Barstock single cylinder in metric

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coulsea

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A couple of years ago I built my first IC engine and my son really likes it so I thought that I would make him one for Xmas.
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There are no plans, I just made it up as I went along. I hope to make a few improvements to fix some of the things that didn't turn out as well as I would like.
Some of the basic specs are: 21mm bore with O ring, 36mm stroke, 8mm fabricated crankshaft, 10mm plate crankcase, 50 mm cylinder, ball bearings on crank and big end.
This would be a good first engine for anyone who wants to build along with me because I don't care too much about accuracy, if one bit is the wrong size you just change the next bit to suit. (Cylinder needs to be close to o ring size). build it in imperial if you want.
 

dethrow55

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hello that a good looking engine . i will follow your build newbie to ic engines .:cool:
 

coulsea

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I have been building this for a week now an d haven't posted anything but it is getting hot now (40 C) so some computer time might be in order.

I started with a length of 100mm x 10mm aluminium and cut off 3 pieces 60mm long. I cut over length to alow for milling the 3 pieces together to make them all the same size and they ended up 61mm. The height of the crankcase sides depends on the size of the flywheels used, I am using 100mm diameter so with the centre of the flywheel level with the top of the side there will be 10mm below the wheel

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The 3 pieces were then screwed together, the lower screws are centred 6mm from the bottom and the upper ones 45 from the bottom. the height of the upper ones is important as you don't want them to foul the cylinder which is 50mm. there is also a hole drilled in the centre of the front plate at the same height as the side plates, giving the centre of the cylinder the same height of the centre of the crank.


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the front plate was then trimmed on the rotary table to give the top edge a curve, you could just take a bit off each corner if you don't have a rotary table.
 

Cogsy

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This should be an interesting build - I'll be following along. One thing I've learnt (the painful way) about flywheel to base clearance is to leave enough space for a finger to pass underneath when you're trying to hand-start it.
 

coulsea

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The next step was to make the bearing caps. I am using 19mm od 8mm id bearings so I cut off a 20 mm strip of the 100mm x 10 mm aluminium, by the time I cleaned it up it is 19mm. cut off two pieces 40mm long and drill two holes 30 mm apart, mine ended up 39mm so each hole was 4.5mm from the end, the main thing is that they both look the same. I used a 12mm end mill to countersink the holes just for looks. I am using 4mm cap head screws.
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I then drilled and tapped the holes in the side plates, they were supposed to be 55 and 85 mm from the cylinder end but I use a 6mm rod to zero the DRO on the end of the plate and I forgot to allow for the 3mm to the centre of the rod so mine are 52 and 82.

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with the end caps bolted on a 13mm hole was drilled, level with the top of the side and in the middle of the bearing cap. an endmill was then used to enlarge the hole to 19mm but only to a depth of 8mm from the inside of the plate, this will leave a 2mm flange on the outside to stop the bearing from escaping. I didn't have a 19mm end mill so I used a 3/4 which is a bit bigger and them filed a bit off the bottom of the cap to get a snug fit. when using small bearings be careful not to put too much pressure on them because they will distort quite easily.


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coulsea

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The crankshaft is the next job. cut off two 50 round steel discs about 6mm thick and clean up on the lathe and drill a 8mm hole in the middle. the spacer in the chuck is a split collet from another job.
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I then used the mill to drill the 6mm bigend hole 18mm offset from the middle and chain drilled the bits to be cut out leaving 17mm wide up to the bigend and the balance weights starting 5mm below the centre hole. cut out and clean up on the mill.

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Assembly is done in the lathe. Each side of the crank is 80mm long, put the shaft in the lathe chuck with enough sticking out to go through the crank web and locktite together, use the tailstock to get the web straight. when the locktite is dry drill and pin (2mm) with more locktite.

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The bigend uses a bearing 6mm id 12mm od with a brass spacer on each side to keep the bearing in the middle.
Put one side of the crank in the chuck and the other side in the tailstock and line them up by turning the chuck by hand.. I locktite one side of the bigend shaft and and let it cure before doing the other side because it is easier to line up one side at a time especially if it is hot and the Loctite goes off quickly. It can be a good idea to wait until the Loctite has properly cured before pinning.
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if all went well you should now have a straight crank shaft. make a couple of spacers to keep the crank on the middle of the main frame, 1mm or so slop is good, don't make it a tight fit.
 

coulsea

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I haven't been posting as I have been building but I have been taking photos so its time for a catch up.
the gears are next, when I first started making engines I couldn't find anywhere in Australia to buy gears at a reasonable price so I decided that I had to be able to make them. there is a lot of confusing maths involved in making gears but I finally worked out that if you use involute gear cutters the only thing that you need to know are the size of the blank and how deep to cut. to be able to make a 20 tooth and a 40 tooth gear you need 2 cutters (module 1) which will cost $25 for both from ebay, they might be cheap Chinese rubbish but for brass gears they do the job. I use a 6 inch vertex rotary table.

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the 40 tooth gear and the cam are one piece, the gear part is 42 mm diameter and the cam part is 28 mm both 5 mm thick. to make the cam I use the rotary table and a boring head in reverse.

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set up the boring head so that it cuts on the inside of the circle a larger diameter that the cam blank and slowly cut into one side, I cut about 0.25 mm at a time by moving the mill spindle down and then up, move the table across and repeat. when you have taken 3 mm off as in the picture then turn the rotary table one turn of the handle and take another cut, repeat until about 8 mm has not been cut and your cam is finished.
If none of that makes any sense have a look at this video by chuck fellows
 

coulsea

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I missed a photo on the last post so here is a pic of the finished cam
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to mount the cam on the frame there are calculations to work out how far apart the gears are supposed to be but I just put the frame in the mill vice and the shaft that the cam is mounted on in the chuck and adjust until the gears are running well together, this allows for any errors that occurred when making the gears.
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the shaft for the cam is 6mm threaded 3mm all the way through and is fixed to the frame with a 3mm screw and a washer on the outside again held on by a 3mm screw, there is also a brass washer between the frame and the gear.

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coulsea

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the last post had a photo with the cylinder attached and I haven't covered that yet so here goes.
I was going to make the cylinder from 50mm cast iron but couldn't get any so it is made from 50mm aluminium with a cast iron liner.
the liner is made from 35mm cast iron with a 34mm flange 3mm thick on the head end then 28 mm for 62mm and the 5mm that goes into the frame is 25mm giving a total length of 70mm, it is bored out to 20mm. the aluminium part is 62mm long bored out to 28mm and a recess on the head end to take 1mm of the 34mm flange in the liner. the fins are 4mm thick with a 4mm gap and 4mm deep except for the first one on the head end which is only 2mm deep so it doesn't expose the head bolts. the liner is held in the aluminium with Loctite.
it all bolts to the frame with 4 4mm bolts on a 36mm diameter bolt circle.
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the bore had a good finish after boring so just had a quick rub around with some fine sandpaper, there is no need for any lapping or polishing.
 

coulsea

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just a couple of additions to the last post.
the bolt holes in the aluminium part of the cylinder should be done first, I use the DRO on the mill to drill the bolt holes, with a centre mark done in the lathe the four holes were drilled and tapped on an 18mm radius. the same was done on the frame end plate and then the centre hole enlarged to 25mm.

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coulsea

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the next part is what I call the cam follower and is just a lever that is moved by the cam and will have the push rod attached,
it is made from aluminium and in hindsight should have been longer so that the pushrod could be attached above the roller instead of below it.
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milled 8mm off the side leaving a 12mm square on the end. the 8mm will clear the 5mm thick gear and 1.5mm washer.
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shaped the end square into round on the rotary table
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made the roller and shaft to fit into a recessed hole, the shaft will be held in place with a grub screw
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positioning so that the roller is level with the centre if the cam and the lever tilts back on the low part of the cam and forward on the high part of the lobe.
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it is held onto the frame with a 6mm shaft internal threaded 3mm on each end similar to the shaft for the cam gear. pictured sitting on top of the lever is the outside spacer/cap that is custom built to make up for the fact that the shaft is a bit long. I normally make the shafts too long because I am making it up as I go along and don't know what washers I will use or even how big the part will end up.
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in this last photo you can see that I milled a couple of mm from the part between the pivot and the roller, there is no reason for that but it adds a bit of detail to the part and makes it look more complicated than it really is.
 

coulsea

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The conrod is next. it is made from aluminium 120mm long 32mm wide and 10 mm thick.
the first step is to drill and thread for the big end bolts, I am using 3mm cap head screws 20 mm long. next cut off the bigend cap 10 mm long and screw it back together, it is good to centre punch a couple of marks because unless your cut is perfect the two bits will only go back together one way. you will end up with something like this.
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the big end is a 12mm bearing that is already on the crankshaft so I drilled an 11mm hole and then enlarged the middle to 12mm on the rotary table, because I don't like taking the chuck off the RT I made a plate full of threaded holes that can be used to clamp parts onto.
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I then drilled the little end 4mm hole 100mm from the centre of the big end and milled 10mm off the top and bottom of the conrod leaving 10mm on either side of the big end centre. for shaping the conrod I use a jig which is a scrap piece of metal that has 6mm threaded holes, I drilled and threaded a new 4mm hole 100mm from an existing 6mm hole to bolt down the conrod straight with the vice and the another 4mm hole offset by 2 mm from another existing hole, that will hold the conrod at an angle to give the tapered top and bottom edges.
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the little end was rounded off on the rotary table and cut into the sides 1.5mm, then back to the jig to take the rest of the sides to the same level. there was a bit of back and forth to the rotary table to get it right.
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the offset hole was then used taper the sides
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and the straight hole used to put a grove down the miidle, some more rotart table work to shape the little end to blend in with the rest.
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the final bit was rounding off the big end just to take away that square chunky look. note the 80mm 4 jaw chuck in the 3 jaw chuck, probably not recommended but it saves changing chucks for a little job with light cuts.
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the conrod needs to be small enough that it will clear the back of the cylinder, my taper was 7mm at the small end and 10mm at the big end and 7mm wide and it did touch the cylinder liner, a bit more taper into the cylinder and a file on the conrod fixed the problem.
 

coulsea

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I said earlier that the bore was 20mm but it is actually 21mm because that is the size of o ring that I have. I normally use a square collet block to hold the piston while slotting the hole down the middle and then lay it down in the vice to drill the gudgeon pin hole but my biggest er32 collet is 20 mm so it wont work, in the past I have had a 20mm spigot on the end of the piston but I had parted the piston of without thinking about it. so to get around this I drilled the pin hole and then put it in the rotary table with a rod through the hole to line it up before slotting out the centre id the piston.
the piston is 21mm long, 20.8 mm in diameter the hole for the pin is 12mm from the top and the top of the o ring is 3mm from the top. the o ring is 3mm section so the ring groove is a bit over 3mm wide and deep. I have my o rings a loose fit in the groove. I have seen lots of discussion on proper o ring fit, much of which is based on different applications, this works for me, I have some where the groove ended up far too big and they still work.
I burr the pin holes with a cold chisel to keep the pin in place.
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coulsea

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the flywheels are 100mm diameter and 15mm thick
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to get the recess on each side the same I mark each side of both flywheel right at the start, first the outside groove on all 4 sides (2 flywheels) and then the inside groove, this saves the problem of coming back to do the second flywheel a few days later and trying to work out what you did on the first one.
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take 3 - 5 mm off each side depending on how mush time you want to spend on it.
I am using taper locks to hold the flywheels on because I have never had much success with grub screws.
the taper locks have about a 6 degree taper, I say about because I am not going to spend the time using a dial indicater to set it exactly, the problem with this is that everything has to be done on the one setting and you will probably never make another one the same.
I start by turning a piece of steel to 25mm and then down to 11mm for 8mm
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set the top slide to 6 degrees and with the lathe in reverse machine the taper on the back side of the part until lever with the flange.
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cut it off so that the flange is 3mm thick and drill 3 holes to bolt to the flywheel, drill and tap another hole between two of the others to be able to jack the two bit apart for when you want to remove the flywheels. when you have finished both parts move on to the fly wheels, this time using the lathe in forward and cutting the taper in the front side of the hole
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take light cuts continually checking the fit of the other part and stop when you have about 3mm gap between the flange and the flywheel, the pen mark on the tool is at 10 mm to allow the 8mm long taper on the other part lots of clearance when compressed.
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drill and tap the holes in the flywheel before you cut the taper because you have a nice straight hole from which to measure. you can now but the split in the flange and taper and bolt it all together.
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coulsea

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just a quick note about the con rod piston length. this one ended up with the piston being 9mm down the bore at TDC, this will give it plenty of compression to run. the piston is very easy to make and is an easy way to change the compression ratio. by my calculation this one works out to 5:1
 

coulsea

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The head is made from 50mm cast iron 20 mm thick with the valve guides being part of the head.
10 mm is lathed down to 20mm diameter and the 4 x 4mm mounting holes drilled, these are on a 38mm circle to go outside the 34mm flange on the cylinder. it is then mounted on a square plate to be able to put it square in the mill vice.
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The valve guide holes 4mm down and 4.5 across from centre
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then excess material milled away.
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next onto the rotary table to get the valve guides round
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back onto the plate at an angle to drill the plug hole (1/4 32)
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the holes out to the side for the carb and exhaust are 5mm to the centre of the valve guide and tapped 6mm at the ends. the carb will be horizontal and the exhaust is out the bottom to the side a bit.
the holes inside the head are 4.5mm in as far as the holes coming in from the sides and then the valve seats are cut with a 45 degree countersink tool.
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coulsea

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the valves are made from 6mm rod 30mm long with the stem lathed down to 3mm and a 45 degree face on the head.
when machining the stem I do it in stages to try and reduce flex.
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the springs are from a generic kit from ebay with the exhaust spring being a lot firmer than the inlet. the inlet spring takes a bit of trial and error to get the correct length even after you get it to run it may still need a bit of fettling. they are held together with a brass collar that has a step to locate the spring and a depression to locate a wire pin that goes through a hole in the valve stem.
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the rocker post screws in to the head inline with the valves and as close to the edge of the head as is practical to thread a 4mm hole. the rocker is equal length on either side of the rocker post. the ratio of length of the rocker on either side can change the effect of the cam lift, we have 3mm lift on this cam so allowing for a bit of gap and equal rocker will give at least 2mm lift which should be enough.
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the exhaust is 6mm copper tube soldered to a brass thread and then nickel plated.
the valves are lapped in using some fine diamond past and the head gasket is made from printer/photocopy paper soaked in oil, this one was a letter so you can see writing on it.
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coulsea

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coulsea

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the fuel tank is a 20mm brass tube with brass end caps, 6mm screw filler and an outlet in the bottom soldered together with stay bright tin solder. it is mounted to the frame with a P shaped aluminium bracket with a grub screw to hold the tank in place.
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coulsea

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The push rod attaches to the rocker with a clevis an into a slot in the cam follower, it has a kink in it to line everything up.
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The ignition is a rcexl cdi with a hall sensor trigger. the hall sensor is glued to an aluminium bracket which is like a circle with a tail that supports the wire, the magnet is on a disc on the crankshaft.
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