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Big stroke 55 cc one cylinder ICE

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Roger B:
That's interesting that you can 3D print channels in things  :thinking:

You could also retain the piston pin using grub screws from the open end of the piston.

AlexS:
Ah that is also a option!

AlexS:
Update. Last couple of days when have spare time, busy with maintance other work on motorcycles. But yesterday finished machining of valve stem guides, already pressed in cylinderhead quit well. Would later post photo's.

3D printed X Turbolence Piston

Today continue with development of the 3d printed piston.

Rework of piston pen boss. Reduce mass from 47 to 40 grams. Add oil channel on top of piston pen boss to fed oil (trying) to connecting rod.

Changed dimension of piston pen OD from 13 mm to 10 mm (ID 6 mm). Calculated shear stress of both cross section piston pin (safety factor 2 after 380 Mpa x 0,33 for spring load). Occuring surface pressure of piston pin to aluminium boss section of piston (safety factor 3+). Used SAE ICE handbook for common calculated dimensions. Piston pin should be between 8 and 10 mm.

Because smaller piston pin, more room for thicker wall of piston crown and internal combustion room. Now 3 mm. SAE showed 2,5-4 mm.

Need a couple of FEM calculations.

Modified the oil cooling loops of the piston squish section for better fitment. For outer loop added a channel to reach them.

Main top ring cooling loop. Idea is that when piston moved downwards, it push remaining oil in to the channel (second picture). Loop is 350 degree around the piston. Exit at the other side of the piston.
So far I have seen Porsche use a infeed channel right under the piston. This is also a option but then need of a oil pump and nozzle under the correct position of the piston bottom.

Well maybe tomorrow time to try to 3d print it at home in PETG. One at 100% scale (39mm) and one x times larger. Cutting the piston in halves to look at channels and stiffness (the poor man FEM simulation or analog!)

AlexS:
Valve Guide Upgrade

Here are the photo's of the assembly of the new fitted valve guides in the cylinderhead.

Pressing the sinter bronze valve guides in to the head was quit easy. By freezing the guides, and before pressing them in to the head, I have heated locally the hole with a nice hot flame. +-0.050 mm press fit when cold at 20 deg.

Add M5 thread to the valve stem of the inlet valve. Cleaned the valve a bit.

Installed it in to the head and using two thin M5 nuts to fix the valve assembly. Before I have used a circlip, which is not great at these jumping forces of the valve movement. Now easy to assembly.

Exhaust valve need more work to ensure good air tightness. Because years ago I have some coaxial error between valve and seat. 

AlexS:
3D printed X Turbolence Piston

Two weeks ago continue developing the new piston.

No changes on what I write down on last post.

Test printed with a okay filament of PET-G. I am not very experience with 3d printing (the piston has alot of small details, could be printed better with a smalles 0,2 instead of 0,4 mm nozzle), but result is okay to check dimensions and stiffness.

Also have printed as a half section view! Could test with piston rings of Gy6 piston


Balance shaft assembly

A couple of years ago already have calculated an course CAD drawn the balance shaft assembly. Would use two primary balance shafts to counter the oscillating mass of the piston assembly and +-1/2 weight of the connecting rod. Before define the exact weight and dimensions of the balance shaft and added weight on the crankshaft I need to produce the new piston and connecting rod.

But. Let just try to make 3x custom gears to connecting these shafts. Goal is to home 3d print it. Use PET CF, carbon fiber reinforced, easy to print and less influence on creep and moisture I have read. Later could print it from Nylon to more resistance to flex and wear. Also a filament of IGUS is a possibility, it has some of Teflon included (self lubricating), but have heard that it take to trail and error when printing.

Out of memory Herringbone gears 36 teethes, axis to axis 54 mm, module 1.5. Same dimensions of a straight gain of Meadler.de. Why herringbone, it look great and may reduce noice and les vibration and rotational movement between gears.

Already have raw CAD drawn a test mounting to see how two gears moves. Work in progress!

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