# Good plans for a "modern" single cylinder?



## apullin (Aug 8, 2011)

Hey folks. I am currently hunting around for plans for a small engine to build, something 4-stroke, air cooled, gasoline fueled, ring seals, and as many ball/needle bearings as possible. Something around 35-50 cc's would be great, but I should be able to scale to that fairly easily.

And as far as the "modern" part, well, it would be ideal if it was an overhead cam design. I think the model agricultural and tractor engines, while nice, aren't quite what I'm looking for.

Thus the search for plans, rather than designing from scratch myself: I'd like to start with something that's already been proven to work, and had some debugging.  

A single or boxer twin configuration would probably be "best", since I think those are the easiest to make?
Jerry Howell's V-twin engine looked interesting, but I would like to elide the complex gear train for driving the valves, and there's the extra complexity of the oddly shaped crank-case.

Here's a couple that I've been looking at:
http://www.cad-modelltechnik-jung.de/baumotor/1_zy_vier.htm (higher displacement would be better)
http://www.cad-modelltechnik-jung.de/baumotor/4_zy_box.htm (pushrod)
http://hamiltonupshur.tripod.com/    (#2 and #4, pushrod )

Advice? Recommendations? It's all welcome. I will have access to CNC machines for most/all of this work, and I'm a CAD wizard, so none of that should be a hang-up.


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## John S (Aug 8, 2011)

Nemitt ?

http://modelenginenews.org/cardfile/ne15s.html


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## Mosey (Aug 8, 2011)

What would you think of a scaled-down version of a Ducati desmodromic single?
There are abundant drawings of those engines around. Shop manuals and parts books are readily accessible, too.


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## apullin (Aug 8, 2011)

That Nemitt engine does look fairly neat, I'll have to email the guy to ask about getting plans...

I think desmo valves would probably be *super* difficult to get working. I've heard that getting them dialed in on a real bike is hard enough, so coupling that with designing & manufacturing them ... phew. Although it would be quite well suited to the application of this engine: a high mileage competition vehicle.

Although, I would certainly take a look _if_ the plans already existed.... you say drawings do exist?


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## John S (Aug 8, 2011)

Andy,
Unfortunately Malcolm Stride the author is dead but there are plans out there and it was covered in Model engineer in 2006 or such like.
I have some plans but at the moment I'm sorting out 4 big boxes of books and drawings from a guy who recently died, not Malcolm, and there are some drawing in there for this engine plus at least 4 copies of the build book.


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## apullin (Aug 8, 2011)

Hrm, interesting. There's so many stories of these old guys making this amazing stuff, and by the time I've learned about it, they've passed on. A guy names Henry Parohl made a Wankel style rotary engine that I'd *love* to build, but unfortunately, there were no plans for it. Oh well.

So, would it then be considered "OK" to ask someone to photocopy the plans and mail them to me? Or scan? Or is there a better way to track them down? It looks like there are some back issues available via Ebay ...


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## bearcar1 (Aug 8, 2011)

What is it exactly you are looking to do with this said "already engineered" engine if I may ask? For someone that is a wizard at CAD with access to CNC machines, I would not think that they would find complex shapes any problem at all. Just curious. Have you ever built any type of engines before and what types/sizes. An introduction would be nice too as long as we are asking for things.


BC1
Jim


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## steamer (Aug 8, 2011)

apullin  said:
			
		

> Hrm, interesting. There's so many stories of these old guys making this amazing stuff, and by the time I've learned about it, they've passed on. A guy names Henry Parohl made a Wankel style rotary engine that I'd *love* to build, but unfortunately, there were no plans for it. Oh well.
> 
> So, would it then be considered "OK" to ask someone to photocopy the plans and mail them to me? Or scan? Or is there a better way to track them down? It looks like there are some back issues available via Ebay ...




NO actually it's not OK.  We take copywrite material laws rather seriously on this board.
If you google model engine you will find many perveyors of plans to chose from by Model Engineer, Model Engine Builder, ect, whom I am sure would be glad to sell you a copy for a modest price.

Please tell us how you make out with your search.

Dave

PS I would be remiss if I didn't point out that your expected to post in the welcome section and tell us about yourself.  We like to know whom we are inviting into our home.

Thanks


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## apullin (Aug 9, 2011)

> What is it exactly you are looking to do with this said "already engineered" engine if I may ask?



Sure you can ask. I'd like to put together an engine platform for a student high mileage vehicle competition. That is, the engine will actually be used to provide traction power to a lightweight "vehicle (pretty much an aluminum ladder with wheels on it). A lot of engines in this application are Honda GX35's and such that are extensively modified, and I thought to perhaps approach it from the other end: a 'custom' engine. Strip out what isn't needed, and build in the pieces that would need to be added anyway.

And, yes, you're right, that the level of complexity of the parts in one of these engines is not particularly high, and shouldn't be too much CAD work to generate. And as for the CNC part, well, I hope that that will just make the goal of a custom engine that much more achievable: instead of needing a year of special setups and such, I can reduce several hours of, say, using a boring head into just a scant few minutes on the CNC.

But if I do just generate a design from nothing ... there is an 'X' factor there. That is, I might need to work through issues (rings? oiling? etc) that others have collectively resolved with decades of experience.
And, really, as I've started to see, there's not *that* much difference in all the designs for these really simple, unconstrained engines, not mimicking something else that already exists.
I will be adding computer controlled EFI and spark ignition, but those are systems that I know how to adapt, and already have the hardware for.




> copywrite material



Ah, sure, ok. The question was motivated from learning that the designer has passed away, and thus the plans can't be bought first hand anymore, so it _potentially_ mightn't be a copyright issue. Consider the seemingly difficulty in sourcing this particular set of plans, I'll likely have to discount the NE15S as a posibility, and go with something that's still available.


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## steamer (Aug 9, 2011)

Check with model engineer. They have back issues of the Nemitt

Dave


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## bearcar1 (Aug 9, 2011)

If it is a student competition, what engineering ideas have they (the students) come up with in order to meet any criteria set down in the project? Seems a shame to have such events and merely bastardize a design that has already been proven or modified from something else. 


Jim B.


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## Mosey (Aug 9, 2011)

apullin  said:
			
		

> That Nemitt engine does look fairly neat, I'll have to email the guy to ask about getting plans...
> 
> I think desmo valves would probably be *super* difficult to get working. I've heard that getting them dialed in on a real bike is hard enough, so coupling that with designing & manufacturing them ... phew. Although it would be quite well suited to the application of this engine: a high mileage competition vehicle.
> 
> ...


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## Jasonb (Aug 9, 2011)

The basic Nemett design can also be adapted, something like this will get you closer to the 35cc you wanted though the blower may not do much for economy 

Also take a look at the various engines in Model Engine Builer Mag, for the price of a back issue or two you will get the plans and description of the build.

J


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## Mosey (Aug 9, 2011)

Here are several shots from the Work Shop Manual suggesting what the Ducati engine entails. Looks like it would be more than a weekend's work!
If there is interest, I will look for engineering drawings, but this would be an epic project.


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## apullin (Aug 9, 2011)

Mosey  said:
			
		

> Here are several shots from the Work Shop Manual suggesting what the Ducati engine entails. Looks like it would be more than a weekend's work!
> If there is interest, I will look for engineering drawings, but this would be an epic project.



Ha, yeah. Although, I don't need the integral transmission. It's really just the head. Doing the cam geometry should be pretty straightforward in Mathematica, but it's all the small parts ... the springs, washers, bumpers, seals, etc. Hence the hunt for an existing design, so I could build and be running withing a couple of months, so I can get right into drivetrain adaptation, EFI, tuning, etc.


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## gbritnell (Aug 9, 2011)

I could build and be running withing a couple of months, so I can get right into drivetrain adaptation, EFI, tuning, etc.

Whoa there friend!!! Methinks you think this is a lot more simple than it is. First off in this world of 'model engineering' there's not much in the way of EFI. The subject has been tossed around but at present there isn't much out there for us. 
Second, unless you have studied camshaft design that subject alone can get pretty deep, engine working rpm, torque ranges, manifold designs, etc. Then there's the question of how you're going to heat treat and grind it. 
I don't think there are many of us on this or other model engineering forums who have designed and built 'working engines'. 
I would suggest that you start with a small motorcycle engine and make performance modifications to it. That way you have a good base to do your experimenting and beside that there are parts available should something go wrong.
gbritnell


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## Mosey (Aug 9, 2011)

Amen!
And just a bit of information to share...my 50 year old Ducati engine still goes together without crankcase gaskets, just metal to metal castings, and doesn't leak a drop. Awsome.


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## mu38&Bg# (Aug 9, 2011)

Other university teams have managed to come up with engines from scratch. It didn't happen in one year however. There is plenty of info on the web. Some detailed, some not. Cam design is not a trivial task, fortunately it won't be critical in the application you're looking at. Making a few parts on CNC is no faster than doing it manually. The actual cutting time is small, it's the setup that adds up. None of the model engines are designed to be efficient. No model engine has your concerns about rings, oiling, etc. sorted for efficiency. While every engine has a crank, piston, and head, the resulting operating efficiency is all over the map. Set your goals at 200g/kWh and see how close you can get. Designing an engine from scratch take quite a bit of effort. Producing one to meet specific goals, takes development. Even if you take an existing design your needs are so different from a basic engine that I doubt it will save any time. There is a reason many engines are based on the Honda's design. EFI is standard for this application, it doesn't seem to be optional anymore.

If this is for the Shell Eco Marathon you have your work cut out. Based on the work I've seen on past teams websites, it takes an ongoing effort to be near the top.

BTW, if I remember correctly past rules required the use of a certain make of engine block and/or head. In recent years the engine design has been opened to scratch built engines.


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## apullin (Aug 9, 2011)

gbritnell  said:
			
		

> Whoa there friend!!! Methinks you think this is a lot more simple than it is. First off in this world of 'model engineering' there's not much in the way of EFI.



Yes, I do know that. But EFI system is completely done already, as a separate thing. That is, the pressure source, low flow injectors, electronics, code, etc, is already done. That's the easy part.

Now, as far as a desmodromic valve configuration and such, that was just a pipe dream suggestion that someone else fielded, and since there are no existing plans, it's not really an option.




			
				dieselpilot  said:
			
		

> Other university teams have managed to come up with engines from scratch.



Ah, I knew I'd drum up someone who was familiar with the competitions 
Teams don't seem to put too much effort into their websites, so the information isn't always there. There's plenty to be learned at the competition itself, as people share quite openly on-site.

Shell eco-marathon is open engine design. SAE Supermileage requires the use of a Briggs & Stratton block. I am targeting my efforts just to the former.
I consider a lot of the engine designs a little bit "silly", since many of them now use essentially every part from a Honda XR50 engine, and it's just physically supported by the aluminum crankcase of the B&S engine. Just trying to think laterally.



> Designing an engine from scratch take quite a bit of effort.



That's why I'm looking for some initial plans, a 'bootstrap'. I mean, I could just show up on a riding lawnmower; that'd be the least amount of development hours ;D


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## steamer (Aug 9, 2011)

I could suggest a Dale Carnige book.... :

Apullin....have you built an engine before?

I ask that question quite earnestly...

Dave


PS  We're still waiting for the message from you in the Welcome section.


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## Cedge (Aug 9, 2011)

Apulin
Good luck with the student project, but you've obviously misread the nature of the local community. You've asked for proprietary drawings to be copied and that is a huge taboo here. As I recall, at least back in the bronze age of my own ancient educational experiences, a student was expected to design his own project rather than copying or piggybacking on other peoples already established works. Long and short.... sorry dude, but we're not here to augment your GPA by handing you a ready to build project.

We often help brainstorm, work around technical problems and lend high levels of moral support and encouragement, but only with those who are willing to do the required work themselves. I, for one, find your approach more than a little pretentious and quite negative in nature.

Steve


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## Tin Falcon (Aug 9, 2011)

This is a hobby board. Folks that build and occasionally design engines for fun. A few here may sell engines or plans for profit. 
If you are engineering student tasked with a design project then start designing. Do not expect anyone here to hand you a set of engine plans so you and your buds can enter a competition. Engineering is about problem solving. 
You need to design and build. And if you want help I suggest you listen carefully to advise given. 
Tin


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## apullin (Aug 10, 2011)

Hrm, seems like some pretty harsh language being used.



			
				Cedge  said:
			
		

> You've asked for proprietary drawings to be copied and that is a huge taboo here.



I think you should re-read my post, and pay attention to the language. It's quite clear that I am asking if it is indeed "taboo" to ask for that set of plans, considering they are not even available for purchase. I didn't ask for someone to send me a copy; my conjecture was about the appropriateness of such an inquiry. It just seems that you're reacting to something that didn't even happen.



			
				Cedge  said:
			
		

> We often help brainstorm, work around technical problems and lend high levels of moral support and encouragement, but only with those who are willing to do the required work themselves. I, for one, find your approach more than a little pretentious and quite negative in nature.



While I did lead out my original post with a general call for "advice" and "recommendations", that was in the scope of the genesis of the post: searching for available sets of plans. Someone asked about the application, and I was more than happy to share, but I haven't solicited anyone to implement a solution for me. If anything, I've continually said, "starting point" 

I'm not sure what part of it you count as pretentious.




			
				Cedge  said:
			
		

> sorry dude, but we're not here to augment your GPA by handing you a ready to build project.



This doesn't have anything to do with GPA. You assume far too much, and it reflects very poorly on you.





			
				Tin Falcon  said:
			
		

> This is a hobby board. Folks that build and occasionally design engines for fun. A few here may sell engines or plans for profit.
> If you are engineering student tasked with a design project then start designing. Do not expect anyone here to hand you a set of engine plans so you and your buds can enter a competition. Engineering is about problem solving.



I'm not even sure how to respond to this in a metered way; again, I think you've misread my words, and have taken me for some kind of a beggar or thief. I'd sure like to buy the plans, but if you look at the thread of the discussion, stemming from the initial reply, the issue is that _the plans are not available for purchasing_. I even say on the same line that I've seen there is some limited availability of the source material via eBay, *and* further ask if there would be alternate ways of getting a set of plans. I just don't know how to be more clear about it, really.

I urge you to compare the content of your reply to, say, the first reply in this thread. I ask about existing designs, and someone tells me about a design that exists. Your reply hasn't really brought us anything, except a judgmental, uncouth tone. I'm well aware that engineering is "about problem solving". I am trying to solve a problem here: finding a starting point in a large design space.




			
				steamer  said:
			
		

> Apullin....have you built an engine before?



Several low temperature Stirling engines. And I've "built" engines in the sense of "assembling" car engines, but that's just nuts/bolts/minor fitment. I haven't fabricated an IC engine, hence the search for a starting point.

I think I'll just order those pushrod boxer plans from Germany, since they are readily available, and I'll post some details on what I come up with in 6 months or so.


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## Tin Falcon (Aug 10, 2011)

Apullin:
You are correct; your first post is asking about recommendations on engine plans. It is hard to do that without the full picture - the basic who, what, when, where, why, etc. It was not stated until a later post why you looking for the plans. Introductions do help a lot here. You accuse us of assumptions but made little attempt to give us a clear picture of who you are and why you are here until we asked a lot of questions. 

Clear communication is an engineering skill. Clear questions will more likely lead to clear answers. 

If you can lose the defensive tone , listen and ask nicely for the help you need, we can likely help you. Butting heads with administrators and mods and senior memberswill not get you help. 
Tin


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## Iron Cat (Aug 10, 2011)

Well, Good MORNING!!

Apullin, I've just read through all the posts on this thread. I have to admit, I don't always agree with Tin Falcon - but his last post is right on the mark.

Right up front, folks here like to get to know each other. Since members use so many different 'handles', hail from all walks of life, and post from virtually every part of the globe, it's considered a simple courtesy. I saw more than one query to that regard, which repetition finally led to a few small bits of a picture of 'you'. Those random bits pulled together, weren't as concise as a single, opening intro - including a clear explanation of your needs and intents.

In the past, there HAVE been students who have come here, definitely expecting too much to be done FOR them. Unfortunately, in the wanderingness of your posts, even I can see where that could be inferred. Your last post claims it's not so with you, and I expect anyone reading it (including Tin) will breath / has breathed a sigh of relief. The more recent, and gradually more intense, posts that you decided needed a defensive response, would not have, had you been more clear from the beginning.

Can I make a suggestion, engineer-to-be? Try to create one organized, helpful request - with the who (that's YOU - a bit of a bio, please?), what, when, where, why, how stuff needed for an organized, helpful response. The folks on this board, especially amongst the "administrators and mods and senior members", are ALL ABOUT helping. If you choose to present yourself as ready-to-learn, I honestly think you will be pleased with the results.

My two cents worth, tooooooo early on a Wednesday morning .............. zzzzzzzzzzz


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## steamer (Aug 10, 2011)

Iron Cat

Dale couldn't have said it better! ;D


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## doc1955 (Aug 10, 2011)

You say you want a starting point over and over so attached are a motor to use it's inthere some where just need to release it ;-) 

View attachment STARTING_POINT.pdf


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## Tin Falcon (Aug 10, 2011)

Doc I think this guy may need some help understanding what is in the box. before he tries to think outside.
 We are here to help all that want to learn and put out some effort. 
Tin


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## Cedge (Aug 10, 2011)

Nothing said so far changed any of my perceptions of the situation. My comments are the same as I'd give to my own kid or grandkids. Sorry if they caused you discomfort.... it's one of those grandfather things. 

Steve


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## dalem9 (Aug 10, 2011)

Hi all I am a newbe here,And I have read alot of the post for the last few months. I was almost afarid to ask a questions because of a post that I had read about someone who was looking for a fast and easy way to get some plans , I am not here to to have someone do all the work for me And would never ask that . By what I have read you guys really know your stuff.My dream in life is to build a live steam loc.And this I am doing .I am A self tought michinist I have only had metal shop in high school. I finely got the tools that I needing to achive this goal. I have been working on this engine for eight years . I need help on how to figure out the oriface size for my burner for I have changed the fuel from coal to butane . I have bought lots of books to try to figure this out but have not been able to as of yet.I am the guy who every one in the neightor hood comes to for help ,But I have no one to turn to ,so I am so very happy to have found this site Thanks Dale


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## 1Kenny (Aug 10, 2011)

Hi dalem9,

There are some really helpful guys in the Boiler section that should be able to help or get you in the right direction. Don't be afraid to ask. Some may bark like a dog, but they don't bite.

Kenny


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## dalem9 (Aug 10, 2011)

Thank you very much I will check out Dale


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## steamer (Aug 10, 2011)

doc1955  said:
			
		

> You say you want a starting point over and over so attached are a motor to use it's inthere some where just need to release it ;-)



There is no need for insults.  lets all be civil please.

Dave


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## mu38&Bg# (Aug 11, 2011)

I see. The main point I'm trying to make is a model engine design is not going to be anything like what you are after. If you've studied engine design, just get on with it. It really isn't an easy task. I've been studying engine design on my own for about 4 years now and the volumes of texts and papers available is incredible. You have to start somewhere, but I don't think a model engine design will help much. Model engines are first and foremost designed to be easy to produce. This limits the power output and efficiency. A model engine design will begin at maybe 500g/kWh what will yo do with that? The Honda GX35 is 360g/kWh. One more thing, most model plans are scarce on surface finish, surface treatment, and fit & clearance details. Google is your friend. There are plenty of sites for Eco Marathon teams some having quite detailed specs. The rest is up to you. Performance varies dramatically at Eco Marathon from 1000+km/l to 60km/l with a huge 20% difference from first to second place. How engine design and driving come together, I don't know.

I've been working on an engine design for a year now, for a model airplane type application. Having countless RC engines to look at, it was easy to see what technology is used. It's fairly simple. I wanted to see what was more state of the art for little engines and purchased a Honda GX25 and found a drastic difference in design. By looking at several existing engines I'm fairly confident what I came up with will work. If it were me, I'd start dry based on the existing teams data.

Which injector are you using? Or were you able to get the tiny Bosch just for Eco Marathon?

What are the basics design specs so far?


Having been on message boards for so long and even when I worked in the hobby industry where we sold electric motors, so many projects begin as "top secret" that it doesn't bother me. Ask the right questions and the details come out. If they want help, details are shared and normal discussion ensues. Sometimes the individual didn't know what they were doing. Other times it was an engineer just a bit outside his field. If they didn't want to share details you just move on.

For those that don't know US copyright law says a work is protected for 70 years after death of the author. Longer if the family chooses to extend it or less if they choose to forfeit.

Greg


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## apullin (Aug 12, 2011)

dieselpilot  said:
			
		

> Which injector are you using? Or were you able to get the tiny Bosch just for Eco Marathon?



I'm not familiar with the "tiny Bosch injector". The injector we, and a lot of other teams, use is a Keihin injector that flows around 33 cc/minute. This does work for the power ranges that we're looking at, but at fairly low duty cycle.
I've built an experimental injector based on that one, whereon I removed the orifice tip at the very end of the injector and put my own new end on, with a smaller orifice. The stock orifice has two 150 micron diameter holes in it, and I've been able to reliably make 30 micron diameter holes using the UV laser in my lab, so we should be able to trim the fuel flow way, way down. Flow testing is forthcoming.



			
				dieselpilot  said:
			
		

> What are the basics design specs so far?



I wasn't quite expecting to delve into design specifics in this thread, but I have your attention now, so I may as well. Of course, I understand that no "model engine" already has this feature set. I'm pretty long-winded, so this is going to be long.

The design specs are loose so far; the 35-50cc displacement is chosen based on power requirements and estimates of achievable power per displacement.
That being said, we know it'll be: 
- 4-stroke
- air cooled
- gasoline burning
- throttled
- fuel injection (easy for me, granted necessary tuning)
- computer controlled TCI spark (easy for me)
- As many ball bearings as possible
- Electric start
- compactness / lightness
I've seen plenty of _terrible_ e-start additions, and it's a classic example of how adding it afterwards is a lot of effort for mediocre results.

Overhead valve & cam are desired based on the significantly higher HP/liter that's been achieved with that configuration. I understand that this might be a red herring; I've considered that it might be "better" to have relatively low power/displacement, if higher thermal efficiency can be had in such a configuration. I can't fully optimize the design in a single shot, so ... that is being elided for now.

A desired feature would also be ... ease of construction, so once I produce all the CNC programs and jigs, I can easily spin off multiple copies of the engine.
I mean, making a cylinder should only take a few _minutes_ of cutting time on CNC lathe. And the liners/sleeves could be directly finished to 25 micron concentricity! If I built a honing tool, I could probably even finish hone them right in the chuck.
Interestingly, I often hear scoffs when I say how I want to reduce this thing to a series of automated manufacturing steps, but I think there is a serious boon therein.

Targeted engine speeds are for a single stage transmission, but there's only so far that can be practically taken (~10:1 with a huge output sprocket). Building a reducer box directly into the engine would be a neat feature, I think. That nice mini T5 transmission would be great! But the complexity of that in and of itself is so huge.
I don't think adding an integral speed reducer will be hugely difficult.

As many ball bearings as possible; possibly even little end con-rod needle bearings. Every model engine I've looked at so far uses little end bushings.
Oiling system is to be determined, and I was hoping to learn something about that by looking at a myriad of engine designs on this scale. I've had some ideas about how to do it using just a slinger and a minimal sump, or possibly a pre-pressurized oil reservoir.
Sort of on that sub-topic: Jerry Howell's V-twin engine is specifically described, on his website, as "able to run all day long as a generator". That certainly hasn't seemed to be the design goal for a lot of other model engine projects (nothing wrong with that), which makes me want to compare his design to others, so I've ordered a set of plans for that, too.

A counter-balancer would be great, too, although I've not seen one on a model engine yet. And since I can only afford junky, old motorcycles, I've not even dismantled a real engine with a counter-balancer in it.

So, desired/concept:
- DFM, in the context of CNC
- Integral speed reducer
- counter-balancer
- solenoid compression release

I hope that gives some picture of what feature set I am hoping to achieve. A motivator for a "ground up" engine was that addition of these to existing commercial engines would be equivalently as time consuming and complex as just designing it in from the start, and that there can be great value in integration. Very often, people are aghast at the mention of EFI, and the complexities therein; having extensive electronics and programming knowledge, that part will not be the challenge. Lastly, I'm also interested in just because, well, I am interested in the hobby. I've always wanted to build model IC engine, and it just happens that I think this is a really salient application.


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## steamer (Aug 12, 2011)

OK We have some substance to discuss.  A well thought out argument also.

I can find nothing amiss with your logic.  I will take your word on EFI.  A fall back plan would be simple carburetor, but you know that already.

If efficiency and ball bearings are the main thrust, you may be able to use a simple splash lubrication system and forgo an oil pump, which can be fussy in smaller sizes.  Getting oil up to an overhead cam may be a problem, but you could lay the engine down and let gravity help you there.
Specific power output will clearly have some bearing here.

What kind of environment is this engine going to run in?....in a lab or "down the road"
I would ditch exposed overhead rockers and pushrods if your going to get it dirty.  This would apply to a mileage competition car as well, as dirt will always find a a way, especially with exposed, oily surfaces.  Button the engine up with rocker covers ect

Getting prints of Jerry's engines would have been some advice I would have given. It's very mature of you to think of that, and act on that, on your own.

Am I to assume that your will use a simple clutch mechanism?  If your chain driving , watch your overhung loads, not only on the shaft, but the engine/gearbox housing also.


Better. ;D



Regards, Dave


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## Admiral_dk (Aug 12, 2011)

Forget about the balancer in such a small engine as there's no benefit and more friction loss. I can't say exactly where a balancer starts to help, but we're in the 150-200 cc area.

Likewise - I do not think that a small end needle bearing will do much difference with splash lubrication.

You can use the camchain to lift oil up into the cylinder head - it's been done on motorcycles.

Run the crankcase under heavy vacuum will lower the pumping losses quite considerable - use the exhaust to make it with a oneway valve.

I will not say it can't be done, but it will cost you a small fortune to make an engine anywhere near the quality of a Honda engine.


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## bearcar1 (Aug 12, 2011)

Adding flys**t to the pepper shaker....... I would certainly think that a toothed belt arrangement in the final drive would be of benefit over the usage of a chain and sprocket. It would be a lot fewer possible places for a mechanical failure to occur as well as not having to deal with lubrication factors. Especially in an exposed to elements environment. As for the valving, personally I would steer away from pushrods and rockers for some of the same reasons. EFI in my opinion would have huge advantages, probably the highest priority area to focus on would be the aspiration ducting and the overall frictional losses generated internally. 

BC1
Jim


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## steamer (Aug 12, 2011)

I would agree with the timing belt option for the reasons Bearcar1 has stated.  Probably lighter in weight also.

However, It's been done in cars and motorcycles for years with chain and from a splash lubrication perspective, it could provide some useful oil transfer.

That decision would be one of those design trade offs you hear about... ;D

Dave


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## apullin (Aug 13, 2011)

Steamer: You've made some good points there. Making a doubly supported output shaft should be straightforward and very worthwhile.
Valve train should/will be enclosed. That Nemitt engine *really* looks the part, since it already has that. Along the same lines, it has that copper tube running from the head to the case, which must have something to do with oiling, and thus, I'd really like to take a look at how the oiling system there is done; since they're not using the belt to lift oil up into the head, there must be something else ... 

The nearest equivalent "modern" engine I've seen is maybe some engines by Schillings, although there's zero availability of plans, as far as I can tell.

The clutch is _secret_ for now. There are rules in place that your clutch has to supposedly "completely disengage", but enforcement of that rule is lax.
Fallback is just to have the correct bushings to apply the commonly used types of clutches (machinery or go-kart). My estimates of the complexity of a 'custom' clutch system are that it would be as or more difficult than just a basic running engine.


I'd definitely like to use a timing belt. Tiny chains have been problematic, and doing a belt is seemingly pretty easy; forgiving alignment, plenty of parts available cheaply.

Aspiration/ducting will be an interesting issue, due to the aspect ratio of the intake pipe, due to the smallish diameter, so any length increases will quickly make it straw-like.

Admiral_dk: I gave thought to the balancer just for smoother running. The vehicles are often very light, so light that their lawnmower engines are 25% of the overall weight. Those things don't have counterbalancers, and the vibration of the whole system can be quite severe.
You really think that making an engine of any "quality" will be really expensive? It's just aluminum and bearings and such ... maybe a few bits of exotic 4000 series aluminum will be needed for the pistons. I suppose if I want to try and arrange to get them cylinder Nikasil plated or anything, that will start to cost for custom setups in someone else's shop.

The exhaust->vacuum idea is great, but as I understand it, you need a highly "tuned" exhaust to actually get that to work? But that should be an external part that can be made after-the-fact, and I'll check it with a vacuum gauge down the road somewhere. And intake-to-crankcase ventilation is explicitly disallowed, unfortunately.


A prof was was just today goading me into making a carbon-carbon composite block, cylinder, piston, and conrod.... phew, now that would be pretty challenging and expensive ...


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## 1Kenny (Aug 13, 2011)

Hi apullin,

Running a belt to drive the camshaft is a good idea. A couple engines I've seen had a hub with a slip pully on the cam. It had two slots for bolts 180 degrees apart so the cam could be degreed to the crank. The hub was threaded for the bolts and the slip pully had the slots to adjust degree. The Gates site is a good place to learn about belts and pullys involving loads and sizing.

Kenny


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## Admiral_dk (Aug 13, 2011)

How shall I put it ...?... I'm sure I can make a OK engine if I have access to the right tools. Given more time I'm sure I can improve it to be a good engine, but there's quite a step from there to a great engine (reliability, performance etc.) - the scale do of cause depends on the expectations and demands. I'll be very happy with first pop on my first engine, but knowing myself, I know that soon after, it's not enough and I'll rise the bar for what I expect from my own projects. In the Japanese motorcycle industry there's a saying about the brands and there racing efforts : Yamaha - Win sunday => sell Monday, Suzuki - Race what we sell, Kawasaki - Rich boys racing (MC division is like 1% of a very big company), Honda = NASA ~ The most advanced solutions to the problem.

I'm not a Honda man, but I certainly respect them and it will cost millions to create and develop an engine similar to any Honda model.

Until a few years ago, just about every lawn mover sold here in Denmark had a Brigs & Stratton engine and they are from 175 to 350 cc up where I said it will make a difference - but you talk about making a 35 - 50 cc engine - make the piston and conrod light enough, a decent balanced crank and you'll have no problems - a Honda CD 50 never made any vibration you could feel.

Create the vacuum by welding a 4-6 mm. inside diameter tube perpendicular to the exhaustheader, at least 20cm. from the head (for heat reasons) connect the oneway valve with a silicone tube - voila.

Best wishes
Per


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## 1Kenny (Aug 13, 2011)

Something to read about camshafts. 

http://harveycrane.com/

Kenny


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## mu38&Bg# (Aug 13, 2011)

Many teams publish basic numbers. You have put quite a bit of thought into this already. Obviously there are some unknowns that have you concerned. Visiting the team sites would address many. Like cog belt drive being very common for cams. Teams post the data because they know making everything come together is much harder than having the data. One of the engines I've seen had a very large "something" on the crankcase. I can only guess it had something to do with crankcase ventilation, but it was huge.

Your understanding of how CNC is used is very basic. I certainly doubt you can run one or even a few cylinder liners and expect the sort of tolerance you think you'll achieve. If you are very familiar with the machine, the tooling, the material, etc., you might get a part that's pretty close. The kind of tolerances you're talking about require an expert operator to achieve. My father runs setup and production on CNC lathes, using softer material and much smaller parts, and has to chase the machine to get a 25 micron tolerance. One comment, you won't be honing the liner until it's installed in the block unless you can be assured the block is as round as you want the finished cylinder to be or the liner is stout enough that it won't distort.

Nemett has a tube connected to the head. Fluctuation of crankcase pressure forces some oil to the top. You could get creative and check valves in a few locations to assist the flow. Most of the Eco engines seem to have open top ends. For the short time they run, lubrication can be handled a variety of ways. On vibration, I think most is due to single cylinder torque.

You really should just get on with a design. You'll find, much as I did, making everything fit to meet design goals will be the hard part. These engines run ridiculous compression ratios. Valve timing, valve clearance, valve lift, valve angles, piston and combustion chamber shape, etc., will all interact in the final outcome of the design.

Cost, won't be out of line. If you have access to machines that can handle the sizes of parts involved, costs will be mainly tooling and fixtures. Grinding cams could be tricky. If you plan on using something other than a simple cast iron ring, a stock ring for a production engine can be very inexpensive, or a custom faced ring might be hundreds if not thousands. Checking to see what parts are available and basing the bore around that might be well worth the investment in time. Similar to the wrist pin bearing. Most <35CC engines use an 8mm wrist pin and corresponding needle bearing, maybe 6USD for both. Stray from that and you'll at least have to make a wrist pin, harden, grind, etc.

It's a great project to be involved in. Sometimes I think about going to college to get in on one of these. Good luck.

Greg


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## steamer (Aug 13, 2011)

I agree with Greg here.  Get on with the design...that takes more time than most people realize.

Lots willl get sorted then.  Pick a direction and keep moving.

Dave


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## steamer (Aug 13, 2011)

A prof was was just today goading me into making a carbon-carbon composite block, cylinder, piston, and conrod.... phew, now that would be pretty challenging and expensive ...


Yes....and ask him to pitch in during the layups too...see if he changes his mind. :

Dave


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