piston fit

[Jeff Lutz]

As additional information, the following metals are listed in order according to their thermal conductivity amounts. It can be easily seen that brass & steel would not be the most desireable metals to use for a head. All numbers are BTU/in/hr/ft squared/deg F. All the numbers can be found on any available metal's specification sheet from Google.

1018 cold rolled steel - 360 BTU....

#360 brass - 804 BTU....

2024 aluminum - 840 BTU....

2017 aluminum - 930 BTU....

It doesn't take a rocket scientist to figure this out.

"Andy, I guess where the peppering can be seen should be expected since the brass has a thermal conductivity 1/2 of aluminum."

Jim, The truth of your statement above is not reflected in your list of Thermal conductivity.

I will say that when comparing brass to aluminum it is far from correct to make statements like, "Brass and aluminum expansion is close." ~ Jeff L. or "brass has a thermal conductivity 1/2 of aluminum." ~ Jim A.

Aluminum alloys will expand as much a 50% more or 50% less than many brass alloys. While the Thermal conductivity of many Aluminum alloys are within + or - 20% of each other, Copper alloys (brass) swing very widely, Some are in fact 1/2 of aluminum, but other copper alloys are more than double that of aluminum.

Therefore I think it would be proper to specfy the particular alloy one is refering to when making these claims.

If you go back and read before I said aluminum and brass expansion is close, specifics were covered. Marty and Jim had already said they used 2024 aluminum. Marty said he was trying 360 brass (yellow brass). 360 brass is 11.3, 2024 aluminum is 12.9, close, not the same. Those 2 materials were being compared. 5052 upto 7075 aluminum are all in the 13.1-13.2 range. 360 brass does not conduct heat nearly as much as the mentioned aluminum alloys.Do some research and you will see Jim is close to being correct saying about 1/2 on conductivity of 360 brass versus any of the above mentioned aluminums.

 

[Andy Brown]

As additional information, the following metals are listed in order according to their thermal conductivity amounts. It can be easily seen that brass & steel would not be the most desireable metals to use for a head. All numbers are BTU/in/hr/ft squared/deg F. All the numbers can be found on any available metal's specification sheet from Google.

1018 cold rolled steel - 360 BTU....

#360 brass - 804 BTU....

2024 aluminum - 840 BTU....

2017 aluminum - 930 BTU....

It doesn't take a rocket scientist to figure this out.

"Andy, I guess where the peppering can be seen should be expected since the brass has a thermal conductivity 1/2 of aluminum."

Jim, The truth of your statement above is not reflected in your list of Thermal conductivity.

I will say that when comparing brass to aluminum it is far from correct to make statements like, "Brass and aluminum expansion is close." ~ Jeff L. or "brass has a thermal conductivity 1/2 of aluminum." ~ Jim A.

Aluminum alloys will expand as much a 50% more or 50% less than many brass alloys. While the Thermal conductivity of many Aluminum alloys are within + or - 20% of each other, Copper alloys (brass) swing very widely, Some are in fact 1/2 of aluminum, but other copper alloys are more than double that of aluminum.

Therefore I think it would be proper to specfy the particular alloy one is refering to when making these claims.

If you go back and read before I said aluminum and brass expansion is close, specifics were covered. Marty and Jim had already said they used 2024 aluminum. Marty said he was trying 360 brass (yellow brass). 360 brass is 11.3, 2024 aluminum is 12.9, close, not the same. Those 2 materials were being compared. 5052 upto 7075 aluminum are all in the 13.1-13.2 range. 360 brass does not conduct heat nearly as much as the mentioned aluminum alloys.Do some research and you will see Jim is close to being correct saying about 1/2 on conductivity of 360 brass versus any of the above mentioned aluminums.

From Matweb dot com 360 brass 798 BTU... 2024 alu. 840 BTU.... I did the reseach. Jim also mentioned 2017 alu. 930 BTU... Somewhere Jim mentioned 544 bronze 604 BTU... No body said we were specificly refering to 360 and 2024 in this thread. Others have mention BeCu heads 720 BTU... At one point Steve Wood was making heads from 2011 alu. 1180 BTU. ...and I use an alloy different then all of those.

Lots of variety going on here.

Jeff, Where did you get these numbers? "Coefficient of thermal conduction (btu/hr-ft-*F) of aluminum is 104, when brass is 67" ~Jeff L.

For 360 brass I find 798 BTU-in/hr-ft2-*F. For 2024 alu. I find 840 BTU... This reflects a 5% difference, not 1/2. Now if you compare 544 bronze (an alloy Jim mentioned) it's TC is 604 BTU to 2011 alu. 1180 BTU... the difference is in fact 51%, about 1/2 and reflects somewhat the difference in your 104 and 67, but that difference does not match your two alloys of 360 and 2024, which is only about 5% difference according to the source on Matweb.

This is why I suggest specifics.

 

[dwilfong]

So let me talk this out thermal conductivity is the rate that a metal will transfer heat.

so if the chamber temp changes the water will pull the heat out of the metal faster making the metal at the surface of the chamber that the fuel contacts cooler.

Good thing or bad thing?

 

[Jim Allen]

One of the problems with finding answers to what is being discussed is the lack of information about these thermal conductivity numbers. Jack asked, where do I find numbers about bi-metal systems. There are none!

As far as aluminums are concerned, the higher the alloy number the lower the thermal conductivity number. If it was necessary to use something with the highest thermal conductivity number, silver would be number one followed by copper, then gold. I imagine we are using what seems to work & that solution has been found by cut & try.

I think it is safe to say there is a definite relationship between high thermal conductivity & high electrical conductivity when you look at the possible materials to choose from. Maybe cut & try is the only solution.

Jim Allen

 

[Marty Davis]

When I started using brass head buttons, I set them up with the same "snap fit" into the liner. I found that the brass expanded to an extent that it actually enlarged the liner at the top so that the fit went away between the piston and the liner.

I have started making the fit of the head button .001" per side or .002" total. Now, I don't have the problem of the liner losing fit. I imagined that a head button that had that much clearance would increase the volume of the combustion chamber because of the side area of the projection. Looks like I was wrong on that.

A side note: John Ackerman had some contact with an applications engineer from Alcoa. Here is his response to this:

"I found it through an applications engineer who worked for Alcoa.. got him

through their flight department and he gave me the first piece.. the alloy

is 2011.... the pits we were seeing on our other buttons was like ammonia being

burned out of the aluminum itself so it was not detonation at all.. the 2011

never had the burn spots..the other thing it did not do was oil can and puke

out the glow plugs."

John Ackerman

Maybe I will re-visit the 2011.... Available here: http://www.mcmaster.com/#standard-aluminum-rods/=iuyrm6

I think that Andy is probably correct that the brass doesn't show the detonation because of the hardness of the brass.

 

[RodneyPierce]

I dont want to side track this, but does anyone have a way to accurately cut a turbo plug head yet? The taper is what Im worried about. Getting something that will seal up with the correct taper. I would like to visit this 2011 aluminum myself here. Im currently using 5052, but am always up for trying something different.

 

[Jim Allen]

"So let me talk this out thermal conductivity is the rate that a metal will transfer heat."

David,

"Thermal conductivity is the transportation of heat from higher temperature regions to lower temperature regions. How that transportation occurs is through a mechanism of atomic vibrations. The total thermal conductivity of a material is the summation of phonons (vibrational waves within the materials lattice) & by the movement of free electrons."

Hope this helps.

 

[Jim Allen]

I dont want to side track this, but does anyone have a way to accurately cut a turbo plug head yet? The taper is what Im worried about. Getting something that will seal up with the correct taper. I would like to visit this 2011 aluminum myself here. Im currently using 5052, but am always up for trying something different.

I ground the angle to match on the drill used to tap the 5/16-32 thread. Both the drill & the tap had steel collars to set the proper depth. If you have access to a CNC lathe, it can be programed to cut the thread & then the tapered seat in one operation.

Jim Allen

 

[RodneyPierce]

Jim, unfortunately I dont have access to a CNC lathe. Do you know what that taper is off hand? Perhaps I can find someone to grind it? And I believe the thread is an M8 if Im not mistaken?

 

[Jim Allen]

Jim, unfortunately I dont have access to a CNC lathe. Do you know what that taper is off hand? Perhaps I can find someone to grind it? And I believe the thread is an M8 if Im not mistaken?

I don't know which turbo plug you are using. I use the Nelson. Its thread is 11/32-32 & its taper is 35 deg.

 

[steve wood]

When I started using brass head buttons, I set them up with the same "snap fit" into the liner. I found that the brass expanded to an extent that it actually enlarged the liner at the top so that the fit went away between the piston and the liner.

I have started making the fit of the head button .001" per side or .002" total. Now, I don't have the problem of the liner losing fit. I imagined that a head button that had that much clearance would increase the volume of the combustion chamber because of the side area of the projection. Looks like I was wrong on that.

A side note: John Ackerman had some contact with an applications engineer from Alcoa. Here is his response to this:

"I found it through an applications engineer who worked for Alcoa.. got him

through their flight department and he gave me the first piece.. the alloy

is 2011.... the pits we were seeing on our other buttons was like ammonia being

burned out of the aluminum itself so it was not detonation at all.. the 2011

never had the burn spots..the other thing it did not do was oil can and puke

out the glow plugs."

John Ackerman

Maybe I will re-visit the 2011.... Available here: http://www.mcmaster....um-rods/=iuyrm6

I think that Andy is probably correct that the brass doesn't show the detonation because of the hardness of the brass.

i have used the 2011 for several years.nothing special here.i'm now using the 360 brass.will not go back to aluminum on a nova, period.

there is a lot of talk on here how the brass is not as good and it shouldn't work and it won't work,and the thermal conductivity is wrong,da,da,da.maybe,maybe not.

a couple years ago on this forum i read that some of the teather car guys and some plane speed control guys where using brass,so i thought i would give it a try. well from our testing in the nova,i found it does work.i know other people that are running buttons i made in the 1.01's,with very good results. "The ones you made for my 101`s added about 3000 loaded RPM. Never seen another single part pick the engines up as much as the Brass Button. I would assume that it allows the engine to Burn More of the Nitro that is already in the fuel. Big Power and Rpm Gain!!!!!"...... this is a quote from a customer. i know i just shipped 8 of them out monday,so they must work for someone. o, i just made a pair for the vac 91.they will be available after testing.but hey maybe it doesn't really work,and in a year we will go back to aluminum again.kinda like some of the other stuff that has been tried for awhile that really worked.remember the dual plug heads?

 

[dwilfong]

"So let me talk this out thermal conductivity is the rate that a metal will transfer heat."

David,

"Thermal conductivity is the transportation of heat from higher temperature regions to lower temperature regions. How that transportation occurs is through a mechanism of atomic vibrations. The total thermal conductivity of a material is the summation of phonons (vibrational waves within the materials lattice) & by the movement of free electrons."

Hope this helps.

Yes it is what I called the theory of undulation when I was a teenager. :huh:

The girls loved it when I explained how every thing is moving in undulating fluid motion eaven if you can't see or feel it. :wub:

All thy guys thought I was full of it. <_<

I see thing have not changed that much. :lol:

 

[Andy Brown]

When I started using brass head buttons, I set them up with the same "snap fit" into the liner. I found that the brass expanded to an extent that it actually enlarged the liner at the top so that the fit went away between the piston and the liner.

I have started making the fit of the head button .001" per side or .002" total. Now, I don't have the problem of the liner losing fit. I imagined that a head button that had that much clearance would increase the volume of the combustion chamber because of the side area of the projection. Looks like I was wrong on that.

A side note: John Ackerman had some contact with an applications engineer from Alcoa. Here is his response to this:

"I found it through an applications engineer who worked for Alcoa.. got him

through their flight department and he gave me the first piece.. the alloy

is 2011.... the pits we were seeing on our other buttons was like ammonia being

burned out of the aluminum itself so it was not detonation at all.. the 2011

never had the burn spots..the other thing it did not do was oil can and puke

out the glow plugs."

John Ackerman

Maybe I will re-visit the 2011.... Available here: http://www.mcmaster....um-rods/=iuyrm6

I think that Andy is probably correct that the brass doesn't show the detonation because of the hardness of the brass.

i have used the 2011 for several years.nothing special here.i'm now using the 360 brass.will not go back to aluminum on a nova, period.

there is a lot of talk on here how the brass is not as good and it shouldn't work and it won't work,and the thermal conductivity is wrong,da,da,da.maybe,maybe not.

a couple years ago on this forum i read that some of the teather car guys and some plane speed control guys where using brass,so i thought i would give it a try. well from our testing in the nova,i found it does work.i know other people that are running buttons i made in the 1.01's,with very good results. "The ones you made for my 101`s added about 3000 loaded RPM. Never seen another single part pick the engines up as much as the Brass Button. I would assume that it allows the engine to Burn More of the Nitro that is already in the fuel. Big Power and Rpm Gain!!!!!"...... this is a quote from a customer. i know i just shipped 8 of them out monday,so they must work for someone. o, i just made a pair for the vac 91.they will be available after testing.but hey maybe it doesn't really work,and in a year we will go back to aluminum again.kinda like some of the other stuff that has been tried for awhile that really worked.remember the dual plug heads?

In many cases, but not all, we are restricting water to keep heat in our heads for more power. So, if keeping heat in is what is needed than a head material with a lower T.C. rating will do the job of holding the heat in. If we need better cooling, then an alloy with a higher T.C. will help. The 360 brass has a lower T.C. rating (798 BTU) than many Alu. alloys. There are some alloys with T.C. BTU ratings as high as 2500 and some steel alloys go well below 200 BTU.

Another thing to think about. Distance is part of the Thermal Conductivity equation. Therefore a thick button will not transfer the heat as fast as a thin button if the water path is only applied to the top of the head (like Nova 21's). Therefore adjustments can also be made by varying the thickness of the button too.

 

[Andy Brown]

-_-

Jim can I please just get one of your motors.... I find it hard to believe that the very competent Rossi's would ignore such a minimal change for such great claimed gains. Is the hp improvement confirmed on a dyno.Just curious. So with just the change in button material I can expect significant hp and rpm gains in my nitro if I buy one of your buttons Steve Woods? If so I may need to buy one.

Hugh

Hugh, Rossi's main business is car engines. They have no water cooling, so 360 brass may not work in that evironment.

 

[hugh hargett]

"In many cases, but not all, we are restricting water to keep heat in our heads for more power. So, if keeping heat in is what is needed than a head material with a lower T.C. rating will do the job of holding the heat in. If we need better cooling, then an alloy with a higher T.C. will help. The 360 brass has a lower T.C. rating (798 BTU) than many Alu. alloys. There are some alloys with T.C. BTU ratings as high as 2500 and some steel alloys go well below 200 BTU.

Another thing to think about. Distance is part of the Thermal Conductivity equation. Therefore a thick button will not transfer the heat as fast as a thin button if the water path is only applied to the top of the head (like Nova 21's). Therefore adjustments can also be made by varying the thickness of the button too."

Andy, does that mean that it would be hard to make a claim of more hp just based on button material alone?

based on what Ive read it seems there are many other variables to consider???? besides just the material .

thicknesses, cooling orifice and channels, etc...

 

[Andy Brown]

"In many cases, but not all, we are restricting water to keep heat in our heads for more power. So, if keeping heat in is what is needed than a head material with a lower T.C. rating will do the job of holding the heat in. If we need better cooling, then an alloy with a higher T.C. will help. The 360 brass has a lower T.C. rating (798 BTU) than many Alu. alloys. There are some alloys with T.C. BTU ratings as high as 2500 and some steel alloys go well below 200 BTU.

Another thing to think about. Distance is part of the Thermal Conductivity equation. Therefore a thick button will not transfer the heat as fast as a thin button if the water path is only applied to the top of the head (like Nova 21's). Therefore adjustments can also be made by varying the thickness of the button too."

Andy, does that mean that it would be hard to make a claim of more hp just based on button material alone?

No Hugh, It just depends on the application. What makes HP in one set of conditions, may not make HP under another set.

 

[dwilfong]

There are allot of variables in the temp of the chamber.

What I have seen is that at 220deg the power is at its peek and failure is at the 270 mark that is measured at the case just above the ex port.

I have made buttons with the probe in the head right next to the camber. but have not had the chance to take it to the limit.

more testing is needed.

I am working on ex gas probe next. have used it in the past but did not have a good test program in place to see what is what.

Testing takes time and lots of parts if you run it to the full extreme to see where the limits are.

The advancement of the Eagle tree system in the past few years has mad testing in real time on the water under any condition a god send for info gartering.

Static dyno test are a great tool but on the water under running conditions is the real deal as I see it.

Logging in a race will show true results.

More testing to come. Have a race to prep for at the moment. Will see what the logs tell after this one.

I will be logging temp in the head at the case at the top of the ex port RPM and MPH.

May have the ex gas temp ready will see.

Those of you coming to the race in Charleston come and see me we can check the logs after the heats on my laptop.

David

 

[hugh hargett]

-_-

Jim can I please just get one of your motors.... I find it hard to believe that the very competent Rossi's would ignore such a minimal change for such great claimed gains. Is the hp improvement confirmed on a dyno.Just curious. So with just the change in button material I can expect significant hp and rpm gains in my nitro if I buy one of your buttons Steve Woods? If so I may need to buy one.

Hugh

Hugh, Rossi's main business is car engines. They have no water cooling, so 360 brass may not work in that evironment.

Im a bit confused coz this leans to the opposite of what steve said about rossi " he will never go back to aluminum....... after trying brass"

if nova and rossi are still one in the same Im confused now :wacko: . I also though the original question of brass was helping with detonation???? you all decided that it(brass) just doesnt "show it" so how do you deal with it? It got lost somewhere in this discussion.

 

[steve wood]

-_-

Jim can I please just get one of your motors.... I find it hard to believe that the very competent Rossi's would ignore such a minimal change for such great claimed gains. Is the hp improvement confirmed on a dyno.Just curious. So with just the change in button material I can expect significant hp and rpm gains in my nitro if I buy one of your buttons Steve Woods? If so I may need to buy one.

Hugh

Hugh, Rossi's main business is car engines. They have no water cooling, so 360 brass may not work in that evironment.

Im a bit confused coz this leans to the opposite of what steve said about rossi " he will never go back to aluminum....... after trying brass"

if nova and rossi are still one in the same Im confused now :wacko: . I also though the original question of brass was helping with detonation???? you all decided that it(brass) just doesnt "show it" so how do you deal with it? It got lost somewhere in this discussion.

nova rossi,and rossi,are 2 different companys.brothers that parted company about 30 years ago,i think

 

[hugh hargett]

Oh ok so we are talking about two different motors or were we?????? Now that I got Your attention Steve did i understand you to say that in your motor (Nova or rossi) which ? you saw significant increases in your rpm and hp with the simple change of a head button you sell? I also asked have you confirmed these improvements of performance on a dyno?