Big stroke 55 cc one cylinder ICE

[Roger B]

That's interesting that you can 3D print channels in things 

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!

[Roger B]

3 D printed herringbone gears is an interesting concept     

This is a gear I photographed many years ago in a Hamburg docks scrapyard.

[crueby]

Interesting photo Roger - I never had a close look at a herringbone gear, it does make sense now that the center would not have the teeth meet up, never realized that would be the case.

[Roger B]

Apparently my picture is of a double helical gear, a herringbone gear's teeth do meet in the middle. Both have interesting manufacturing problems   

[AlexS]

Agree just a test print of the gear. Indeed it is rather a double helical gear, no theeth meet in middle section.

Already produced a second one with printing with supports and higher extruder temperature. Without fixing tool, both gears match quit well. Would print the test fix tool later.

Piston

Simulated in Autodesk Nastran. Result quit Okay, only need to add a stiffening around small end boss to bottom side of oil scraper ring (inside of piston) There was a safety factor of 2.5 as lowest of whole piston by 53 bar combustion pressure.

[AlexS]

3D printed X Turbolence Piston

Hi there!

After a summer break. Let continue when the rain is falling!

In June tried to make some FEA simulations of version 2 of the piston. Result was that peak maximum von mises stress around 200 MPa and area's around 150.

Currently made a modification. Add some thickness at the piston crown from 3 to 5 mm. I searched and 2.5-3 is good enough for forged piston. This piston would be SLM 3d printed, maybe with a heat threatment. A thicker 5-6 mm piston crown thickness is more recommended for the heat build up (open structure?).

Today made a simular simulation with load 63 bar maximum combustion pressure (according to 1:7,5 compression ratio).

Result showed peak stress around corners of the oil channel 0f 117 MPa. What more leading is the stress area inside connection bottom of piston crown to skird of 92 MPa.

I already adjust internal geometry for more flexibility between piston crown combustion chamber and right small end bush, which already without making hte crown thicker give lower stress around that area.

So far I found that SLM AlSi10Mg have RP0,2 yield strength around 160 MPa as build and 290 MPa heat threaded.

Same as the piston pin recommend safety factor 3 for this medium duty piston.

Result in maximum allowable von Mises stress of 53 as build and 97 MPa heat threaded.

I could adjust geometry. Weight is almost the same as current cast GY6 chinese piston that currently running.

But would contact a supplier that can produce a heat threaded part with increased strength.

3D printed X Connecting Rod

The current connecting rod would not match with higher piston. Connection rod is almost finished. Also 3d printed. Maximum stress is around 300-333 MPa.

Option is to produce it as titanium or Maraging steel (M300). I am leaning to select marging steel, due resistance to fatigue stress and machinable for me. Density is higher ofcourse. But the current aluminium large connecting rod is 44 gram and titanium 30 margensteel should be around 60 grams.

Yes, why difference stress left and right leg? because it include a oil supply channel from small end to big end. Why? because it is easy to add when printed!

FEA safety factor margensteel are around 3-4 without heat treatment!


3D printed camshaft in development, next. to much info for now.

Good night

[MJM460]

Hi Alex, thank you for taking the time to post this.  Great to see FEA being used to develop a model design.  And most interesting results.

(Now to apply it to my boiler design!)

How do you intend to make the piston to your final design?

MJM460

[AlexS]

Hi MJM460,

If you need a design FEA of your boiler, let me know. I can try it with Autodesk Nastran. I use it only for design and not validation.

The idea is to produce this piston is to outsource 3d print it with SLM as homogeneous structure. As a tip form an other member of this forum, Craftcloud give you an overview of wide range of materials and suppliers.

Yesterday I saw that the site ask 40 euro for printing an piston including shipping. Search to the supplier it self and upload there the model. And it ask 16 euro I think there should also need shipping which is half of price for a single part. I have idea's to create more 3d printed AISI316 parts for additional upgrades (I have for years idea of dry sump oil system, which could 3d print tubing and spray nozzles). But maybe to much for one upgrade. Oil lines could be printed as Nylon PA12 (maybe with a vacuum chemical coat, but could be over engineered for an model engine running in mineral oil!) it is quit common material MJF or hard lines AISI316 or even aluminum. All collecting and printed at one supplier to reduce shipping price.

Printing the model with oversize and extra material top and bottom side to possible to fix in chuck and center. Creating a 3d model where I can reuse 100% final model with additional material.

After 3d printing I was thinking to mill the piston skirt in an 4 axis setup where one side is oval. And after that make skirt to correct size in a lathe.

[AlexS]

Well I just use this project for testing and enjoy of making something!

3D printed X Connecting Rod

In more detail about version 3 connecting rod. Current aluminium rod has 75 mm distance between centers. New one 72mm.

Weight as material titanium 30 grams without bearings. 53 grams with bronze bearings. They might be adjusted to smaller ones, but see if there are good reamers for smaller size. I think it is good to ream the holes before press fit the bearings.

Maragingsteel M300 without modification model 52 grams without and 75 grams with bearings.

Current rod is 44 gram.

I have to re calculate needed counter weight of crankshaft en balance shaft to fully apply weight oscillating and rotating weight. Or just to deal with a bit of % of not taken in counter weight which I read in SAE ICE book without balance shafts is 100% rotating and 50-60% oscillating mass.
Currently mass large aluminium connecting rod + piston only rotating is taken account in counter weight no oscillating (0%) add extra mass without balance shaft would already improve if I understand it correct!

Contacted supplier 3d printing:

"Firstly, all 3d printed aluminium pieces are heat treated. Generally, Maraging Steel is strengthened via ageing at approximately 500 °C (900 °F), “heat treatment is divided into many types. For instance, “surface heat treatment”, “induction heating treatment”, “vacuum heat treatment”, “isothermal quenching”, “martensitic isothermal treatment”, etc. The heat treatment carried out for the (Maraging Steel) in daily practice is just the basic one. "


Stay tuned. work in progress!

[MJM460]

Hi Alex, that is indeed a generous offer, and much appreciated.

I would be most interested to see the FEA for the boiler.  It is not needed of course, the model boiler codes don’t give much credit for advanced design and analysis methods, but it would be interesting to see how the standard details stack up.

I assume by design, not verification, you mean that you use the analysis to identify the high stress areas then modify the design to get stresses closer to the average.  Like wise you could refine the low stress areas to more efficiently use the material.  But verification would mean proving the design overall met the code requirements for the specified load/ pressure.  I am happy to avoid the issues involved in verification, as it is all designed to the code requirements, and more than adequate for my modest pressures, and a very simple standard arrangement.  More interesting is just where are the higher stress areas in those standard design details.

If you still feel you would be willing to give it a try, I will put together a data sheet with all the necessary information and send it in a pm.  I could then start a separate thread when there are some results or conclusions available. 

Of course, it’s a very theoretical exercise, that will not change boiler design in the model world, but understanding such things, and improving them while staying in code requirements can only make our boilers safer in general.

Thank you

MJM460

[AlexS]

Okay. If there are drawings available is great to add. PM me with the your email. There we can share data and communication if needed. Good to have a separate topic to share results.