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Attention Corvair Builders

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Brady

Joined: 26 May 2008
Posts: 182
Location: Poulsbo, WA

Posted: Fri Dec 12, 2008 12:52 pm Post subject: Attention Corvair Builders

To Whom it may concern:



We have updated our website, www.magnificentmachine.com, with some technical articles that are aimed at answering the most common questions relating to our products and the Corvair.

Also these articles address some of the more common engine issues and some of the ways in which we address them.

This section is called Tech Talk and is where we will post all of our Products Testing Data.



The articles are written by "Uncle Mike" because he is a far better writer than I am and his engine building experience goes far back to the days of Flat head engines and probably back to the days of wooden spokes though he won't admit it. Smile



The First Forged 4340 crankshaft sample is now in an engine case with a cam shaft and will be running before too long.

This engine will be equipped with our entirely NEW rotating assembly as well as the rest of our newest products.

The first set of all aluminum Nikasil Cylinders will be installed and tested on this engine as well.

We will have this engine at the upcoming Corvair College #13 being held In Livermore, CA.



For further details of the Corvair College #13 event see

www.flycorvair.com or

www.flaglvk.com



Thank you,

_________________
Brady McCormick
Poulsbo, WA
www.magnificentmachine.com

FlyGuyTililDie

Joined: 22 Jan 2009
Posts: 26
Location: Germany/Italy

Posted: Sun Jan 25, 2009 2:33 am Post subject: Re: Attention Corvair Builders

Hi Brady,



Your products look gorgeous!  I'm certain I'm going to have to at least get those carbon fiber valve covers.



I have a question regarding the crankshaft:  What is the advantage of the forged over the billet or vice versa?  What do you expect the price of the billet to be after the forged in available?



thanks



James

Brady

Joined: 26 May 2008
Posts: 182
Location: Poulsbo, WA

Posted: Sun Jan 25, 2009 11:47 am Post subject: Re: Attention Corvair Builders

James,



Thank you very much for your kind words.

We have worked very hard to bring the best products we possibly can to our small community.



The Carbon fiber products are in limbo at the moment due to an unfortunate mishap with the molds.

We are in the process of making new molds and should be back on track soon.



The Forged VS Billet debate goes way back, and there are camps on both sides of this river who will argue until they are blue in the face. But, to date, I have heard no argument that would sway my opinion either way.

Assuming of course that all else (alloy, quality of alloy & design) remained equal.



The main advantages are in the efficiency of production.

A billet Crankshaft produces more wasted material and consumes more labor and machine time. This is why they are usually more expensive than forged crankshafts. 

However if you are only making one or two crankshafts they are considerably less expensive than the forging dies that are required to forge the crankshaft.



A forged Crankshaft produces much less wasted material and consumes much less labor and machine time and there fore are usually cheaper per unit than the Billet Crankshafts.

However, Like I mentioned before the tooling is very expensive and is only worth while if you plan on producing hundreds or thousands of crankshafts.



At the moment only the Billet crankshafts are readily available.

The forged crankshafts must be produced in large numbers, and so far the demand has been less than what would justify a full run.

I fully expect this to change once we have one flying and fully tested.



Once the forged crankshafts are available, the billet crankshafts will increase in price substantially. 

I am only offering them in the interim until the forged cranks are in full production. 



I feel strongly that it is necessary to make available a safer option than the OEM crankshafts if at all possible. And as long as my costs are covered I am willing to do so to support the Corvair community so it can remain a viable option for sport aircraft. 



I invite you to take a close look at our other products as well, like our MagVair Pistons and Con Rods for example.

These are top notch products of exceptional quality at a very fair price.



The rotating assembly is the foundation of the engine and everything else depends on it.



Those that were lucky enough to make it to the Corvair College #13 that was held at the First Light Aircraft Group facility in Livermore, CA got the opportunity to see these products in person.



Sorry for the long winded response. 



Take care,

Brady

_________________
Brady McCormick
Poulsbo, WA
www.magnificentmachine.com

FlyGuyTililDie

Joined: 22 Jan 2009
Posts: 26
Location: Germany/Italy

Posted: Sun Jan 25, 2009 2:02 pm Post subject: Re: Attention Corvair Builders

Thanks Brady for the info.  I have been looking very closely at all of your products.  The one that interests me the most right now are the aluminum cylinders.  How is the availability on those babies?



I want to build a 3100 (120 hp)  Right now being stationed in Germany (Italy starting in March), I have no way to build a plane so I thought I would start with the engine.  I'm still in need of a core engine and a way to get it to Europe.



James

Brady

Joined: 26 May 2008
Posts: 182
Location: Poulsbo, WA

Posted: Sun Jan 25, 2009 7:31 pm Post subject: Re: Attention Corvair Builders

James,



For those outside the US it is very difficult to find Core engines.



I can put an engine kit together for you if you are interested.

An engine kit will have several advantages for those overseas.



1. shipping is minimized to only those parts that will be used in the final assembly.

2. the engine is shipped as a collection of "parts" and so there are some tax & import / export advantages as opposed to an assembled engine.

3. your project is streamlined because all of the parts are already cleaned and prepped for assembly.

4. Buying a kit engine will allow you a substantial savings on parts and shipping because you buy them and ship them all at once.



If you are interested in an engine kit please contact me off list to discuss your preferences and options.



The aluminum Cylinders are still in the development stage and are made to order. You must be aware that they have not been flight tested and have only recently been running on an engine. 



The 3100 is not an easy engine to build and requires several special machine operations to open the case and heads for the larger cylinders.

There are two ways to get to a 3100:



The first is to use a standard stroke crank with 94mm cylinders.

This has not been done with aluminum cylinders yet and there is some concern whether or not the aluminum cylinders bases are wide enough to maintain a proper seal. Only time will tell.



The second is to use a 3.125" stroked crankshaft & 92mm cylinders.

This is conceivably the better way to go because the case is not machined as far and therefore retains more metal around the head studs.

In addition, this option also will have a wider cylinder base and is more likely to maintain the seal. 

This option has no running example as of yet, though it is our intention to build and test one.



All of the running 3100's to date were built using modified VW cylinders & pistons.

This option obviously works well and there are several flying examples.



Best wishes,

_________________
Brady McCormick
Poulsbo, WA
www.magnificentmachine.com

FlyGuyTililDie

Joined: 22 Jan 2009
Posts: 26
Location: Germany/Italy

Posted: Sun Jan 25, 2009 10:10 pm Post subject: Re: Attention Corvair Builders

Brady,



So I assume (thinking linearly and interpolating) that a 92mm bore with the standard 2.94" stroke would yield a 2900 cc engine with 110 hp.  Has anybody tried this yet?  Is the cost not worth the extra 10 ponies and the few pounds shed?



What are some of the other considerations with stepping up to a larger stroke?  Are there going to be any clearance issues?  



Also, I have read the the heads on the later 140 hp engines were better having to do with both quality and valve angles.  Are these heads able to be used on our applications?  Would there be any advantage to it?



thanks



James

FlyGuyTililDie

Joined: 22 Jan 2009
Posts: 26
Location: Germany/Italy

Posted: Sun Jan 25, 2009 10:26 pm Post subject: Re: Attention Corvair Builders

After more research on aluminum cylinders I am finding diametric opinions on the issue. 



I seems there are many advantages to having aluminum cylinders: better cooling, less weight etc.  Those who oppose say the issues deal with the qualities of aluminum.  It expands and contract with heating and cooling causing a few problems, usually being broken studs.  This was something that was addressed often in the Porsche forums.



It seems now that there is new stud technology to compensate for this i.e. ARP studs.



William Wynne says this in his 2007 tech notes, "Aluminum cylinders require testing. The two main concerns are finding a ring package that will not destroy the bore and dealing with the expansion of the aluminum cylinders, which has the very real possibility of pulling the studs out of the case or imprinting the head gasket area."



Perhaps having a steel sleeve would prevent the ring damage.  



What are your thoughts on making a hybrid cylinder?  Would it be feasible to have a steel or iron core with aluminum cooling fins pressed over it?



thanks



James

Brady

Joined: 26 May 2008
Posts: 182
Location: Poulsbo, WA

Posted: Mon Jan 26, 2009 12:47 pm Post subject: Re: Attention Corvair Builders

James,



I will try to answer your questions in order and in enough detail without being too long winded. 

This may be difficult for me, but I will give it a shot. 



The shortest stroke crankshaft I offer is a 3". this is only slightly stroked from the original dimension of 2.9375.



This crankshaft and a 3.622" (92mm) bore will net 185.4 CID.

(3.038 liters)



The 3.125" stroke crankshaft and the 92mm bore will net 193.1 CID.

(or 3.164 L)



The power gains are not dependent on displacement alone.

their are several other factors involved and this can become a very in depth conversation, But suffice it to say that the power gains can far exceed 10 "Ponies".

In addition, to our application the torque rating is far more important.

I have heard it said that horse power is what sells engines and torque is what fly's the airplane.



When I plan an engine build; I look for what will produce the most power in the intended rpm range. I assume you don't intend to spin your propeller faster than 3500 RPM so an engine with loads of torque in that rpm range is what we are after.



Stroke improves torque.

Displacement improves torque.

Cam profile plays a large part.

Intake velocity is important. (small valves)

Intake volume is less important.(big valves)



whether the gains justifies the cost is entirely your decision. 

another colorful saying in this industry is:

 "Power costs money, how much do you want?" 



Aluminum Cylinders:



Ah yes, the "diametric opinions".

Please remember that most of these are just opinions from people who have never run a Corvair with aluminum cylinders much less held aluminum cylinders in their hands.

However they do have a friends, sisters, boyfriend who had an uncle who knew this guy once. 

The key thing to remember is that this is by no means new technology and the list of successful applications these days is nearly endless.



I have heard all these stories and most of them are misinterpreted and or missing critical details. 

For instance the Porsche example; the studs only pulled out of the magnesium cases and so they went back to the aluminum cases.

Also these engines were producing substantial amounts of horse power far beyond what we are after and power = heat. 

Excessive Heat is what causes the problems and the cars ability to cool the engine is far less than that of the aircraft application.



The Coefficient of thermal expansion is measured in millionths of an inch per degree, per inch of material. 

356 T-6 Aluminum's Coefficient is about 12

The length of cylinder between the case and the head of the Corvair is 4".

So lets assume our engine will never see 500 degrees F and use that as our worst case scenario.

With this we get 0.000012 x 4" x 500* = 0.024"

Now, this may sound like a lot but remember our studs are expanding also.

Steel has a coefficient of about 6.

so we get 0.000006 x 4" x 500* = 0.012"

So what we end up with is only a 0.012" difference.



Let me say at this point that if your engine sees 500* we have other serious problems.

So, if we keep the engine running in its normal temperature range we can expect to see far less movement. I don't expect to see any problems but without actually testing the set up I can not definitively say. That is why we are building the engine to test.



I have 2 sets of aluminum cylinders for the Corvair and I have yet to run them my self. However we do have a set of 94mm running in a customers sand rail with no problems as of yet. I have not seen this engine and I don't know how many hours are on it but so far so good.



I will have my engine with the aluminum cylinders running shortly and then I will have all the test data in my shop.

Only time will tell.



The hybrid cylinders you mentioned have already been done and there are flying examples. 

They do not offer the weight savings and are approximately the same price.



William invited me to the last Corvair College #13 held in Livermore, CA.

He got to see the Aluminum cylinders in person.

He of course reserved comment until they are running and tested, but he did not express any immediate concerns to me at that time. He is not one to withhold an opinion if he sees anything that concerns him. He has always been very open and forth coming with me in the past.



140 Heads:

There are several examples of 3100 engines running 140 heads and I believe a few are even flying.

The 140 heads are very popular with the hot rod and sand rail guys and so they are very hard to find and very expensive when you can find them.

The bigger valves in the 140 heads have less aluminum around them and are known to drop valve seats.

I do not fee that the increased valve size is much advantage at the lower rpm range and so I do not consider them a must have.

I actually prefer the 95 horse power heads because they also have the open combustion chamber and can be modified to maximize the quench height with out diving the compression ratio through the roof.

These heads are easy to find and cheap.

Also the small valves are good for the intake velocity and therefore good for torque.

I have tested 95 HP heads on a flow bench and they will flow about 106CFM (at) 28" of H20 in their stock form which will accommodate up to about 163.7 horse power.

Certainly more than we what to subject our little airplanes to? 



So much for trying to not be long winded eh?

_________________
Brady McCormick
Poulsbo, WA
www.magnificentmachine.com

FlyGuyTililDie

Joined: 22 Jan 2009
Posts: 26
Location: Germany/Italy

Posted: Mon Jan 26, 2009 1:40 pm Post subject: Re: Attention Corvair Builders

Thanks a bunch Brady,



This is the kind of help and information I was hoping to get by joining this forum.



My #1 concern is maintaining reliability.  It seems by now that most of the weak components of the corvair have been exposed, most recently being the crankshaft.  With nitriding and a 5th bearing, the additional stress can be mitigated.



You had mentioned cam application.  Are you a fan of the OT-10 or do you recommend something else?  



Also, I see that it has been a popular choice to have the crank milled down to -.10   I still don't know the reason for this and perhaps you could clarify.  Is this just so they can radius the edge of the journals?  If so, do they make rounded main bearings?



I admit I am a complete novice when it comes to this and I look up to you educated folk to show me the way.  You have been great Brady!



I'll send you another PM on getting my project started.



James

Joemotis(at)aol.com
Guest

Posted: Mon Jan 26, 2009 4:17 pm Post subject: Attention Corvair Builders

Have you purchased William Wynne's conversion manual yet?

 By the way, you turn a crankshaft on a lathe to get rod and main bearing  journals to a standard undersize such as .010 not mill them.

  

 Do not archive

  

 Joe Motis

  

  In a message dated 1/26/2009 1:41:27 P.M. Pacific Standard Time,  flyguytilidie(at)aol.com writes:

  	  Quote: 	
		  James 	


 From Wall Street to Main Street and everywhere in between, stay up-to-date with the [url=http://aol.com?ncid=emlcntaolcom00000023 ]latest news[/url].

  [quote][b]

Brady

Joined: 26 May 2008
Posts: 182
Location: Poulsbo, WA

Posted: Mon Jan 26, 2009 5:59 pm Post subject: Re: Attention Corvair Builders

James,



The Corvair has flown nearly 45 years (since 1960) without nitriding or the fifth bearings, with relatively no problems until recently. 

The rash of recent crankshaft failures are due to several factors and I think the most important is an aging crankshaft that is Fatigued.



Some of the Crankshafts were subjected to prop strikes, extra long prop extensions, propellers that were not indexed properly, excessive RPM and these engines were producing far more horse power as well as airframes that are much faster and more nimble. This all adds up to more force exerted on the crankshaft.

In addition to the extra forces all these crankshafts were 45+ years old with unknown & undocumented Histories. So you never know if the crankshaft has experienced sever over heating, oil starvation or catastrophic engine failure.



This is why I started to manufacture new crankshafts.



The Nitriding is done to bolster the fatigue strength of the crankshaft.

But it can not erase the previous 45 years of use or abuse.



The fifth bearing concept is to limit the forces exerted on the crankshaft to begin with. I think this is an excellent idea and there are several to choose from most of which have flying examples.

I do not however feel this is a substitute for a new crankshaft.



The Magna fluxing can only tell you that the crankshaft is not cracked right now. It can not tell you when it will crack or that it will not crack tomorrow.



When a crankshaft has worn to the point of increasing the oil clearance beyond specified limits, the crankshaft is ground on a crank grinding machine to a known under size and over sized bearings are installed to make up the difference.



Reliability is of the utmost importance and I hope that people will not put budget before safety.



The new crankshafts are produced with the largest radius's passable yet accommodate the use of standard width bearings. The main bearing journals are radius-ed to .125" & the Rod journals are radius-ed to .100". They come completely machined for the aircraft application (safety shaft) and  come with a new Gear. They are made from high quality 4340 alloy.



The original OEM crankshaft was made from 5140 alloy and has an ultimate strength of about 86,000 psi.

The 4340 crankshafts have an ultimate strength of about 165,000 psi,

so you can see that in material alone we have increased the strength about 79,000 psi. (almost double)



With the increased radii and heat treating we further increase strength and durability.



Cam Shafts:

The OT-10 camshaft profile is a very popular one.

It works well and is readily available.

Most of the Corvairs flying are probably using this cam.

this camshaft was designed for the automotive application and peaks a bit higher in the RPM range than what I think is useful to the aircraft application.



I had a cam cut to a profile that we designed to peak a bit lower in the rpm range and that is intended to focus on torque, it will be tested in our next engine build shortly.

If this proves to be advantageous we will offer cams in this profile.

_________________
Brady McCormick
Poulsbo, WA
www.magnificentmachine.com

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