Wood Spoke Wheel: Design Theory

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Model T Ford Forum: Forum 2005: Wood Spoke Wheel: Design Theory
Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis on Monday, February 25, 2008 - 09:39 pm:

Any wood wheel experts out there? What keeps spokes tight? Are they a tight fit between the hub and the felloe, or does the "Tightness" come from the twelve wedges all working in conjunction with one another? I suppose it could be both, but the tolerances of all parts would be critical.

When spokes become loose, I've heard of shimming them. Where do you shim them? Between the spoke and the hub or between the spokes' wedge to wedge fit?

How hard is it to remove a hub from a wheel and leave the wheel intact? Disregarding any rust from the inner and outer hubs holding them together, will the hub come right out of the spoke assembly, or does it have to be pressed out? Or does the whole wheel have to disassembled in one step (TeePee-ing it)?


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Harrison on Monday, February 25, 2008 - 11:27 pm:

I'm far from an expert, but I have rebuilt my own wheels. When you tighten the spokes you put shims between the end of the spoke and felloe. Just pieces of sheetmetal with slots in them. I have done it before and it works. It works best if you have a spoke jack, which pushes from the felloe between two spokes.

When you take them apart, just remove the bolts and knock them apart with a hammer. Usually it doesn't take much for them to fall apart.

The hub should be a press fit in the spokes. To put them together make a teepee out of the spokes with the hub in the middle then press it all together. I built a kind of press out of wood and a piece of thread-all.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Pawelek on Monday, February 25, 2008 - 11:57 pm:

Hal, Here are some pictures of what David is describing. I have never personally used spoke shims or a spoke jack...Michael Pawelek
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Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Aber on Tuesday, February 26, 2008 - 12:40 am:

If you are going to shim them consider it a temporary fix and begin thinking about respoking. The only issue on disassembly is you will likely have to grind off the bolts which hold the hub in place since they are suppose to be peened over when installed. So, always order new bolts and nuts..you won't be able to reuse the old ones. Other than that, it is a matter of overcoming years of grime etc. between the hub and the spokes but they will eventually come out. I have often just cut through old spokes on one side to get the others to loosen themselves from the hub.
As for putting spokes in I recommend the device created by member John Regan. Pictured below, it takes almost nothing to construct and if you only use it on you 4 wheels it saves time and brings them in just right. John has a demonstration on the other website and can be contacted on this website just by asking.
Good luck, but don't make too many compromises with those wheels because the results can be very serious.



Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Aber on Tuesday, February 26, 2008 - 12:51 am:

I meant to add one other caution, which I faced myself. My spokes looked great, they had been professionally refinished in the early '70's but started to click. When I disassembled my first wheel, I dropped a spoke and it shattered on the garage floor. Turned out the inside of this very good looking spoke had a bad case of dry rot. Since these were originals repainted, they gave no sign of THAT weakness. I did my other wheels at once and in each case found internal dry rot. I believe that they had been sitting on the bottom on the wheels in the barn when I pulled the car out and had been bad from day one. In each case there were at least three spokes which were bad on the inside.
The other thing is, buy only hickory spokes. Don't go with oak. This forum has proved a long time ago that new oak spokes do not have the "give" required to counteract the pressures placed on a wheel when turning the car.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ross Benedict on Tuesday, February 26, 2008 - 03:05 am:

When you take the spokes apart, number them in a clockwise direction (or Anto-clockwise if you so choose). This will allow you to reassemble without working on a jigsaw puzzle that you may never get right.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Tuesday, February 26, 2008 - 11:06 am:

I have often toyed with the idea of a test for spokes, or complete wheels. The ideal would be a test that could be performed using the weight of the car, so it could apply to any car, not just a Ford.

Unlike metal that bends, wood yields very little - up to the point of failure. A non-destructive test for ultimate strength is best, but maybe not achievable. A go-nogo test would be better than nothing, for sure.

I believe the most important test for wheel spokes is "Impact Bending, Height of Drop Causing Failure," found here: http://www.woodbin.com/ref/wood/strength_table.htm

Static strength tests are much easier to do and control, but not so relevant as "impact bending."

Any ideas?

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Jeffrey Cole on Tuesday, February 26, 2008 - 11:35 am:

Like a dummy,during Hurricane Hugo,during the eye of the storm I went outside to see what was damaged.I was a good ways from the house when the storm came back and wound hugging a large oak tree till the storm passed.Hickory and Maple trees seem to be able flex better in the storm that oak or other trees.so that would tell me the wood would be more flexiable in use on something.
Dogwood is known for hardness.It is used for example,on the guide blocks on our sawmill.Never seems to wear.

So Hickory would be my choice for spoke wood.

Uh, Bill,you forgot the photo of our first "spoke press" we tried at a tech session.My f150,it werent heavy enough,so we tried a Excursion.Nobody had thier Kenworth with them that afternoon or I guess we woulda tryed 1 of them!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis on Tuesday, February 26, 2008 - 12:50 pm:

Did anybody else have flashbacks to Gilligan's Island while reading Mack's post? ;-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas J. Miller on Tuesday, February 26, 2008 - 01:41 pm:

Rick,

My thoughts. Looking over your fixtures, the first one probably comes closest to approximate the loading during failure. A spoke clamped in a fixed hub with a cantilever load at the tenon would show the worst loading. I would have a fixture that approximates the formed hole in the felloe that would load the tenon while holding the other end clamped. Since wood spokes work in comression while rolling straight, a sideload would be the worst force it would see. I don't see braking or acceleration being a greater contributor than a sideload.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem on Tuesday, February 26, 2008 - 02:39 pm:

To answer some of the original questions. The spokes are primarily tight due to the twelve wedges working against each other and directing radial forces out towards the felloe. The hub nose must be snug in the center hole but should not be the sole reason for the tightness of the spokes within the confines of the felloe. This condition would allow for gaps in the wedged spoke ends which will lead to the spokes shifting about the hub.

The spoke jack idea, with shims between the spokes and felloe is an old one. It may work for a while. Some of my wheels have been tightened a bit different. I insert an exhaust pipe expander in the center hole and tighten it as much as I can. The spokes are then driven out tight against the felloe. This movement leaves gaps between the wedged spoke ends which I shim with either hard wood or dimpled metal. (Dimpled to help ensure they bite into the spoke and don't work out.) After removing the expander, the spokes stay tight. However, now the center hole is enlarged. It's then necessary to wrap shim around the hub nose to ensure the snug fit of the hub.

There's a limit to any of these schemes however. These practices are for minor looseness, in wheels with very sound spokes, that have good tennons where they fit in the felloe. At some point, new spokes are essential and to fool yourself that these little tricks will avoid a costly investment will ultimatly put your car, and it's occupants, at risk.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Jeffrey Cole on Tuesday, February 26, 2008 - 04:11 pm:

A barn find T or wheels that have been out in the elements are exsposed to the same things as lumber in a home or structure,and shares the same enemys.I have found wood wheels to have termite damage that wasnt obvious till you poke at them.
I do remember baby powder being used on the spokes I watched last time being installed.it helped them go together alot easier.

And whatever you do,be sure when you drill the holes,that the holes are drilled so the bolts go between the spokes,not thru them.that weakens them alot drilling thru the middle.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis on Tuesday, February 26, 2008 - 05:55 pm:

A lot of good information here guys. Thank you very much. Some of it, I was just curious about, but I have to admit, I am considering doing a little wheel work. Not sure what I'm gonna find in there, but I know I have one bad spoke, at least. There is some rot on the tenon end. None of the others seem to have any soft spots and with the exception of one other, they all ring clear when tapped. That other one is slightly loose, but doesn't appear to be rotted. I'll know more when I get it apart. Thankfully, this is one of the fronts, not a rear. I'll bet TT 23" TT spokes are hard to find.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Aber on Tuesday, February 26, 2008 - 09:06 pm:

Mack is right, it all has to do with having the right tool, and his Ford was obviously NOT the tool we needed.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Nelson Jones on Tuesday, February 26, 2008 - 10:29 pm:

I pressed my spokes & hubs under the trailer hitch on the rear of my motorhome. !6000lbs. Worked for me. Nelson


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Mikeska on Tuesday, February 26, 2008 - 11:09 pm:

Bill Aber,

It looks to me like you need an F 250.

Paul


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, February 27, 2008 - 02:18 am:

I agree with your analysis, Thos. In fact, the rearend locked up at 60 on me back in '02 and flatspotted the tires, but the red oak spokes were unhurt. A 10mph side load broke a wheel.
http://pweb.netcom.com/~rickydik/safety/safe3b27.html

Surrounding the tenon is more realistic than what I tried.

Now, how do we make a fixture to hold the hub end solid, and what can we use for an accurate and repeatable impact device?

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas J. Miller on Wednesday, February 27, 2008 - 07:23 am:

For accurate and repeatable, how about a pendulum with a protractor scale? More or less a sledge hammer of a known weight on a ball bearing pivot. Calibrate the starting point of the hammer, have it hit the tenon block squarely, and the relative breaking force can be calculated.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, February 27, 2008 - 08:29 am:

Excellent. Now, how do we secure the hub of the spoke in the horizontal plane?

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By jack daron-Indy. on Wednesday, February 27, 2008 - 11:00 am:

Gents, no one spoke shares all the load nor the side-load when cornering. You would need a very elaborate wheel set up with a side press and a means of measuring the actual pressure, while the wheel is turning. Spend abot $10 grand ,wreck 10-12 rebuilt wheels and you might be getting close to understanding the problem. Or you could just properly rebuild the wheel,and tour on down the road?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Wednesday, February 27, 2008 - 11:28 am:

I think Jack has sort of hit it. What you guys are really doing is re-engineering the spoke. While this is OK to do, the "proof is in the pudding" meaning of course that how well the spoke holds up is ultimately what it is all about. Ford did the engineering and posted their stress test to be applied to each spoke which was the simple setup using 2 points of suspension and a force midway applied. But what they did NEXT is what is terribly important - they then built millions of wheels with those specs and they were NOT known to be prone to failure on daily use on roads at least twice as bad as anything we have been on for a few minutes. As an engineer I would LOVE to have that kind of proven data on anything I have ever designed. Make or buy a new spoke EXACTLY to the factory drawing from EXACTLY the wood they used and then sample test some of them to make sure they meet Ford's spec and build your wheel with them. Doing it any other way is to go it alone and to be different than the millions of successful wheels that were made and used.

Just my .02


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, February 27, 2008 - 12:08 pm:

True, guys, but there are thousands of cars today, not just Fords, with spokes of unknown age, material and strength.

There is a need to know when it's time to re-spoke.

Douglas Fir hardens with age; does Shagbark Hickory? Is there a safe age limit? Should it be 8 years, like has been suggested for tires?

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, February 27, 2008 - 12:15 pm:

EXACTLY what wood did Ford use, John? I have been led to believe it was Shagbark Hickory, but maybe it was Pignut or Shellbark Hickory; both of them are stronger. What are Lang and Snyder selling?

I know one wheelwright using Pecan Hickory, which has only half the impact strength of Shagbark, and has been argued to not be a hickory at all.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By jack daron-Indy. on Wednesday, February 27, 2008 - 06:42 pm:

Ricks,You have IMHO fallen into a catch 22 trap. The specs are out there,and if you make a spoke that falls within those specs ,you could expect it to perform at least as well as the originals. There are still good solid spokes around that are approaching 90+ years old. Are they still safe,will they break? Who knows. A brand new one can break. It like asking someone to guarentee you'll never get hit by lightening. At some point you have to go ahead on faith that what you have is sufficent. (if you test each spoke to it's breaking point ,you'll never have enough to respoke a wheel.) Aged spokes vary in that they have all been stored/used differently so how you could determine when they should automatically be changed is another unsolvable mystery.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Jeffrey Cole on Wednesday, February 27, 2008 - 08:56 pm:

That is correct Bill.Even with about 4 of us bounceing on the bumper,still,didnt do the job!
Glad I got that embarruseing dent fixed to on that fender.forgot how bad that thing looked.

When it comes to the wood.Someone like Hap that has done alot of research may could shine light on the wood used.BUT I would be willing to bet,more than 1 wood was used for the sake of supply if nothing else.But it had to be something of the hickory sort.
I know wood when it drys gets hard to a point,but I dont know that we would want the wood getting Very hard as it wouldnt flex under stress.Our roads are much better than they were years ago but that still doesnt mean there is room to be slack.
I would think what ever the Amish folkes use in their wheels should be suitable for ours.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Wednesday, February 27, 2008 - 10:14 pm:

Alas even our modern cars don't give service intervals out to 81 years!

As I have posted many times - the drawing says "Hickory" and states "MUST STAND AN AVERAGE PRESSURE OF 2500 LBS.,WITH 2000 LBS. MIN., PRESSURE TO BE APPLIED MIDWAY BETWEEN BEARING POINTS 6-1/2" APART AS SHOWN IN SKETCH"

In the sketch the leftmost bearing point is exactly 1" from the felloe end of the spoke along its largest diameter thus the 1" distance does NOT include the tenon. So go break some spokes.

If you want to know what the term "Hickory" meant in those days I would suggest you get a few issues of "Hub and Carriage Monthly" that was published to the buggy and wagon trade from about 1850 to 1930. In the back of that magazine they kept very carefull track of ALL the various wood species in North America and the estimated reserves since that was a relevant item of interest during that period.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas J. Miller on Monday, March 03, 2008 - 08:26 am:

I found a document that shows a couple of photos of pendulum impact testing on forest product samples. Unfortunately, no mention of hickory in the report.

http://www.fpl.fs.fed.us/documnts/fplr/fplr2109.pdf


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Monday, March 03, 2008 - 11:54 am:

That's great, Thomas. Maybe correlation can be made from the data on this site:

http://www.woodbin.com/ref/wood/strength_table.htm

I don't see the correlation at a quick look, however. At the very least, this shows how to make a testing machine. I wonder now if the Ford method found by John Regan is really an impact test. At any rate, this tells that an impact test is most telling in wood that may have been exposed to deterioration.

rdr


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