The design of a new puch cylinder

Jurrian Mulder /

Hello,

I'm new to this forum, but I'm definetly not new to 2 stroke stuff

My name is Jurrian Mulder, I'm from the Netherlands.

I do a lot of tuning for 2 stroke engines, especially puch engines.

Currently I am designing a new puch cylinder, which will have 45mm bore.

I have only designed stuff until now, not casted anything yet.

First 2 pictures are from the first model I made, currently I'm working on version 3.

don't expect many updates through time, I'm doing a engineering study at the time..

Here are some pictures of the things I've done so far.

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Re: The design of a new puch cylinder

No intake on the cylinder? What Puch is case induction?

Re: The design of a new puch cylinder

Jurrian Mulder /

well, mine is:

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Re: The design of a new puch cylinder

Ľ̷̝̽͒i̶̛̼͑͠ȁ̸̧̛̽m̵̻̟̯̀̅ ̷͎̙̽̊F̶̲̺͑̓ F /

Nice, you may want to change the fin design a little bit if you are casting it, the ends may come out with a lot of pockets. Also on the transfer ports, between the fins and the port add a little bit more metal like the rest of the cylinder. With casting a thin spot like that may cause issues

Re: The design of a new puch cylinder

Cool! Fun to see all this happening.

Re: The design of a new puch cylinder

Probably Fred /

Make it for reed induction/reed intake on cylinder, A lot of people don’t want to cut and mod their case for reeds especially people like me who run za50 engines

Re: The design of a new puch cylinder

Looks awesome! Show us some of your previous builds

Re: The design of a new puch cylinder

It’s okay but you never casted anything before and really bizzy at the moment so call it a pipe dream

Re: The design of a new puch cylinder

Dirty30 Dillon /

> Overpriced Parts Wrote:

> -------------------------------------------------------

> Make it for reed induction/reed intake on cylinder, A lot of people

> don’t want to cut and mod their case for reeds especially people like me

> who run za50 engines

He's not making this cylinder for "a lot of people," seems like he's making it for himself.

In which situation, Case induction is a lot more efficient.

Re: The design of a new puch cylinder

Jurrian Mulder /

> Overpriced Parts Wrote:

> -------------------------------------------------------

> Make it for reed induction/reed intake on cylinder, A lot of people

> don’t want to cut and mod their case for reeds especially people like me

> who run za50 engines

Little chance it's going to be on the market, for such a cilinder you should go to heiko tuning (htparts.eu). He's currently producing a puch cylinder with a reed intake.

Re: The design of a new puch cylinder

Jurrian Mulder /

Buttcheeks BUZZARD Wrote:

> -------------------------------------------------------

> Looks awesome! Show us some of your previous builds

Current engine with dynograph

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Polini 50 puch project. Soon on dyno

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Re: The design of a new puch cylinder

13 hp 👌🏻 Nice!

Re: The design of a new puch cylinder

Johnny Braaapp /

I'll be keeping an eye on this. Nice work!

Re: The design of a new puch cylinder

Super cool!

Re: The design of a new puch cylinder

Looking forward to these projects!

Re: The design of a new puch cylinder

I much rather see someone start making cnc cases to fit a jog cylinder. It would be simple to design compared to a cylinder

Scooter cater blended into a E50 Tranny

Re: The design of a new puch cylinder

Jurrian Mulder /

some info about this project so far:

exhaust duct will be remodelled, not happy with it at the moment. I'm gonna try to draw a aprilia rsa125 canal, and go from there.

I also made a e50 upper case in cad file. If anyone needs it, look it up at grabcad.com (search for puch e50)

Re: The design of a new puch cylinder

RSA is an amazing cylinder to pattern after. Looking forward to your progress.

Re: The design of a new puch cylinder

Probably Fred /

Hoping for a 74cc polini cylinder kit not a smaller 50cc one

Re: The design of a new puch cylinder

Jurrian Mulder /

little update here,

for our racecup the list of legal cylinders has been given free. this means, the cylinder designed by myself is actually allowed to take part in the cup. soon more info on how they are going to be made (and probably by who...) stay tuned.

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Re: The design of a new puch cylinder

Big Fins! 45mm is still the race-spec bore?

Re: The design of a new puch cylinder

Jurrian Mulder /

> Josh G wrote:

> -------------------------------------------------------

> Big Fins! 45mm is still the race-spec bore?

Yess, along with a 43mm stroke and air-cooled.

Re: The design of a new puch cylinder

I dunno if it's hubris or I'm just too dumb to know I can't do it, but I've signed up to try to cast this bastard. Im going to be taking lots of photos and stuff but probably slow on the updates since it's getting crammed in with all my other projects.

Mostly I'm really excited to work with Jurrian and learn some of his hard won knowledge in tuning and testing procedures. I've cast a few really difficult parts so I know what goes into this, but this is a level that I haven't achieved so far.

Re: The design of a new puch cylinder

Eric Davenport /
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Re: The design of a new puch cylinder

whooo, good luck!

Re: The design of a new puch cylinder

Eventually, I'll get back to casting mine...

Re: The design of a new puch cylinder

I’m going to post as much as I can about the cylinder casting process on here, Jurrian and I have exchanged a lot of emails (he either speaks excellent English or is kind enough to translate for me) and I think we have a good plan. He owns the design of the cylinder, porting, etc so I won’t share those numbers, but since I’m developing the casting process I will post what I learn.

I have decided to try the ‘swing for the fences’ approach and do a direct burn out lost-PLA. In this process the positive is 3d printed from PLA using an FDM printer, then it is cast in a block of plaster, and put in a burnout oven to melt the plastic out. Molten metal is poured into the cavity left behind and when it cools, the plaster is broken away. This is the fastest process when it works, but can be extremely frustrating when it fails since you waste a week of work, and a lot of money in plaster.

I’ve only successfully cast one part with this method, but I learned a lot after failing 8 times that will help me with this part. Its 8 less failures I will have on this one. The most important thing is to design the mold flow into the 3d printed part. The plaster is very brittle during the burnout process and breaks easily if there are small unsupported pieces so I’ve asked Jurrian to make some design changes to the fins and some other parts to ensure the plaster is well supported and structurally sound.

Re: The design of a new puch cylinder

When designing a casting you design the part, then you design the mold, then you design the tool to form the mold. It helps to think of the plaster mold as a finished product in itself, then think of the tool as a finished product. In order to make the part fill correctly, you must follow Campbells rules for casting, if you want to get into casting it’s the cheat codes and 10 commandments all rolled into one, go read it. I’ve been thinking about mold flow for casting a cylinder for 5+ years while taking long poops or deer hunting or watching rom-coms with my wife so I have a pretty good plan for this, which I shared with Jurrian.

The sprue is where the molten metal enters the mold. You want to think of this like a beer bong. You know how when you do a beer bong right the beer goes down as a solid slug of liquid, and when you do it wrong it gets all mixed with air and foamy? Exactly. Air mixing into molten metal causes little fragments of aluminum oxide skin to form which shows up as porosity which is bad. To avoid this you want to have a smooth pour that fills the sprue completely. By running the sprue down the middle of the part you will get good flow everywhere and also the sprue will stay hot, allowing the mold to continue to fill as the metal cools and shrinks. You always want to have a gooey center to your casting so you don’t get shrinkage voids.

The next feature is a large well in the bottom, this will capture any debris and let the liquid metal settle down before evenly filling the mold from the bottom. You always fill from the bottom so the air gets pushed up. As the mold fills, the molten aluminum will combust deposits on the surface, especially residual burnt plastic, so you need to give that a chance to rise. If the aluminum is above the burning plastic, those gasses will get trapped and cause more flaws. This is why you never ever ever pour straight onto the top of a mold, it just doesn’t work and if the gasses are bad enough it can pop and spatter in your face.

The flow from the well into the actual part itself is very important, you need a single ‘front’ like a wave. Anywhere the aluminum is being exposed to air it will form that oxide skin, so its kinda like when you see lava going into the ocean. If two ‘waves’ come back together the skin will keep them from knitting and you will get weird knit lines which are a significant weakness in the part. If the wave moves fast and in a single smooth motion, the aluminum behind the wave will still be hot enough to incorporate and you won’t have that problem. For the cylinder using the entire base gasket surface makes the most sense.

At the top, the mold will be open-faced. This means the whole top surface will be open to the atmosphere. This is used in submersion casting and is probably how real 2t cylinders are cast in permanent molds. This way the entire top surface becomes a riser that will be cut off and any imperfections get chopped off in machining. It’s a lot more metal waste and machining time, but when you need a very high quality casting this is the best way to do it. Also, this way the mold will burn out upside down and everything will come out. When you burn out the PLA, anywhere it sits it will soak into the plaster almost like oil, and burn when it gets hit with molten aluminum.

Re: The design of a new puch cylinder

That’s a great write up, I learned some new words and concepts.

Looking forward to your progress!

Re: The design of a new puch cylinder

Yeah lots of words, haha, very boring, just trying to share for anyone who wants to try something like this at home. There will be more pictures soon.

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