OT - 7075 aluminum strength vs. steel questions.

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Model T Ford Forum: Forum 2013: OT - 7075 aluminum strength vs. steel questions.
Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Nebraska on Wednesday, August 21, 2013 - 04:32 pm:

A young machinist in Lincoln said he could fabricate a front axle from 7075 aluminum (he thought it would be easier to do with his equipment).

Knowing nothing about material strength or machining/fabricating, I thought I'd check the forum for advice. A few questions I have:

Can a front axle be made (and be safe) from this material?
If so, would it be less expensive?

I think I'd like the front axle to duplicate the Model K. This way, if the racer project ever "grows" into a roadster project, I have a correct front axle. We already have a frame that is almost identical to the Model K frame.

Thank you in advance for any advice or information,

Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis in San Jose area, CA. on Wednesday, August 21, 2013 - 04:46 pm:

Using Young's Modulus as a guide, steel is 3 times stronger than aluminum.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Wednesday, August 21, 2013 - 04:47 pm:

7075 is pretty good stuff!! It would not scare me at all. I can't comment of the price.

I can get you one cast from 4140/4340 chrome moly steel as well as the spindles. It could be made pretty much how ever you want it to look

If you had one that could be used for a pattern thAt would save some money. Yes it will be very slightly smaller due to shrinkage when the metal solidifies

Ductile iron might also be considered. Many front end parts (spindles etc.) on new vehicles are made of ductile iron

I would not consider cast aluminum or of course cast iron.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Byrne - Racine, MN on Wednesday, August 21, 2013 - 04:49 pm:

Rob, don't even consider it. Not even close in strength for that application.


Top of pagePrevious messageNext messageBottom of page Link to this message  By mike_black on Wednesday, August 21, 2013 - 04:49 pm:

Rob,
Thought you might be interested--mixed in with some misc parts (horns, etc) in the Jul Aug Horseless Carriage Gazette classifieds was a pair of K sidelights for sale.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange on Wednesday, August 21, 2013 - 04:58 pm:

A fascinating book comparing the various steel and aluminum alloys is Carroll Smith's "Engineer to Win". I highly recommend it, for that matter I highly recommend all his "to win" books, they are well written in a practical and straightforward manner (unlike most textbooks).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Wednesday, August 21, 2013 - 04:58 pm:

My guess is that while it may not break, it will flex more than steel. I'm not sure what steel your axle is made of, so I couldn't look up the properties, but 7075 Aluminum has a tensile strength of 83 ksi and a yield strength of 73 ksi. That is more than a lot of steels, but not all. On the other hand, it has a modulus of elasticity of only 10,400 ksi, while most steels are 3 times that. I'm not a metalurgist and it's been a long time since Materials class, but I'm thinking you will have a strong but flexible axle. I'd shy away from that.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Wednesday, August 21, 2013 - 05:00 pm:

Bob,

I think you forgot to tell him it is NOT for a static museum piece! Run, don't walk, away from the idea.

Although I'm a babe in the woods on a K, the front axle is 'similar' to a T is general design, right?

Simple rules of thumb...

Steel Alloy has about a 3.0 to 3.5::1 minimum 'stiffness' advantage for the same 'shape' over the aluminum...

The tensile in steel alloy which is not post heat treated is about 3 times more than even the best treated aluminum...

The yield strength of a steel alloy (say 4140) will be about 4 times greater than a 7075 piece.

Whats this gobbletygook mean?

The first one says deflection for the same shape will also be at that 3.0 to 3.5::1 ratio for the same applied load...you wind up with spaghetti.

The second one says it will snap at 3 times lower impact load or bending load than a steel alloy one...

The 3rd says that is will bend and stay there at 1/4 the load the original axle would carry.

My numbers are mental approximations on the quick, subject to error without a look-up, but I think I'm pretty darn close!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Nebraska on Wednesday, August 21, 2013 - 05:34 pm:

OK guys. That's why I bring my questions here. Thank you for the advice. The Model K was advertised as "all Vanadium Steel'. I believe there were different grades (compositions, blends, mixtures, obviously I don't know the terminology) of vanadium steel.

Yes, the Model K axle is similar appearing to the Model T (and NRS), only much larger. The Model K weighs about 2500 lbs, with a good portion of the weight on the front axle due to the engine weight.

And yes, this will be a "go fast" racer, not a museum piece.

Thanks again guys for all the great help,

Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By John W. Oder - Houston, Texas on Wednesday, August 21, 2013 - 05:49 pm:

Maybe not period appropriate but here is my idea - cast steel ends welded in a slightly bowed 4130 tube. This one has kingpin inclination to accommodate front brakes. Track on this one is but 50".


smaxle


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Olsen on Wednesday, August 21, 2013 - 06:16 pm:

Please don't use Aluminum.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Nebraska on Wednesday, August 21, 2013 - 06:18 pm:

Chris,
I've gathered that :-)

You don't know if you don't ask.......


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Wednesday, August 21, 2013 - 06:29 pm:

I have a '13 Ford F150 Raptor (you know the factory off road race ready truck). It has aluminum front suspension control arms. Yes I would tweak the design a little to go fabricated aluminum. I would not trust a cast aluminum axle. It would be too difficult to get a casting that was good for the whole length.

John
I really like your design. The drop is maybe a little more severe than I might go for, but nice anyway. The tilted kingpins of course give modern car handling, which I now have on my '27 T roadster.
Brakes
The easy choice is trailer brake backing plates, maybe even the drums, but more research would be advised. They are GOOD and readily available complete for a good price. The electrics can be converted to cable mechanical or just go hydraulic.
Sure you can cobble something together from some old vehicle, but if you need parts at "Resume Speed" Nebraska, it might be a challenge


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Wednesday, August 21, 2013 - 06:45 pm:

I would seek a machinist who could carve a front axle from 4140 steel billet stock. It should not be too difficult or expensive to make, provided that you can supply adequate design criteria.

I know an outstanding machine shop in Lincoln Nebraska - I was there yesterday. Duncan Aviation has one of the best machine shops on earth, but may not be interested in working on your automotive project. I bet there are competent machinists in Lincoln, or any other major city in the world, who could do this job.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Wednesday, August 21, 2013 - 08:06 pm:

My un asked for opp is build it out of real old time parts wheather or not the brand is exact! It should be worthy of the K engine and if you use too much new it run's the risk of being a fibberblast vw.Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, August 21, 2013 - 10:39 pm:

Not all big car parts were up to Ford standards. A spindle broke at low speed on a local 1910 Stoddard Dayton; you know, the type that was the pace car for the first Indy 500. A friend then checked and found a crack in a spindle on his REO.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Wednesday, August 21, 2013 - 11:32 pm:

What does Mark Freimiller have to offer from his treasure trove?

You might Also consider some thirties straight axles, maybe even a light truck axle.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Nebraska on Wednesday, August 21, 2013 - 11:49 pm:

Thanks for the suggestions. I'd like to stay somewhat close to the original racer, or "clone" our Ks front axle.

This is a 1905 photo of the racer. I don't have any pics of the six cylinder racer as it evolved towards 1908.


The axle is already taking on the appearance of the Model K axle (and similar to the future NRS cars and eventually the Model T).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Philip Berg on Thursday, August 22, 2013 - 12:48 am:

As a guy who spends his days working in aerospace I'd go with the tube axle suggestion or find a used axle from another car.

Doing a one off 4140 billet axle would be prohibitively expensive in my book.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Thursday, August 22, 2013 - 01:41 am:

Knowing Rob has his head screwed on straight I'm more concerned about the "young machinist in Lincoln" who would even THINK of such a thing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthony Bennett on Thursday, August 22, 2013 - 02:57 am:

Bugatti made what were possibly the best front axles ever.

You can still buy them.

Aluminium too ;)


http://www.brineton-eng.co.uk/vintage/vintage-main.htm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Nebraska on Thursday, August 22, 2013 - 07:59 am:

Anthony, interesting.

Yes, if I find an "I beam" style axle I'd go with that. And with Hershey coming up, who knows what treasures I might find.

Thank you,

Rob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Thursday, August 22, 2013 - 08:23 am:

I think I've read about a Peterbilt(?) truck from the 50's with no front brakes but an aluminum axle.. Aluminum axles can be made strong enough for heavy weights, but the cross section needs to be beefed up compared to steel to compensate for the lower tensile strength and lower modulus of elasticity.

The specific weight is about one third of steel, but the beefier cross section needed for strength often makes the finished product in aluminum weigh about half of a comparable steel part - at about the double price to produce :-)

One thing you can't compensate for completely is metal fatigue - but it's very unlikely your racer will ever reach the fatigue life of a properly designed front axle in aluminum - alu con rods in the engine would be another story.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Dufault on Thursday, August 22, 2013 - 08:31 am:

Brineton axle in US dollars...

https://www.google.com/search?q=%C2%A34180.00&oq=%C2%A34180.00&aqs=chrome..69i57 &sourceid=chrome&ie=UTF-8

Axle ONLY


Top of pagePrevious messageNext messageBottom of page Link to this message  By keith g barrier on Thursday, August 22, 2013 - 08:43 am:

Trucks have been using aluminum axles for years. don't know the alloy but that info I'm sure can be had. Saves a great deal of weight. Also hubs are very common of aluminum. It is amazing how much stronger aluminum wheels are than steel. KB


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthony Bennett on Thursday, August 22, 2013 - 09:23 am:

If your Bugatti is worth $300k then $4200 is 1.4%

So if you had a 1910 model T you'd probably pay $560 for a front axle if it was worth $40k

Even if you had a run of the mill restored T for $7500, a new axle that was straight & didn't need the threads fixed would be well worth $105

I'm working on the wrong cars... lol


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Thursday, August 22, 2013 - 10:00 am:

Allow me to clarify something I said above.

I’m not saying to run away from Aluminum as an axle material…I was replying also to Rob apparent desire to form a ‘K’ replica axle out OF aluminum! THAT just doesn't work.

As Roger correctly points out…any shortcomings in natural material properties for an ‘interchange’ of materials can be overcome by changing the ‘size’ and ‘shape’ of the cross-section.


Top of pagePrevious messageNext messageBottom of page Link to this message  By keith g barrier on Thursday, August 22, 2013 - 11:45 am:

I believe you are correct on that George, Super Bell has a axle patterned after I think 32 ford that would work and is available. I have no affiliation with them but was impressed with their specs on said axles. KB


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen - Nebraska on Thursday, August 22, 2013 - 12:59 pm:

Thanks guys. This is a pic of an early Model K "with her clothes off". I'd like a racer/speedster frame to resemble this as much as possible. As it turns out, the 1905 Ford six cylinder frame and front axle/suspension look similar (leading me to believe the K was designed based on lessons learned from the racer).



Then, imagine a similar chassis, with a hood and Model K radiator. Somewhat similar to this Model K speedster, except with only exposed buckets and fuel tank behind the hood and small dash/firewall (no cowl).





.


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