My First Engine Build

[Mechanicboy]

I use solvol autosol as a final polish to both piston and cylinder, but never with the piston in the cylinder. That is simply a recipe for failure; the only thing that should come between a piston and a cylinder is oil. Trust me, I have in excess of 50 engine builds behind me of more than 40 different designs.

I have never had trouble to lap the piston straight into the cylinder and compression is still good as before for several years in my model engines. The method I learned from Jan David-Andersen (model engine maker who produced these D-A engines) when I received the book about model engine construction authored by Jan David-Andersen. The main problem is that there is no practical training of younger generations to lap the piston / cylinder and lap the piston into the cylinder.

Download and read this book who are translated from norwegian to english https://www.google.no/url?sa=i&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwiLkYK9kOTeAhUHiiwKHYLGA08Qjhx6BAgBEAI&url=http://adriansmodelaeroengines.com/catalog/attachments/Jan%20David-Andersen%20Diesel%20Motor.pdf&psig=AOvVaw2WvPUWuEUXUmX55vXsP3Sa&ust=1542843069001768

And the history about these D-A engines.. http://blhf.org/DA-motorer

 

[minh-thanh]

Check to see if your piston is round. Sounds crazy, I know. WOB

And check if your cylinder is round. ?? check it with light.
I did some pistons in accordance with the not round cylinder
Some changes when I make font-bearing and crankshaft, I think it will be more closed.

 

[KenC]

Forget using a ringed piston since there is a lot of science in the design and making of piston rings to get them to work properly. Modern engines of around 3cc never use piston rings as they are a source of difficulty and never necessary.
From the fuel suction tests you have done I think fuel suction is not the problem, just so long as ALL the port positions in the cylinder and crank are as per the design. IF, and with all due respect to a first time builder, if all your dimensions are as per the drawings, all that is really left is your piston and cylinder fit. Ideally the bore should be slightly tapered, in your case half a thou from the bottom to the exhaust ports, then at the most a tenth or two from the ports to the top of the cylinder. I say "ideally" because a parallel bore will still allow an engine to run, just not at its best. The surface of the cylinder should have a mirror finish, use a wooden lap soaked in metal or chrome polish for the final shine. Forget all about the cross-hatched finish on commercial engines, this is the result of using a hning machine, and is of no importance. Mirror finish is better. The piston should be parallel, lapped to a similar mirror finish, and it should enter the cylinder up to just past the exhaust ports. An engine finished this way will be tight to turn over top dead centre, and when freed after a run, you should be able to turn it to dead centre, release it, and it should hold compression still at tdc without a leak for at least a few seconds. Just tap it from tdc and the piston should bounce down the cylinder under residual cylinder pressure. If you put your piston at tdc and it stays there for ever, even after you nudge it, the fit is too slack to run, even for a glow engine where piston seal is not so critical as with a diesel.
So, firstly, check, double check, then check again, that the engine is totally built to the dimensions on the plan. Yes, I know you have already done that, but do it again, or get a pal to do it for you. When you have done that, put your ringed piston in the bin, re-finish the cylinder, and make a new piston. Do not ever, for any reason, enter the piston into the cylinder with anything other than a meticulous cleaning with acetone, and a sloshing of light oil. If all of that fails, send the engine to me and I will sort it out for you. Seriously.

 

[justisla]

Fit a carb off another commercial engine. OS or Irvine- but do not use MDS they are useless carbs. You may have to make a sleeve adaptor to fit but make sure it is airtight. Then use an electric starter with a prop spinner on the prop.

 

[Mechanicboy]

Ideally the bore should be slightly tapered, in your case half a thou from the bottom to the exhaust ports, then at the most a tenth or two from the ports to the top of the cylinder. I say "ideally" because a parallel bore will still allow an engine to run, just not at its best. The surface of the cylinder should have a mirror finish, use a wooden lap soaked in metal or chrome polish for the final shine. Forget all about the cross-hatched finish on commercial engines, this is the result of using a hning machine, and is of no importance. Mirror finish is better. The piston should be parallel, lapped to a similar mirror finish, and it should enter the cylinder up to just past the exhaust ports. An engine finished this way will be tight to turn over top dead centre, and when freed after a run, you should be able to turn it to dead centre, release it, and it should hold compression still at tdc without a leak for at least a few seconds. Just tap it from tdc and the piston should bounce down the cylinder under residual cylinder pressure.

Funny to read your comments,.. not all is correct..

Mirror finish surface is not really good idea, we need oil pockets in the cylinder/piston surface to last long time. Also dull gray surface after lapping is done. When the engine is assembled, it must be pinch when the piston is on way to TDC in the cylinder which means the cylinder is tapered. The tapered cylinder is created by the piston who is lapped into the cylinder at final stage, also push piston into in same time rotate the piston to create tapered cylinder. Never use wood as lapping tool, better copper, brass or aluminium due the wood is too soft. See at this link http://modelengineeringwebsite.com/Super_Tigre_12.html

In next post i am showing the unused engine in box with lapped cylinder/piston who are not mirror finished.

 

[KenC]

At the temperatures that our engines run at, do you really think oil will be retained in the grooves produced by a Delapena or Sunnen hone? Don't be so silly. And give me abreak, lapping a piston into a cylinder? I wonder what experience you have. Haveyou ever seen the surface finish on any of the high performance 2.5cc engines built in Russia for control line team racing? I guess not. They are polished using jewellers rouge to mirror finish. Likewise the tether car engines, the 1.5cc glows run at up to 48000rpm. Try that with your groovy finish. And I certainly never suggested to use wood as a lap, just wood soaked in metal polish for a final polish. If you do not have either the knowledge nor the experience of building high performance engines, it wouldbe better not to mislead novices with your imagined ideas. On the subject of cylinder taper, you are on the right lines.
I just read the link in the above post. He may be a competant engineer, but his piston/cylinder methods are not good. Honing bushes for a Quorn cutter sharpening machine are not the same as the requirements for honing a model diesel engine piston and cylinder. Is is all to easy to publish articles as if you are an expert. You would be better served to read my guidance on piston/cylinder fitting in the back issues of Model Engine World in my series on the construction of the Thaler diesel, or on our Motor Boys web site of MEW edited by my pal the late and much missed Ron Chernich.

 

[Mechanicboy]

The proof is these photo of factory produced D-A engines produced by Jan David-Andersen --> The picture tell more than you can talk about mirror like surface in cylinder and piston. In fact there is cross hatched surface in the cylinder and the piston by lapping. Did you not read Ron Chernich wrote in his homepage: The surface must be dull cray when the cylinder is ready lapped? As you see there is not mirror finished without cross hatch, the new piston has still marks of lapping while the used engine do not have more marks of lapping after the engine is running-in, also the piston has porous surface since the piston is cast iron and will remain oil inside to lubricate between cylinder and piston. With other: We can't do it better with tools to keep all tight tolerance before the engine is adapted by running-in. Also "the mountains" in the surface will be worned out to "the plateau mountains" then the fit of piston/cylinder get correct tolerance under running-in. In case the surface is mirror like (without cross hatched/dull gray) and will be difficult to adapt the piston into the cylinder and create the tapered cylinder. The ABC, ABL etc engines has cross hatched surface and porous aluminium piston as you can see with magnifier of same reasons to keep cylinder and piston lubricated. You can find the plan of D-A Satelitt in "Motor Boys International" book by Ron Chernich, there will you find my name.

 

[Mechanicboy]

KenC,.. as i wrote in earlier post: Did you not read Ron Chernich wrote in his homepage: The surface must be dull cray when the cylinder is ready lapped? Also no mirror like surface...

 

[minh-thanh]

Hi KenC !
I'm a new ,and still learning and I'm not sure I understand about it

and it should enter the cylinder up to just past the exhaust ports. An engine finished this way will be tight to turn over top dead centre, and when freed after a run, you should be able to turn it to dead centre, release it, and it should hold compression still at tdc without a leak for at least a few seconds. Just tap it from tdc and the piston should bounce down the cylinder under residual cylinder pressure. If you put your piston at tdc and it stays there for ever, even after you nudge it, the fit is too slack to run, even for a glow engine where piston seal is not so critical as with a diesel.
.

I have a question
If I remove the plug and turn the shaft,The piston moves freely in cylinder Or it will be a bit tight near TDC ?

 

[Mechanicboy]

Hi KenC !
I'm a new ,and still learning and I'm not sure I understand about it

I have a question
If I remove the plug and turn the shaft,The piston moves freely in cylinder Or it will be a bit tight near TDC ?

Hi Minh-Thanh..

It must be tight near TDC to keep compression. If the cylinder was parallel, the compresion will be lost when working temperature is rising..

Except case hardened steel cylinder and steel piston, there is not tapered cylinder due both expanding about the same size (you can push piston in both way in the cylinder without pinch in the Cox engine). The degree of hardness is not the same in the cylinder and the piston to prevent galling. The surface is more mirror like unlike from lapped steel cylinder/cast iron piston and need short running-in. It's difficult to make the steel cylinder and steel piston in home workshop and it cost too much to buy the special grinding/honing tools.

 

[KenC]

Don't waste your time quoting Ron's wisdom to me. Ron was a computer prof at Brisbane university, and much of what he knew about engineering he learned from myself and the other motor boys. It is rather silly to quote Ron's website to me since I was a significant contibuter to the site. Ron was a great guy and missed by all of our group. His website will remain a good reference source for many in the model engine hobby.
And the cross hatch pattern on cylinders is produced by the use of a Delapena or Sunnen hone (or similar machine) and is not a requirement, it just happens to be good enough. My own machine when I was engine building was a bench model Sunnen, but I always polished for the final finish after lapping.

 

[c_mario]

Wow Guys,
Take it easy. I appreciate your differing points of view and your offer Ken. Both of you obviously have had success in building engines and have your own techniques that work for you and that's great. I am convinced its the piston cylinder fit, so I will proceed down that path again. Will put ringed piston in bin and do cylinder and piston again. I do find it difficult to measure the cylinder taper thou. I do have those little telescoping bore measuring tools but I don't think I am using them correctly. Like these https://www.machineryhouse.com.au/Q618?gclid=EAIaIQobChMIk4Xdm7L23gIVyYRwCh2dDwFjEAQYAiABEgJeZ_D_BwE
Regards
Mario.

 

[f2cf1g]

Those things are no use for the tolerances applicable to pistons and liners. To have any hope of measuring taper accurately you need a bore gauge. However, that's not necessary provided you follow Ken's advice and lap the liner and the piston using the techniques described on Ron's site. I too was a computer consultant but even so successfully built an ML Midge diesel using that method. Took five goes at the piston though.

 

[KenC]

It is not really about different points of view. An engine finished with a dull grey appearance or a commercial cross-hatched pattern will clearly run and if done correctly, it will run very well. But it is just plain silly to say that it is a requirement for pistons and cylinders to be finished this way. It is also a bit pointless to quote texts written in 1945 by someone who eventually became a commercial engine builder, and to show examples of his vintage engines, and in so doing to ignore progress. It also pees me off to be told how I should have been building enigines over the last 20 years by someone who appears to have limited experience of engine building and modern techniques, and who goes on to quote the writings of Ron Chernich, who was one of our own group.
But to return to tapered cylinders. The telescopic gauges are not easy to use but can be of use if a direct reading bore comparator is not available. Basically any measuring kit is better than none at all. Interestingly I see that bore comparators from China are available on eBay for a fraction of the cost of the Mitutoyo versions that I used. For sure bore taper makes an engine run well, but a parallel bore will still work and allow an engine to actually run, which is surely all a beginner with his first engine build actually wants isn't it. It would be a naive first builder who though he was about to produce a high performane engine for his first attempt. I guess most first engines are destined to sit on a shelf after their first run, rather than destined to take to the air as did most of my own engine builds.
I joined this forum because as an experienced engine builder and one of the original members of the Motor Boys, I thought that even though no longer actively building engines, I had something I could contribute to the hobby. I now see that I was wrong to think that, and I shall bow out and quit banging my head against the wall. Life, mine at least, is far too short.

 

[ShopShoe]

f2cf1g,

I would say that I agree with you on bore gages.

But, FYI for c_mario and others (me included), I think the video below provides a very good tutorial on how to successfully make use of the telescope gages. My accuracy improved a lot once I used the techniques Abom presents.



Just trying to be helpful,

--ShopShoe

 

[KenC]

His technique is exactly how I do it but I have a further comment. I have expensive telescopics by Moore and Wright, and some cheaper chinesebudget ones. If I lightly snug the clamp, rock it in the bore and then withdraw it, I like to tighten it a bit more to make sure it does not change when using the mike to measure it. When I do this with the Moore and Wright, it holds its setting. When I do this second tighten with the cheaper gauges, the setting changes. So beware if you use cheap gauges.

 

[Mechanicboy]

It is not really about different points of view. An engine finished with a dull grey appearance or a commercial cross-hatched pattern will clearly run and if done correctly, it will run very well. But it is just plain silly to say that it is a requirement for pistons and cylinders to be finished this way. It is also a bit pointless to quote texts written in 1945 by someone who eventually became a commercial engine builder, and to show examples of his vintage engines, and in so doing to ignore progress.

Yes, you (KenC) wrote without to try it self with your own model engines after the method from 1945, it's not important to speak about to compare these engines either it's vintage or modern. Jan David-Andersen wrote the book in 1945 and you can't ignore how he wrote who was easy to create and lap the piston/cylinder without problems who are explained in the book. I did as he explained in his book how to create and lap the cylinder/piston, never had problem with my model engines when i created and lapped the cylinder/piston. Then you can not continue to bombard and ignoring all that I have shown and written in previous comments.
See at this link, Jan David-Andersen is a true engine enthusiast. After he stopped making engines for sale from 1950 to 1964, he continued to make engines for his own use. Here he shows one of his recent creations in 9/14-2015, see this movie after the MOV.file is downloaded..
http://blhf.org/sites/b/blhf.org/files/688d5caaa75f923139f1443bdb631288.MOV

About measure the cylinder with measuring tools, use cylindrical plug gauge or steel ball in right bore size (with brass shaft soldered on the steel ball to hold with fingers) to control the size and check taper since not all home machinist has expensive measuring tools such as bore comparator.

 

[minh-thanh]

Hi c_mario !
I have advice for you
Although I have made two engines with cylinder diameter 16mm and a engine with cylinder diameter 13.3mm , I just want to find out: how it works, everything, .... I have to say is really I hate do it again. Do not waste time with it. It does not prove anything.
If you want to challenge the ability : OK, let's continue ,But It does not prove anything.
Otherwise, make the engine different with a larger diameter cylinder.
Or converted it into a 2 stroke engine with ignition and flywheel (I did the same with all my engines and it was easy to run) And enjoy the results .

 

[Naiveambition]

Not meaning to hijack the thread , but I have a question on the bore gage use.
How do you know that the guage is centered in the bore when you tighten. When I was using them I had to adjust till it felt centered then tighten , even so it took me a few times to get a repeatable reading. Now given they are a cheaply set and i do not expect much in accuracy. Do the more exspensive ones have tighter build tolerance fits that would not allow side movement in the guage.

 

[Mechanicboy]

Not meaning to hijack the thread , but I have a question on the bore gage use.
How do you know that the guage is centered in the bore when you tighten. When I was using them I had to adjust till it felt centered then tighten , even so it took me a few times to get a repeatable reading. Now given they are a cheaply set and i do not expect much in accuracy. Do the more exspensive ones have tighter build tolerance fits that would not allow side movement in the guage.

In really the bore diameter is never in 100% exact in measure in the home workshop. The important is the marks of tool is removed from the cylinder by lapping and the piston is adapted to cylinder under lapping operation. In fact the measuring tool to control the bore is rare used under lapping. In the mass production in the factory the bore gage is used to control the nominal measure in the bore under lapping operation.