Wooden spoke grain discussion

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Model T Ford Forum: Forum 2011: Wooden spoke grain discussion
Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Wednesday, December 28, 2011 - 10:52 am:

I have always been taught that, when buying a hammer the grain direction is a very important consideration, in that it is best to have the grain running in line with the direction of impact. Ideally, the grain should run in line with the longer side of the oval shaped handle. The weakest hammer handles, that are most likely to break, are those whose grain runs opposite of the direction of impact. This has served me well over the years because, as purchasing manager for my railcar repair company, I hand select every sledge hammer we purchase based upon this criteria and we very rarely break a handle. I have also had the same wooden handled claw hammer for 25 year because of this attention to grain direction.

It seems to me that this consideration of grain direction is even more important in the selection of spokes for one's Model T.

The question remains, which grain direction would be best. It seems that the most stress is put on the spokes when cornering, so that the strongest and most desirable spokes would be the ones with the end grain going crossways in line with the sideways movement of a cornering wheel (Spoke B).

I suppose, ideally, the best of both worlds and the strongest wheel could be attained by having every other spoke a type A grain for the straight, inline movement of the wheel and every other spoke, a type B grain to handle the sideways movement of the cornering wheel.

What say you?

Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Henry Petrino in Modesto, CA on Wednesday, December 28, 2011 - 11:07 am:

Jim,

I don't know the answer to your question, but I'm very anxious to hear what other folks have to say about this. I have wondered the same thing since I first started reading about spokes, how they're made, the best wood, etc. Your illustrations show clearly what seem to be opposing properties based on grain direction.

Thanks for asking the question!


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey on Wednesday, December 28, 2011 - 11:35 am:

Jim,
That's not a bad idea, every other spoke. I would think the other option would be the diagonal grain direction, provides some strength in both directions. I suppose with that thought then, every other spoke should go diagonally opposite!
If you look at replacement closed car top bows; it appears some manufacturers have no concept of grain direction--I've seen some really bad grain orientation on them!
T'
David Dewey


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez - Templeton, CA on Wednesday, December 28, 2011 - 01:05 pm:

Jim, you are correct in you analysis. If the mill provides Quarter sawn lumber, then the grain can be oriented as you describe by the craftsman cutting the spokes.

Most mills today prefer to slash cut the logs reducing waste, but the planks will show curved grain longitudinally which will be difficult to orient in the manner you discuss.

Slash or plane cut lumber is what you see today in most tool handles, which frustrates me when trying to select a new shovel or hammer. -John


Top of pagePrevious messageNext messageBottom of page Link to this message  By George - Cherry Hill New Jersey on Wednesday, December 28, 2011 - 01:09 pm:

Jim,

I always applaud your approaches to the way to sort things out, and this too could be a good one...

I have but one cautionary since we are discussing the overall safety of the car. What I have found in attempting to reverse engineer some of these Ford 'secrets' is that a modernistic view towards the way Ford did some things is not a solution in many cases. Ford did what they did because they 'thought' it was right, then 'evolved' to get rid of issues they found in use.

The 'proper' answer to your point is to look at original wheel spokes and determine the grain preference Ford used. A proper sampling of 'varished' oldies would bring this to the forefront quickly.

You are correct in that all wood species have different physical properties based on the orientation of the grain for the application.

I hate to beat a dead horse, yet many try to go to published schedules for wood predicted behavior to find a new 'solution'...when I'm not sure myself that the current definition the US Foresty services uses for 'second growth' hickory is the SAME as that used by Ford. What I can say as a material scientist is that this too is easy enough to 'verify' from an old spoke as 'rings per inch' is the ultimate qualifier...forget the modern schedules. Ford specified '2nd growth Hickory', it was probably Shag Bark hickory...and was probably based on a given forest source of the time...take a sample of original spokes on a 'rings/inch' basis and we either HAVE a correlation to the later published schedules, or we don't.

I took a quick look at one original wheel I have 'au naturale' sitting inside the garage door and it looks to me that End Grain pattern B was the choice by Ford...I'll look closer to see and at others if you would feel it might help.

Just my own O2...but I've always been a bit loathe to try and add 'stiffness' to anything Ford...simply because in my opinion most of the put-rights of evolution while based ON some level of scientific method, were for the most part originally only 'guesses' at the first offs and the subsequent scientific method was based on how the guesses performed as in some areas, Ford WAS writing the book as it went along.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Hjortnaes-Men Falls, WI on Wednesday, December 28, 2011 - 01:25 pm:

Wonder if Stutzman's or Calimar's could answer this question???


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode - Onalaska, WA, USA on Wednesday, December 28, 2011 - 01:26 pm:

With all things being equal I say that the "B" orientation would be the best. I have never seen or heard of a wood spoke wheel failing in the line of movement direction, they always fail from a load to the side. This makes sense because to fail in the line of movement, all spoke have to fail at the same time but only a few spokes have to fail from a side ways loads.

With that being said, it is more important that the spokes are cut with the grain running parallel to the axis of the spoke regardless of the growth ring orientation. Or better yet, split (rather then saw cut) out, then shaped so that the direction of grain is guaranteed to be inline with the spoke. I learned in college and have seen it many times, the most common cause of failure in otherwise correctly designed wood structures is caused by excessive slope of grain. Unlike the growth rings the slope of the grain is not always easy to see.

Here is a link that tells how to check the slope of grain.
http://www.pilotfriend.com/experimental/build_7.htm

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Wednesday, December 28, 2011 - 01:51 pm:

Coincidentally Jim (Thode), I was in the process of making a drawing of the very thing you discussed illustrating that, not only is the end grain orientation important, but, so too is the grain direction. As you can see in both illustrations, the end grain is straight and desirable, but it is equally important to consider the direction of the grain through the length of the piece. The upper illustration, shows that a straight grain that continues all the way up the length of the spoke from one end to the other is far more desirable than a grain that angles off to one side and does not continue for the full length of the spoke. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode - Onalaska, WA, USA on Wednesday, December 28, 2011 - 02:20 pm:

Jim P.
I think your drawing is missing an important part. The total slope of grain includes both the slope of the growth rings and the slope of grain in the same face as the growth rings. You can have a section of wood with the growth rings parallel to the axis and still have the grain slopping. Most all trees seem to have some spiral grain as they grow.

Note in this tree, if a board/spoke was cut parallel to the tree, that the grain (show up as cracks in the photo) would be sloping quite a bit.





Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Christopher Lang - Brentwood Bay, BC on Wednesday, December 28, 2011 - 02:34 pm:

Straight grain is important. Whether it be any way of the first three Jim posted, wouldn't matter to me. It's the grain run-out that can be troublesome. -That's what Jim Thode is talking about. That being said, a little run out is no big deal. All the spokes are under-load when corning anyway. No spoke is ever bearing the whole burden at once, even at standstill or when driving straight.

For general interest, The furthest right picture of end grain in Jim P's first post, is the most desirable to steam-bend, you always have better success when bending perpendicular to the grain.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode - Onalaska, WA, USA on Wednesday, December 28, 2011 - 04:43 pm:

Christopher,
You are correct, a little runout may be okay. All structurally graded lumber has a specified limit of slope of grain for each grade. The more slope of grain, the less allowable stresses will be allowed.

The problem with wood for wheel spokes is that for the average person, they can not go to the store and buy structurally graded hickory. Most wood available is graded for appearance only. It turns out that for most folks they have to grade their own wood, no matter if they cut it out of a tree of buy it at a lumber yard. It also follows that the slope of grain is a most critical element in the strength and the least understood part of structurally graded wood. Most anyone can see knots and sloping growth rings but not as many know how to check for slope of grain.

The link I posted has a good short description of different ways to check the slope of grain.
http://www.pilotfriend.com/experimental/build_7.htm

Then the question becomes, what is the allowable slope of grain for hickory Model T spokes? For critical aircraft parts the link suggests that a maximum 1 in 20 slope would be fine. That would probably be a reasonable limit for spokes. I wounder what specification Ford used originally?

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Thursday, December 29, 2011 - 06:49 am:

Thank you all for your contributions. Very interesting and useful discussion on an important topic. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Nicholas Lingg - Tarboro, NC on Thursday, December 29, 2011 - 08:23 am:

Good spokes should be split from straight grain Hickory not sawn. Spliting will tell you if the grain is going the right way.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Thursday, December 29, 2011 - 08:30 am:

That's what I was thinking Nicholas. It is the only sure way to guarantee that the grain will be straight and true for the entire length of the spoke. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Hatch on Thursday, December 29, 2011 - 09:00 am:

I think I read somewhere that the secs for the wood for spokes said that it was to be split not sawed.
Also, a few years ago my Father met a man at a campground that was burning in his campfire some Hickory blanks. When ask what they were, he said that his company made blanks for hammer handles. My Dad said they looked like spoke blanks. The fellow replied " Strange you should say that, my Grandfather made most of his money shipping spokes to Henry Ford" They were from Cuba, Alabama.


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