# 1:8 scale 3HP buffalo twin marine engine



## mikemott (Oct 27, 2014)

This is the engine that I propose to build the bore is .375 inch and the stroke is .5 inch.
 I am in contact with the owner of the boat and engine, and am building the boat also in 1:8th scale, the boat is called Skipjack and is located in the Muskoka region of Canada







Once I get comfortable with how this board works I will be able to organize my posts clearly. 

Michael


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## GailInNM (Oct 27, 2014)

Michael,
From reading your other posts and looking at your web site, you certainly have all the skills and and equipment necessary to do a successful build of the engine you propose.

If you have any photos or links to the prototype engine I, and others, would be interested in seeing them.

I have built a pile of engines in the 3/8 X 1/2 inch bore stroke configuration and have learned a few things about them. I am currently building a few more to power some more 45mm (Gauge 1) locomotives.  If I can be of any assistance to you please ask.  

Gail in NM


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## mikemott (Oct 27, 2014)

Hello Gail, thanks for the compliment. I am waiting for the owner to get me more information about his particular engine, in the meantime I have been gathering as much information as I can about the early small Buffalo engines, the website Old marine engine has by far the most information that I have been able to find.This link to the section on The Buffalo engines, is all I have at the moment.

I have begun making a concept drawing of the engine, it takes a bit of time to prep them to post because I have to change them from my old version of Autocad LT200 to another program that can save to PDF or Jpeg.





the drawing is full size the cap screws for the con rods are 1x72

Michael 

View attachment engine.pdf


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## GailInNM (Oct 27, 2014)

Michael,
Concept drawing looks good.  Thanks.
For the benefit of other viewers here is a direct link to the Old Marine engine website, and the photo from it.
http://www.oldmarineengine.com/history/Buffalo/Buffalo.html









Since you are new to HMEM you may not have seen the following threads. You might find them useful for design and construction ideas.

First is Kel's build of a 4 cylinder version of Tiny.  It is overhead valve, as opposed ty your side valve, but is water cooled

http://www.homemodelenginemachinist.com/showthread.php?t=10240

Second is Bills Briggs & Stratton scale model, which is side valve.

http://www.homemodelenginemachinist.com/showthread.php?t=5343

I too run older versions of ACAD.  For me the quickest way to generate JPG's and PDF is to plot them within ACAD and then scan them.  I have a modern scanner that will output JPG or PDF quickly to a file that I can then publish.  Has the advantage that I can also scribble notes on the plot with a pen that then show on the published item. 

Gail in NM


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## mikemott (Oct 27, 2014)

Gail thanks for the tip regarding the pdf's and Jpegs I have done that but forgot. I will check out those other builds.
Michael


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## mikemott (Oct 29, 2014)

One of the issues that I am facing is the fact that the cylinder body and head appears to be one piece,. a couple of questions come to mind and I have been searching through the various sections looking for an answer but have not yet satisfied myself of the answers.
The first one is that it appears that the valves are inserted through the top of the cylinder then capped with some hex "bolts"
This also appears to be the same with the spark plug.

One thing I have considered is to basically build an inner core and an outer shell to form a cavity to accommodate the water cooling. 
Does this sound like a good or doable idea?

Michael


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## Jasonb (Oct 29, 2014)

Quite a common way to do things, make the outer casting and bore it out to take separate cylinder liners. You can open out the central part of teh bore to form a waterspace. Or fabricate a "box" on have holes top & bottom for the liners.

This launch engine build may give you some ideas

http://www.modelengines.info/naphtha/Main/


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## mikemott (Oct 29, 2014)

Jason Thank you for the link, I was smiling all the way through the pictures of the fabrication of the crankcase and cylinder case. I have been thinking about building the crankcase the same way.

michael


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## kf2qd (Oct 29, 2014)

A little off topic, but...

PDFs can be created easily using PDF Creator. It installs as a printer driver and can produce a PDF from any program that prints. No need to scan it after printing it.

There is also a PDF Creator Plus but that is a for money program.


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## mikemott (Oct 30, 2014)

After some long sessions at the drawing board and reading through a lot of threads pertaining to the very small engines particularly the "Tiny" thread. I have drawn a slightly more developed plan of the 3 HP buffalo engine.
The general arrangement is obviously not complete yet, any feedback regarding my direction so far will certainly help me continue with the design. 

These drawings show my thinking so far, normally I would be racing away cutting material but in this arena I am still climbing up the learning curve.

Michael 
















View attachment Buffalo 3HP sheet 1.pdf


View attachment Buffalo 3HP sheet 2.pdf


View attachment buffalo 3HP sheet 3.pdf


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## mikemott (Oct 31, 2014)

This evening I did a bit of test machining of the top piece of the cylinder head. It still need some finishing as it is a bit rough yet.

The cavity on the top side will get a cover sweated on and the plug body will thread through the cover plate.
the 4-48 threaded holes will allow the valve rods to be inserted so they can be seated. after they are placed then the plugs can be threaded in.

The top piece will be sweated onto the lower part which will then form the whole cylinder assembly.

Michael


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## mikemott (Nov 3, 2014)

Pressing on the last two days have been taken up machining more of the cylinder head.
I made a couple of support blocks to fit inside the lower section of the cylinder so that I could finish off the outer shell and ports. they are set up so that the 10-32 screws also screw into the spark plug threaded section of the top part.

















Next some careful filing to bring the flats to the rounded shape of the water jacket.









After a lot of hand work the shape is getting closer to what I think looks like the original. The liner is just a test piece.

















The valve stems are going to made from some robust sized sewing needles the diameter is .046









It is a bit of a surprise as to how long this small machining takes. The most challenging part was the inlet and outlet ports, because the amount of material is very limited.

Michael


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## mikemott (Nov 3, 2014)

I am seeming to have difficulty adding the pictures inline without having a string of attachments at the end?

Michael


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## mikemott (Nov 4, 2014)

after removing the support plugs I noticed that I had in fact cut into the water jacket with the port drill.






I decided that I could sweat in a plate to block the holes so machined up a sleeve then parted off two rings and cut them to fit into the water jacket space.





Also added the inlet for the water between the exhaust valves, that way there will always be fresh cold water at the hottest part of the cylinder head.





the holes for the cylinder liners still need to be reamed 13/32 and a plate made for the inspection hole in the jacket. 








Michael


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## Herbiev (Nov 4, 2014)

Looking great Michael. Great pics.


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## mikemott (Nov 5, 2014)

Herbie thank you.
After spending most of yesterday contemplating what I have done so far, I have made the decision to start over, I have worked on this concept model long enough now that the little changes that I kept making mainly to deal with the water jacket were not going to satisfy my mind.

In order to maintain the external appearance of the engine and to provide adequate water circulation, and to keep the wall thicknesses withing some reasonable limits I am changing the bore to .3125 bore with the same .5 inch stroke. and increasing the diameter of the valve heads to .156 changing a few of the assembly methods.
I am presently working on the new drawings and preparing the blank pieces of metal.

Michael


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## mikemott (Nov 8, 2014)

After a lot of long hours machining and then starting over, then starting over for a third time I am finally on track. I also decided that I needed to make the bolting flange integral to the rest so I will only need to add an oval plate with two holes for the bottom of the cylinder liners. 








The holes through the side wall were bothering me too much, so started again, Disaster struck quickly because I datum-ed from the wrong side on the mill and machined a nice swath right down the side of the water jacket.






Pictured is the third cylinder under way and going pretty smoothly considering the previous starts.

I made a change to the bore to 5/16 kept the stroke the same, this will give me quite a bit more space for the water flow through the top of the engine.





Again the most time consuming part was the inlet and outlet ports, All my machines are manual, and I spent the better [part of yesterday fitting a 6 inch dial vernier to the fore and aft motion of the table, This made the set up so much easier than readjusting my 1/2 inch travel dial indicator.

Michael


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## johnmcc69 (Nov 9, 2014)

Nice work Mike! I admire your persistence. Looking good.

John


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## Brian Rupnow (Nov 9, 2014)

A very interesting build. I will follow this.---Brian


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## mikemott (Nov 12, 2014)

Started to work on the new head part today, I also figured a simple way to use the mill to tap the spark plug holes without having to change the set up from drilling. I put a couple of 1/16th flats at right angles to each other close to the threads of the tap and slipped  a 1/2 inch thick aluminum disk with a couple of set screws at right angles to the lower position and then used the drill chuck as the guide by finger tightening the tap in the chuck lowering it to the work and then just releasing it enough so that it slid out toward the work.





The tap is a 6 x.05mm it was the finest thread size in the range that I wanted for the spark plugs.

I also made a small .155 inch end mill with a .015 radius at the face so that I could cove the space in the combustion chamber a little. it is simple but works well enough at the small scale I am working with. I turned it up out of some drill rod then shaped it on the large diamond wheel grinder that was surplus from an opticians lab.







Made a test cut to check that it was going to work.




There is still a lot of hand work left to finish shaping but I am pleased with the progress.









Michael


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## mikemott (Nov 19, 2014)

Further progress on the cylinder head the curved top required a new cutter 





Some of the shaping to the top has been started with files, and the bottom plate is fitted to the water jacket.
















The liners are reamed and a press fit.





The bottom of the liners are flattened on both sides to ensure that they stay in place, they will slide fit into the top of the crankcase  





The start on the crankcase.





Michael


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## mikemott (Nov 22, 2014)

After doing a few experiments with the valve stem springs and keeper, I have increased the diameter of the valve-stem to .060" inches leaving the narrow section for the keeper at .046"

This was one of the early tests using the .046 stem the spring is .078 in diameter and the wire is .011. the keeper was a bit fiddly. I can safely increase the stem diameter and still maintain the .078 diameter springs the length of the springs are ..259" presently I am learning how to wind them so that there is a double coil at each end with the wider spaced turns in between. I have found that it is better to make them this way rather than winding a length then stretching it out to form the compression spring.






The crank case is progressing well at this time also. there is a fair bit of hand filing to finish up the corners because I do not have the requisite end mills to do all this work on the milling machine.






The next picture shows the flats on the sides of the liners slipped through the top of the upper part of the crankcase.





Michael


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## mikemott (Nov 24, 2014)

Some further progress on the crankcase I ended up making another cutter to make the recesses on the bolting flange.







This picture shows the recess right off the mill







The holes for the camshaft bearings and the back opening in the case.







Still need to finish filing the top part.







A close up of the new cutter, I needed a long reach and small diameter, the diameter is .086, it is a simple single face-cutter design easy to make out of drill rod.







Michael


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## mikemott (Nov 27, 2014)

further progress the oilpan and lower crankcase are a composite of a machined piece and some bent sheet.





machining away the areas that will be hollow





fitting the parts the central cross member is relieved to allow the oil to equalize.





test look at overall assembly





more





last one for now.





Michael


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## mikemott (Nov 29, 2014)

A milestone today I roughed in the main bearings.

















I am taking some time deciding whether to fabricate the crankshaft or machine it from some bar.

Michael


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## Cogsy (Nov 29, 2014)

It's looking really nice so far. You do great work.


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## GailInNM (Nov 29, 2014)

Michael,
You are doing a marvelous job on this engine.  Hard to believe the amount of progress you have made in only one month.
Gail in NM


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## mikemott (Nov 30, 2014)

Al and Gail thanks for your kind remarks, it means a lot from such accomplished modelers.
began work on the crankshaft, I decided to fabricate it from gauge-plate and drill rod

















I test fitted the parts together and will get them accurately aligned before silver soldering the lot together then cut away the two parts of the main shaft between the con rod shafts.









Michael


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## gbritnell (Dec 1, 2014)

Hi Michael,
Excellent work on your engine. It's always nice to see something unique being built . As I'm sure you have read on many other posts one of the most important things it to get the valves sealed well. This is one of the most critical processes in getting an engine to run well.
Keep up the good work.
gbritnell


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## mikemott (Dec 2, 2014)

George Thank you for your encouraging comment.
I silver soldered the crankshaft together today and it was a success as far as the soldering goes





I used a couple of pins with the diameters set to the spaces between the plates the silver solder was preplaced by bending some fine strips around the shafts on the outsides of the bearing areas 





Cut out the parts not needed, and began to make the classic mistake of cutting out the wrong part on one of the cylinders so this crankshaft will have to become just a placeholder which I can use to fit and work the con rods and pistons. To say I was gutted would be an understatement because I had just finished saying to myself "don't cut away the wrong bits" I went ahead and finished cleaning it up so that I could use it for test fitting purposes knowing that i now have to make a second shaft.





I was pleased that it did not warp and when fitted into the bearings spun nicely between my fingers.





Next to work on the con rods and pistons.





Michael


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## idahoan (Dec 2, 2014)

I'm enjoying the progress on this interesting little engine. Sorry about the mishap on the crankshaft; I'm sure the new on will be just as nice or better than the first one.

Thanks for taking time to post your progress.
Dave


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## mikemott (Dec 5, 2014)

Thanks Dave, Glad you are enjoying the build.
I took a break from the crankshaft for a change of pace and built a couple of priming pots for the top of the cylinder head, these were really fiddly things to make but they will work, I used some tapered clock pins for the taper part of the body.





the tiny handles are silver soldered.





overall shot





This is quite small





I think that the next engine will be a little bigger.

Mike


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## mikemott (Dec 7, 2014)

I made some new stop cocks and finished shaping the top part of the cylinder head .









I am pleased with the way it shaped up.





Michael


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## Dan Rowe (Dec 8, 2014)

Hi Mike,
I just found this thread and enjoyed reading it through. Nice work I will be reading your progress.

Dan


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## necchiom (Dec 8, 2014)

Impressive! With compliment.


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## mikemott (Dec 9, 2014)

Hi Dan nice to have you along, Moshe thanks 

I am working with some very small gears from an old Edison servomotor to build the reversing mechanism this first picture shows the small gears for scale and possible use.





The next picture shows the progress drawing incorporating the gears I have already resized the lengths of the pinions, today i am going to make the casing.





Michael


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## mikemott (Dec 9, 2014)

some further progress on the gearbox.





















There is still a fair bit to do to get it all working smoothly on the engine it does work though with respect to the reverse so now the mounting will be sorted and the cone and lever mechanism.

Michael


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## kuhncw (Dec 9, 2014)

Mike, you are doing beautiful work and this is a great thread.

What is the surface with all the holes that you use when silver soldering?

Regards,

Chuck


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## mikemott (Dec 9, 2014)

Hi Chuck , thanks for the kind remarks
The block with the holes is a soldering pad used by jewelers
https://images.search.yahoo.com/yhs...+soldering+block&hspart=mozilla&hsimp=yhs-001

michael


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## mikemott (Dec 17, 2014)

I have been working and reworking the gearbox, I have made three of these now and the final one has some 48dp pinion wire for the gears getting the band clamp to work properly has also taken a fair bit of fiddling and filing.









This is version number 2 of the band clamp, the lever has one side angled to match the clamp so that as it rotates forward it releases the clamp. When it is finished the clutch will also engage at the rear of the gearbox causing the whole gearbox to rotate with the crank and prophaft locking the planetary gears inside.






The clutch is being made with the top of an allen head cap screw.












Also made a flywheel 

Mike


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## mikemott (Dec 18, 2014)

Added the clutch.





Mike


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## mikemott (Dec 24, 2014)

the clutch is working now and I have begun work on the pistons.













jig for drilling wrist pins and for machining the inside.





















time for Christmas stuff now.

Mike


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## mikemott (Jan 1, 2015)

A bit more progress on the con rods A small holding fixture to work on them was needed because I do not have an indexing fixture for the chuck.











I marked the area that still needs to be removed, the bolts are temporary just for the machining.







I used the lathe as a shaper for working the top end of the con rods, they are held on a tight slide fit pin, and I took .002" cuts with a round nosed bit held sideways in the tool post, I have cut gears this way in the past. it is slow but works well.











The result after the initial shaping.







then a bit of work with the rat tail file 







after the brush with a hand held brass wire brush, it is ready to mount.







The  con rods are now attached







Mike


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## mikemott (Jan 2, 2015)

More progress on the rod

split and soldered ready to turn





bored out to 1/8th





parted off





split ready to place in the big end





hard button to act as guide when filing to final shape





it fits













Mike


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## mikemott (Jan 6, 2015)

I have got the pistons in and moving smoothly now.

The next work has been on the camshaft, the first attempt ended in a costly mistake by grabbing the wrong handle on the mill I turned the table handle instead of the rotary table handle.





I changed course and decided to use the lathe as a shaper. I made the indent to lock the spindle using the main wheel of the back gear set up on the Myford.

















only .008" to go after cleaning and polishing I will bore and ream to .125 then drill for the locking pins and then part off and harden the cams, when I do the final positioning I will use some loctite then pin then to the shaft.

Mike


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## mikemott (Jan 11, 2015)

After finishing the camshaft lobes i made some cutter for the 75DP timing gears





Then set up the rotary table in the vertical position to shape the gear blanks.









The quill and cutter were locked because I could only hold the cutter in my drill chuck and I will not use it for milling as it is dangerous.





back to the lathe for finish work





the gears meshed perfectly.









The gear is actually on backwards I need to still turn the eccentric for the water pump





Mike


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## mikemott (Mar 22, 2015)

I have been busy on the engine working on the water pump and associated piping. I ended up making a 6x80 tap to make a couple of unions for the piping.

















The small tubes were bent with some home made tube benders the tube was annealed and filled with some styrene rod bent then re heated to burn out the styrene, this worked very well.





next I tackled the spark plugs I cut a couple of 1/8th square strips of a corian cutting board.





turned them down to .078" and drilled a .028" hole for the music wire electrode.





The body was made from a piece of Allen head key that was annealed it was 9/64 across the flats





I tested the plugs with a pietz cristal and they seemed to spark OK.
After filing and fitting the water cavity cover the circular plates have been turned from 3/8 bar stock.





some 00x90 round head screws were machined up from some 00x90 hex head bolts , the stock 00x90 round head screws were too large in diameter.









and to bring it all up to date the excentric cam parts are now being made from some stainless.













That is all for now 

Mike


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## deverett (Mar 23, 2015)

Why can't I see any pictures in this thread?
Other threads e.g. the Merlin build show the pictures without any problem.

Dave
The Emerald Isle


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## mikemott (Mar 23, 2015)

Dave I don't have an answer the pictures are linked from Photobucket. they are in "my30mm" under buffalo engine, it is public.

mike


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## mikemott (Mar 26, 2015)

A bit more work, 

















Mike


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## mikemott (Apr 2, 2015)

I have been working on the valves 





I used the flywheel as a weight for lapping the valves.













then parted off the valves from the stock.





cleaned them up ..





next on to the lifters.





mike


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