I need ramps to load my logs on the mill with a hand crank winch, what size steel tubing should I go with? Local metal place quoted me $98 for each ramp sized at 2"x3"x5' with 1/4" thickness. My brother says its overkill for rolling logs onto the mill. Most of my logs are probably around 1200-1600lbs right now but I plan on getting bigger ones for sure up to 3000 lbs. Could I get away with 2"x2"x5 at 3/16 thickness instead?
Yes. and even thinner. Mine are 1/8" x 2" x 4" x 8' and I put supports midway (sometimes 2) for heavy logs - 3000 to 4000 pounders. This way I don't have to lift such heavy steel ramps.
Thinner than 1/8? Do you think 2"x2" @ 1/4" thick is sufficient?
The key is using the vertical supports. Closer spaced supports increase the capacity significantly.
The only way to really know is to plug the numbers in and do an analysis. There are many online tools to do this. Many of the steel suppliers have calculators on their website.
This same topic was discussed on here a couple weeks ago and included a detailed analysis.
I would use rectangle over square any day. Mine are 2x4 1/4 wall I believe. I'm happy with them but as Kellogg said 1/8" wall is probably sufficient.
Quote from: Daburner87 on October 04, 2021, 06:41:45 PM
Thinner than 1/8? Do you think 2"x2" @ 1/4" thick is sufficient?
EDIT: In my lunchtime haste, I overlooked a key piece of information: Stress equals Mc/I where M is your moment (caused by your loading), c is half of your section depth, and I is your moment of inertia. Because these have different section depths, you really need to compare the ratios of the c/I (the lower the better). I also added the weights to make it easier to follow (hopefully).
The capacity is a function of the wall thickness AND the depth. Basically, you want the section with the highest moment of inertia which for a rectangle is (1/12)(width)(depth)^3. Because this is a hollow section, the void is subtracted out. As you can see the depth gets cubed, so you get a lot more strength from a deeper section (i.e. more bang for your buck) as shown below. From my steel manual, the moment of inertias for the shapes discussed are shown below. For the rectangular sections, these are oriented with the long side vertical.
HSS2x2x1/8: I = 0.486, c = 1", c/I = 2.06, weight = 3.04 lb/ft
HSS2x2x1/4: I = 0.747, c = 1", c/I = 1.34, weight = 5.38 lb/ft
HSS3x2x1/8: I = 1.30, c = 1.5", c/I = 1.15, weight = 3.90 lb/ft
HSS3x2x3/16: I = 1.77, c = 1.5", c/I = 0.85, weight = 5.59 lb/ft
HSS3x2x1/4: I = 2.13 , c = 1.5", c/I = 0.70, weight = 7.08 lb/ft
HSS4x2x1/8: I = 2.65 , c = 2.0", c/I = 0.75, weight = 4.75 lb/ft
The last two sections are comparable strength-wise, but the 4" section is lighter and should cost less. Both are about twice as strong as the 2x2x1/4 section (1.34 vs 0.70/0.75). Compared to the 2x2x1/4, the 4x2x1/8 is also lighter and should be cheaper.
Additionally, you could consider buying a higher grade of steel which would allow you to go smaller. I don't know if you have the option, but a grade 50 steel will be stronger than a grade 36. I don't know the cost differential.
Lastly, as others pointed out, the span of your ramps is also a factor. You are talking about 5' ramps, but others have 8' ramps with supports. Even if the logs are the same weight, it would be tough to compare directly since they result in different bending stresses. As someone pointed out, there are calculators available online that can help you out with this.
I know it is a lot of information and jargon, but ultimately the deeper the section, the better. I hope this helps.
Here's a calculator: https://www.roguefab.com/tube-calculator/
scroll down to the rectangular tube section and put in your values. The maximum stress will be when the log is at the center of the tube. As btulloh said, if you put a vertical support at the center, you have now cut your length of tube (for stress calculation purposes) in half.
A safety factor of 1 shows you the max load before permanent bending.
2x2x.025" x 60" long (A36) steel tube will support about 2500lbs.
Same tube but 30" long can support twice that with the same max stress.
Consider that if your ramp consists of two such tubes, you could probably get away with about 5000lbs on it.
If you put vertical supports under the center of each tube, 10k is possible.
I recommend looking at I beams, as they are stronger pound for pound than tubing (should be cheaper for the same strength) in bending.
Quote from: ajsawyer on October 05, 2021, 03:53:28 PM
Here's a calculator: Tube Calculator - Round, Rectangular & Square Pipes Capacity | Rogue Fabrication (https://www.roguefab.com/tube-calculator/)
scroll down to the rectangular tube section and put in your values. The maximum stress will be when the log is at the center of the tube. As btulloh said, if you put a vertical support at the center, you have now cut your length of tube (for stress calculation purposes) in half.
A safety factor of 1 shows you the max load before permanent bending.
2x2x.025" x 60" long (A36) steel tube will support about 2500lbs.
Same tube but 30" long can support twice that with the same max stress.
Consider that if your ramp consists of two such tubes, you could probably get away with about 5000lbs on it.
If you put vertical supports under the center of each tube, 10k is possible.
I recommend looking at I beams, as they are stronger pound for pound than tubing (should be cheaper for the same strength) in bending.
A couple things to add/consider:
1.) I wouldn't use a factor of safety of 1.0. Typically for allowable stress design, we use 55% of the yield stress which is 20,000 for grade 36 steel.
2.) The calculator approximates the calculation based on the dimensions you enter. In reality, the corners are rounded and the design wall thicknesses are less than the nominal. It might sound nitpicky, but for the smaller shapes it appears to result in the calculated stress to be lower by 10-20% than the actual.
I never much liked steel ramps because of the possibility of logs slipping or winch failure. I dug a level spot for my mill to set in and built a log deck that's easy to roll logs onto and then a straight shot onto the mill over some 4' long timbers.
(https://forestryforum.com/gallery/albums/userpics/59254/IMG_20210228_132755601.jpg?easyrotate_cache=1614559460)
(https://forestryforum.com/gallery/albums/userpics/59254/IMG_20210228_132740756.jpg?easyrotate_cache=1614559462)
I've had 16' long x 28" white oak on it and no problems. Best part is that you can load the deck and saw several hundred or even 1000 bf without parbuckling each individual log.