# Opposed 4 cylinder 4 stroke



## geoff_h

Hello, this is my first posts to the forum but I have been reading, admiring and learing by reading here sense Ive started machining.

This is my 2nd IC build. 400 hours work over the last 7 months and about 400 parts finally came to life and I got it running reliable yesterday. 

It currently runs on glow fuel but I would like to eventually convert it to gas and fit a CDI ignition.

I dont have any build pics, just pics of the parts as they where completed.

The engine is a 120cc 4 cylinder 4 stroke. The plans are from Germany. I did a fare amount of modifying and redesigning the parts. More to experiment then to fix problems. Also to convert all the metric dimensions to imperial as thats the only tooling I have.

Here is where I found the plans. They have many aero motors and that is my real passion. 
http://www.cad-jung-shop.de/epages/62479729.sf/en_GB/?ObjectPath=/Shops/62479729/Categories/Bauplane

[ame]http://www.youtube.com/watch?v=IKeifHljhjg[/ame]

2nd test run 600 rpm idle 5200 rpm at 3/4 throttle.

[ame]http://www.youtube.com/watch?v=-sv1kC3jiUs[/ame]


The pistons and rods are 2024, intake and exhaust is 304, cast iron cylinder sleeves, valves are 416 and bronze on the valve cages and bushings. 

The exhaust tubes where filled with lead bent using a custom made bender then the lead was melted out.

I made a custom valve seat cutter that I learned about from this forum and it worked perfect, only a light lapping was needed.

The valve springs are wound on the lathe using a technique I found online. They are then stress relived in a toaster oven. They where easy to make but tricky to make all the same. 

The rods have needle bearings in the big end and bronze bushings in the other.

The roller rocker arms are 6061 with hardened W1 rollers and roller shafts.


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## lazylathe

Looks great so far!

Judging by my poor eye you have a CNC machine at your disposal??
All the parts look great!

How about an intro post in the Introductions section?
Tell us a bit about you and what you do!

Andrew


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## geoff_h

The head gaskets are turned from .005 copper shim stock in aluminium jigs the other gaskets from .020 copper.

The rings are cast iron and made using a technique from SIC where they are turned to size then heated on a mandrel to hold the new shape.

The fuel splitter is brass and silver solidered

The brass intake and exaust couplers are free to turn on the 304 tubing and have brass flanges silver soldered in place to hold them into the ports. This allows them to be set to any position then the coupler is tightened to hold them in place.


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## geoff_h

lazylathe  said:
			
		

> Looks great so far!
> 
> Judging by my poor eye you have a CNC machine at your disposal??
> All the parts look great!



Thank you. 

Everything was made manualy on a 13x40 Import lathe and 9x46 Wells Index mill.


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## cfellows

That's a great looking engine. Runs very nice. I especially like how low it idles.

Do you have any pictures of the crankshaft? I'd be interested in seeing how you hold it together.

Chuck


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## geoff_h

This was the first crank built to the original drawings. Its turned from 1144 and the rod journals are hardened shaft. There is a splined connection to allow for 2 bearings in the middle of the crank. Everything is held together with machine screws.

The crank proved to be weak and in the first runs the front crank sheared at the bolt that pinches the rod shaft.


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## geoff_h

Here is the 2nd version of the crank and rods. Crank is again 1144 and the rods are 2024 with bronze bushings in the small end. the big end is reamed and held together with 2x 2x56 screws. The crank is made in 2 parts and turned between centers. Not shown is the coupler that holds the center joint. Its just a tube with the id the same as the bearings to be a firm slide fit onto the crank halfs and holds them together as 1 removing any side play from the bearings.

The 2nd set of pics show how the crank is supported in the case. 2 bearings in the nose, 2 in the middle and 1 in the back.

The holes in the bottom of the case allow oil into the cam housing and are countersunk for o-rings to seal them.

The drive key is custom made.


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## geoff_h

The carbs are standard RC carbs with new throttle arms made.

The first cam was made of W1 but when hardened twisted and was not usable. All part of the materials learning curve I guess. The 2nd cam was redesinged and made of O1 and was thicker diameter between the lobes to try and allow it to be more stable when hardened. It is 270 intake 270 exhaust and 110 degrees between the lobes


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## geoff_h

Everything put together and ready to run. Now the real fun starts, to try and refine it.


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## mu38&Bg#

Beautiful. I'm going to guess, die maker?


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## geoff_h

dieselpilot  said:
			
		

> Beautiful. I'm going to guess, die maker?



Thank you. 
Im not a profesional machinist. Just like to tinker and make things.

Geoff


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## lazylathe

Awesome work!!!
You have a lot of talent!!

There are a few of us from the Southern Ontario on the board.
I am in Woodstock.

Love the video!!
Are you going to put it in a plane and fly it??
That would be the ultimate scratch build!!!

Andrew


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## geoff_h

lazylathe  said:
			
		

> Awesome work!!!
> You have a lot of talent!!
> 
> There are a few of us from the Southern Ontario on the board.
> I am in Woodstock.
> 
> Love the video!!
> Are you going to put it in a plane and fly it??
> That would be the ultimate scratch build!!!
> 
> Andrew



Thanks to everyone for the kind words.

I live south of Woodstock in Port Rowan. Not sure if I am going to fly it. I have never had a plane bigger then 28% and this would need 35% or bigger, a big investment in money. Also it goes through alot of glow fuel. On gas it would be much cheaper to fly.

Thanks
Geoff


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## Lakc

geoff_h  said:
			
		

> Not sure if I am going to fly it. I have never had a plane bigger then 28% and this would need 35% or bigger, a big investment in money.


You can always add lead to the tail. 

Nice job!


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## geoff_h

Had another good test run today after some intake tweaks. 600 rpm idle 5200 at 3/4 throttle.

It hits the wall at 5100-5200rpm with throttle remaining. I think the valves are starting to float. Next step will be to make a stiffer set of valve springs and a stronger set of pushrods. 

[ame]http://www.youtube.com/watch?v=-sv1kC3jiUs[/ame]


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## metalmad

Nice Job Mate
that thing has a bigger prop then my lawn mower has blades, I love it !! :bow:
I want one :big:
great job
Pete


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## Hinckley_Bill

My Dad was a 30+ year Tool and Die Maker from "the old school".....if he had lived long enough to enjoy himself he would have marveled at the work you have done on a home setup.

Thanks for inspiring us.

Bill


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## MuellerNick

Hi Geoff!

A really nice and clean looking engine. Great work!
Sad, that you had to give up on the Hirth-coupling of the crankshaft.

Only thing I have to criticize is the intake manyfold. It is not to your standard. But you intended to replace it later anyhow, right? 

Great work!
Nick


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## JaamieG

Very neat crankcase design.
Excellent work.
Cheers,
Giacomo


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## agmachado

Hi Geoff,

Very nice job... and thank you for share with us... including the germany web site with others engine plans!

Cheers,

Alexandre


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## petertha

I just realized this engine was posted Aug-2011. Hope I have not missed the maximum allowable time period for dumb, newbie questions! 

Can you elaborate on the crankshaft. I'm drawing up something similar right now & your parts are very intriguing. Appears the socket cap screw tightens the pin into position, but the slit goes inboard in the counterweight direction. Maybe this was because it would more throw radius than what could be accomodated in the crankcase if the slit & bolt  feature were on the outboard side?

- how did you make that slit extending from the crankpin hole?
- are the crankpins keyed to the counterweight parts in that slot, or just clamped?
- can you elaborate on jig or method you got the assembly aligned beforehand?


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## JaamieG

The low rev humming is lovely.
Neat and high quality work.
Thanks for sharing all the awesome pictures and videos.
Cheers,
Giacomo


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## Tin Falcon

Nice how did I miss this one . good work.
Tin


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## wildun

That's a really great effort, I must say!


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## Art K

Geoff,

Your engine is quite impressive! At 120cc what is your bore and stroke? Out of curiosity having both cylinders on the same rod journal do you got much vibration? I'm working on my own design for a flat four that is 117cc. 1.375 x 1.212.

Art


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## geoff_h

Thanks everyone for remarks. Sorry for the late replys, have not been on the forum in a while.



petertha said:


> Can you elaborate on the crankshaft. I'm drawing up something similar right now & your parts are very intriguing. Appears the socket cap screw tightens the pin into position, but the slit goes inboard in the counterweight direction. Maybe this was because it would more throw radius than what could be accomodated in the crankcase if the slit & bolt  feature were on the outboard side?
> 
> - how did you make that slit extending from the crankpin hole?
> - are the crankpins keyed to the counterweight parts in that slot, or just clamped?
> - can you elaborate on jig or method you got the assembly aligned beforehand?


 

You are correct, the bolt is located between the pin hole and counter weightfor clearance. There is very little room inside the crank case. I had to drawthe entire motor in solid works in order to check and make clearance for the differentcranks and rods I tried.

The slit into the crankpin hole was made by locking the crank into the lathechuck, custom grinding a parting blade and putting the blade horizontal in thetool post and parallel with the ways then with the carriage wheel going backand forth like a shaper, taking a small amount off and turning in the crossscrew. It took a while to do all the parts but once the blade was oriented togive a good cutting and relief angle was simple.

The pins are not keyed just a very close reamed fit. I must have tested 40 differentcombinations of drills, feeding rates, speeds, lubricants and reamers in orderto get one that would consistently give a good fit. The pins are made from bitsof a hardened rod I ground to length.

The crank parts where made individually with lots of effort to locate thecrank pin hole accurately in each half. I then loosely assembled the cranktogether in the crank case halfs with the bearing carriers tightened down.Then the bearings align the crank and small adjustments where made by hand toget it to turn as free/true as possible then tightened the bolts to clamp thepins.


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## geoff_h

Art K said:


> Geoff,
> 
> Your engine is quite impressive! At 120cc what is your bore and stroke? Out of curiosity having both cylinders on the same rod journal do you got much vibration? I'm working on my own design for a flat four that is 117cc. 1.375 x 1.212.
> 
> Art


 

It was very smooth at all rpms. I built a single cylinder .27ci flat head 4 stroke turning a 9" prop that vibrates that same test bench much more.

Stroke is 31mm, bore 35mm


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## flyingtractors1

Not a professional machinist? I'd say a very expert one. Beautiful work. Ralph


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## ///

Very nice work Geoff. Like Tin, I'm not sure how I missed this. :shrug:
I love the sound of a boxer, so much so I drive a Scooby daily ;D
Would one day like to model an EJ205 engine.


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## Niels Abildgaard

Hello Geoff

Enjoy pictures of full size Hirth 504 crankshaft parts.105 mm boreand 115 stroke
How on earth did You make Yours  and why did You change the construction as it was not the Hirth coupling that gave in?

Kind regards

Niels


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## ///

Neils, I was about to ask you how the hell all that worked.
I was trying to figure how to screw those items together tightly without a gap in the 'teeth'.
Then I saw the spline for a tool inside the 'bolt'* and had an '_ahhhhh_' moment which was very quickly followed by a '_huh?_' moment as I realised screwing the bolt thru would mate the parts but wouldn't actually tighten them.
But that moment was then soon followed by an '_*Ahaaaa!!!*_' moment when I inspected the 'bolt' more closely.
That system is pure genius!

*(please forgive my lack of correct terminology for items I've never seen before)


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## Niels Abildgaard

Hello Simon

It gets worse.

The later versions had an undivided crankcase  so assembly was one part after the other from one end ; six hardened main bearings,eigth side pieces,four conrod bearings and four conrods.
Crankshaft was first assembled without conrods and  given final grinding.The relative positions was marked on the parts; everything taken apart and then put together with conrods inside crankcase.
Common consent in danish airforce ,that opperated both,was that it was a better engine than the british hanging fourcylinders used for training aircrafts.

Kind regards

Niels


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## geoff_h

flyingtractors1 said:


> Not a professional machinist? I'd say a very expert one. Beautiful work. Ralph


 
Thank you, honestly I was 27 when I built this motor and had owned a lathe for 2 - 1/2 years. I had never used or touched any type of lathe or mill before I bought one. Never had any formal training, just had lots of questions and do alot of reading in places like this forum. Then spent even more time experimenting and making lots of scrap parts. 



Niels Abildgaard said:


> Hello Geoff
> 
> Enjoy pictures of full size Hirth 504 crankshaft parts.105 mm boreand 115 stroke
> How on earth did You make Yours  and why did You change the construction as it was not the Hirth coupling that gave in?
> 
> Kind regards
> 
> Niels


 
I did not use it on the other cranks that had 1 piece rod journal and throws because there was not enough space between the throws to installand tighten a bolt. It also would have been difficult to index the coupler on each half so the rod journals where perfectly aligned.

I made it by putting the part in a lathe chuck on a rotary table set horizontaly and at a slight angle to the table with a wedge. The crank is vertical. the table needs to be at an angle so the teeth being cut would have full contact from the od to the id. Without the angle as the adjacent teeth merged towards the center of the crank the height of the tooth gets smaller and the teeth form a concave shape if looking across the entire diameter. Used a drill point endmill to do the cutting. 

http://www.shars.com/products/view/19206/316__SE_Solid_Carbide_Drill_Mill_4_Flute_90_Degree_Point_


When I cut the teeth in each half I had not drilled the hole for the rod journal or cut the counter weight as I did not want to try and index the coupler to align the rod journal. Figured it would be easier to make the coupling then with both half&#8217;s fastened together drill the rod journal and cut the counter weight. I supported the bottom half of the crank drilled the hole and cut the counterweight then without moving the setup bolted the other half of the crank to the coupling and did the same to the top half.

It took a lot of time and thinking to figure out how to make it but once I had it figured out was rather simple to make.


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## barnesrickw

Making cams intimidates me without a CNC.


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