??? In Regards To Quench & Compression

[GPH85]

I've got pictures of the mods now, but you can't tell a lousy thing with the cheapo camera I was using I may post some later anyway, after I get the URL's for them uploaded and try to explain what I did along, so maybe, just maybe you'll get some sort of idea of what I did from them...

I don't plan on buying a dyno anytime soon much less anytime at all, unless I've just got some money to spend Good Luck on that one too I guess...

What kind of numbers did you get from your C72, if you've done this to it yet? I went ahead and did this today since it was raining and I got the other saw fixed in the matter of a few minutes

Greg

 

[ol'homey]

Haven't tried anything yet. My torque wrenches are all the clicker type so that won't work. I do have a tach, postal scale, some rebar, a welder, and a junk sprocket and shoes. It wouldn't cost anything to give it a try so I might just do it. I mentioned to a friend tonight that I was thinking about building a small engine dyno and was looking for a hydraulic pump. He's going to send me one that's rated at around 30 HP. It's big and has a splined input shaft so I'm not sure how easy it will be to put a pulley on it so i can couple it to a chainsaw etc. I will need some kind of pulley system for gear reduction as the pump will have a max. rpm of probably around 2k. The good news is I won't need a scale to measure torque just a pressure gauge between the pump output and flow control valve. Hydraulic motor torque (in-lb) = Pressure (Psi) x motor displacement (in3/rev) / (2 x Pi)
The bad news is 1) I've got to figure out a way to couple it to the chainsaw sprocket. I'm guessing weld a small (2"?)pulley to the sprocket and install a big one (10"?) on the pump? and 2) there will be some friction losses in whatever pulley system I use which will lower the HP delivered to the pump, which will lower the measured HP.
Measuring the torque directly off the clutch like you did eliminates these losses. I'll post pics of the pump whenever I get it. In the meantime let me know if you have any ideas as to the best way to couple a chainsaw to a hydraulic pump.

 

[GPH85]

Here's just a thought on an easy way to couple it up, that doesn't involve changing sprockets left and right "say when you decide to dyno someone elses saw for them for example, or multiple saws you personally own"...

All chainsaws turn what... Chain (mainly), so why not purchase different pitch chains of just drive links, or as far as that goes, you could use old wore out chains that have had the depth guides and teeth filed or cut off of... Then all you would need would be a gear "in essence" to connect to the pump... You could even have multiple pitches "for different chains" on this one gear "side by side"... Yes you are going to have frictional loss, but it wouldn't be as bad as a rubber belt slipping or something of this nature... Plus if you use a belt setup, driven off of the saw, you would have to have a tensioner = further frictional loss...

You know something OL'Homey... You are about the most knowledgeable person on here, that I have seen so far, in regards to math formulas and the ability to think "outside of the box" I've currently got plans for building a flow bench, but have yet to purchase the two gauges needed for me to complete it. I was originally hoping to have it done so I could see if the porting I did on this cylinder was beneficial or not...

Well, the chain idea is something. Something, perhaps, that would be the easiest for you to hook up different saws to... You could use just the two pulley setup... The smaller sprocket (1st pulley) and then a large multi sprocket gear (2nd pulley) on the pump Of course this would multiply torque "as would any pulley setup", so you would need to find out the difference in the output straight off of the saw compared to the dyno readings...

It's a thought...
Greg

 

[GPH85]

OK, as stated these pictures turned out absolutely horrible. You can't tell heads nor tales from them hardly other than something's been done...

First one is of the cylinder installed on the saw with the piston at BDC. Although you probably can't tell it, the piston edge lines up, nearly perfectly, with the bottom edge of the exhaust port.



This next one is a pic of the modified exhaust port. The stock exhaust port had the divider "bull nosed" or rounded, which for anyone who knows airflow, this is only good for incoming air, not outgoing flow, so I "knife edged" or sharpened this divider. This way it would shear the exhaust without creating turbulence or drag. I have also taken out the very most outer "bumps" of the exhaust ports and made the outer edges of the exhaust ports straight into the cylinder (widened the ports slightly). Then after all of this was done, I polished the port to the best of my ability "again to let go or shear the exhaust flow, instead of creating an air border or surface boundary in the port". This is a up-close picture of all of this, but turned out blurred...



This is my modified intake ports vs. the stock intake ports. All I did to these ports was first drew out the area inside where the gasket would be. Then I opened the ports out to this area and "funnel" shaped them. I then blended this all back into the stock port configuration of where it goes into the cylinder. By doing this, I increased velocity of the incoming air, inturn "hopefully" flowing more air/fuel into the cylinder. The ONLY thing I wish I had done differently here is modified the stock port configuration to where it would have been blended into the cylinder better than it was "it kinda made a small sharp turn into the cylinder". I also "bull nosed" the divisions inbetween the intake ports, so air would "hug" the port walls instead of shearing and bouncing around in the ports = less turbulence = more smoother airflow into cylinder



This is with both sides of the cylinders intake ports modified in the same manor to one another...



I hope you can see things better when you click on them to view their larger images... If you need more information, all you have to do is ask

I didn't have the extremely small porting tools required to do something of this "small port" nature, but I did the best I could with what I had (porting tools for cylinder heads)...

Greg

 

[buck futter]

nice job on the transfers,
on the exhaust why do they put that flow inhibiting divider in the port?

Has someone helped you out or is this from your prior experience with 4 strokes?

keep having some fun

buck

 

[Patrick62]

Here is a hyrdaulic pump idea for the tinkerers out there

Use a high speed pump. How about a power steering pump from a car? Most of them that I have seen are geared about 1 to 1 or so, and before you state that it won't work think about how fast they turn when you have it cranked up to warp 9. 6000-8000 RPM is still possible. I do not know if it would cavitate...

Use a scrap bar and weld some fittings on there to mount the pump. Use a old nose sprocket to drive it with. Then you can calculate the gear ratio between the pump and saw sprocket. PS pumps are rated to a max of about 1200 psi, and somewhere around 2 gpm.

Just a thought...

-Pat

 

[ol'homey]

A power steering pump might work. With the hydraulic pump I was going to measure the pressure between the pump outlet and flow control valve and convert that into torque with the formula I posted. If I knew the displacement of the PS pump I guess the formula would work with it too. Otherwise I would have to mount the pump shaft in a bearing so that the body of the pump could rotate about its shaft. Then i would have to attach a lever arm to the pump body so i could measure the torque with some type of scale.
What I'm thinking so far is that the simplest way to couple to the saw is to take a small 1.5-2" steel pulley and weld it to an old worn out sprocket. If I want to test another model saw like a Stihl i would find an old sprocket and weld another pulley to it. Wouldn't this be easier and cheaper than finding and modifying a sprocket nose bar for each model saw?
I bet Madsen's uses a bar and sprocket nose to connect to their dyno. If so they will still have friction loss in the bar,chain and sprocket nose and they will have bar oil flying everywhere. As the chain wears it will stretch and its pitch will change. So as they test different saws with different sprockets on that same chain there may differences in wear between the chain and sprocket that would make the pitch slightly different which would rob power. If they used a new chain and saw sprocket each time I bet the torque measurements vary all over the place as the friction loss will vary between chains and will be greatest when they are new. With a belt system I would be using the same belt and move the saw forward or backwards as needed to achieve the same belt deflection measured midway between the pulleys. Neither system is perfect.....

 

[GPH85]

This is all from my experiance with cylinder heads from 4 cycle engines... I know 2 cycles are a WHOLE other ballgame, but air flow is still air flow, right I forgot to say where I slightly knocked the outer "sharp" edges of the exhaust divider "where it ties into the cylinder and exhaust flow begins"... I did this to slightly "bull nose" the "entrance" to the exhaust ports... If I had had a tig welder, it would have wound up looking a tid bit different... I would had then raised and tied in the floor of the exhaust port better than what the stock setup allowed me to do... I could then have shaped the roof of the port in about the same manor, allowing for better flow "smoother" flow... I wish I had a digital camera to really take some good pictures... With all the "blurr" and "light glare" in these, you really can't tell what was done...

OL'Homey, your right on that one. I never looked at it that way "chain stretch effecting outputs"... Plus the more I think about, the worst it sounds... Look at it this way right. A chain has a certain amount of play in it right? OK, so now everytime you make a pull the "play" in the chain is absorbing or rather dissapating your torque output = less noted torque and in turn = less noted power... On top of that as you stated, a different chain would have different results...

If you do go with a power steering pump setup, you can buy power steering pump "output testers" that allow you to close and open the output line on the pump "allows you to put different loads on the pump outlet"... I'm pretty sure this is correct, because if it allowed you to close the input hose, it would just spin and slam the steering wheel input shaft one way or the other Unfortunately the "valve" itself is not by any means cheap (I think up around a thousand or so dollars-not an exact quote)!!!

Greg

 

[GPH85]

In fact after thinking about it more, if you do go with the higher rpm capable power steering pump... Why not use a direct coupling setup, since your going to be changing out sprockets anyway, like what I used to measure torque output of my saw... You could have a cheapo socket welded to a shaft that's connected to the pump... Even put a universal on each end of the shaft, if you like, to get rid of any possible binding... Then you don't have any at all frictional loss "you'll still have a very small amount, but not enough to worry about". I got to thinking about the pulley setup some more and I really think your looking at more headaches then it's worth here A belt drive has to be extremely tight, to keep from slipping, unless your using a cogged or toothed belt and even then you have to worry about perfect alignment to keep the belt from jumping off...

Just a thought...
Greg

 

[ol'homey]

Yes, I agree that a direct connection to the clutch drum would be best. The reason I was thinking pulleys was to lower the input rpms to something a hydraulic pump could handle. We need to try to find out what the max rpm of a typical power steering pump is. If it can turn at least 10k rpm without any problems then we could do a direct connection to the sprocket drum. My gut feeling is a typical power steering pump you can get cheap from a junk yard won't hold up at 10k rpm. When i start shutting off the output and the pressure starts building and it's still turning 7-8k rpms it sure would make a mess if the pump failed, blew up or locked up. With the belt drive I'm thinking like a 2" on the sprocket and say a 12" on the pump. Then at 10k the pump would only be turning a comfortable 1666 rpm. The belt would also help isolate any vibrations or slight alignment problems between the saw and pump. Even though the belt will take up a little HP you will still be able to get consistent torque and HP readings which is the main goal. The readings might be a little conservative due to the friction loss in the belt/pulleys but that's OK with me.

 

[GPH85]

True There's always an up and down way of looking at everything, right

Since your going with the pulley setup, will you atleast be using a cogged or toothed belt? Atleast with this, you wouldn't loose too much power or torque through the drive setup and should be there abouts to what the saw is actually putting out...

 

[ol'homey]

I haven't decided on anything yet, just kicking around ideas. Who knows somebody might tell us about a 12k rpm pump for $20 ! Remember we are only talking about 5ft-lb of torque here. Torque is what makes belts slip and we don't have much. I've got an optical tach I could use to measure the rpm of both pulleys and make sure there's no slippage.