Author Topic: 1 eight scale 3HP buffalo marine twin  (Read 27546 times)

Offline mike mott

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1 eight scale 3HP buffalo marine twin
« on: December 11, 2014, 05:31:01 PM »
This is the beginning of my little engine. it is for a model boat, of an open launch built in 1909 for Andrew Mellon there were two launches made they are 19 feet long and are in the Muskoka Lakes area.

M Model will be 28 inches long and is built to a scale of 1:8 the hull will be built with steam bent ribs and Cedar planking. the engine is mostly brass and silver steel the bore is .312 and the stroke is .5

I have made a few mistakes in getting going on this engine, I started over three times and now things are moving along well.
Like all (prototype ) work designing something to represent a full size artifact in scale requires some creative solutions to parts which get very small.

I am familiar with a lot of modelmaking practices having done it commercially for a long time, but building a working engine is new to me. the little engine in my profile picture is a non working rotary engine for the model of the McCurdy Biplane that is in the Canadian Aviation Hall of Fame.

So I will add more information as I restructure the posts for this build

First a picture of my original concept drawing and a shot of the real engine and the real boat. The pictures of the engine and boat are Courtesy of the owner of the boat who has been very kind in answering a ton of questions about the boat and supplied me with a lot of pictures of the boat. the owner has given me permission to post the pictures.

mike


If you can imagine it you can build it

Offline b.lindsey

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #1 on: December 11, 2014, 05:43:06 PM »
That will be a nice project Mike. The size of the engine is getting pretty small at that scale...could (and I take it HAS)  presented some interesting challenges but I will be looking forward to it.

Bill

Offline mike mott

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #2 on: December 11, 2014, 05:49:05 PM »
Looks like I will have to use a picture hosting site to get the pictures in line with text rather than attachments at the end of the text.

First I decided that I needed an easy way to tap small holes, so I am now using collars over the taps and tap the hole right after drilling  by using these collars I can feel the cutting without unduly imparting too much pressure, this also helps to keep the mill quill lower that with adding any of the neat designs that I have seen for this task.



this is a large tap 6 x .5 metric. I am also using a lot of 0x80 which has its own collar.

I have also had to make a few cutters to achieve some of the different cuts I have needed, this one for the cavity in the top of the cylinder which on the full size engine is a cast space and contiguous with the rest of the cylinder, there was no way that I could make this engine that way with any hope of making it run so I have separated the top of the cylinder to be able to deal with valve ports and the water jacket areas.



This next picture shows the test cut for the combustion area that the mill will be used for the radius is .015"



will add further progress soon.

Mike
If you can imagine it you can build it

Offline tvoght

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #3 on: December 11, 2014, 06:33:23 PM »
I'm looking forward to watching your progress, Mike. The prototype engine sure is pretty.

--Tim

Offline Roger B

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #4 on: December 11, 2014, 07:16:58 PM »
Good looking build, I will be following along  :ThumbsUp:  :ThumbsUp:
Best regards

Roger

Offline mike mott

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #5 on: December 11, 2014, 07:20:50 PM »
The most tricky part was drilling the inlet and exhaust holes (still a bit gun-shy after the first mistake) I had to set the block up with a compound angle, for each hole the inlet ones on the outside and the exhaust ones in the middle. Now the hand work filing the surface shapes is under way. I also increased the size of the valve heads to .125 from .093 inches. The bore of the cylinders is reduced to 5/16 from 3/8ths in order to get more space for water circulation.

 I finished shaping the insert for the bottom of the jacket sweated it in place and bored the holes for the sleeves, also did some shaping of the top part of the cylinders. after making a second milling cutter for the curves on the top.



The stainless sleeves are reamed and fitted, they are a press fit. there are also a couple of flats filed into the bottom sides to prevent the sleeves from dropping by being keyed to the hole in the top of the crankcase.





one of the difficulties of working with the small sizes is that when drawing they are as big as the screen and it is a constant effort to remember the real size as I am drawing.  when an area looks about right and then I realize that the dimension might be only 1/64th I have to do some rethinking.





Mike
If you can imagine it you can build it

Offline mike mott

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #6 on: December 11, 2014, 07:52:41 PM »
I had to make another cutter to make the recesses in the main flanges
A close up of the new cutter, I needed a long reach with a small diameter cutting edge to fit next to the body of the case. it is hardened drill rod the diameter at the cutting face is .086" The bolt holes are .060 and the case it tapped ready for the 0x80 bolts.



I have  drilled the holes to accept the camshaft bearings they are larger because I need to be able to clear the raised cams.



 it looks like the gears for the timing are 64 teeth and 32 teeth respectively. I do not have dividing plates for my rotary table and so it makes sense to use divisions of 360 for making the gears. all the standard gears that are in the ball park for the diameters that I am locked into are not the correct ratio of 2:1. 64DP comes the closest.



I have decided to bite the bullet and make them to a DP of 75 which gives me 60 teeth and 30 teeth for the diameters that I need so now I also need to make the gear cutters for both sizes which means a number 3 cutter and a number 2 cutter. My 48 DP cutters which I made a few years ago are just too big.

There is a great article in the Model Engineer October 1 1971 issue by D J Unwin on how to make gear cutters with all the formulas for making them.

Set up the table of offsets to machine the curved inner surface of the oil pan, and after two hours of cranking the block back and forth the shape slowly emerged. I lowered the cutter .010" for each pass.  Next I will cut away the negative areas where the cranks will rotate and either side of the bottom of the crankcase then flip it over to finish off the bearing recesses. then a brass shell will get soldered onto the cross members, creating the hollow shape.



I made it this way because I was stumped as to how to get the inside shapes of the oil pan, I suppose I could have set up a boring bar and scooped out the recesses the only issue with doing it that way was being able to have an opening underneath the central bearing beam to allow the oil to move about in the bottom and equalize rather than being isolated to each recess. the other advantage to making it this way is is that I will be confident that the wall thickness will be consistent.

 The picture shows the material being removes that will become the hollow areas' some parts were machined by the numbers and the bulk was just milled away by eyeballing it.



Next the 1/32 thick sheet was annealed and curved over a steel bar.



It took a while to get it fitted cleanly, the flat area on the middle bearing wall is to allow the oil to pass through to equalize both chambers. After soldering them together I roughed out the half round bottoms for the crankshaft and drilled and tapped all the 0x80 holes for the studs.

I looked at all my stashes of steel wire and rods looking for some .060 to make the steel 0x80 studs from. I could not find any that was exactly .060" I then came across a most unlikely source, the re-bar ties left over from building the house just happened to be .060 the stuff threaded up a treat. had to make a small open ended wrench to get to the valve side because of the overhang.







first assembly of the 1/8th shaft to see the basic proportions.

 

Mike






If you can imagine it you can build it

Offline jschoenly

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #7 on: December 11, 2014, 08:03:53 PM »
There's a 1:1 Scale one of these engines for sale in NY right now on Engine ads:

http://www.enginads.com/classifieds/showproduct.php/product/106898/cat/8

Keep up the great work.  I really love seeing these posts!
Jared
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--- Model Engineering and Home Shop Hobbies in all Forms! ---

Offline mike mott

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #8 on: December 11, 2014, 08:24:23 PM »
Thanks Jared, my that engine looks to be in rough shape.

the parts for the crankshaft.
First I thinned down a piece of 1/8th gauge-plate to .094 then drilled and reamed 8 holes to 1/8th diameter.



Next I cut the piece into the four plates for the sides of the con rod bearings part of the crankshaft, I used a new blade in the jewelers saw.



A 1/8th set of dowels were slipped through the holes and the group were clamped in the vice and filed to shape.



Then polished up with 400, 600, and 1200 wet and dry sandpaper., I like it when I can get a reflective surface, then I know it is pretty smooth.



I turned up the .344" long 1/8 inch diameter shafts for the big ends of the con rods and did a dry assemble to see how the whole lot looks.



My silver soldering was a great success..... not so with the clean up  made the classic mistake of beginning to cut out the wrong piece



I went ahead and cleaned it up because after letting the universe know what a silly move it was with a little colourful language, I wanted to see how the shaft fit and can also use it as a placeholder to test fit the con-rods and pistons knowing that I do have to build a new one.



The following sequence shows most of the steps and elements in the stop cocks.
First picture shows some 1 inch tapered clock pins cut to length prepared for soldering



I am using tapered clock pins for the stop cocks







In the palm of my hand for scale



next I will add the section on the reverse gearbox.

mike


If you can imagine it you can build it

Offline mike mott

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #9 on: December 11, 2014, 10:33:45 PM »
 I had some gear-heads from some pretty old servomotors full of very tiny gears and pinions all with micro ball races. I stripped these apart to see if there was anything that I could use to fabricate the revers mechanism with.


With a bit of careful re-machining a couple of pinions and one of the main drive gears I think I will be able to pull this off, the progress so far.



The entire gearbox is covered with a protective shield (no doubt to prevent feet or clothing from getting snagged) on the full sized boat. So I am working with some drawings from the day showing how these gearboxes worked, and fitting in the gears that I have to make the mechanism work.

The originals used a series of clutch plates and the forward /reverse lever either caused the outer casing to be rigid hence letting the internal planetary gearing to impart a revers motion to the prop shaft, or they clamped the prop shaft and casing together causing the whole body to revolve giving a forward motion. The vertical position of the lever caused a neutral position for the prop.
 
Here is a drawing of the progress of this design so far, I have re-machined the pinions already the shafts were pretty hard and it was nerve wracking to say the least.



I am made the outer casing of brass, this will allow the gears to seat in brass giving a quasi bearing, similar to an old clock where the gears are steel and the clock plates brass.





All dry assembled I also spotted three holes for some 0x80 bolts to ensure the casing and cone stay together and do not move relative to each other. I did check the reverse by rotating the prop to see that it actually worked to this stage. still a long way to go to get it all mounted and working in situ.



The gear for the prop fits through the end that will be shaped with the cone recess. this short video shows the revers mechanism in operation.

I have now started to make a new gearbox with some 48DP brass pinion wire which has 10 teeth, the shafts will be .062 wire, I have made this decision because the very tiny gears are an unknown quantity for me, even though they do work.

It did work though so I am pleased about that. here is a short video.
   
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mike
If you can imagine it you can build it

Online Dan Rowe

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #10 on: December 11, 2014, 10:48:23 PM »
Nice work on that gear box Mike, It looks like you have plenty of spare parts for the first design so it might be useful for some other project.

Dan
ShaylocoDan

Offline Roger B

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #11 on: December 12, 2014, 07:30:58 AM »
Magnificent work, and so small  :praise2:  :praise2:
Best regards

Roger

Offline mike mott

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #12 on: December 14, 2014, 06:11:31 AM »
Dan , Roger  Thanks for your kind remark.

I have reworked the gearbox now for the third time regarding the casing and with these small gears the precision is critical I have discovered.

here is a video of the new gears and casing.


Everything runs very smoothly now.

I followed the formula for determining the pitch circles and found that things were a bit tight, so added .005" to the circle and it made a huge difference.  this is probably because I am using some 48DP pinion wire for the whole mechanism to keep things simple.

Mike
If you can imagine it you can build it

Offline fumopuc

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #13 on: December 14, 2014, 08:05:37 AM »
Hi Mike, from my point of view, this little gear box is a masterpiece.
Kind Regards
Achim

Offline PStechPaul

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Re: 1 eight scale 3HP buffalo marine twin
« Reply #14 on: December 14, 2014, 09:21:33 AM »
Quite impressive and excellent work on such tiny parts. I'll be following with interest. Thanks for sharing your accomplishments.  :praise2: