V-TWIN---MAYBE V-4

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Mentioned above was the 100.000miles for car engines. Multiply that by between 2 and 5. to 200,000~500,000miles. The durability tests for cams and followers in an engine were done at idle (Muggins being the engineer to specify the test and test rig). Idle (in the profiles and contact loads for regular car engines) is the hardest speed for durability, as the oil supply is adequate - but contact pressures at their highest due to dynamic acceleration and deceleration forces not having much effect:
The Cam profile on a flat follower (OHC twin-cam with bucket follower designs) leads to gentle opening then to an acceleration peak which "flings" the valve open at higher speeds, allowing the spring pressure (increasing with valve opening) to absorb that kinetic energy of valve motion so at Peak revs the system will happily run "forever".. But at idle the mechanics have to be "dragged up the hill" of the cam and "drag all the way down again". This "dragging" wipes the surfaces of oil as the contact "sees" full spring load all the way up and down the cam, hence hardest for durability - and the tests ran for the time equivalent to 200,000 miles of "normal" driving. It may sound extreme, but the design and parts eliminated warranty concerns for cam wear.
I guess Brian's parts will be as good!
K2
 

Bentwings

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When making a cam how important is it to have a radius on the flank? There is only a few thousands of lift and the action actually takes place at the nose. As long as the valve opens and closes at the proper time how does a gentler action make it any better. We are talking about engines run at low speeds and for limited time. If the cam or cam follower wore out after 5000 hours none of us would ever see it. I have made cams successfully with a straight flank as shown on several plans that I have followed.
Little un clear on question, if you men flat relative to the axis you are probably right . Unless there is large valve spring pressure and you don’t have a good splash lubrication , you will wear out long before the little engine. A radius profile is to promote lifter rotation a straight profile might be better for roller lifters. I’ve got a number of two stroke engines that have hundreds of hours at full throttle full load maximum rpm , often operating far above normal temps that still run just fine and have the same compression as new most four stroke Rc guys say the same thing just use quality oil and compatible cam and lifter materials auto enginges usually have cast or sintered cams that are relatively hard good finish, lifter are chilled iron and basically quite hard I never wore a race cam out , a couple broken rollers wiped out roller cans but 600+ Pounds on the valve seats was not unusual Hogson radial engines show plastic lifters cams are very gentle .
 
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I have never heard of anyone on this forum using Teflon to make cam followers. I have used it on this small engine and they perform great as they are self lubricating.
 

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Hi Brian, Just something I am not sure about from your video? It Looked like the cam timing was Inlet (nearest to the flywheel you are rotating) opened-closed - and immediately the exhaust opened-closed. - Then a dwell... for compression and firing. Surely this sequence is wrong and the normal rotation of the engine would be the reverse direction? Of course it doesn't matter while demonstrating the action for valve gear, but will be important for the starting of the engine, and perhaps the quick release connector on the end of the flywheel?
I guess you have not got your directions of cams "muxed-ip" and will be running counter-clockwise at the flywheel?
Or am I muxed-ip?
K2
 

Brian Rupnow

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Today I assembled the cams for the other cylinder and made up a pair of pushrods. The rockers now operate on both sides when I turn the engine over. I went across town to Hercules O-ring and begged a couple of 1" i.d. Viton o-rings to use for my head gaskets. This is getting harder and harder to do---I used to know all of the Management there, and they gladly gave me whatever Viton rings I needed in exchange for $5 for their coffee fund. The management is all new there now, and they don't know me. I find it difficult to order Viton o-rings in the sizes I need unless I want to buy a thousand of them. I leak tested my gas tank by filling it full of Naptha gas and setting the engine on a piece of white paper overnight. The paper had no tell tale stains on it in the morning, and the fuel level stayed the same in the tank overnight. I have to make up gaskets for the bottom of the cylinders where they attach to the crankcase.---There is no compression there, but the engine has an oil base and splash lubrication, and if I don't put gaskets there it will leak oil.
 

Brian Rupnow

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Today was the day to start thinking about piston rings. I have a number of heat treated rings which were originally made when I built my 7/8" bore horizontal i.c. engine. Whenever I set up to make piston rings, I make a bunch of extras, and they do get used up. These pistons are prototypes. They are made of cast iron, and the top two ring grooves get the heat treated cast iron rings. The third groove down from the top of the piston get a single Viton o-ring. (Which you can see on the left side of the picture). Theory here is that the Viton rings will give immediate good compression to start the engine. After the engine has started on it's own and ran for an hour, the cast iron rings will "wear in" to the cylinder to provide compression. The rings in the picture haven't been ground for flatness nor "fit" to the pistons, that will be done tomorrow.
9bwGjS.jpg
 
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Clever thinking Brian. I hope it works. My only concern is that the Viton ring may wipe the oil from the bore so effectively that the cast iron rings have insufficient lube to avoid scuffing/seizing...? But you will only find that out if things go wrong. I am sure your initial runs will be short, low powered, and you'll check to see how the rings are bedding-in... so you should be OK. Even so, I should be inclined to add the finest smear of molybdenum grease to the bore during assembly, as while this may slow the bedding-in process, it should also prevent any scuffing/damage to rings and bore. But a tiny amount on a finger should do..?
Only a thought, your thoughts (and experience) are probably better?
K2
 
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Just another thought... along he lines of an Engineer fitting parts... Have you considered using engineers' blue on the bore, fit the rings to a piston and pass it up and down the bore, then see where the blue transfers - or not?
Or:
I should be tempted to even just simply try the cast iron rings on the pistons and run (with cylinder heads and valve gear to gain compression in the cylinders) for 5 mins or so driven by your trusty electric motor. (no fuel or ignition). Then check the rings have a witness polish all around, and some compression is evident, before trying to run on fuel?
Or have you already checked?
K2
 
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Hi Claudio, When I worked on compressed air powered cylinders, we had PTFE seals, working on rotating or linear action ground stainless steel shafts. - Lubricated with a silicon grease. (NOT the regular mineral oil LM grease or anything like it - that absorbs moisture and forms acids...). I suspect silicon grease may help the "self-lubrication" of the PFTE? It was a requirement for the 40 years maintenance free life of my product (max. 5000 cycles).

K2
 

weldme

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Hi Claudio, When I worked on compressed air powered cylinders, we had PTFE seals, working on rotating or linear action ground stainless steel shafts. - Lubricated with a silicon grease. (NOT the regular mineral oil LM grease or anything like it - that absorbs moisture and forms acids...). I suspect silicon grease may help the "self-lubrication" of the PFTE? It was a requirement for the 40 years maintenance free life of my product (max. 5000 cycles).

K2
 

Brian Rupnow

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Today the cast iron rings were finished "to size" and installed on the pistons. The Viton ring was added to the pistons as well. Using a tapered ring compressor, the pistons were installed into the cylinders. Ended up being a very tight fit, but they are in, the cylinder walls didn't get scored in the process, and I'm happy with the fit. In this picture, the pistons have been shoved thru the cylinders until the piston pin hole is just visible, enough to get the piston pins started into place. The rings are all still compressed in the cylinders. One of the things about a small bore engine using knife and fork connecting rods is that the connecting rods (at least the forked one) won't fit thru the hole in the cylinder. This means that the piston pin must be installed thru the piston and rod while the rods are still attached to the crankshaft.
WSJBPh.jpg
 

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Great stuff! I'm really looking forward to seeing this run!

Any further thoughts on making a "second half" to make it a V-4?

-Dave
 

Brian Rupnow

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The pistons with rings are installed in the engine. It is very, very stiff. It is too stiff to consider running on it's own. I used a cheater bar to turn the crankshaft thru 360 degrees, and when I was sure there were no definite "Hardstops" in the engine, I turned it over 200 times by hand. This freed things up to the point where the engine would turn over, but still stiffer than Hell. I filled the crankcase with oil, gave a shot of oil down each cylinder (the heads are not on the cylinders). I put my 8" v-belt pulley on the crankshaft and my two inch v-belt pulley on the electric motor I have, connected them up with a v-belt, and set it up to run for a half hour out in my main garage. I don't have any work planned for the rest of the day, as I'm off to see my friendly neighborhood dentist this afternoon.
 
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