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[ShadowGoat]

Hey! Found this forum while looking through some engine design related resources. I'm looking to design a very simple 2 stroke single cyclinder engine as a fun personal project, and figured this would be a good place to ask for advice. I have minimal engine design experience beyond decent knowledge of how they work, so it'll be fun to learn!

 

[ChazzC]

Hey! Found this forum while looking through some engine design related resources. I'm looking to design a very simple 2 stroke single cyclinder engine as a fun personal project, and figured this would be a good place to ask for advice. I have minimal engine design experience beyond decent knowledge of how they work, so it'll be fun to learn!

Welcome! If you could give us a little more background and your general location I’m sure there are members who can help.

 

[minh-thanh]

Hi @ShadowGoat
Welcome to the group.!

 

[awake]

Welcome to the forum!

 

[ShadowGoat]

Welcome! If you could give us a little more background and your general location I’m sure there are members who can help.

Mainly just here for resources and the ability to ask questions, but I'm on the east coast around DC. I have enough machining experience and tools to make the parts I need, so I'm mainly just looking for design advice. I'm trying to make the sort of two stroke where the piston acts as a valve to open and close the inlet port so that I don't need to mess around with reed valves or anything like that, but I suspect knowing the rough placement of everything is not enough to be able to actually get to a working final product. Currently I'm designing it around a 1.6ish inch piston diameter with a 2 inch stroke length, but those are just numbers I threw out while trying to get a rough design down. Most of my design experience is from other projects, and not engines, so this is kinda new to me.

 

[GreenTwin]

Welcome, glad to have you.

Hopefully someone can guide you.

.

 

[jumps4]

Here is a very informative book online about 2-stroke engines that may help:

https://www.2strokeengine.net/gordonjennings/twostroketunershandbook.php
steve

 

[Lloyd-ss]

Welcome to the forum. You will find the help you need here.
That's a good size engine, 69cc. Will this be a complete design-build?
I am a few hours from DC.

 

[ShadowGoat]

Hopefully complete design build. It is quite possibly too large, I just went off of some numbers that seemed reasonable (and also would make it easy to use mounting hardware I had lying around) but in hindsight I might scale it down, especially in terms of the piston size. Do you have a good size recommendation? Also I'm just estimating the transfer port diameter and exhaust as 0.4 inches in diameter which could be a completely nonsense estimate, so some advice relative to that would be helpful. The pdf that was sent by jumps4 was interesting and I'll definitely be reading through it as well.

 

[Lloyd-ss]

One approach is to find a existing 2 stroke engine that you like and use it as a basis for your design. Certainly nothing wrong with getting an assist like that and I think many/most model engines are done that way.

 

[JP2]

This site has a nicely detailed two stroke design/drawing with plenty of information.

http://machineconcepts.co.uk/aeromodelling/brians_engine/stunt_engine_7.htm

 

[Lloyd-ss]

This site has a nicely detailed two stroke design/drawing with plenty of information.

http://machineconcepts.co.uk/aeromodelling/brians_engine/stunt_engine_7.htm

Wow! a ton of info on all of those pages. Shadow, don't let it scare you, that is at the experienced craftsman level. Just concentrate on getting something that works. It doesn't have to be beautiful, too.
I really like the machine set-up and fixturing tips. The way he uses the Dremel tool post grinder (on page 2) set up at an odd angle (almost like a cup wheel) for cylindrical grinding is clever.

 

[ShadowGoat]

Thanks for the resources! I've been absorbing a lot of info and I'll probably redo what I have so far using these pages as references. Not sure when I'll get around to building since I have a few other projects I'm doing concurrently but this feels very doable.

 

[Bentwings]

One approach is to find an existing 2 stroke engine that you like and use it as a basis for your design. Certainly nothing wrong with getting an assist like that and I think many/most model engines are done that way.

I agree model engines have huge engineering backing so many issues are solved before they are even prototyped. Nicasil cylinders are a big one modelers can’t beat this on garden engines last for ever given even minimal service. I’ve at lest 100 hours full throttle on one of my-war bird engines it had no mercy treatment . Full throttle lean outs, unbalanced props a couple hard prop strikes still starts and runs perfectly.

 

[Lloyd-ss]

.................................. Nicasil cylinders are a big one modelers can’t beat.........................

I am not familiar with that. Could you please elaborate a little? Thanks so much.
Lloyd

 

[GreenTwin]

There was a fellow in San Francisco who races two stroke motorcycles, and he started casting his own cylinders in 356 aluminum.

He was sending his cylinders off to get the Nikasil process, which is some sort of electroplating process on the bore, which eliminates the need for a cast iron sleeve, and gives a very hard wearing surface.

He had some cylinder failures, and so he started pressing in his own cast iron sleeves, and he reported better performance and a cooler cylinder operation with the pressed-in cast iron sleeve.

I think the Nikasil process is more a convenience and cost-savings operation for the manufacturer, mostly.

As the guy in San Fran mentioned, the pressed-in cast iron sleeve was also replaceable, whereas the Nikasil cylinder cannot be reused (check me on that).

.

 

[Lloyd-ss]

There was a fellow in San Francisco who races two stroke motorcycles, and he started casting his own cylinders in 356 aluminum.

He was sending his cylinders off to get the Nikasil process, which is some sort of electroplating process on the bore, which eliminates the need for a cast iron sleeve, and gives a very hard wearing surface.

He had some cylinder failures, and so he started pressing in his own cast iron sleeves, and he reported better performance and a cooler cylinder operation with the pressed-in cast iron sleeve.

I think the Nikasil process is more a convenience and cost-savings operation for the manufacturer, mostly.

As the guy in San Fran mentioned, the pressed-in cast iron sleeve was also replaceable, whereas the Nikasil cylinder cannot be reused (check me on that).

.

I apologize if we are hijacking the thread, but just a little bit more.

Green Twin, I did some reading about the Nickel Silicon Carbide plating process (it can be stripped and replated) and it offers some savings as you say, tothe manufacturer. I remember the Chevy Vega blocks that were a 17% silicon aluminum casting. A356 is 7%. But both methods sound pretty complex and not too DIY friendly. As is usually the case, our model building choices always boil down to what we have access to. Thank you. Lloyd

 

[Bentwings]

I am not familiar with that. Could you please elaborate a little? Thanks so much.
Lloyd

 

[Bentwings]

Nicasil spelling? Is an anti wear surface on cylinder walls . It’s hard as can get rarelybeears unless badly mis treated. Usually small engines especially two strokes . There are few failures weed eaters last for ever as do chain saws it’s also used on four strokes. Sayportsble generators I had on go 15?years before it was stolen. I yhinkbthrbjspanese invented it. It’s better than hard chrome I know it does not hone very well. It’s hard to renew cross hatch on a worn cylinder better to just purchase a new one I tried boring one time wrecked boring tool . It’s been around for a long time I’ve not heard of any companies that apply it after market not really sure of its composition just that rings seat almost instantly and stay that way. I’ve got three two strokes that have excellent compression and run very well I don’t worry about oil mix just so there is some in the gas. The cyl walls look brand new. My son has a large landscaping business and they use weed esters all day long the things usual break something irreparable then the thing goes in the recycle bin never seem to have piston or ring issues. I wish we could have had it on race car stuff . It seemed like we were constantly replacing sleeves the process may even be on hydraulic cylinders too . In industry they hardly ever failed usually seals or broken parts even big dirt machines more than likely broke the cylinders or parts but never really wore them out. Dirty oil usually wrecked seals or caused excess wear some place else.