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Is this frame and rail design good/bad?

Started by MikeySP, January 24, 2019, 01:37:47 PM

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MikeySP

I designed the following frame based on materials I have on hand:

  • 3" square tubing 1/8" wall (Edit: the 3x3 is stacked so the final dimension of each side is 3"x6")
  • 2"x2"x1/8" angle iron

Can you offer a critique of the design.

I want a very accurate cut so I am able to mill very thin wood for certain projects.
I prefer to avoid spending the money on cold rolled steal, so i thought about using the flush cut angle grinder jig in the bottom picture to make a very level surface and run the casters on that. The angle cut jig makes very nice angled profile, but it was designed for making rail for a CNC router and I cannot see a mill needing side to side precision like a cnc router would.



 


 


ladylake


 No way is 3 x3 x 1/8 strong enough for the main rails on a mill.  Maybe if stationary and supported real good every 2 feet. I'd be using 3 x6  x 1/4 at least for the main rails.  Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

MikeySP

Steve, you did notice that I stacked the 3x3x1/8 effectively making a 3x6x1/8 with two additional midway horizontals?

Just wanted to be sure you were evaluating the doubling up vs a single 3x3x1/8.

bwstout

I think your strength would depend on how for apart you plan to put you log bunks as they will add structural strength to the overall bed and rails. I double stack 3x5 1/4 with a 5 x1/8 c channel with a a 1/4x 1 angle for the tracks so for no issue with it flexing under heave loads. 38" x 14' has been the heaviest.
 
home built mill

MikeySP

I figured to make it wide enough for a 32"-36" log.

charles mann

I used 2x8x1/4 20' for my main beams, with 11 2x6x1/4 6' for bunks, spaced 23 3/4" apart on my first attempt. After getting it completely welded up, i noticed an 11/16" belly in my main beams. 

I listened to the folks on here and went with 2x6x1/4 for the beams and salvaged all the bunk beams. 
It took me 2 days to slowly stitch weld the entire mill bed up, to ensure i didnt over heat any section, plus i tacked the main beams to 4 4' tall i-beam saw horses. It was a PAIN to crawl around, under and over everything, but i have NO sag. 

As to 1/8" tubing, and double stacking, you might be safe, since you'll in essence, have a 3x6x1/4 tubing, maybe adding extra bunks like recommended, may work for you. 

Did you happen to have that material already onhand, which is why you are thinking of using it? 
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

MikeySP

Charles, I do have about a 150 ft of 3x3x1/8 and 120ft of 2x2x3/8.

Also, you said that I would end up with a 3x6x1/4. Actually it will still be 1/8 thick accept where the two pieces touch. I wish calculating strength was simple, as I could take the recommended numbers and calculate what I am proposing and beef it up until all is well. Oh well, I am being made to think and I won't do this unless someone knows it will work. I bet if I made it a truss it would work. Not sure if that is a good idea as it will get pretty deep 12" +/- tall track beams. 

Anyways. Thanks for chiming in everyone.

BigZ La

You could double stack the 3x3 you have and buy some flat plate to one side the double stack. That would make it strong and not cost much. 

Don P

Or combine the ideas, that flat plate between the 3x3 tubes would form an I beam/ truss which would be considerably stiffer than plating it on the side.

If you want to figure it out read up on calculating the section properties of combined shapes. With those numbers and the loads and spans it wouldn't be difficult to plug into a beam calc and get deflections. If this is ground mounted on a slab, the slab can be the stiff beam doing the work, the steel would be spanning zero. Another thought, can you trade some of it for some C channel or I beam for the rails, or just buy a couple of pieces for rail. I think welding and risk of distortion is going to eat up any savings in trying to fabricate a pair of dead straight beams.

Southside

One question I have is if you use that angle grinder jig are you removing any surface hardening and creating a situation where you will have excess wear impacting accuracy?
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charles mann

Unless you are going to mill balsa wood, the deminsions you gave, those 32-36" logs will wreak havoc on 1/8" material. I opted to save $ when building my dog/atv trailer. I went with 2"x2"x1/8" angle, and spaced the cross beams 12" apart and used 2x6 treated lumber, the trailer (6'x12') still twisted. I stiffened it up with 2 3/8" drill pipe, running stem to sternum. Point is, 1/8" is too lite of material. 

I made a $1200 mistake in just material alone and had to start back from scratch. Go ahead and spend the $ and get 1/4" wall, minimum, and take your time. 
Even if on a concrete slab/footings, the top of the frame is still thin and weak and will get crushed under those logs over time. Im sure my 1/4" wall will get pounded by the logs i will be loading onto it. 
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

MikeySP

Ok, I see what you mean. Even if I where to make it a truss and made it stiff enough to stay straight, the thin wall would be getting beat to death from the tonnage of logs. 

Where do I go from here? Is their a thread that shows the frame design and materials thickness Cooks, Timber King, or another proven design uses? Has anyone ever done a successful homemade cantilever mill? 

Is this where a Texas Ben or Linn set of plans comes in? I don't have to dig for every grain of gold. For example, I have read countless threads, watched countless videos on DIY sawmills, and I still don't know what the correct dimensions ought to be. along with a thousand other details. I am sure I could make a mill right now without a jot or tittle more of info; however, I am positive that it would have an enormous amount of bad assemblies that I would regret later. 

Thank you all for helping me to avoid walking off a cliff. 

-Mike


MikeySP

Charles, Did I understand you correctly that a 2x8x1/4" rail flexed while a 2x6x1/4 was straight? Confused. -Mike

Kwill

Quote from: MikeySP on January 25, 2019, 12:29:16 PM
Charles, Did I understand you correctly that a 2x8x1/4" rail flexed while a 2x6x1/4 was straight? Confused. -Mike
He welded the 2x8 all up at one time and it bowed. He took a couple days to weld the 2x6 up keeping the metal from getting to hot and it stayed straight.
Built my own hydraulic splitter
Built my own outdoor wood stove
Built my own log arch
built my own bandsaw sawmill
Built my own atv log arch.
Built my own FEL grapple

Kwill

The best way to do it to keep everything straight would be to drill and bolt everything together. It would be lots of drilling. a mag drill would work great in this instance.
Built my own hydraulic splitter
Built my own outdoor wood stove
Built my own log arch
built my own bandsaw sawmill
Built my own atv log arch.
Built my own FEL grapple

charles mann

Quote from: MikeySP on January 25, 2019, 12:29:16 PM
Charles, Did I understand you correctly that a 2x8x1/4" rail flexed while a 2x6x1/4 was straight? Confused. -Mike
Yes, the 2x8 was had a smile, all though i wasnt smiling. 
I had the 2x8 supported by 3 RR cross ties, 1 on ea end and 1 in the center-ish. A member suggested that bc i used 2x6 for my bunks, there was an uneven heating, caused by continuously welding, even though i made 1-2" welds, caddy-cornering ea weld per bunk, then moving to another bunk, caddy-corner away, and that i didnt give the 2x8 time to cool down enough before applying heat to it close enough to affect it. I didnt have a belly at CoB, came out the nxt morning and noticed it. 
The 2x6s were tacked sown to the i-beams after squaring and plumbing the rails up. I started with the end caps, just tacking them, actually, tacked everything first, then the middle bunk, and finally the lat 2 for the day. I stitch welded the first 5 bunks, till they were fully welded, and i checked level/plumb after ea stitch. The next day, i installed the remaining 6 bunks. I then installed the 2 2x2x3/8" angle tracks. After cutting it from the i-beams, i was still level, and i used a string instead of relying on just box store 4' level. 
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

charles mann

Thanks for explaining in shorter detail than what i did. I get diarrhea of the fingers sometimes, and for many yrs, mostly in the 13 of the mil, i was always told elaborate my statement bc i always gave simple marine corp understandable statements. 

@Kwill 
Temple, Tx
Fire Fighting and Heavy Lift Helicopter Mech
Helicopter and Fixed Wing Pilot

bwstout

I bought Texas Ben's plans it was 10.00 well spent drawing are easy to follow has some of them in 3D to make it easy to see. I did not follow it to the spec but used it for a base to began and made modification from a lot of the mods found on this forum.
home built mill

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