modified merlin heads

[AirDOGGe]

Re: modified merlin heads

I race cars, circuit, hillclimb and speedway, there is no prize money at all for circuit, but you pay entry fees, for winning my class at national hillclimb championships, I won $100...but entry fee was $250...

Now THAT sounds like a complete rip-off.

Nobody expects a 1st place pot to cover their costs, but it should at LEAST be more that the entry fee. That's just plain robbery.

next years world origami championships are going to be paper view...

As long as it's not the air race championships...

[RAD2LTR]

Re: modified merlin heads

Hey, I autocross and vintage race no payoff there either. For vintage roadracing it runs about $1000 a weekend for me to play, and that is camping in the paddock and eating cheap. Autocross only runs me about $75 per event after fuel and entry fees are factored in. That is for a total of about 4 minutes of racing and 4 hours of driving to get to and from the event. No pay off.

I must say that vintage roadracing is like stepping back in history. Its pretty cool to line up with famous winning race drivers, in the cars they raced back in the day. You really can't argue about taking the track with a Ferrari 275 GTO next to you. Although, there is always the chance that the 275 will try and take me out. At least the guy will have the $$$ to fix my car As for me hitting him, unlikely, I'll just give him the posittion if he really wants it. I know I can't afford to fix his car

Will

[Blue Foam]

Re: modified merlin heads

flow bench results (at 28")-

Lift is .540", I'll let the numbers tell the story, hp figures are V12 aspirated:

Lift - stock - ported - stock hp - ported hp
.1 -111.5 - 110.2
.2 - 206.1 - 224.6
.3 - 295.0 - 325.0 - 910 - 1002
.4 - 344.2 - 400.4 - 1062 - 1235
.5 - 365.2 - 443.7 - 1126 - 1368
.55 - 373.6 - 460.6 - 1152 - 1420
.6 - 380.0 - 469.1 - 1172 - 1447
.65 - 388.1 - 479.6 - 1197 - 1479
.7 - 388.8 - 480.1 - 1199 - 1481

So, at the lift to be used it's up 87cfm & goes from 1152hp potential (NA) to 1420hp potential, so with 29psi boost, plus reduced pumping losses, the power increase will be quite large...

So...

A 30% increase in power or a 50% decrease in blower drag for the cost of a little shop time leads to nothing but derision and more "we do it this way because we've done it this way".

I work on Jets and Sport. The pilots there expect progress.

[MRE]

Re: modified merlin heads

Maybe they have money.

[Blue Foam]

Re: modified merlin heads

Maybe they have money.

Ask Bob Button how much he spent on Voodoo. Plenty of money there. My point is that this port work doesn't look like a very expensive job when done by someone who knows what they're doing, like this guy did.

BTW, we did a fully controlled test on wing smoothing on a 500 mph aircraft with a 40% laminar airfoil. The on course photos before and after documented that we went from pretty rough with paint popping off of leading edge rivets to absolutely smooth under load.

Not one mph difference.

The Reynolds number is simply too high. Sure looked good though.

Take some of that bondo labor and put it into the ports and real performance might be had. Lots of people spend time and money on what they know how to, not what matters.

[MRE]

Re: modified merlin heads

I'am sure all that ''bondo'' didn't help Dago go as fast as it did....The head work should be done,I was thinking about the trying of different superchargers/turbos,ect. How much more HP do you think the prop can convert to speed?

[51fixer]

Re: modified merlin heads

I'am sure all that ''bondo'' didn't help Dago go as fast as it did....The head work should be done,I was thinking about the trying of different superchargers/turbos,ect. How much more HP do you think the prop can convert to speed?

One of the big problems with heads is they crack. I have had dozens of cracks weld up in a set of heads before. I've seen coolant residue in the exhaust port of a head with less than 10 hrs on it. I've seen cracks between valve seats.
If you want to remove material in the name of airflow can you document how that will benefit the long term longevity of the heads? You won't without expensive and time consuming testing.
In Aviation safety has to be demonstrated with testing. RR would dyno an engine for 50 hrs then tear it apart. What ever was a problem got redesigned and then retested. Cracking in the heads has always been a problem with significant improvements made over time with the various versions produced.
I don't see improvements in performance that may sacrifice safety being an improvement unless you can prove that the porting, with its material removal, won't cause cracks to develop in the altered areas. Are you willing to run an engine on a dyno, at power for 10, 20, 30 hours? This will consume 65 to 150+ gallons per hour of fuel at 5+ bucks a gal.
Collect this data successfully and people might be more inclined to use your technology.
Until this is proven in flight, for extended periods, it is a non-aviation technology that has yet to be proven in flight.
Again the back fire screens and intercooler core offer some limiting factors for airflow to the heads. The design of the induction trunk between the heads works but is designed to fit the engine space rather than the highest airflow possible.
There are many great ideas presented here. They just need to be tested on a dyno to proven themselves as practical and safe. Thats aviation.

[RichH]

Re: modified merlin heads

In this application, I gather that material wasn't removed. Material was added...

[morerevsm3]

Re: modified merlin heads

One of the big problems with heads is they crack. I have had dozens of cracks weld up in a set of heads before. I've seen coolant residue in the exhaust port of a head with less than 10 hrs on it. I've seen cracks between valve seats.
If you want to remove material in the name of airflow can you document how that will benefit the long term longevity of the heads? You won't without expensive and time consuming testing.
In Aviation safety has to be demonstrated with testing. RR would dyno an engine for 50 hrs then tear it apart. What ever was a problem got redesigned and then retested. Cracking in the heads has always been a problem with significant improvements made over time with the various versions produced.
I don't see improvements in performance that may sacrifice safety being an improvement unless you can prove that the porting, with its material removal, won't cause cracks to develop in the altered areas. Are you willing to run an engine on a dyno, at power for 10, 20, 30 hours? This will consume 65 to 150+ gallons per hour of fuel at 5+ bucks a gal.
Collect this data successfully and people might be more inclined to use your technology.
Until this is proven in flight, for extended periods, it is a non-aviation technology that has yet to be proven in flight.
Again the back fire screens and intercooler core offer some limiting factors for airflow to the heads. The design of the induction trunk between the heads works but is designed to fit the engine space rather than the highest airflow possible.
There are many great ideas presented here. They just need to be tested on a dyno to proven themselves as practical and safe. Thats aviation.

one thing to consider would be, are the cracks caused by heat, or cylinder pressure, a combination of both, or something else entirely.
if it is cylinder pressure, the head work will allow the same power to be delivered to the prop, with lower cylinder pressures due to less power required to drive blower, lower pumping losses etc, but in order to fit a plenum chamber to gain maximum benifits (these heads will not need backfire plates now either), you would then be trading off some drag in the airframe because you would need a bulge on the cowl, without having wind tunnel testing, my gut feeling is power increase would far outweigh drag increase, turbos mounted behind the engine in the space occupied by the supercharger would free up huge amounts of horsepower if what I hear is correct, and it takes 800-1000hp to drive the supercharger at high boost levels. again, you could run less boost, and lower cylinder pressures and heat, and still make more power, suitable props may be an issue though

[51fixer]

Re: modified merlin heads

one thing to consider would be, are the cracks caused by heat, or cylinder pressure, a combination of both, or something else entirely.
if it is cylinder pressure, the head work will allow the same power to be delivered to the prop, with lower cylinder pressures due to less power required to drive blower, lower pumping losses etc, but in order to fit a plenum chamber to gain maximum benifits (these heads will not need backfire plates now either), you would then be trading off some drag in the airframe because you would need a bulge on the cowl, without having wind tunnel testing, my gut feeling is power increase would far outweigh drag increase, turbos mounted behind the engine in the space occupied by the supercharger would free up huge amounts of horsepower if what I hear is correct, and it takes 800-1000hp to drive the supercharger at high boost levels. again, you could run less boost, and lower cylinder pressures and heat, and still make more power, suitable props may be an issue though

Some issues are that the heads available for use have been run through many thousands of hours of use and are predisposed to cracking. Roush welded up dozens of cracks during our last overhaul in the heads. They have been used and are satisfactory for there purpose. Modifying them just simply changes all kinds of things. Thickness of the structure in the heads, heat flow and retention. I've had leaks around valve seats and cracks between valve seats. I'm not saying what you want to do won't work, its just with aviation you have to prove it'll work with long term ground based testing and then go fly. If you want to change the cowling and exhaust you gotta prove those through testing as well.
It's tremendous costs to do so. And then you got to convince the FAA it is safe to fly. Nothing flys without their approval. All it takes is a no from them and you aren't going anywhere. And they can say no just because.

[Blue Foam]

Re: modified merlin heads

If you want to remove material in the name of airflow can you document how that will benefit the long term longevity of the heads?

Looking at the pictures of the work, they ADDED material. Adding a reinforcing plate to the intake runner side, installing larger seats, and capturing the added port material between them would probably reduce cracking.

Most head cracking is caused by the thermally driven expansion of the valve seats. That's why they crack around the seats: the seat expands and puts more stress on the aluminum than it can handle. This is why most Continental and Lycoming heads crack between the seats. The intake side is cold, the exhaust seat is hot, and the aluminum between the two is thin. TBC's help a lot in this area and are used by any decent engine builder.

As far as it goes with the FAA, once an aircraft is in "Experimental-Exhibition" category, it's an experiment.

[51fixer]

Re: modified merlin heads

Looking at the pictures of the work, they ADDED material. Adding a reinforcing plate to the intake runner side, installing larger seats, and capturing the added port material between them would probably reduce cracking.

Most head cracking is caused by the thermally driven expansion of the valve seats. That's why they crack around the seats: the seat expands and puts more stress on the aluminum than it can handle. This is why most Continental and Lycoming heads crack between the seats. The intake side is cold, the exhaust seat is hot, and the aluminum between the two is thin. TBC's help a lot in this area and are used by any decent engine builder.

As far as it goes with the FAA, once an aircraft is in "Experimental-Exhibition" category, it's an experiment.

Convince them them to add this to your operating limitations. One of the items listed is what you are supposed to use as data for maintenance. The Spit Mk XVIII I maintain has maint and Insp requirements written into the operating Limitations. It is in the Exp-Exhibition Category but we try not to operate it as an ongoing experiment.
For heads Roush does a ton of them. They are on the leading edge the knowledge base for this stuff. What they do with welding is incredible. They have engineers and a DER that writes up specs for what they do. Through their process they get many item repaired using their FAA approved methods that otherwise might become scrap.
But We still get antsy just drilling a broken exhaust stud as a slight deviation or going a little too deep puts you in a coolant jacket.
For the different heads used on Merlins they have many differences internally. What you might be able to do as an alteration on one version may end up being an immediate leak or issue on another version.

[Sparrow]

Re: modified merlin heads

Heads crack because the valve seats expand???? Really? Heads crack because they get overheated. And Rich is right, just because it's experimental, that doesn't mean you can do whatever you want.

[IcePaq]

Re: modified merlin heads

The expansion rate of dissimilar metals in cylinder heads can cause cracking but a fairly common reason is not even temperature itself but rather temperature differential of different areas within the same casting.

[Big_Jim]

Re: modified merlin heads

...yeah, nevermind. I'll just delete that.