What You Need To Know About CNC Heads
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Registered User
Joined: Oct 2006
Posts: 74
From: Fayetteville Georgia
What You Need To Know About CNC Heads
Why would you choose hand porting over CNC?
The first thing you have to understand is that CNC machines can’t port heads! They can only copy what the original head porter did. This is called reverse engineering.
Hand porting or custom ported heads and manifolds are better in the respect that the individual doing the work knows your particular application, cam and other pertinent facts concerning your engine. Hence, the heads will produce a better power curve than a universal CNC computer program.
Because the CNC machine cannot actually port a head in the same way as an expert Air-Flow Technician can, the process of making a program to port heads in a CNC machine is very involved and necessarily expensive. And these costs have to be recovered in the end product.
1) The head must be hand ported and flowed. This process can take days, weeks, or months until a satisfactory shape is derived that will perform to the engine builders specifications.
2) The head and port shapes have to be digitized (Scanned). This as an on-line process takes about 14 hour’s, while in an off-line machine takes about 8 hour’s. However, the cost of the off-line machine can be upwards of $20,000.00 dollars, and requires a trained operator.
3) Once this program is completed, it has to be transferred into another computer with a Cad-Cam software application, which costs upwards of $15,000.00 dollars for one that can compute a 5-Axis program, plus the cost of the computer. Once the scanned configuration is loaded into the Cad-Cam program it is corrected for irregularities, imperfections and is generally smoothed out. Once this is accomplished, a machining program is designed to tell the machine where to go and what and when to cut, how fast to cut it and which tool to use. The program also has to tell the head fixture what to do so that the cutter will remain in contact with the head at all times and not make contact with the tool shank or the machine itself. This process can take 14 or so hours. Computer programmers are in short supply and highly paid ($40 to $60 dollars per hour).
4) Once the machining program is established and approved, it is tested to see if it will run correctly. Once this is accomplished, the 5-Axis CNC Machining Center is ready to machine the head. Unfortunately, the program can only machine that particular head and only in that particular way. But it will do an endless array of them in the very exact way to the thousandth of an inch.
OK! Now you’re wondering about the machining center itself?
There are three types of CNC machining centers:
1) Horizontal – these are generally made in 4-Axis mode.
2) Vertical – these are generally only 3-Axis and have to be converted to 4 & 5 Axis
3) Vertical 5-Axis
The state of the art is the vertical 5-Axis but there are many acceptable horizontal machines that will do the job. Here the cost decides what to buy. Both of these machines are going to cost from $200,000.00 to $500,000.00 dollars. The 3-Axis vertical machine capable of doing heads is going to cost between $70,000.00 and $100,000.00. Then there is an additional cost for installing the fourth and fifth axis, which is in the neighborhood of $15,000.00 dollars. Unfortunately, even in this configuration the 3-Axis machine can’t do heads without a complex fixture that rotates in two directions. It requires two rotary heads, one that teeter-totters, and one that rotates 360. The base fixture costs about $70,000.00 and the rotary table’s can cost between $20,000.00 and $60,000.00 apiece, depending on the quality and durability.
Now at an approximate cost $300,000.00 dollars you are ready to port heads in a CNC machining center.
But, do you have any work?
Do you have employees that can run the equipment?
If you are a start up then you have to have more money for advertising, paying employees, paying a real head porter to design heads for you to copy! Alternatively, you have to buy already ported heads and steal (reverse engineer) the configuration. On the other hand, you could hire a real head porter, buy a flow bench and build him a room to do his work.
What other equipment would you need to finish heads?
You have to get a Serdi machine, a surfacing machine, cleaning machines, and a variety of other cylinder-head related items to the tune of another $100,000.00 bucks.
Next thing you have to consider is how many heads are there, and how many different port configurations are there for each of these heads? Then you have to make the decision about how many of them do you really want to do.
Do you want to be able to do whatever comes in the door?
Something else you may want to know about the CNC porting of heads is that if you already have a pair of heads running on your engine and want them ported can the CNC machine port your heads?
If the heads have been extensively milled (Surfaced) the probability is that the CNC machine cannot port your heads is realistic. If they have been angle milled you know for a fact that the CNC machine cannot.
This means that if you want your heads ported and polished you are going to have to find someone that does them by hand. Then does this person have a flow bench and how long has he been using it?
Why can’t the CNC machine port my heads?
Because it uses a computer program and if the program does not have a compensation for the deck to valve-seat dimension then the port work inside the bowl area won’t come out correctly, and it is the short side radius that controls the flow through the valve. If the heads have been angle milled then the whole head is out of dimension and the machine can’t compensate for that thus the porting job becomes junk.
Realistically, if you are a qualified head technician, trained by someone in the field, or by Mondello’s technical school then you don’t have to worry about what type of head to do. You just have to do one cylinder and flow it then go to the next one and so forth and so on. However, you do have to provide yourself with the correct equipment.
As cylinder head technician’s we are faced with this “Propaganda” concerning CNC-Porting and how do we contend with the falling price structure applied to our work?
Real head porting is an art, and a science combined. It takes years of practice just to be able to hold the proportions within the ports to a minimum tolerance and keep the vertical and horizontal lines uniform. Then knowing how to reduce the cutter-marks to a minimum so that the polishing work looks shiny and nice takes a considerable amount of time or at least good training. Personally I’ve trained many head porters and found that it takes at least two years working eight hours a day to be able to accomplish the quality of work I required. A quality head must look good, have evenly proportioned intake and exhaust ports, combustion chambers that allow the intake charge to flow into the cylinder properly and to collect the exhaust gasses into and under the exhaust valve efficiently. It must also have the specific flow characteristics that the engine-builder wants for his particular engine.
What controls this configuration?
The question sounds simple but it’s not, for instance:
What type of cam are you going to use, hydraulic, roller or flat tappet, mechanical, roller or flat tappet. If it’s a flat tappet what diameter is the lifter? What is the lift and duration, what are the timing events?
What is the engine going to be used for is it supercharged, or naturally aspirated, are you going to use N20? If supercharged is it an Engine driven centrifugal, Turbo, Roots, or other? If it’s naturally aspirated what is it going to use for induction; carburetors, how many and what type of manifold; fuel injection, what type and what type of manifold.
What is the displacement of the engine in question, have you chosen the correct head for that application? What valve size is going to make that head perform to its highest potential, in the application you intend for it? What horsepower and torque do you anticipate making, and are they realistic?
These are just some of the questions that have to answered to get a cylinder head to perform at its optimum potential.
Sincerely,
Denny Schmidt
July, 8 2006
Innovations For Internal Combustion Engines Through Air-Flow Technology
The first thing you have to understand is that CNC machines can’t port heads! They can only copy what the original head porter did. This is called reverse engineering.
Hand porting or custom ported heads and manifolds are better in the respect that the individual doing the work knows your particular application, cam and other pertinent facts concerning your engine. Hence, the heads will produce a better power curve than a universal CNC computer program.
Because the CNC machine cannot actually port a head in the same way as an expert Air-Flow Technician can, the process of making a program to port heads in a CNC machine is very involved and necessarily expensive. And these costs have to be recovered in the end product.
1) The head must be hand ported and flowed. This process can take days, weeks, or months until a satisfactory shape is derived that will perform to the engine builders specifications.
2) The head and port shapes have to be digitized (Scanned). This as an on-line process takes about 14 hour’s, while in an off-line machine takes about 8 hour’s. However, the cost of the off-line machine can be upwards of $20,000.00 dollars, and requires a trained operator.
3) Once this program is completed, it has to be transferred into another computer with a Cad-Cam software application, which costs upwards of $15,000.00 dollars for one that can compute a 5-Axis program, plus the cost of the computer. Once the scanned configuration is loaded into the Cad-Cam program it is corrected for irregularities, imperfections and is generally smoothed out. Once this is accomplished, a machining program is designed to tell the machine where to go and what and when to cut, how fast to cut it and which tool to use. The program also has to tell the head fixture what to do so that the cutter will remain in contact with the head at all times and not make contact with the tool shank or the machine itself. This process can take 14 or so hours. Computer programmers are in short supply and highly paid ($40 to $60 dollars per hour).
4) Once the machining program is established and approved, it is tested to see if it will run correctly. Once this is accomplished, the 5-Axis CNC Machining Center is ready to machine the head. Unfortunately, the program can only machine that particular head and only in that particular way. But it will do an endless array of them in the very exact way to the thousandth of an inch.
OK! Now you’re wondering about the machining center itself?
There are three types of CNC machining centers:
1) Horizontal – these are generally made in 4-Axis mode.
2) Vertical – these are generally only 3-Axis and have to be converted to 4 & 5 Axis
3) Vertical 5-Axis
The state of the art is the vertical 5-Axis but there are many acceptable horizontal machines that will do the job. Here the cost decides what to buy. Both of these machines are going to cost from $200,000.00 to $500,000.00 dollars. The 3-Axis vertical machine capable of doing heads is going to cost between $70,000.00 and $100,000.00. Then there is an additional cost for installing the fourth and fifth axis, which is in the neighborhood of $15,000.00 dollars. Unfortunately, even in this configuration the 3-Axis machine can’t do heads without a complex fixture that rotates in two directions. It requires two rotary heads, one that teeter-totters, and one that rotates 360. The base fixture costs about $70,000.00 and the rotary table’s can cost between $20,000.00 and $60,000.00 apiece, depending on the quality and durability.
Now at an approximate cost $300,000.00 dollars you are ready to port heads in a CNC machining center.
But, do you have any work?
Do you have employees that can run the equipment?
If you are a start up then you have to have more money for advertising, paying employees, paying a real head porter to design heads for you to copy! Alternatively, you have to buy already ported heads and steal (reverse engineer) the configuration. On the other hand, you could hire a real head porter, buy a flow bench and build him a room to do his work.
What other equipment would you need to finish heads?
You have to get a Serdi machine, a surfacing machine, cleaning machines, and a variety of other cylinder-head related items to the tune of another $100,000.00 bucks.
Next thing you have to consider is how many heads are there, and how many different port configurations are there for each of these heads? Then you have to make the decision about how many of them do you really want to do.
Do you want to be able to do whatever comes in the door?
Something else you may want to know about the CNC porting of heads is that if you already have a pair of heads running on your engine and want them ported can the CNC machine port your heads?
If the heads have been extensively milled (Surfaced) the probability is that the CNC machine cannot port your heads is realistic. If they have been angle milled you know for a fact that the CNC machine cannot.
This means that if you want your heads ported and polished you are going to have to find someone that does them by hand. Then does this person have a flow bench and how long has he been using it?
Why can’t the CNC machine port my heads?
Because it uses a computer program and if the program does not have a compensation for the deck to valve-seat dimension then the port work inside the bowl area won’t come out correctly, and it is the short side radius that controls the flow through the valve. If the heads have been angle milled then the whole head is out of dimension and the machine can’t compensate for that thus the porting job becomes junk.
Realistically, if you are a qualified head technician, trained by someone in the field, or by Mondello’s technical school then you don’t have to worry about what type of head to do. You just have to do one cylinder and flow it then go to the next one and so forth and so on. However, you do have to provide yourself with the correct equipment.
As cylinder head technician’s we are faced with this “Propaganda” concerning CNC-Porting and how do we contend with the falling price structure applied to our work?
Real head porting is an art, and a science combined. It takes years of practice just to be able to hold the proportions within the ports to a minimum tolerance and keep the vertical and horizontal lines uniform. Then knowing how to reduce the cutter-marks to a minimum so that the polishing work looks shiny and nice takes a considerable amount of time or at least good training. Personally I’ve trained many head porters and found that it takes at least two years working eight hours a day to be able to accomplish the quality of work I required. A quality head must look good, have evenly proportioned intake and exhaust ports, combustion chambers that allow the intake charge to flow into the cylinder properly and to collect the exhaust gasses into and under the exhaust valve efficiently. It must also have the specific flow characteristics that the engine-builder wants for his particular engine.
What controls this configuration?
The question sounds simple but it’s not, for instance:
What type of cam are you going to use, hydraulic, roller or flat tappet, mechanical, roller or flat tappet. If it’s a flat tappet what diameter is the lifter? What is the lift and duration, what are the timing events?
What is the engine going to be used for is it supercharged, or naturally aspirated, are you going to use N20? If supercharged is it an Engine driven centrifugal, Turbo, Roots, or other? If it’s naturally aspirated what is it going to use for induction; carburetors, how many and what type of manifold; fuel injection, what type and what type of manifold.
What is the displacement of the engine in question, have you chosen the correct head for that application? What valve size is going to make that head perform to its highest potential, in the application you intend for it? What horsepower and torque do you anticipate making, and are they realistic?
These are just some of the questions that have to answered to get a cylinder head to perform at its optimum potential.
Sincerely,
Denny Schmidt
July, 8 2006
Innovations For Internal Combustion Engines Through Air-Flow Technology
Registered User
Joined: Mar 2002
Posts: 1,842
From: Bloomfield Hills MI
Re: What You Need To Know About CNC Heads
Heres a good video of a 5 axis machine in action. Although similar the ones that would port heads would move the whole table on the X axis.
http://www.haascnc.com/news/new_file...20Trunnion.wmv
http://www.haascnc.com/news/new_file...20Trunnion.wmv
Registered User
Joined: Mar 2002
Posts: 1,842
From: Bloomfield Hills MI
Re: What You Need To Know About CNC Heads
Usually about 6 hours from what I've seen.
Originally Posted by mgray
Denny, assuming a proper program, how long do you estimate the common CNC mill being used will take to complete all cutting of both heads? I am not talking about a purpose-built machine like Centroid offers.
What tolerances can a professional porter as you mention be expected to hold to?
What tolerances can a professional porter as you mention be expected to hold to?
Thread Starter
Registered User
Joined: Oct 2006
Posts: 74
From: Fayetteville Georgia
Re: What You Need To Know About CNC Heads
M-Gray
The Fadal machines takes 8 hours to do 2 heads
The Bostomatics (no longer in production) take 2 to 4 hours
If you know what you're doing with the machine whatever it is you can generally speed it up once you get used to its ramifications. Bob at CNC tells me he can get some of our stuff done 2 to 4 hours on the tetter-totter. We finally found an imported piece to replace the Bostomatic, and for less money. Bostomatics used to cost 410K or 375K set up for porting.
When doing high-end porting for all out competition we all have a variety of templates to gage where and how much to cu out. I had a custome tell once that after he cc ever runner there was only 5 cc's difference, even I was astounded by that. Chambers I try to keep them at +- 2 cc
I watched that video - way kool
Thanks for your comments
Denny Schmidt
The Fadal machines takes 8 hours to do 2 heads
The Bostomatics (no longer in production) take 2 to 4 hours
If you know what you're doing with the machine whatever it is you can generally speed it up once you get used to its ramifications. Bob at CNC tells me he can get some of our stuff done 2 to 4 hours on the tetter-totter. We finally found an imported piece to replace the Bostomatic, and for less money. Bostomatics used to cost 410K or 375K set up for porting.
When doing high-end porting for all out competition we all have a variety of templates to gage where and how much to cu out. I had a custome tell once that after he cc ever runner there was only 5 cc's difference, even I was astounded by that. Chambers I try to keep them at +- 2 cc
I watched that video - way kool
Thanks for your comments
Denny Schmidt
Last edited by HeadDoctor; Oct 14, 2006 at 08:56 PM.
Re: What You Need To Know About CNC Heads
Registered User
Joined: Mar 2002
Posts: 1,842
From: Bloomfield Hills MI
Re: What You Need To Know About CNC Heads
I wish i had a 5 axis 
, watching that centroid video was pretty sweet. I thought it was pretty cool when I made this when I first bought mine but it doesn't even compare. http://cz28.net/gallery/d/3830-2/DSCN1466.JPG
Do you guys use Mastercam X too? I've heard OneCNC and Featurecam are pretty powerful alternatives? I went with the featurecam setup because it already had post processor support for my specific heidenhain control.
, watching that centroid video was pretty sweet. I thought it was pretty cool when I made this when I first bought mine but it doesn't even compare. http://cz28.net/gallery/d/3830-2/DSCN1466.JPG Do you guys use Mastercam X too? I've heard OneCNC and Featurecam are pretty powerful alternatives? I went with the featurecam setup because it already had post processor support for my specific heidenhain control.
Thread Starter
Registered User
Joined: Oct 2006
Posts: 74
From: Fayetteville Georgia
Re: What You Need To Know About CNC Heads
Rodrigues
I don't have a CNC machine - I'm a wanabe - having financing problems!!
I've been trying to get one since 1996 - We used to think that SurfCam was the best but now I don't know what Bob uses.
If I can get my business back up to where it was a year and a half ago I'd just go for it with an SBA. Now it just looks like a "Field Of Dreams."
Yes there is a vast difference between a street-driven vehicle and a purely racing vehicle. There are drivability issues with either one but one has to be cautious with the every-day driver on many levels.
Some of that caution concerns the gasoline we have to use, and I'm not one to suggest the use of additives to accomplish the more powerful combination because when you run out you're really in trouble. What I generally recomend is that the customer plans out the build before-hand and eliminate any concerns, then just stick to that goal no matter what anyone else says. I tend to stick to basics - but even within that arena you have to learn how to "Think Outside Of The Box" - consequently when you can consistently do that you always have a well rounded performance vehicle. It may not be the fastest all around piece but you know its limitations and can stay within those parameters.
There are many levels of porting from mild to wild and I tend to fit these into someones budget to the best of my ability and their wallet - "Because Speed Costs Money - What's The Velocity Of Your Wallet" therefore I try to fit that necessity.
Thanks for your comments they are greatly appreciated.
Denny Schmidt
I don't have a CNC machine - I'm a wanabe - having financing problems!!
I've been trying to get one since 1996 - We used to think that SurfCam was the best but now I don't know what Bob uses.
If I can get my business back up to where it was a year and a half ago I'd just go for it with an SBA. Now it just looks like a "Field Of Dreams."
Yes there is a vast difference between a street-driven vehicle and a purely racing vehicle. There are drivability issues with either one but one has to be cautious with the every-day driver on many levels.
Some of that caution concerns the gasoline we have to use, and I'm not one to suggest the use of additives to accomplish the more powerful combination because when you run out you're really in trouble. What I generally recomend is that the customer plans out the build before-hand and eliminate any concerns, then just stick to that goal no matter what anyone else says. I tend to stick to basics - but even within that arena you have to learn how to "Think Outside Of The Box" - consequently when you can consistently do that you always have a well rounded performance vehicle. It may not be the fastest all around piece but you know its limitations and can stay within those parameters.
There are many levels of porting from mild to wild and I tend to fit these into someones budget to the best of my ability and their wallet - "Because Speed Costs Money - What's The Velocity Of Your Wallet" therefore I try to fit that necessity.
Thanks for your comments they are greatly appreciated.
Denny Schmidt
Thread Starter
Registered User
Joined: Oct 2006
Posts: 74
From: Fayetteville Georgia
Re: What You Need To Know About CNC Heads
mgray
Here's my answer to your question
If you go to any oval track in the country there are only a given amont of racers that build their own engines, so then you have to find those guys that are doing those engines and try to convince them that you can do a better job that the guy they presently have - very hard to do, no matter what your credentials are. This is also true of the professional engine builders, they get married to the head-guy because there is so much pressure to make legitmate and reliable power, that to change can be catastrophic unless they have a reasonable R&D budget, which most of um don't.
Second: Normal drag-racing circles - here there are 50 to one compared to the oval track market not a bad shift.
Third - The street market - this is 1000 to 1 over the drag market - therefore to me that was a no-brainer - that's where all the work is.
I'de rather be a small fish in a big pond than a big fish in a small pond.
I really don't need the prestege - in my mind I'm already famous - within the circle of professional that know who I am. What I want is a steady flow of work that I can count on month to month.
Denny Schmidt
Here's my answer to your question
If you go to any oval track in the country there are only a given amont of racers that build their own engines, so then you have to find those guys that are doing those engines and try to convince them that you can do a better job that the guy they presently have - very hard to do, no matter what your credentials are. This is also true of the professional engine builders, they get married to the head-guy because there is so much pressure to make legitmate and reliable power, that to change can be catastrophic unless they have a reasonable R&D budget, which most of um don't.
Second: Normal drag-racing circles - here there are 50 to one compared to the oval track market not a bad shift.
Third - The street market - this is 1000 to 1 over the drag market - therefore to me that was a no-brainer - that's where all the work is.
I'de rather be a small fish in a big pond than a big fish in a small pond.
I really don't need the prestege - in my mind I'm already famous - within the circle of professional that know who I am. What I want is a steady flow of work that I can count on month to month.
Denny Schmidt
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Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
Re: What You Need To Know About CNC Heads
Much food for thought here. Thank you for the info. Gotta digest some of it for a while. But I was impressed to learn that it takes hours (nearly a full day?) on a $3-500,000 machine to CNC port a set of heads. No idea it was that time consuming. I guess I was thinking more of stamping out cookie sutters. I can see some of the economic implications. I have access to a (hand) porter who works for a big name pro shop but also does work on the side. The rest of you should be so lucky 
Rich
Rich
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Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
Registered User
Joined: Sep 2004
Posts: 416
From: Helotes/San Antonio
Re: What You Need To Know About CNC Heads
Food for thought....
most small-medium sized head porters who do
in-house cnc porting RENT their machines.
Denny has a sig thats built with the ADVANCED TECH section
in mind!
Sounds like he has a point to SELL.
What do you say denny???
-The Blind Cannot Lead The Blind
Speed Costs Money - Whats The Velocity Of Your Wallet
Inganuity Is The Key To Success
most small-medium sized head porters who do
in-house cnc porting RENT their machines.
Denny has a sig thats built with the ADVANCED TECH section
in mind!
Sounds like he has a point to SELL.
What do you say denny???
-The Blind Cannot Lead The Blind
Speed Costs Money - Whats The Velocity Of Your Wallet
Inganuity Is The Key To Success
Last edited by RedLT4Mike; Oct 18, 2006 at 01:20 AM.
Thread Starter
Registered User
Joined: Oct 2006
Posts: 74
From: Fayetteville Georgia
Re: What You Need To Know About CNC Heads
Mike
Actually that Sig - The bilid can't lead the blind - is for anyone including myself another one of my sayings is "One of the smartest things I ever said was - I don't know"
The speed cost money thing is real old and I have a sign that hangs in the shop.
Inovation is what Hot-Rodding is all about - Lately its been "Who has the latest and greatest part to make my car faster?" So instead of thinking about what to do to solve the problem, or find a book that will give them the information thay ask their friends. Does this friend actually know anything?
Then, too, there is this remark - "My car goes this fast or does this and that" implying that because of that they actually know something. My point is that if anyone wants to accomplish something in the way of speed and ET with their car then look at the real race cars that do that. NHRA - IHRA ORSCA etc. Look in National Dragster for the record that fits what it is that you are trying to do - then investigate it from that angle and actually talk to the guys that are doing it at the track - not your buddy down the street.
As far as myself I've been in this industry so long that I feel its time for me to give back what has been given to me. Realize that I started in the very same way that most others do when I was in high-school. So I began my professional career in the head industry at the age of 16 (1958) and never looked back. I've worked for, run or established some of the well known head shops in the country and been in my own business now for 25 years.
So yes I know stuff, I'm an expert at Engine-Tech. I have guys that call me from all over the US for consultation about engines because they have no access to a dyno and I can always get them within a few HP of what they wanted to accomplish. So long as they do everything I say without cuestion.
Hope that answers your questions and thanks for the comments
Denny Schmidt
Actually that Sig - The bilid can't lead the blind - is for anyone including myself another one of my sayings is "One of the smartest things I ever said was - I don't know"
The speed cost money thing is real old and I have a sign that hangs in the shop.
Inovation is what Hot-Rodding is all about - Lately its been "Who has the latest and greatest part to make my car faster?" So instead of thinking about what to do to solve the problem, or find a book that will give them the information thay ask their friends. Does this friend actually know anything?
Then, too, there is this remark - "My car goes this fast or does this and that" implying that because of that they actually know something. My point is that if anyone wants to accomplish something in the way of speed and ET with their car then look at the real race cars that do that. NHRA - IHRA ORSCA etc. Look in National Dragster for the record that fits what it is that you are trying to do - then investigate it from that angle and actually talk to the guys that are doing it at the track - not your buddy down the street.
As far as myself I've been in this industry so long that I feel its time for me to give back what has been given to me. Realize that I started in the very same way that most others do when I was in high-school. So I began my professional career in the head industry at the age of 16 (1958) and never looked back. I've worked for, run or established some of the well known head shops in the country and been in my own business now for 25 years.
So yes I know stuff, I'm an expert at Engine-Tech. I have guys that call me from all over the US for consultation about engines because they have no access to a dyno and I can always get them within a few HP of what they wanted to accomplish. So long as they do everything I say without cuestion.
Hope that answers your questions and thanks for the comments
Denny Schmidt