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Strength testing - or - Why we use yellow poplar for our bars

Posted by RodandDenise on February 11, 2015

2015 Feb 10 1 testing a saddle tree bar for strength.jpg

It isn’t often that pieces of a tree get to the finished stage before they get rejected by Rod, the final quality control supervisor. If something isn’t going to make the cut, he usually rejects it earlier in the process that this. But this time he was finished the bar before he decided he wasn’t happy with how the back of it turned out. So after he experimented with and destroyed the whole back end of the bar figuring out how to make things better the next time, we decided to do some testing with what was left. It’s been a while since we did this, and thought it might be fun. Besides, it was too long to fit into the wood stove…

2015 Feb 10 2 the set up DSC_1171.jpg

We laid the bar across the feet of the vice so it totally bridged, and got out his three pound shaping hammer he used back when he was shoeing horses.

2015 Feb 10 3 DSC_1145 one.jpg

Then he started whamming on it. One!!

2015 Feb 10 4 DSC_1146 two.jpg

Two!! He was hitting it right at the back of the stirrup groove, at it’s weakest point. Obviously, there is a bit of a time lag between when I hit the shutter button and when the picture is taken.

2015 Feb 10 5 DSC_1147 three.jpg

Three!! As you can see by the rebound, he isn’t just tapping it. He was really whaling on that bar!

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Four!! I was trying to get a picture of the hammer actually hitting the bar, and not a second later. This time, I was too early…

2015 Feb 10 7 DSC_1149 cracked after four.jpg

So after four major whacks, the bar is starting to crack - longitudinally – and only on the front half of the bar so far. This is how yellow poplar usually breaks - if it ever does crack. It doesn’t break across the grain very easily, which is one of the reasons we don’t worry about putting in a full stirrup groove. (This is a good thing, because there are reasons why we won’t make an Arizona bar  - one which doesn’t have a full stirrup groove.)

2015 Feb 10 8 DSC_1150 five.jpg

Five!! Surely this time it will split, right?

2015 Feb 10 9 DSC_1151 cracked more after 5.jpg

Nope. The crack is worse, but it hasn’t broken through yet.

2015 Feb 10 10 DSC_1152 six.jpg

Six!! It’s still intact and bouncing…

2015 Feb 10 11 DSC_1153 seven it finally broke.jpg

Seven!! It finally broke.

2015 Feb 10 12 DSC_1155 broken pieces.jpg

Split totally length wise, and the lower piece broke in half.

2015 Feb 10 12a DSC_1156.jpg

Interestingly, it didn’t break across the back of the stirrup groove. The wood again split along its grain horizontally in the narrowest part of the bar. But the top half was still too long for the stove, so…

2015 Feb 10 13 DSC_1158 eight.jpg

Eight!! With only half the bar, it really flew! Just barely got it in the picture…

2015 Feb 10 14 DSC_1159 nine.jpg

Nine!! Still bouncing…

2015 Feb 10 15 DSC_1160 starting to crack.jpg

But it is starting to crack.

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Ten!! A little late with this photo. It’s already landed, but it’s still intact…
2015 Feb 10 17 DSC_1162 cracked a bit more.jpg

Though it is cracking more with each hit.

2015 Feb 10 18 DSC_1163 cracks lengthwise.jpg
And again, it is cracking lengthwise, not across the grain.

2015 Feb 10 19 DSC_1164 eleven.jpg

Eleven!! We didn’t measure the width across the narrowest point still left at the back of the stirrup groove, but it couldn’t have been more than two inches at most.

2015 Feb 10 20 DSC_1165 twelve.jpg

Twelve!! I finally got one at the point of impact!!

2015 Feb 10 21 DSC_1166 finally broken through.jpg

And the whole bar finally broke all the way through.

2015 Feb 10 22 DSC_1173.jpg

So now it all fits in the stove. First lesson learned – we confirmed we are using the correct wood for our bars. Second lesson learned – if we have any more reject bars, cut them across with the band saw. It will be a lot faster…

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