Archive through October 13, 2009

[hdshine]

Two questions:

1. I tried splitting my 126 last night but couldn't get the coiled spring pin out of the rear coupler. Is there a trick or do I use PB and hammering?

2. What is a good reducer for the Cub Cadet paint? There are no instructions on the can.

Thanks, Dave

 

[dfrisk]

KENDELL - You are correct, the max. torque RPM is WOT under an excessive load to lower RPM to the rpm point of max torque. Max HP is WOT @ 3600 rpm. Only time the two would coincide would be if the engine was running 5252 rpm.

In that case You need some govenor work and most likely a new rod, block & flywheel! As well as clean shorts.

And as You say, I increase engine rpm before I encounter a tough spot when mowing, plowing, etc to an rpm I know the engine will handle the load. As You found out the hard way lugging an engine down almost to the point of stalling gets REAL hard on parts.

DON T. - since loader operation is an intermittant load running at less than full throttle does enable smoother operation of the tractor & hydraulics and gives the engine plenty of time to cool the excess heat built up while loading the bucket. You're running the same way I would.
When I run the loaders on my M & Super H I never run wide open, normally 1000-1200 RPM with a 1650 full load rpm, but then they're water-cooled anyhow.

Another thing with air cooled engines, when run in cold winter conditions they seldom get up to normal operating temp. so more frequent oil changes are recommended. I did an oil analysis on the K241 about a year after I rebuilt it. I'd blown snow for maybe 10-15 hours then mowed my small yard a couple times. Then I got a call from a Buddy to "Mow His back yard". The grass was over a FOOT tall, had the clippings from being mowed twice with a Bush Hog the summer before in the new grass. It was like mowing a hay field! The K241 was at WOT for a L-O-N-G time that afternoon, like an hour. I started hearing a slight knock, idled the engine down at no load and the knock went away and I returned to mowing at a reduced load, cutting maybe 6 inch per pass. The OA said I had WAY too much unburned gasoline in the oil from the cold weather operation blowing snow. But luckily no unusual metals. I suspect a small piece of carbon or head gasket was getting hot enough to start combustion before the plug fired.

MATT G. - What kind of temps are You seeing on your cyl,. head temp gauge? I've seen 300-325 F after idling a couple minutes with the K241 with my RayTech temp gun. That was right around the spark plug at the base of the fins.
The increase in temp after You idle down after a hard pull is called a "Heat Soak". ALL engines do it every time they're shut off after they're warmed up to temp. I imagine if You shut the engine off without idling You would bury the needle on the gauge. Far as the 5 min. warm-up time in cold weather, there's parts of your engine that take even longer because they're even further away from the hot combustion chamber.

I got my 2010 MWSC catalog about 2 wks ago, I need to see if DIGITRON can make Me a combination tach, cyl. head temp, EGT, & oil temp gauge. I've done searches for other data logging equipment, plus checked all the normal gauge mfg's sites. So little time, room, and $$$ and so much data to gather. I may change my mind AFTER I get gauges on the K321. Like KENDELL says, all We've got now is opinions, We need to get some facts or as my old QA Mgr. loved to call it, "DATA".

 

[kide]

The standard tool is a roll pin punch ..search for one with a protrusion in the center of the tip.
As to reducer, what brand and type of paint is it??

 

[rwilke]

Josh O.,
I agree, a curve showing the air cooling cfm vs. engine rpm would be interesting!

Matt G.,
Could/would post a pic of the Kohler Magnum brochure diagram you mentioned having?

Dennis F.,
I agree, such information is model dependent. Although the Kohler Magnum brochure diagram would be interesting, it wouldn't be necessarily applicable to all K-Series engines. In fact, if I was a betting man, I'd bet that the newer engines have a better designed shrouding & cooling package. To expand on your thoughts just a tad, the amount of heat being produced would vary with the HP of the engine, the configuration of the shrouding, the number/missing/condition of the cooling fins on the flywheel and the condition of the leaf screen, are the fins painted or not, etc.

In my opinion, cleaning the debris/dust/oily dirt/etc off the cooling fins and inside the shrouding is a major heating issue and is one of the easiest things we can do in keeping the engine happy. If the exhaust POPS loudly when you turn it off, that is telling you that you should have idled it down to half throttle for approximately 20-60 seconds before turning the key off.

Kendell I.,
You mentioned mower blade rpms for your (OT) Scag, is 10,000 RPM deck (when run at the designed, full throttle setting).
Do you (or anyone else) happen to know what rpms a common 42" Cub deck operate at?
If I was guessing, I'd guess that our old Cub decks don't turn anywhere near that kind of rpms....

Ryan Wilke

 

[rwilke]

Dennis F.,
You bring up a good point (as you usually do) regarding Winter operation warmups.
Do you recall any directions in any of the Cub or Kohler manuals regarding any specific warmup directions?

Regarding heat soak, I practice it in reverse when I use my chainsaw, especially in cold weather. I start it, vary the idle from idle to 3/4 throttle for about one minute. Then I shut it off and let the heat soak thru the saw for another 3-5 minutes. Then I restart it and only make small cuts / brush for the next 5 minutes. That pretty much gets it all warmed up and I can ensure the chain oiler is working properly. Then I can move on to heavier wood cutting /tree felling. I first began my, "start, off, wait, restart" routine when I was riding my air-cooled motorcycle to work. It seemed to make a big difference in the warm up period, much better than having it sit there idling away and trying to foul a plug in the meantime.

Ryan Wilke

 

[dtanner]

This is it (The standard tool is a roll pin punch ..search for one with a protrusion in the center of the tip. )

Jet

 

[rleo]

Question,
Can I attach a CW-36 to an Original?
--R

 

[ccarney]

Ray - Reply -

Yes, with the optional PTO clutch assy mounted on the front of the crank. There are vertical side holes on the brackets that match the Original's frame. The chute bracket goes right where the deck "paddle" would mount.

 

[hdshine]

Kendell and Donald,
Thanks. Will find the right punch.

Kendell, It's Cub Cadet Paint

 

[jmuncie]

The increase in torque as you move along the torque curve from operating rpm down to the peak torque rpm is called "torque rise". It's a measure of the engines ability to compensate for increasing load. As load increases, rpm drops until available torque matches the load. This is assuming that there is enough torque available at the throttle setting to match the load--otherwise the engine stalls. An engine operating at a steady rpm needs to be operating above peak torque rpm for the current throttle setting in order to be able to react to an increasing load without stalling. Also, when operating above peak torque rpm decreasing load results in rpm increasing until available torque matches load. Operating below peak torque rpm, decreasing load results in rpm increasing past peak torque rpm to the point where available torque matches load. Keep in mind this discussion assumes a fixed throttle position.

Governed engines only operate at a fixed throttle position when fully loaded. For our discussion, a graph of torque vs throttle position at a fixed rpm would be relevant, but I can't say I've ever seen that published. I have generated them on a dyno 20 years ago. IIRC, it looks similar in shape to torque vs RPM at WOT. Torque increases with throttle opening, but at low rpm the curve peaks and drops off. Don't know for sure, but I would expect that drop off to be very abrupt on our Kohlers because they're not intended to operate under load at the low governor settings needed to maintain low rpm and therefore, the carbs aren't going to be designed to function at WOT with low air velocities.

I just spent some time looking at fan curves for cast radial fans of similar diameter and rpm to our flywheels. None of them drop off abruptly as rpm drops below the peak flow rpm. In general, it seems that cutting rpm in half cuts flow by 20-40%. They do reach a point, though, where airflow essentially stops. How quickly flow falls off and what speed it stops varies with fan wheel, peak flow rpm, and static pressure drop, but the characteristic general shape of the curve is consistent. Based on the range of rpm where flow stops, I would not be surprised to see that our Kohler fans stop flowing at a speed well within the range of a too low idle adjustment. They sometimes stop flowing in the 600-1200 rpm range at relatively low static pressures. That would explain why the idle speed is to be set in the 1600 rpm range.

I can take an anemometer home from work and plot the a fan curve for a K301 if I can get accurate rpm readings. I have a Fluke automotive multimeter (don't remember the number--it's the model that preceded the 88), but I haven't been able to get consistent readings on the Kohler with it.

As for mower blade rpm, the driven pulley on the 42", 44", and 48" decks is similar in size to the PTO pulley, so rpm would be in the 3600 range. I don't have a deck close by right now, but IIRC the deck pulleys are slightly larger than the PTO pulleys so blade rpm would be even lower. What really matters is blade tip velocity, but it's a safe bet that there's not enough difference in blade length between the Scag and Cub Cadet to make up for the difference in RPM.