Heavier flywheels for the Kerzel hit and miss engine

[Brian Rupnow]

About 6 or 7 years ago, when I first started machining, the Kerzel engine was the first hit and miss engine I ever built. After many trials and tribulations, I ended up with a successful runner. You can see the lengthy build thread here.- http://www.homemodelenginemachinist.com/showthread.php?t=10091 --Although this engine worked very well, and went into and out of hit and miss mode as I had hoped for, it never gave that distinctive "pop"---hiss-hiss-hiss "pop"---hiss-hiss-hiss sound that you associate with full size hit and miss engines, or even many of the model Farm-boy engines I have seen built. I decided that this was the result of my using a Viton elastomer ring on the piston instead of a cast iron ring. The Viton ring seals perfectly, but it creates more drag on the piston than a cast iron ring would. I have often wondered over the years, if an increase in flywheel diameter would have a positive effect on the way my engine ran. A recent post on HMEM by a gentleman named Jim, showed that he built a Kerzel a few years ago, and failed to get it running at all until he made a set of oversize flywheels for it. This got me thinking about my own Kerzel again, and prompted me to measure how much clearance  I had between the existing 3 1/2" flywheels and the wooden base. I just have room to slide a 1/4" thick piece of cold rolled flatbar between the brass flywheel and the base. The gas tank can be slid over 1/4" more to the right to clear a larger flywheel.A phone call to my metal supplier determined that he has a piece of DOM tubing, 4" outside diameter and 3" inner diameter, and that he would saw off a couple of 7/8" thick "rings" for me for $5 each. Since I have exhausted my ideas of "nifty things to build" for the moment, I am going to see if increasing the diameter of the flywheels has any effect on how it runs. The picture here shows my kerzel, setting up on it's shelf, and you can see the 1/4" of clearance under the existing flywheel.

[Brian Rupnow]

This is a video link to the way my Kerzel engine runs now. This is a fairly recent video, taken within the last three months.
<a href="https://www.youtube.com/watch?v=dLkF2nAjOJ8" target="_blank">http://www.youtube.com/watch?v=dLkF2nAjOJ8</a>

[Brian Rupnow]

This is the best running Kerzel I have ever seen.
https://video.search.yahoo.com/search/video?fr=yfp-t&p=kerzel+engine+youtube#id=12&vid=80278183de297601e179f80b616b40e3&action=view

[Brian Rupnow]

Yesterday about 10 minutes after I posted about this flywheel upgrade, a walk-in customer showed up at my door with about 6 hours of machining he needed done. I had to go across town to pick up some 304 s.s. for his job, so I picked up my material for the heavier flywheel rims as well. I have no idea why my supplier cut one ring 1/4" thicker than the other, but for $5 I wasn't about to ask him. I will finish off the customer job this morning, and then see what I can do to machine these rings into respectable flywheel "add ons".

[larry.doucet.37]

Nice work where could I get castings for model ingines


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[Brian Rupnow]

I am going to try for this. The new added weight will be attached to the existing assembly with Loctite 638.

[Brian Rupnow]

Nice work where could I get castings for model ingines


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This engine is built completely from bar stock. The original plans are a free download from the internet.---Or---if you contact me at brupnow@rogers.com I can send you a set of the plans redrawn to suit my build.---Brian

[Brian Rupnow]

Ha!!! That went amazingly well!!! I had to shift the gas tank about 3/8" but other than that the first flywheel slid right into place. Now to turn the i.d. on the second blank.

[crueby]

Nice job on the new shoes for the flywheel! About how much weight do you think this will be adding?

[Brian Rupnow]

Each added "ring" weighs 5/8 of a pound.

[Brian Rupnow]

Yee Hawwww---Lookit the ears on that sucker, Roy!!! I'm not sure what's going to happen with this additional weight on the flywheels, but for $5 and an afternoons work I'm going to find out. I ended up turning the outside diameter of the add-on flywheels to 3.960", just to have a breath of clearance between the flywheels and the wooden base. The only things I had to change were the position of the gas tank and the knob on my Kerzel lever pivot shaft. The gas tank was easy, as it was just Loctited into an aluminum hoop, and the Kerzel lever pivot shaft knob which used to be round is now cylindrical. Everything goes round and round and up and down with no clearance issues, so hopefully tomorrow I'll find out what effect this has on the way the engine goes in and out of hit and miss cycles.

[crueby]

It also gives it a nice contrast to the flywheel, sort of like on whitewall tires.

[Brian Rupnow]

This is the first run with heavier flywheels. It is somewhat inconclusive at the moment. I think there is a bit of noise "illusion" here, because my muffler points down away from the engine, and you can not clearly hear it when it "hits". I may modify the exhaust pipe and bring it up to the top so "hits" can be heard more clearly. It is still going in and out of hit and miss mode with the heavier flywheels on it, but seems to be running a bit fast. I may add a bit of weight to the counterweights, as this is much simpler than winding different strength springs.
https://www.youtube.com/watch?v=lBhIjjYzVyE&feature=youtu.be

[Brian Rupnow]

In order to hear more clearly when the engine fires, I have converted to a stack style exhaust. You can see the old muffler setting beside the engine. the new exhaust is a two piece unit., A brass part is machined to screw into the exhaust port on the cylinder head with a 5/16"-18 thread. The stack itself is made from a section of high nickel content automotive brake line. It is pushed into a hole in the brass machined part and held in place by #620 Loctite. The string tied to the stack has a pair of pliers hanging off the other end, to ensure that the exhaust stack is held truly vertical until the Loctite sets up.

[Brian Rupnow]

I'm finding out interesting things here. The added weight on the flywheels made the engine want to run slower. The fact that the engine was running slower made the governors operate in a different range because of the slower speed, and strangely enough the engine actually ended up running faster!! The cure for this was to add a bit of weight to each governor weight, which made the governor more sensitive and consequently brought the speed back down to an acceptable level. I'm just about where I want to be in terms of speed and hits versus misses, but I have a terrible rattle in the engine. I don't know if this is a result of the needle roller bearings on the crankshaft (they were noisy right from the day I put them in 6 years ago, in an effort to cut down on friction) or just the sound amplification caused by running the engine on my wooden desk. Tomorrow I will try it on the workbench out in my main garage it is any quieter.


https://www.youtube.com/watch?v=m2QLVUGCB_o&feature=youtu.be