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Anyone know how much weight a 4x6 can support?

37K views 11 replies 9 participants last post by  SJK9er  
#1 ·
So I have to lift the engine and transmission out of my car to replace the clutch, and instead of buying a engine lift, me and my dad want to build one into the car port.

What we want is for it to be able to support 1000lbs without failing (safety factor already included)
The carport is held up by telephone poles, and we are going to span directly over them with a block and tackle or something similar.

The only thing I don't know is the breaking point of the 4x6
The span is 10ft unsupported with 1ft supported at each end. The weight will be right at the middle of the span as well. I've looked all over for data on the breaking strength and even looked for my old beam calculations from engineering class. But I still don't because the young's modulus is seemingly impossible to find for wood and even with it my formulas will only give me deflection and I don't know how much the wood can deflect before breaking. I tried finding span tables but I can't find any for a 4x6 and don't really get how to read them.

So does anyone have experience and know this information?
 
#3 ·
would this help?

http://www.awc.org/pdf/wsdd/c2b.pdf

it looks like a point stress load is about 145 lbs if I read it right on a 9' span. Doesn't sounds quite right but you may be better off renting a hoist for a while instead of the extended doctor bills.
 
#5 ·
mythbustingpyro said:
So I have to lift the engine and transmission out of my car to replace the clutch, and instead of buying a engine lift, me and my dad want to build one into the car port.

What we want is for it to be able to support 1000lbs without failing (safety factor already included)
The carport is held up by telephone poles, and we are going to span directly over them with a block and tackle or something similar.

The only thing I don't know is the breaking point of the 4x6
The span is 10ft unsupported with 1ft supported at each end. The weight will be right at the middle of the span as well. I've looked all over for data on the breaking strength and even looked for my old beam calculations from engineering class. But I still don't because the young's modulus is seemingly impossible to find for wood and even with it my formulas will only give me deflection and I don't know how much the wood can deflect before breaking. I tried finding span tables but I can't find any for a 4x6 and don't really get how to read them.

So does anyone have experience and know this information?
There are SO many variables here that it is really hard to say. But, here is a link to a PDF that should allow you to handle your assumptions and go with it. http://www.awc.org/pdf/wsdd/c2a.pdf

It looks like you should keep the total deflection to roughly 0.5 inches on a 10 foot span, though. For floors, they would limit it to 0.33 inches, but for other uses, L/240 seems to be acceptable. I really prefer plywood I-beams for wood based bridges like loading ramps etc. They are much more predictable in terms of the grain and defects being an issue.

Be safe!
CC
[hr]
Too funny that I came up with the same pdf as BullsEye!
 
#6 ·
Thanks. We really want to be able to build in and have it there, because there are a good amount of times we will be doing this type of lift.

Maybe a y support to reduce point load would work well. Maybe use a 6x6 as well. Have also heard things about laminating separate boards together being more reliable than a straight beam.
 
#8 ·
Chop up some 4x4 or 6x6 to use as posts throughout the length of the beam?
[hr]
Or you could use some steel jack stands
 
#10 ·
I strongly suggest you get a engine lift. Seriously. Most lifts are on wheels, which help out exponentially.

Yes, you can minority engineer a wood beam, that may be okay for 4 or 5 lifts, BUT the stress will wear on a beam, add weather changes and over time, you'll asking for an accident or someone to be killed, because something will fail.

Save yourself some grief and heartache, get the right tool for the job.