My Old School Early 70's Magnesium Minilites (not wannabe's)!

[HS30-H]

Hi Jerry,

Are there two water pump pulleys?

I see what appears to be a stock W/P pulley, and also the ( smaller ) Competition W/P pulley with the holes in ( that's one of the ones I'm looking for ) and a water pump pulley spacer ( small dia. with the four slots ). Other item is the ( small dia. ) Alternator pulley.

No crank pulley?

Cheers,

Alan T.

[HS30-H]

Hi Jerry,

There were several different types of narrow-belt crank pulleys. Here's a photo of one type ( attached ).

There was also one large diameter version like this, but with no holes. There were some that were small diameter too.

The narrow-belt pulleys had to be used as a set, so the original crank pulley that went with the Alternator pulley and Water Pump pulley in your photos would have been of the narrow-belt type too. Not stock.

Would be great if you could find it.

Cheers,

Alan T.

[JLPurcell]

After checking my garage attic, if not found, I will look at the inventory list of the box's I took out to Les for the 29 car. Hopefully it will be in one or the other place. JLP

[HS30-H]

OK. Thanks Jerry.

[Carl Beck]

From the Minilite web site: "The original Minilite wheel made in magnesium was probably the most successful motorsport wheel in the 1960's and 70's and in its classic form the design is still winning historic races and rallies today." "We continue to manufacture limited runs of original wheels in magnesium, primarily for racing purposes due to their high strength and low weight (33% lighter than aluminum). These are the ultimate competition wheel for racing and rallying where unsprung weight reduction is required without compromising strength and safety."

If I remember correctly turn 13 is the carousel with an access road leading to it on the outside. I once slid off there and went sideways into and across the access road believing that I had destroyed my wheels at the very least. The concentric bushing in the suspension were spun around effecting the camber but the wheels were not damaged what so ever. I believe this was a testament to their seemingly being indestructible.

Hi Jerry:

The MiniLite statement has nothing to do with the condition nor safety of now 40+ year old magnesium wheels. Yes, it is still a winning "design". Yes, when first cast magnesium wheels are light weight and very strong.

Most magnesium wheels are stamped or cast with their Date of Manufacture - there is a reason for that, and it is important to pay attention to it. Magnesium wheels are designed to meet a specified duty cycle and service life. What metals are alloyed with the magnesium, how the wheel is cast and or forged and machined, how the wheel is designed structurally all play a role in meeting the pre-defined duty cycle and service life requirements.

If I had to guess, I would guess that the Minilite's you have and the American Racing Wheels that I have - were designed for competition use over a period of 5 full seasons or less. I would be interesting to see what warning labels if any, came on them when they were new.

I did quite a bit of research when I was attempting to restore a set of American Racing Le Mans wheels for my BRE Z. Most of the information I trusted came from the guys in the Materials Lab where I worked. So take if for what it is worth.

Magnesium hardens with age and it thus becomes more brittle over time. Within a defined high load impact a new magnesium wheel will actually flex or deform without failing {about three times as much as aluminum}. That same wheel twenty years later, given the same level of impact, may fracture, and that can cause a sudden and unexpected failure..

Then there are variables among/between different qualities of magnesium wheels. Cast or Forged there can be small voids in the original structures, and within these voids there can be corrosion taking place over time, which in turn can cause deep pitting. [the magnesium alloy billets used for Forged wheels can have the same problems as any castings - it is all about process control}. Magnesium wheels are porous - as anyone that runs them knows - they have to be coated to seal them, at least on the tire mounting surfaces to hold air for very long. They are also subject to rapid oxidation and corrosion when exposed to moisture. So moisture and air can penetrate deep into the metal.

As the magnesium wheel ages, these corrosion pits both external and internal to wheel, can develop into fractures in the metal {somewhat like a chip in a windshield can develop into a crack}. While eddy current inspection can help identify these microscopic fractures on the external surface before they develop farther, it takes X-Ray inspection to find potential problems within the metal.

All that said - I do have a set of 40+ year old mag's on the BRE Baja Z. They are there just for show, to roll the car on and off the trailer. I had them inspected {NDI Tech at the local Air Port Service Center} and picked the best 4 out of 8 wheels. Crazy as it may seem - I have driven the car at highway speeds on them as well - but I am well aware of their limits and the risk I am taking. I certainly would not do any of that on 40+ year old mags without having them professionally inspected, and found to be at least currently "solid".

Nor would I sell any 40 year old magnesium wheels to anyone for other than "display" use.

FWIW,

Carl B.

Edited May 9, 2013 by Carl Beck

[JLPurcell]

Hi Jerry:

The MiniLite statement has nothing to do with the condition nor safety of now 40+ year old magnesium wheels. Yes, it is still a winning "design". Yes, when first cast magnesium wheels are light weight and very strong.

Most magnesium wheels are stamped or cast with their Date of Manufacture - there is a reason for that, and it is important to pay attention to it. Magnesium wheels are designed to meet a specified duty cycle and service life. What metals are alloyed with the magnesium, how the wheel is cast and or forged and machined, how the wheel is designed structurally all play a role in meeting the pre-defined duty cycle and service life requirements.

If I had to guess, I would guess that the Minilite's you have and the American Racing Wheels that I have - were designed for competition use over a period of 5 full seasons or less. I would be interesting to see what warning labels if any, came on them when they were new.

I did quite a bit of research when I was attempting to restore a set of American Racing Le Mans wheels for my BRE Z. Most of the information I trusted came from the guys in the Materials Lab where I worked. So take if for what it is worth.

Magnesium hardens with age and it thus becomes more brittle over time. Within a defined high load impact a new magnesium wheel will actually flex or deform without failing {about three times as much as aluminum}. That same wheel twenty years later, given the same level of impact, may fracture, and that can cause a sudden and unexpected failure..

Then there are variables among/between different qualities of magnesium wheels. Cast or Forged there can be small voids in the original structures, and within these voids there can be corrosion taking place over time, which in turn can cause deep pitting. [the magnesium alloy billets used for Forged wheels can have the same problems as any castings - it is all about process control}. Magnesium wheels are porous - as anyone that runs them knows - they have to be coated to seal them, at least on the tire mounting surfaces to hold air for very long. They are also subject to rapid oxidation and corrosion when exposed to moisture. So moisture and air can penetrate deep into the metal.

As the magnesium wheel ages, these corrosion pits both external and internal to wheel, can develop into fractures in the metal {somewhat like a chip in a windshield can develop into a crack}. While eddy current inspection can help identify these microscopic fractures on the external surface before they develop farther, it takes X-Ray inspection to find potential problems within the metal.

All that said - I do have a set of 40+ year old mag's on the BRE Baja Z. They are there just for show, to roll the car on and off the trailer. I had them inspected {NDI Tech at the local Air Port Service Center} and picked the best 4 out of 8 wheels. Crazy as it may seem - I have driven the car at highway speeds on them as well - but I am well aware of their limits and the risk I am taking. I certainly would not do any of that on 40+ year old mags without having them professionally inspected, and found to be at least currently "solid".

Nor would I sell any 40 year old magnesium wheels to anyone for other than "display" use.

FWIW,

Carl B.

Thanks for the input Carl, it is appreciated and not taken lightly. I would not consider this set appropriate for using under high stress or racing at this point in their life. I do think they give a great period correct look for display or show and I would not have any problem driving on them under normal driving and road conditions.

[gnosez]

Thanks Carl. I have had little time to contact or research this issue further. I am tied up on that pesky "red-line" issue in the news. And 26th, it just the sort of thing you should be snorting (See All Red Insects Now). I'm sure you're smart enough to figure it out.

[John Coffey]

As mentioned above, Magnesium and Aluminum age (or work) harden over time. Magnesium much more so. Powder coating, where the wheels are heated to 400F to cure the coating will accelerate the process because that's how AL and MG are artificially aged when wrought.

Heat Treating of Magnesium Alloys :: KEY to METALS Articles