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  1. O

    watercooled 50cc two-stroke.

    This isn't a complete engine build, but will be a modified cylinder, plus various accessories. I will move the Water brake build here, the exhaust chamber modifications, the electric starter installation, the fancy throttle lever, and all instrumentation. for the first build, I will start with a...
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    A balance/friction throttle pull lever for a slide-type carburettor.

    I am looking at bench dyno controls for my proposed engine. The carb has about 35mm pull, and quite a strong spring. I need to oppose the spring so that the lever will stay in one place. The carb spring has a high preload and low rate , so can I do the opposite at the lever end? How would this...
  3. O

    suitable Al-Si alloys for pistons.

    I have heard eutectic -12% si, is good, but google searches give 4032, which is 21% . 21 % Si will have a lot of free silicon in it - hypereutectic. Should I look for a plain eutectic casting alloy in the LM series? Will I have problems with eutectic and expansion in a hot-running engine? There...
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    Finding a source of small quantities of 4032 aluminium alloy bar or ingot.

    I want to make some pistons. Can I buy this material in small quantities? Bar stock would be best for machining. Is it worth while to get a small foundry to cast some in the correct shape? Are castings like this any good for machining? Pistons are nominally 40mm diameter.
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    Machining tools for a micro lathe.

    Where do I get these from? everything online seems to be too big. I have a toolpost that can take up to 10mm tall tool holders. I want 1.5mm thick parting-off tools and tools for making ring grooves, and holders that will fit and bring the edge to the right height. This is about 2mm up from...
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    Loading on grubscrews.

    I have a 15 N-m torque load on a 10mm shaft. torsional stress = 76.5 MPa. Side load at the surface is 7.5 x 10**-2 N, which is easily borne by a 2mm pin. 1) Can I retain this by a normal grubscrew on a 316 stainless shaft? 2) Is this improved by a 1.5 mm deep flat on the shaft? This would help...
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    Details of performance two-stroke engines.

    This is intended for discussion of odd features of performance two-stroke engines. The one that I am interested is the "wobbly exhaust passage". this seems to be very long, with a semi-elliptical outlet. I would have thought the outer exhaust ports could merge at about 30 degrees into the first...
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    Speculation about turbocharged two-stroke singles.

    This is about the crankcase-charged variety. I have found that the record output for a turbocharged 50cc is still around 20 hp. This seems rather low, as that is about the same output you can get using a tuned pipe and no turbocharger. What factors would affect slow progress in gaining more...
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    Motorcycle two-stroke that does not need cylinder oil?

    My memory may be playing tricks on me, but I seem to remember a comment that an old-time manufacturer such a CZ once made an engine that only used the petrol as a lubricant. There is no trace on line, so this may not be true. If it were true, more people would be doing it. A holdup to this...
  10. O

    Lower cost design for a water brake for a dyno.

    The best system for this seems to be a toroidal fluid clutch, but those tend to be expensive to buy or to make, if you can't get a real one from a wrecked car. A torque converter is not so good, as they are made from sheet steel, and won't last running with water. Also, they are complicated to...
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    Finding parts for 125cc watercooled motorbike engines for project use.

    Relevance to engine build projects- I could cobble up a high performance engine, using some commercially available parts. I don't think I will be getting into aluminium castings, though...
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    buying a manual slip roll.

    What is a good make for me to get? I want to roll two-stroke exhaust cones, down to 22 mm inlet and 16mm outlet. Material thickness will be initially 0.2mm stainless, but I may go up to 0.7mm mild steel at some stage. Looking on YouTube, a one inch top roll is required (25mm). All the ones I...
  13. O

    Inlet-side power valves on two-strokes.

    This is an aside from my thread on my two-stroke mods. 1) I saw on "2Stroke Stuffing" where an inlet-side power valve was used. There do not seem to be any articles on this coming up in a google search. Is this a new thing? This raises the possibility of converting a reed valve engine to work...
  14. O

    Surface finish requirement for ball links.

    This is a subtopic of Wobble Plate engines. convention: 10^3 = 10 to the power of 3. - scientific notation- this deals with decimal places. -------------------------------------------------------------------- I have included a detail drawing of the ball link. it has a 10mm ball one end and a...
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    Buying small spur gears off-the-shelf.

    I am looking for standard timing gears that are good for higher temperatures, and capable of being run in mesh at 6-7000 rpm. I think cast iron gears may work, Unfortunately no-one sells them retail. Non-ground steel gears cannot be run this fast. They also need to be machinable, so that I can...
  16. O

    Quatrefoil epicyclic engine mechanism.

    This motion is sort of like a 4-leaf clover. I think it is a Celtic quatrefoil shape, which crosses in the centre. A standard quatrefoil does not cross. It would be suitable for an engine block that rotates, with the pistons moving in and out, but with a scotch linkage style motion. This is...
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    Effective muffler for a two-stroke model aeroplane engine.

    I have an existing muffler for a 70cc engine, which is about 65mm diameter and 300mm long. Output when running is roughly 95 dB when I run it in the garage- blowing the exhaust out the main door. Can I make a muffler that fits in a similar space but is quieter? The outlet pipe is about 16mm...
  18. O

    Wobble-plate axial engine design project.

    This is based on the Duke and the Bristol designs, and is intended to be 3 cylinder air-cooled, rotary valve. 4-stroke, swept volume of 90 to 100cc, intended to have an RC model aircraft propeller drive, about 23 inch prop diameter. this takes 4.5 to 5 hp basic to spin at 6,000 rpm. 6500-7000...
  19. O

    Start on liquid-piston X-Engine build.

    1) has anyone here built one of these? 2) the first step is: work out the gearing ratio and actual forms of the rotor and housing. the rotor is an epitrochoid of parameters 2:1 ratio, d = 1/2 where the generating circle rolls twice round the main circle. the housing is epitrochoid dim 3:1...
  20. O

    Finding a good small cnc cad-cam milling machine in NZ.

    What is a good bed size? 500x x 300y x 300z mm?? 1500w I cannot find any ads for them in Google nz, only on alibaba or ebay. Freight is too much from us, uk, or china sources. Any ideas on brands, models, sizes I should be looking for? Ex china ones are around 4-5000 nz, or $3500 US. what...
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