Vimana Vee Twin

[Modhydro]

I am getting started on a rather neat international project. A while back a man from Slovakia named Juraj Kadora posted on the forums to get help doing a build article on a vee twin he designed and produced castings for. I would have never guessed that I'd be writing a build article for a guy half way around the world. I guess that anymore the world shrinks and shrinks every day. That in itself is a neat testament to the HMEM site.

Another enthusiast from Australia was going to reverse engineer the parts to create 3-D models and then the dimensioned drawings. That leg of the adventure has fallen through and now my older son is doing the CAD work while I will get to have the fun on the machinery.

As Kadora is the driving force behind the project, I am starting the thread with some background on him since that is where the actual credit is due. He is a 56 year old electronics technician who's favorite hobby is machining miniature engines. His thought behind this design was to wind up with something more complicated than a single cylinder 4 stroke, but not too complicated for beginners. He also worked to keep it all within the scope of mini lathes and mills and not require any special tools. He created the patterns such that individuals have enough freedom to finish the out to their own preferences; for example, square or round cylinders, various bore and stroke, size such that bought cylinder liners and pistons can be used.

In a nutshell he produced a casting set and design that can cover quite a spectrum of abilities and creativity. It is sort of an engine builder's dream. With that much leeway, a hobbyist can take it as far as they want to add their own style to it.

Vimana were ancient shiny metallic objects from Indian manuscripts. Hopefully when completed, my Vimana will be a tabletop roaring and maybe even fire-spitting machine like the legends it is named for.

I am starting the thread with a photo showing the very nice looking casting set that he sent. I am in the early recovery from an elbow surgery so things will be slow at first, but getting rolling after that. I need to get the thread going as it will be part of my "therapy." Please enjoy the thread.

Steve Roskowski (Modhydro)

 

[gbritnell]

The engine looks great but here's something I can tell you from building my own V-twin. This one looks to have a V angle of 45 and mine is 90 degrees. That being said the intake manifold gets hot, quick and when it does it boils the fuel away from the carb. I added insulator blocks between the manifold and head which helped tremendously. It looks like the intake tubes are cast into the heads on this engine so I would look at making an adapter plate to go between the carb and intake pipe so an insulator block could be installed.
Another thing I don't see is provision for the ignition timer. Usually on a V-twin this is located off the end of one of the camshafts.
Just something to think about as the reverse engineering drawings are being made.
gbritnell

 

[gus]

The engine looks great but here's something I can tell you from building my own V-twin. This one looks to have a V angle of 45 and mine is 90 degrees. That being said the intake manifold gets hot, quick and when it does it boils the fuel away from the carb. I added insulator blocks between the manifold and head which helped tremendously. It looks like the intake tubes are cast into the heads on this engine so I would look at making an adapter plate to go between the carb and intake pipe so an insulator block could be installed.
Another thing I don't see is provision for the ignition timer. Usually on a V-twin this is located off the end of one of the camshafts.
Just something to think about as the reverse engineering drawings are being made.
gbritnell

Hi gbritnell,

For a 5 secs I got worried choosing the build the V-2 but since cylinders are 90 degrees apart,I am relieved. Thanks for pointing out. Posted engine now on my KIV build list. Today squaring up two sides of V-2 crankcase blank for marking out.Glad to have gb support Gus.

 

[kadora]

Engine is V 60 degrees.
4 rubber O-rings inside intake manifold serve as heat insulator.

 

[Herbiev]

Great looking engine. I'll be following your " therapy" with great interest.

 

[fourstroke]

Well done on producing such an excellent casting set
The finished engine looks fantastic
Dougie

 

[Davewild]

Nice, are the casting already for sale?

 

[Modhydro]

I just got a release from my doctor for very limited use of my arm. I will start making chips very soon.

I don't want to speak for Kadora out of turn, but part of the intention of this build thread is to get all the 2-D drawings together (as well as the solid models), and verify them to each other and the castings. Once we do a complete build, the plans as well as the castings should be available. I am the guinea pig so to speak with help from my son.

Please be patient as we work together to deliver a well checked final product that should greatly enhance other's builds of the engine.

Steve

 

[Modhydro]

I have not had as good of luck with my arm as hoped, but am still making some progress.

I was thinking about how involved to get with hints and tips along the way with this project and decided to make it pretty basic. I figure that I may be able to pass on a trick I've learned here or there and more importantly know that there is a wealth of knowledge out there than can help me learn new ones and make my own work better. Please feel free to point these out so we can all benefit. If things seem too basic by your replies I may skip some explanation, but I think a forum like this is a great way for anyone to learn. Please advise me as we go along and remember that there are all levels of experience looking at these builds.

The casting actually has index lines in it to allow for some quick measurements to verify that cored through bore is concentric with the part. These show in the 2nd photo pretty well. Once I was happy with the part geometry, I simply hand held the casting on my belt sander to remove the core flash and wind up with one side "flat" so I could start the work on the lathe as shown in the 3rd photo.

In the 4th photo you can see the indicator that was used to dial in the concentricity of the casting. I didn't get a photo before that, but a neat thing to get it close is to use the nose of a drill chuck in the tailstock and "eyeball" the hole. On smaller parts a center works well and on larger parts a bullnose center. Between the casting and chuck face you can see an aluminum disk. That lets me push the casting tight to the chuck body on the flat side to keep the casting rudimentarily true to the axis. Since it is captive by the jaws it simply stays put where if you use parallels they are always moving around (unless you use magnets) . You also don't have to remember to take it out like parallels and it also is a mechanical face that cutting loads can push against instead of counting on only the clamping force of the jaws.

The 5th photo shows the carriage stop set so that the power feed runs the boring bar nice and even. At this point I always like to hand turn the spindle just to be sure that there is no chance of a chuck strike or work piece hit through the whole operation travel.

The 6th photo is simply the through bored crankcase.

Steve

 

[Modhydro]

Now that we have the cross-bore done, I was able to breath a sigh of relief as I am always somewhat nervous holding something as irregular as the OD of this part.

Swapping back to the three jaw chuck I was able to face off first the raw side that hadn't been decked as shown in the first photo. For this I lock the carriage for a better cut with no chance of creep. To determine the amount to remove, I simply measured the casting width, subtracted the finished width and took half of it off. Once this was done, I put it on the surface plate and put a scribe all around at the desired width.

Once I got close to the scribe line, I marked the chuck/part rotational relationship (chuck key up = cylinders up ) I removed the crankcase and measured the width. Putting it back in the same orientation, it was easy to use the compound screw for very accurate removal. A neat trick is have it set at 30 degrees from straight like the 3rd photo. My the magic of trigonometry or geometry, your cut on the part's face is exactly 1/2 of what you read on the compound dial. For example, if you need to remove .030" of stock to achieve the final size, you would need to move the compound .060".

The next photo simply shows the crankcase to this part of completion. Measuring the width showed about .002" more at the top than the bottom. I hand lapped it a bit to bring it into a reasonable parallel for moving onto the next work.

The last photo in this installment shows probably the biggest improvement to the old Logan that I have ever made. It is simply the light over the work. It is an old doctors office light that I found at Goodwill. It is very bright and easy to move around depending on what you are doing. Even my sons who are just 18 and 20 cannot imagine working on it without it. Another thing I like is having the whiteboard and bulletin board right behind it. It keeps notes and drawings easy to see and right where you need them.

Hopefully tonight my neighbor will come over to move the rotary table to my mill so I can get onto the next operations.

Steve

 

[Capt,n John]

Nice looking engine you built. Have you test run it yet? Best Regards, Capt,n

 

[Modhydro]

Kadora, the designer and builder of the first one has. I am simply doing a build forum for him as English isn't his first language, although from all my correspondence with him you wouldn't know it. I'd say his grasp of the language is better than many Americans you meet in public these days!



Here is a link to a video of his running and running very nicely I might add.


[ame]https://www.youtube.com/watch?v=f-WqSjO9NJI&feature=youtu.be[/ame]

 

[gus]

Captain n John,

Please convey my compliments to builder. Hand primed and hand flip start!!!!! This one feat I am dreaming of with the Howell V-2 I am now building. th_wav

 

[Capt,n John]

Compliments to the builder. Very nice job & a nice running engine. I wonder what type of ignition was used? Best Regards, John

 

[Modhydro]

The one running was simply glow ignition. It can be adapted to anything you would like though. I may do mine as a battery spark.

I did get help getting the rotary table on the mill and made the centering spigot for the crankcase last night. I will get more work done on it this weekend and get more photos posted of the progress.

Steve

 

[Capt,n John]

Here is something you can try & it works great. Mix one gallon or part of gas to 2 parts of glow fuel. Use a O.S. Max "F" glow plug. The engine should run very good & Idle right down to a very slow RPM. You do not need to mix a whole gallon....just say 8oz of gas with 16 oz of glow fuel. I will add a link to a video If anyone is interested to sow it running. Best Regards, john

 

[Modhydro]

I was able to proceed with some more work on the crankcase as for cutting the cylinder decks, tapping the holes and boring out the cylinder bores.

There are multiple ways to attack the next steps. One is to do it on the mill. For this method I am showing the setup for the flycutting the decks.

In the first picture I measured the angle between the faces and found it to be 119 degrees. This means that you have to offset the angle by 1/2 degree in the vice so that it is splitting the difference as shown in the third photo. Photo #2 shows a dowel pin that it is hanging on in the vice jaws. This winds up acting somewhat as a third hand and also then being a solid reference surface to index the vertical height of the milling cutter to face them off.

I am lucky enough to have a rotary table so opted for that method instead but wanted to do a photo representation of an alternate means.

 

[Modhydro]

It may sound somewhat corny, but my rotary table is a special tool to me. My dad's best friend gave it to me about 10 years ago. Alex was actually who inspired me to get involved in machining and doing things just like this. Every visit to our house was accompanied by books or magazines for me to digest. Trips to his place were an absolute adventure. It was like a museum (or indoor junkyard) of mechanical stuff. As a kid I couldn't wait to go there.

He heard that I bought a mill and loaned it to me. He made sure that he told me it was on loan or until he "croaked." He also followed that up with "I'm not looking for a mill." Every time I use it I get to remember him and give thanks for the time he took to teach me stuff. Pretty sneaky old guy, huh.....

Anyway, back to chip making.

The first photo shows the centering spigot that fits snugly in the center hole of the table. In order to center the crankcase on that I made the adapter ring that was a light slip in the crankcase through bore. The last part of the setup is the shim that fits between the workpiece and the table top so that the cutter doesn't get into it. This works very well to keep things true when flipping it for both sides. You just need to find the center of the table once and you are done indexing.

The next photo shows the edge finder truing the as-cast decks. I guess I should have shot that photo from farther back. Without something for frame of reference you can't really tell the table is even turned. Remember that the top angle was 119 degrees so I had to run the table to 30.5 degrees off center. I brought it in to verify alignment and then rotated 61 degrees the other way. It indexed very well so I was then able to set it to the intended 30.0 and cut the decks. Unfortunately the only mill I had long enough didn't cut all the best, but still OK for what is needed.

I didn't get photos of drilling the holes in the face, but it is pretty simple. I have a DRO on the mill so it was a simple X-Y operation. When the hole was under a clamp, I simply undid one at a time and repositioned it.. Before removing it I put a straightedge (a ruler for the purists) on each side and put a sharpie mark on the table. With it flipped over this gave me a good starting point before indicating the now cut edge in at 30 degrees.

 

[Modhydro]

Once the features were completed on both faces it was time to make a home for the cylinders. I put the crankcase on the same dowel "hangar" and then leveled it with a digital protractor. I double checked the level by using the feeler gage between the deck and a mill cutter. A slight tap with a rubber hammer and it was set true.

I indexed the DRO for the center of the work piece in the X axis and then the peak between the cylinders. From there is was again simple X-Y work for the 4 tapped holes. Once they were done, I got out the boring head and worked the cast holes open to the spec in the drawing.

Once both sides were done, it rotated to vertical in the jaws for cutting the connecting rod clearances inside. This was just a simple plunge cut, but again setting the depth of the cutter off of the dowel pin made and easy job out of that.

The last photo shows it ready to do the tapping.

I guess this may be a point to ask for some advise on the write up. Is it too basic? Should there be more photos? Less? I am open to ideas that can make this the most beneficial for all. You won't hurt my feelings so please let me know. This is for all of us not just myself and Mr. Kadora.

Steve

 

[PaPaMitch]

Hi All,
Been lurking around here for a long time.

I like the thread so far. Lots of good info. I think I need a set of those castings. GRIN!

Mitch