to ask.
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