Webster Build Questions and Progress

[Danuzzo]

I have asked preliminary questions in other threads about my Webster build (my 1st I.C. engine). Now that I have completed the framework (see photos below), I am ready to start the cylinder. I am trying to build this engine with materials I have on hand.

I understand that the plans call for Cast Iron or 12L14 for the cylinder (I have neither in the correct size). The question of today is which is the better material to use for the cylinder, steel or stainless steel (sorry I don't' know the grade of either)? What I do know is the stainless will be much more difficult to machine. Between the 2 choices, is there a better one? Also, would the material for the piston be any different?

 

[Vietti]

Appreciate your problem. But consider you are going to invest hundreds of hours in your build and you don't want to end up with an inferior engine because you scrimped on proper materials. Just my thoughts.

 

[Sprocket]

I have not built a webster, but if the plans give you a choice, and you have either, use what you have.
If you are buying stock, 12L14 is very nice to machine, and except that it has a tendency to rust, it would be a fine choice. Cast iron is relatively easy to machine but can be very messy, if that matters. I would not choose stainless.
What is the piston made of? Iron rings or O rings? Either aluminum or cast iron should work for the piston, but what do the plans say?
Just my thoughts.
Doug

 

[Danuzzo]

Thanks Vietti and Sprocket, but I am trying to stick with material I have on hand, and I have lots of time.

Another thought. I do have 12L14 in 1" diameter round bar that might be used as a liner for a steel cylinder, if that is a good idea?

EDIT: The 12L14 I have won't work, it is just under an inch diameter.

 

[minh-thanh]

Check the link and see what you have on hand.

https://www.homemodelenginemachinist.com/threads/not-bad-for-a-college-student.34303/post-381344

Aluminum vs aluminum: Bad - But I saw a forum member use them and the engine ran quite well, and I also made stirling engines with aluminum pistons and cylinders and they ran fine (6mm cylinder diameter)

https://www.homemodelenginemachinist.com/threads/lets-make-a-4-cylinder-flat.35711/

- The question for you: Do you just need an engine that runs well enough?? Or do you need it to run and the best, most durable possible??

 

[Danuzzo]

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- The question for you: Do you just need an engine that runs well enough?? Or do you need it to run and the best, most durable possible??

Thanks for the links. Good question. I just want it to run well, with durability not being a significant factor, but some durability is desired.

 

[minh-thanh]

Hi @Danuzzo .
" I just want it to run well, with durability not being a significant factor, but some durability is desired."
My experience : Work with whatever steel I have on hand for the cylinder , pistons made of aluminum or cast iron , I have made cylinders with welded steel tubes and they are good enough for long time

 

[Jasonb]

If you have got steel then try it, may be a pig to machine if it is unknown but could be OK and maybe only a bit harder to machine than the leaded 12L14.

CI or Aluminium piston with O ring would be my suggestion for a beginner. lapped cast iron piston and no ring can wait for another project down the line.

 

[Danuzzo]

If you have got steel then try it, may be a pig to machine if it is unknown but could be OK and maybe only a bit harder to machine than the leaded 12L14.

CI or Aluminium piston with O ring would be my suggestion for a beginner. lapped cast iron piston and no ring can wait for another project down the line.

I have already machined the steel I have and it does fine; but, yes, it is not anywhere as nice as 12L14.
I was wondering about bearing bronze for the piston due to it's lubricity. I have plenty in stock.

Thank's minh-thanh and Jasonb.
Decision made. I will proceed with the regular steel, and continue to contemplate the piston.

 

[minh-thanh]

Aluminum, steel, steel grade ......for cylinder.., Piston without ring, with CI or O ring.. But there is only : make the best cylinder possible. For me, cylinder is the most important part.
Luck is not in this "game", But still wish you luck and please update !!

 

[werowance]

i have substitued 1215 high phosphur steel in place of 12l14. it machines every bit as good as 12l14 and is much cheaper. leaves a nice bright finish like 12L14 but was a whole lot cheaper to purchase. it still rusts quickly like 12L14 does. was told it was pretty much the unleaded version but the high phosphur makes it machine just as easily. idk about the alloys and such but i do know it was easy to machine and my engine is still running just fine using it for the cylinder

 

[Danuzzo]

I have started the cylinder using "regular" steel. Coming along. Got it from 1.75 diameter to 1.5 diameter, and I have drilled a 1/2" starter hole (going to buy a 5/8" drill today) for the boring bar. The boring is of course going to be the critical part, trying to bore with no taper is going to be a challenge for me. Tips on boring the 2.5" distance with no taper on a 1941 South Bend 9a are welcome.

 

[awake]

Danuzzo, I made my Webster with a steel-lined cylinder and a cast iron piston - for exactly the reasons you name, using the materials that I had on hand. It runs nicely. You can see details in the thread titled "Steel Webster."

 

[Danuzzo]

Danuzzo, I made my Webster with a steel-lined cylinder and a cast iron piston - for exactly the reasons you name, using the materials that I had on hand. It runs nicely. You can see details in the thread titled "Steel Webster."

I am very familiar with your thread. I have studied it closely. Great thread.

 

[awake]

Thanks!

 

[Danuzzo]

Almost done with the cylinder. Fins are done and I hope the bore is done. Just need to finish cutting the end to fit the cylinder block, and of course drill some holes.

I have an interim question or 2. First of all, I bored it to .7822", as best as I can measure it with a telescoping bore gauge. Plans call for .783" to lap to a finish size of .875". This may be a dumb question; but here goes anyway. Does it matter for an I.C. engine if the finish size of the bore is .780" or .790" (tolerance on plans, if I am interpreting correctly, is +/-005").

Second question has to do with taper. The Notes page of the plans pertaining to Sheet 4 state in part "make sure to bore it straight and without any taper." I am having some difficulty measuring taper with the telescoping bore gauge. Hard to say for sure if there is any taper. Maybe, I am measuring a taper of no more than .0003", but the last measurement I took showed no taper or maybe .0001". How critical is this? Is the designer talking Tenths when he says "without any taper"?

The reason I asked the 1st question is that if there is significant taper, can I attempt to remove the taper by going up to a finished bore ID of .790" instead of the specified .785"?

 

[Nerd1000]

Almost done with the cylinder. Fins are done and I hope the bore is done. Just need to finish cutting the end to fit the cylinder block, and of course drill some holes.

I have an interim question or 2. First of all, I bored it to .7822", as best as I can measure it with a telescoping bore gauge. Plans call for .783" to lap to a finish size of .875". This may be a dumb question; but here goes anyway. Does it matter for an I.C. engine if the finish size of the bore is .780" or .790" (tolerance on plans, if I am interpreting correctly, is +/-005").

Second question has to do with taper. The Notes page of the plans pertaining to Sheet 4 state in part "make sure to bore it straight and without any taper." I am having some difficulty measuring taper with the telescoping bore gauge. Hard to say for sure if there is any taper. Maybe, I am measuring a taper of no more than .0003", but the last measurement I took showed no taper or maybe .0001". How critical is this? Is the designer talking Tenths when he says "without any taper"?

The reason I asked the 1st question is that if there is significant taper, can I attempt to remove the taper by going up to a finished bore ID of .790" instead of the specified .785"?

Firstly, I think there may be a typo: I would bore to a diameter of 0.873" if lapping to 0.875", while your plans seem to have 0.783." lapping 90 thou out is possible, but you'll spend a long time doing it!

On taper: your piston needs to fit with an appropriate clearance in the cylinder across the whole stroke. The engine will not care if you make the bore a little bigger, you need only make the piston the right size to match the bore. A small amount of taper (0.001" or so) is acceptable, so long as the small diameter is at the top of the cylinder. In fact because the top of the cylinder usually gets hotter than the bottom, a little taper that way will make the cylinder properly cylindrical once the engine has warmed up.

The correct clearance depends on the material used for the piston. For a aluminium piston about 0.001" per inch of bore is the rough rule of thumb, a little more would also be ok especially for a model that doesn't run much.

With the Webster engine I strongly advise using an aluminium piston. The reason for this is that the lighter piston will help minimise the vibration of the engine, my Webster has added counterbalance weight on the crankshaft to help reduce this further but still shakes itself so hard that it must be clamped to the bench in order to run.

One other suggestion: the standard design asks for the flywheel to be attached to the crankshaft using a pair of roll pins. This doesn't work very well in my opinion, I would suggest you use a key or solid dowel pins.

 

[minh-thanh]

@Danuzzo !
What are your plans for the piston? with rings, without rings, cast iron rings or O-ring??

 

[Jasonb]

Piston and ring can be sized to the bore so a thou or two each way won't hurt but you do want it parallel.

Simple way is to hone/lap your cylinder and then make the piston. When you get close to size on the piston use the cylinder as a ring gauge trying both ends. If it only enters one end and not the other then you know you have a taper so go back and hone/lap it out.

 

[Danuzzo]

Thanks for all the responses. Good points by all. Nerd1000, thanks for pointing out the typo. I do have time, but not that much patience . Also, the more I measure the bore for taper, the more I am getting either no taper at all, as far as I am capable of measuring or no more than .0001". I will measure again today once I complete the head end of the cylinder and get it off the chuck.

It appears that it has been aptly pointed out that the piston material and/or ring choice is an important consideration. As pointed out a few posts ago, the cylinder is made of some mild steel. It looks like many of you opine that an aluminum piston is the way to go. Is that with or without rings. I do note that Awake used a cast iron piston for his steel webster. I have suggested a 12L14 piston and am also wondering how a bearing bronze piston would work. I have plenty of 12L14, bearing bronze, and aluminum for the piston size. Further detail on material with or without rings and fitment would be greatly appreciated.

Also, many questions on lapping/honing the cylinder bore. 1. What is the difference between the lapping and honing?
2. Is the purpose to make the bore very smooth? My bore came out smooth with the lathe, at least to the naked eye and feel.
3. Is it necessary to hone or lap if rings are used, or is it dependent on the material of the piston?