Oscillating I.C. Engine

[Brian Rupnow]

Brian, how are the vibration of the oscillating engine?

Probably bad, but I can't really tell. Every engine I build is screwed firmly to the wooden test bench with four #8 woodscrews, one on each corner. When you start an engine using an electric drill as I do, you absolutely do not want the engine to move. You don't want it to suddenly start and jump onto the floor, destroying months of work.I don't balance my engines. I build them, I run them, I video them,, and then they go "on the shelf". Different people have built the engines I design/build and complain because the engines "jump all over the place" when they are running. When someone posts a video of one of my engines running, not bolted down, and "walking" across the floor because of imbalance in the rotating assembly, I feel somewhat insulted. My mandate is to build an engine that runs. If someone wants an engine "balanced and blueprinted", then the onus is on them to look after that aspect of building the engine.----Brian

 

[Brian Rupnow]

-It's funny how, as you solve the most common issues (poor compression valve timing), then you begin to focus on the OTHER problems. The first set of problems keep the engine from starting. Once you have solved the issue of getting the valves to seal, and your engine will actually start and run, then the second set of issues rears it's head----How to keep your engine running. And once you have your engines so they will start, and keep running, then you start wondering about the issue of "How do I get it to fire ONCE like the full size engines, and then immediately go into miss cycle for 8 or 10 revolutions, then hit again ONCE and repeat the cycle. My flywheel design boils down to "best guess". Right now, I think my flywheel is too heavy. There is simply too much inertia to overcome for that 1" cylinder to fire one time and bring it up to speed. The engine has to fire multiple times to bring it up to a speed where the governors will engage the miss lever. I don't believe it is an issue of the governor spring being too strong or too weak. I think the flywheel simply has too much mass for the bore of the cylinder. I'm not sure I will do anything about it, but I am wondering.---Brian

 

[Brian Rupnow]

Guys--I truly do appreciate your comments and the fact that you stopped by and said Hi. I fully realize that to many veteran machinists, what I am making are just "nonsense toys". However, I find them exciting, and my machining skills improve with every engine I build.---Brian

 

[Gerhardvienna]

..........what I am making are just "nonsense toys". .................

Hi Brian
Isn`t that what we all do? Making expensive nonsense just for fun:hDe:
But I love it, spending time at the PC for planning and much more time at the workbench to build things up:fan:
At the time I`m NOT at the workbench, at that high temps above 35deg Cel. it`s much too hot for working, the next days will be cooler weather, so I can go on again.

.............and my machining skills improve with every engine I build.---
Absolutley correct!!!!!!!!!!!!!!
Regards
Gerhard

 

[jimjam66]

Brian, I submit that the bulk of the denizens of a forum titled 'Home Model Engine Machinist' are anything BUT veteran machinists and therefore we enjoy your build threads very much indeed! Please don't stop on account a few who whine about things like vibration ... pretty please?

 

[Roboguy]

Don't forget all us beginner's (I can't be the only one!) who learn so much and get very inspired by reading these threads.

Brian, thanks again for taking the time to share with us all.

Cheers
James

 

[Barnbikes]

Don't forget the dreamers who wish they could build something as cool as what you do.

 

[Brian Rupnow]

JimJam--I wouldn't categorize people who complain about something legitimate as "whining". Their complaints are real---The engines I build aren't balanced. They do "jump around" if they are not bolted down. To be honest, it never crossed my mind that people would ever even attempt to start an engine which wasn't bolted down. Balancing engines is a kind of VooDoo art, that requires a lot of static balancing of parts and calculating weights of spinning assemblies before they are even made. There is a whole branch of science devoted to balancing rotating non uniform masses. I could do it---if I wanted to take the time to. Simply put, my engines are NEVER ran unless they are bolted down, so it's kind of a non issue for me. Those who do have a concern about it will have to balance the engines themselves. We have one excellent builder/poster from Australia that built the Rupnow engine #1 and then posted a video of it "walking" across the floor as it ran, due to it's out of balance condition. He posted a video of this because he found it amusing. He didn't do it to be negative, and he wasn't whining.----Brian

 

[Cogsy]

We have one excellent builder/poster from Australia that built the Rupnow engine #1 and then posted a video of it "walking" across the floor as it ran, due to it's out of balance condition. He posted a video of this because he found it amusing. He didn't do it to be negative, and he wasn't whining.----Brian

Glad to hear this bit Brian - I certainly wouldn't want to insult you and you're right, it did amuse me. However with the rubber feet on a good non-slip surface the engine happily sits in one spot without being bolted down.

As for vibration, sitting on my 2 stroke dirt bike and giving it a good rev gives a certain 'tingly thrill', that's almost naughty...

 

[Brian Rupnow]

As a point of interest--I have been running the engine intermittently over the last few days searching for that "sweetest of sweet spots" where the carb setting and ignition timing are just about at the perfect spot. I have continued clipping half a coil at a time off the atmospheric intake valve spring, until I am at the point where I can barely feel any compression at all in the valve spring when pressing on the valve stem with my finger. (I have removed a total of 2 1/2 full coils since the engine first ran.) Each time I removed half a coil, the engine ran better.----Now, something I read about in regard to intake valves. I have always reamed the valve guide with an "on size" reamer, and turned the valve stem for a very precise fit in the guide. Of course, the more precise the fit is, the more drag is created on the valve when it opens and closes, and the more important perfect concentricity becomes between the valve guide bore and the actual valve seat. The piece I recently read said to make the valve stem about .001" to .0015" under-size from the bore of the valve guide. This removes any potential "drag" on the valve stem, thus allowing a more lighter and responsive valve spring. It also takes away some of the need for absolute concentricity between the valve guide and the valve seat.--The valve can "float" a little bit concentrically, ensuring a good seal between the valve face and the valve seat. I had inadvertantly turned the intake valve stem a bit smaller than I ususally do, but I thought of the article I had read and decided to use the valve anyways to see what would happen. It appears that the article was correct.

 

[canadianhorsepower]

Hi Brian
this is not to poke you but look at the stats
on almost 8000 of your likes given sucks.
other peoples do great work and you don't even
tell them "GOOD WORK" it's back fires

cheers

 

[Swifty]

Brian, thinking about your comment on the clearance between the valve stem and guide, I always assumed a close fit was necessary to stop any air being drawn down in the gap, but this could probably be balanced by a slightly richer carburettor setting. It's only when you stop and think about these things that other ideas spring to mind.

Keep up the great work, how do you like the new mill with readout, are you planning you next project yet ?


Paul.

 

[barnesrickw]

Why would somebody go through the trouble of even calculating stats like that if it were not intended to poke? #transparent.

 

[canadianhorsepower]

Why would somebody go through the trouble of even calculating stats like that if it were not intended to poke? #transparent.

If this message was for me I didn't have to calculate the stats.
It's on your page by HMEM

 

[Brian Rupnow]

Swifty--I love the new mill and readouts.The mill is very powerful, no more blown fuses and the readouts are just wonderful. I wish that as Luc suggested, I had went for the 3 axis readout package. There is a readout on the Z axis which comes with the mill, but it is small, poorly lit, and difficult to read.---Brian

 

[Brian Rupnow]

Luc-I didn't know it worked like that. Let me see if I understand this--I'm supposed to give lots and lots of "likes" to people so that I get lots and lots of "likes" in return? There used to be a song about that "We belong to a mutual, Admiration Society".

 

[Journeyman]

Hi Brian - Well I for one "like it", I have followed the whole thread with great interest including the spin-off milling machine saga. Thank you for taking the time not only to design and build such a novel machine but to make the extra effort to document the build in such great detail.

As far as pressing the like button, well that sort of smacks of what the youngsters do on Twitbook or Facer to gain an imaginary army of friends!

Well done again, looking forward to the next project...

John

 

[canadianhorsepower]

Luc-I didn't know it worked like that. Let me see if I understand this--I'm supposed to give lots and lots of "likes" to people so that I get lots and lots of "likes" in return? There used to be a song about that "We belong to a mutual, Admiration Society".

Brian,
plz don't get me wrong on this, it's nothing personal. But being in a teaching environment I've seen this more than you can think and I hate it. We are both member on another group and the discussion have been going on for over a year to have a straight "LIKE" button. I kind of feal bad when I see peoples building your "personal engine plans AND FREE" and then complaint cause it vibrate:wall::wall:
All I can say is Keep up the great work, nice design and they always work Thm:Thm:Thm:
and I must say You have the BALLS to design them from scratch

and other will ***** at them from scratch

 

[Brian Rupnow]

The engine is running good. Very good!! I have everything dialed in now to the point where I don't see much room for improvement.---BUT---The engine still has to "hit" 4 times consecutively before it ramps up enough speed to go into "miss" mode. A weaker governor spring won't fix this. With a weaker governor spring, the engine will go into "miss" mode immediately, and not build up enough speed to keep going and "hit" again. A stronger governor spring will make the engine run faster, but not do a lot in terms of hit to miss ratios. I have to get rid of some of the mass in that flywheel. Right now, as it sets, the flywheel weighs 3.2 pounds, and of that 3.2 pounds, 2.72 pounds is in the outer rim. If I set the flywheel up in the lathe and carve away the inner surface of the rim by 33% of the existing thickness on both sides, the rim will then weigh 2.15 pounds.-This equates to a reduction in mass of roughly 21%.---In fact, since I have to remove it from the chuck and turn it around to machine the other side, I can even try it on the engine at the "half way" point where I have only carved away 10.5% of the existing mass. On one hand, I hate to carve up a reasonably pretty flywheel. On the other hand, it didn't cost me anything but my time, and I really would like to have a hit and miss engine that hits once, misses for 5 to 8 cycles, then hits again.

 

[bazmak]

It seems simple why not remove say 5% at a time and note any
improvements then we can all have feedback