# "Topsy"  0.375c.c. compression ignition engine



## roadrage17 (Jun 3, 2009)

This is my first build it is a engine called "Topsy" 0.375cc compression ignition engine by G Hugh.
Should be an interesting first build , got the plans , going to start it next week . 
It should look like this hopefully...



Pictures to come ...

Thanks Roadrage.


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## Maryak (Jun 3, 2009)

RR,

Good luck with your build. IMHO these are fascinating little engines.

Plenty of piccys please 
	

	
	
		
		

		
			





Best Regards
Bob


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## GailInNM (Jun 3, 2009)

Roadrage,
Small compression ignition engines are fun. 
I am just finishing up a work in progress thread on a series of three that are about 1.6 times the displacement of yours. If you have not seen it, it is at:

http://www.homemodelenginemachinist.com/index.php?topic=4422.0

There are a few tips in it that work for me. Of course everyone has their own way of doing things. 

Please keep us posted as it progresses, and of course photos are always appreciated. 

Gail in NM,USA


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## itowbig (Jun 4, 2009)

ya i got to keep tabs on this build . ;D


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## roadrage17 (Jun 4, 2009)

heey guys 

thanks GailInNM ive had a quick look and some of the processes you did wer interesting.
hopfully get some build time tomoz so some pics then.

thxs roadrage


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## roadrage17 (Jun 5, 2009)

oki here we go first day 

Thought i wud make a start on the crankcase .
its made out of dural. have plenty left over for muck ups lol.








Then here we go think i went overboard on the amont of pictures
Also my camera died so theres no pics of me on the divideing head.




























Show you how small it is.






well thxs for looking , its starting to look like something lol

Roadrage


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## 90LX_Notch (Jun 5, 2009)

Very cool roadrage17! Thm: Did you purchase the plans or are they a download?


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## roadrage17 (Jun 5, 2009)

90LX_Notch they are purchased from http://www.myhobbystore.com there are loads of other plans aswell

thxs for your comment 

Roadrage


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## 90LX_Notch (Jun 5, 2009)

Thanks roadrage17 for the prompt answer.


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## roadrage17 (Jun 9, 2009)

had few hours build time so heres some pics of what i a have done...

My set up.






Putting the rads on the underside of the crankcase..






What i ended up with after my lunch break hehe...






thats all for now 

thanks roadrage


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## Maryak (Jun 9, 2009)

RR17,

Very nice. :bow: Gee it looks to be very small, can you put a rule against it in some future shot please. ???

Edit: 
	

	
	
		
		

		
		
	


	




 Just looked at it in your hand - "IT IS SMALL"

Best Regards
Bob


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## roadrage17 (Jun 9, 2009)

hey guys

i have a question when i get to lapping the cylinder and piston , im not really going to have a clue.
the piston going to be made out of cast iron and cylinder out of EN25 or 24 cant remember similar to toolsteel i think .
the way im thinking about is to turn up a piece of material to the size i want to cylinder bore to be and just run it up and down on the lathe with some lapping paste.

questions..
1. Is what ive just said correct?
2. What material should i use to lap?
3. How much should i be under sized on piston or cylinder?
4. should i mate cylinder and piston.


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## roadrage17 (Jun 9, 2009)

haha :big: thxs bob , yes it is small i didnt realize that it would be that small lol. 
And more still got to come of it yet. Not going to be much bigger and 1" .

RR17


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## Maryak (Jun 9, 2009)

RR17,

Bob's version of lapping.

1. If your lap is made to the bore size then the bore will be oversize when its lapped. I try to machine the bore to 0.001" undersize and the last thou is removed by the lapping process. The lap must be small enough to accommodate this plus some lapping compound plus working room - say 1/64". The lap to cyl length ratio should be a minimum 3:1, i.e. the lap should be 3 times longer than the cylinder.

2. Ideally the lap should be of a softer material than the object being lapped - definitely NOT harder.

3. cyl 0.001" under piston 0.001" over.

4. Most definitely - I do this by mating them with tallow after the piston has entered the bore about 80% of the way by a hand push.

It is very important that ALL traces of lapping compund are removed before attempting to mate the parts.

Hope this helps. ??? ???

Best Regards
Bob


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## roadrage17 (Jun 9, 2009)

Thanks bob all helpful and i saw your video on it and thats the way im going to do it .

One question though say that the piston had to me 1" , so i would turn it down to 1.001 like you were saying, but with the lapping material did you mean the 1/64 is how much it should be undersize to the piston so 0.984 is what i should turn the lap to . Am i just confusing myself. sorry if im not making sense :big:.

thxs 

RR17


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## Maryak (Jun 9, 2009)

RR17,

Yep, it's easy to get confused. 

For a piston and bore of 1" nom. 

cylinder length 2" - Lap length min 6" lap diameter 0.985"

Piston length 3/4" - Lap length max 1/4" lap diameter 1.015"

The 1/64" clearance applies irrespective of the aimed for diameters, (within reason).

Hope this helps.

Best Regards
Bob


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## roadrage17 (Jun 9, 2009)

Got you bob thxs for your help, Im sure you will come in handy when i get stuck ;D
any reccommend lapping paste to be used? 

Best regards RR17


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## Maryak (Jun 9, 2009)

RR17,

I use automotive valve grinding paste fine, followed by dremel polishing paste, and lastly tallow for the mating.

Best Regards
Bob


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## ozzie46 (Jun 9, 2009)

Maryak  said:
			
		

> RR17,
> 
> I use automotive valve grinding paste fine, followed by dremel polishing paste, and lastly tallow for the mating.
> 
> ...





  Bob,  What does the tallow do? I never heard of this before. I have heard of lapping and such but not mating and tallow. I thought the lapping took care of the fine fit.

  Ron


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## Maryak (Jun 10, 2009)

Ron,

The tallow acts as a wetting agent and allows movement between 2 parts which would not be possible using lubricating oil. In the case of a model CI engine the compression ratio is from about 16:1 to 20:1 and relies on the fit of the piston and contra piston in the cylinder to achieve this. The wetting action of the tallow allows the final face to face mating to a very fine tolerance. The mating is complete when the tallowed power piston will pass all the way through the cylinder with a reasonably tight hand push.

Hope that explains it. ???

Best Regards
Bob


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## ozzie46 (Jun 10, 2009)

Bob, Is this just done on non ringed pistons or is it needed on ringed pistons as well?
  I'm hoping to get into IC engines eventually.

 Ron


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## Maryak (Jun 10, 2009)

Ron,

IMHO this mating process is not required where rings are used. The piston and cylinder are not in contact, only the rings and cylinder, (a much smaller surface area). The rings are compressed to fit the cylinder and have a specified clearance across the ring gap when compressed into the cylinder via the ring grooves in the piston. This in turn exerts pressure between the ring and cylinder which for a model SI or steam engine should be around 6 to 8 psi and for a CI around 12 to 18 psi, providing the necessary seal for compression and preventing blowby into the crankcase. 

As an aside I did some research into piston ring tribology and when I compared this to an 1890 fitting and machining book the difference in the results from the boffin formula in the tribology to offset by X/64" in the old machinists book was infinitesimal. Our ancestors new more than we sometimes give them credit for.

For a good result piston rings should be made from spun cast iron, irrespective of cold formed or heat treated.

Hope this explains a little more about a very fascinating aspect of pistons and cylinders. Many thanks to Mr Ramsbottom and Mr Lanchester pioneers who ran rings around their contemporaries. :

Best Regards
Bob


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## roadrage17 (Jun 10, 2009)

Here some more pics for yous...

Had some time to put the hole in where the cylinder going to be screwed on ...

The reason this was done on the lathe is theres a small step on the inside.

Centering it on four jaw chuck (took some time)






Slooooooooooowly getting there.






And it finished, with some cleaning up to do on it.





Thought i would share some other projects on the go...

My flintlock.






My Lathe.






Think I've got to many projects on the go for an apprenticed haha

Best Regards

RR17


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## ozzie46 (Jun 10, 2009)

Thanks Bob.

  RR17
 Good work, I cant believe how small this is.


 ROn


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## roadrage17 (Jun 10, 2009)

Yeah ROn lol it will sound like a bee in a tin can if it starts.  

RR17


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## Maryak (Jun 10, 2009)

RR17,

Nice job on threading the crankcase. :bow: :bow:

Best Regards
Bob


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## roadrage17 (Jun 11, 2009)

AARRRRRRRRRRRRR  

The first mistake has happenned , misread the drawing and the hole thing rong because of it :

Oo well , the fun is in building it. 

So ill have to make anouther one ill update u guys once i get back to where i was .

Best reagards

RR17


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## Maryak (Jun 11, 2009)

RR17,

Think of it as a test piece to determine the possible ways of going wrong. My come in handy box has a large collection of these test pieces.

Best Regards
Bob


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## Seanol (Jun 11, 2009)

RR,
As you saw in my WIP post, I made some mistakes too. What helps is having more stock sized and ready to go! With the lessons I learned from the first I should have netter luck next time around.

Sorry to hear about your misfortune and look forward to seeing this little beast run!

Sean


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## roadrage17 (Jun 11, 2009)

Yes bob thats what i will call it a test piece the first of many im sure.



As you can see from one of my first photos ive got enought for bout 5 more of these crankcases haha :big:

cheers Sean looking forward to seeign your beeing put together think i might do i bigger one next time.

Best regards 

RR17


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## roadrage17 (Jun 23, 2009)

i Am glad to say the crankcase and also the fuel tank are nearly done so new pics on the way 

Best regards RR17


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## 90LX_Notch (Jun 23, 2009)

Looking foward to seeing them RR17.


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## roadrage17 (Jun 26, 2009)

Right guys back to where i was and a bit further.





As you can see the new crankcase has been made with a near finshed fuel tank. Also i have finished the carbaretor off on the Crankcase. 

Best regards


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## Seanol (Jun 26, 2009)

Roadrage,
Looking good!

I have had some setbacks but I am still forging ahead.

Can't wait to see it together!

Sean


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## roadrage17 (Jun 26, 2009)

Thxs for the interest guys.

Sean ive been following yours aswell and i think i should of made two aswell lol.

Best regards RR17


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## Seanol (Jun 26, 2009)

RR17,
I am making 4! 
I started on a second crankcase and was side milling for the mounting tabs. As i kept feeding the mill in I noticed the mounting tab getting lower and lower...

The Ti pulled the endmill down out of the collet!

So on to #3...

Sean


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## roadrage17 (Jun 26, 2009)

Owch that sucks but at least you wont have that happening again on your third. 

I look at it this way if you make a mistake, and then remake it but make a different mistake than last time, you've made progress.
And eventual you will finish it but with loads of lessons learnt in the progress.

Do you all your machineing at home, cause at the moment i do all mine at work when i have spare time. 
Any machines you would recommend for me to buy. Also at work we have DRO ( digital read out) which i have always used . i no most machines out there dont have them is it hard to get as accurate without it or am i just being stupid.

Best regards 

RR17


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## Seanol (Jun 26, 2009)

RR17,
All my stuff is at home. I lucked into an older 13x40 lathe and I have a 6x26 grizzly mini bridgeport.

As I am biased I would recommend the bigger stuff as even on the 6x26 heavy cuts are out!

Without a DRO you will do a lot of measuring. They make it easier and you won't get bit with backlash issues. On the other hand, $600 and up will buy a lot of material/tooling! ;D

I have more time on my hands then money (read none of either) but I believe that when I am good enough at measuring I will look into the DRO as a way to go beyond where I am at now. My learning curve is so steep I need to get speeds and feeds down so I am not buying endmills all the time :big:

Here is my stuff from the "show us your lathe thread":


			
				Seanol  said:
			
		

> Here is my lathe and mill:
> 
> 
> 
> ...



Good luck with your decision and share it with the board,
Sean


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## roadrage17 (Jun 26, 2009)

Thanks for the quick reply sean. Gave me some ideas . Nice lathe and mill you have .

Best regards RR17


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## roadrage17 (Jun 26, 2009)

A questions for you guys out there is it nesscary to lap the main bearing and the crankshaft together. Or can i get away with a good finish and nice fit? 

Any comments would be helpful.

Best regards RR17


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## GailInNM (Jun 26, 2009)

RR17,
The Topsy has such a long front bearing that there should be no need to lap them, but because it is a front rotary valve a good fit will be necessary. On my small engines, I turn the crankshaft a few "tenths" oversize and then polish to size with 600,800,1000,1200 abrasive paper in order with a drop of oil. I back the paper with a piece of ground steel like a parallel. This will not take out all the machining valleys, but will smooth out the hills to give more of a bearing surface.

Nice work on the Topsy. The way you are going it will be a fine engine.

Gail in NM,USA


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## roadrage17 (Jun 27, 2009)

Thanks For the reply GailInNM very useful and i will put it to use in this project of mine 

Best regards 

RR17


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## roadrage17 (Jun 30, 2009)

more progress  . Bored out and screw cut for the fuel tank to screw in . and also pressed the main bearing in .







Best regards RR17


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## roadrage17 (Jun 30, 2009)

There are some problems im having though because of the size of the engine i cant use a boaring bar, i tried to grind one up but it just chattered to much. For example to do the main bearing i would of idealy boared it near size then ream it out. instead im having to use a drill then ream it, But the drills are wondering! So im doing the best i can. Next Engine BIGGER lol. Like the one your doing sean. 

Best regards RR17


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## Seanol (Jun 30, 2009)

RR17,
As long as you use aluminum you will be fine. Ti is for the birds! 

Sean


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## roadrage17 (Jun 30, 2009)

Yeah point taked Sean , 

Regards RR17


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## DavesWimshurst (Jun 30, 2009)

RR17,
The chatter problem and crooked drilling problems can be alleviated by using D bit reamers as described recently: http://www.homemodelenginemachinist.com/index.php?topic=5251.0
The D bit should make a straighter hole which could be reamed with a standard machine reamer if the D bit doesn't give a smooth enough finish. Adjust shaft size to suit.
Hope this helps.
Dave


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## roadrage17 (Jul 1, 2009)

heey guys quick update ive looked more closely over the drawings and ive found out im missing quite a few dimensions on the cylinder, and few other things. So for now the project on hold till i get some more.

However on a brighter note ive got some drawings from hom shop machinist i think it is, and the engine called "Alpha". Ill get some pics up have started the crankcase so far.

Best regards RR17


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## Seanol (Jul 1, 2009)

RR17,
Sorry to hear about the Topsy, I was looking forward to it. Can't wait to see the new "Alpha" project!

Looking forward to it,
Sean


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