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First time "timberframing" questions.

Started by Joe Hillmann, March 18, 2014, 12:01:51 PM

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Joe Hillmann

I am building a sawmill and am too cheap buy steel for the bed of the mill.  My plan is to build the bed out of 4"x12" pine beams.  When looking at it from above it will look like a ladder with two 18 foot 4x12's running side by side about 3 feet apart and 8 4x12's connecting the longer ones kind of like rungs of a ladder.  My original plan was to build it with lots of metal hardware and threaded rod pulling the two 18 footers together.

Now I am thinking about joining them with mortise and tenons that are either drawbored together  or with through tenons that have wedges driven into them to keep them tight.

I would prefer to drawbore them to prevent the ends of the tenons and wedges from sticking out but I worry that as the beams dry the wood will shrink and the draw bored joints will become loose and I will have no way to tighten it up.  If I use wedges, if the joints become loose I can just pound the wedges tighter to tighten them up. 

So my questions are:
    Would you recommend draw boring or wedging or using metal hardware to make the joints?

     What is the easiest way to cut the mortises without special tools?  I plan to drill out the majority of the wood then use chisels to clean them up.

    Are there any pitfalls I should look out for when making mortise and tenons this size?

Jim_Rogers

With the amount of vibration and thumbing when you roll over a cant, I wouldn't use mortise and tenon joints, draw bored or through tenons.
I'd use steel so you can tighten them up when the loosen up, which they will do when they (the 4x12's) dry out.
I would make the 4x12's boxed heart for sure.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

MattJ

I was going to go the cheap route as well with timbers.  After thinking about the movement during seasons, headaches in trying to keep it aligned, and then all the hundreds in hardware I was going to have to buy I reconsidered steel.  The build I did was using 2x3x3/16 steel tube, and 1/4" angle for the tracks and bunks.  It has worked great and the total steel bill was under $500.  If you want to be cheap perhaps try to get scrap steel.  I guess this hinges on if you have access to a welder.  Here is a link of my project build.

https://forestryforum.com/board/index.php/topic,66815.msg1001833.html#msg1001833

Thehardway

I am to cheap to buy blades for my band mill.  I was wondering if there is any way to make them out of wood.  Maybe I could epoxy carbide blade inserts to some thin strips of wood and bond them together in loops??  Maybe a wooden motor would work too.  Could I make it out of lignum vitae?

Just kiddin.  ;D

I am sure it can be done but I think you are asking for a lot of trouble for a small savings.

If I had to do it, like Jim says, I would forgo the M&T joints.  I would and just use half lap joints and through bolt with galvanized bolts and large washers that can be tightened as the wood shrinks, swells and moves in the weather.  How do you intend to get the carriage to ride on the bed?  Most use steel wheels on angle.
I think it will be very difficult to dog down your logs tightly without racking your bed and getting your wheels out of alignment.  Nothing worse than trying to cut on a twisted bed or with misaligned wheels.  Your boards and timbers will be far from straight and it could be dangerous due to binding of the blade.  Anyone who has had a blade bind will tell you things can get ugly quick especially on a manual rig.  Think things through first before proceeding but don't let me discourage you. Rome wasn't built in a day and we all must choose our own battles.
Norwood LM2000 24HP w/28' bed, Hudson Oscar 18" 32' bed, Woodmaster 718 planer,  Kubota L185D, Stihl 029, Husqvarna 550XP

Joe Hillmann

Quote from: Thehardway on March 18, 2014, 04:16:44 PM
  How do you intend to get the carriage to ride on the bed?  Most use steel wheels on angle.
I think it will be very difficult to dog down your logs tightly without racking your bed and getting your wheels out of alignment.  Nothing worse than trying to cut on a twisted bed or with misaligned wheels.  Your boards and timbers will be far from straight and it could be dangerous due to binding of the blade.  Anyone who has had a blade bind will tell you things can get ugly quick especially on a manual rig.  Think things through first before proceeding but don't let me discourage you. Rome wasn't built in a day and we all must choose our own battles.

I plan to build a steel frame on top of the wood frame with steel tubing for guides for the rollers (I may end up going with angle iron instead of the tubing) 

Andy White

Joe Hillman,
Keep in mind the very large amount of sawdust that will fill all the spaces between the "ladder rungs" of the frame. This will be very time consuming to clean out, and will be necessary to prevent the beams from staying wet, and leading to rot. Don't ask me how I know.     Andy
Learning by day, aching by night, but loving every minute of it!! Running HM126 Woodland Mill, Stihl MS290, Homemade Log Arch, JD 5103/FEL and complete woodshop of American Delta tools.

Joe Hillmann

I had not given that any thought.  I planed to mount the frame on cinderblocks and shims so the bottom of timber would be 9 inches off the ground.  Although over time it is pretty easy to build up that much sawdust.  I don't expect it to be in any one location for very long so I don't know if it will be a problem.

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