Webster Build

[Brian Rupnow]

Let it run tight, but be sure and use lots of oil in the fuel during the first hour of running. About 20 parts naptha to 1 part 2 cycle engine oil. Once it has been run in, back off to 40 parts naptha to one part 2 cycle oil.

 

[simister]

Thanks Brian, I have a quite a lot to do before I get to the stage of running the engine. I actually think that it is too tight too run the way it is. I may need to gently take off just a few 000's more.

 

[Longboy]

If you can detect by hand the piston with ring sticking in bore, Webster isn't gonna like it. Your O-ring with a proper width piston groove will rotate within the groove. To check the depth of the groove, place piston into cylinder with O-ring on.....if it doesn't go, the O-ring is above the surface circumference of the piston. Deepen the groove another 2-3 thousandths and try it again till its right!

 

[simister]

I have now taken a few thousandths off and I think it is now OK. It runs in the cylinder by hand without shuddering. If I put the palm of my hand over one end of the cylinder and with the other hand slowly withdraw the piston there is quite a lot of suction. Likewise when I compress the piston I can feel the spring in it as the air compresses.

So, hopefully it is ok.

 

[Mechanicboy]

Sim,
You have done the right thing with the bore, honing puts the fine scratches on the cylinder walls, allowing the metal rings to bed in nicely with the bore,
John

This is near correct, we must have fine scratches in bore to save oil in the pockets and improve lubricating on piston ring. Same too with lapped piston/sleeve. The blank mirror surface in bore is bad to keep oil on place and make more worned piston ring/sleeve. Before running in the engine, the surface has "mountains" and after running in is done, the surface has "plateau mountains" with oil in "valleys". Crosshoning will be 45-60 degree in the bore.

The Webster engine do not have the oil controlled piston ring due there is not closed crank case with oil inside. Also it has 2 compression ring on piston.

I prefer piston ring instead O-ring in gas engine.

 

[Blogwitch]

MB,
I didn't mention oil retention because it had been made in previous posts.

John
I do know you are well on your way with this engine and should have mentioned earlier, unhardened silver steel (drill rod) should not be used on small engines that will produce any moisture, and all small i/c engines do to some extent, as well as ones running on air or steam. It might look ok for a while, but once it gets put away on a shelf for any length of time, you will most probably have corrosion showing where you have used the silver steel. I refurbished a lot of engines for other people, all types, air, steam and i/c, and came across this problem with many of them. Invariably I fitted ground stainless rod as replacements and no further problems were reported. In the UK ground stainless can be obtained in smaller sizes from RS.

With regards to types of fuel. For many years I run on what the late, great, Bob Shores came up with. He used pump gasoline with 10% WD40 added for running in, then when run in, he swapped over to 5% WD40. About half a pint of the 10% was enough for running in, you wouldn't want to mix up too much.
I found it perfect for my i/c engines, and even though a bit of oil comes out of the exhaust, I have never had a fouled plug and any residue carbon that builds up in the cylinder head just wipes off with a cloth.
Just to confuse you a little, this is a friends Webster running using a Minimag magneto that I built as the prototype to try out whether the plans were OK and to test if it would all run. This proves that it does, and does make the engine a little different from the rest. This mag will be used on a R&B engine when I get around to building it.

[ame]https://www.youtube.com/watch?v=8r9ivpUR0T8&list=UUbmnXOvtxx1wUp4fFjFLsfA&index=4[/ame]

John

 

[kquiggle]

John -

That's a very timely tip on not using unhardened drill rod. I'm working on the valve block for my Webster right now, and was thinking about using drill rod for the valves - I'll switch to stainless steel instead.

Thanks again.

 

[Blogwitch]

Hi K,

Stainless is usually the recommended material for valves on these small engines anyway.

I could never bring myself to use drill rod for items associated with fairly high temperatures such as inside a cylinder, as it needs heat to harden it. I always wondered if it could become too brittle in use and snap. Maybe not, but the thought was always in the back of my mind.

John

 

[simister]

MB,
I didn't mention oil retention because it had been made in previous posts.

John
I do know you are well on your way with this engine and should have mentioned earlier, unhardened silver steel (drill rod) should not be used on small engines that will produce any moisture, and all small i/c engines do to some extent, as well as ones running on air or steam. It might look ok for a while, but once it gets put away on a shelf for any length of time, you will most probably have corrosion showing where you have used the silver steel. I refurbished a lot of engines for other people, all types, air, steam and i/c, and came across this problem with many of them. Invariably I fitted ground stainless rod as replacements and no further problems were reported. In the UK ground stainless can be obtained in smaller sizes from RS.

With regards to types of fuel. For many years I run on what the late, great, Bob Shores came up with. He used pump gasoline with 10% WD40 added for running in, then when run in, he swapped over to 5% WD40. About half a pint of the 10% was enough for running in, you wouldn't want to mix up too much.
I found it perfect for my i/c engines, and even though a bit of oil comes out of the exhaust, I have never had a fouled plug and any residue carbon that builds up in the cylinder head just wipes off with a cloth.
Just to confuse you a little, this is a friends Webster running using a Minimag magneto that I built as the prototype to try out whether the plans were OK and to test if it would all run. This proves that it does, and does make the engine a little different from the rest. This mag will be used on a R&B engine when I get around to building it.

https://www.youtube.com/watch?v=8r9ivpUR0T8&list=UUbmnXOvtxx1wUp4fFjFLsfA&index=4

John

They are great tips - thank you.

I was wondering about the fuel mix. In Australia that would be unleaded fuel with a WD40 mix? Would it be preferable to use the higher octance fuel or not.

John

 

[Blogwitch]

Bob Shores just stated pump gas (or so I thought), so I always used unleaded, and it worked just fine in my little engines.
Buying a gallon would be way too much usually as you may well know, gasoline deteriorates with age, so maybe a quart would be the max mix for a lot of running.
I have never tried it, but they now reckon this 'green' gasoline for garden motor powered machines is the way to go, in that doesn't 'go off' like normal petrol, plus it doesn't have that awful petrol smell. I do use the green spirits based version for running Stirling engines with a wick burner, and that has no smell at all.
But anyway, after reading Bob's old post again, for reasons unknown to myself, I used gasoline instead of Coleman fuel as recommended by Bob in these tips on here (although old, they are well worth reading)

http://www.floridaame.org/Tips.htm

I also noticed that Bob used to use drill rod for his valves, but even so, I would still use stainless for mine.
What would the world be like if we all used and did the same things all the same way?

But it all still works fine for me.

John

 

[simister]

Thanks John,

I will just use the standard un-leaded with the WD40. I am still quite away off finishing the engine. I have now fitted the piston in the cylinder and it showing quite good compression.


John

 

[simister]

Well, I am slowly getting there. I finally finished the piston, crankshaft and crank. I silver soldered the crank, pin and shaft from 3 separate pieces which seemed to work ok. When I first set it up I found the shaft was binding in the bearings. I took a a few thou off the crankshaft with some fine emery and it is now running freely.

I can now turn it over with a battery drill and it seems to have good compression and I can hear the suction from the inlet as the piston retracts.

I have now received the cast iron ready to make the flywheel. The plan has an option to add three .750 holes to the flywheel. I would like to do this for looks, but was wondering if it is better to leave and have the advantage of the slightly extra weight. Would this be a consideration or not make much difference?

John

 

[Swifty]

Hi John. Drilling the holes in the flywheel just for looks is no problem. Most of the momentum of the flywheel comes from the outside, you may have seen flywheels with aluminium centres with shrunk on outer steel rims, or flywheels with spokes.

Paul.

 

[kquiggle]

Looking good! Where did you get the cast iron for your flywheel?

 

[simister]

Looking good! Where did you get the cast iron for your flywheel?

Thanks Paul, in that case I will drill the holes, as I think it gives it a little more character.


Kquiggle, I got the cast from the link below (around A$26). The problem is that postage may be the killer if it is sent to the US. If you send Bob (owner) an email, you will find him very helpful. If you have any problems, let me know and I can give him a call for you.

John

 

[simister]

Hi Kquiggle,

ooop's forgot to put the link in. Here it is.

http://www.minitech.com.au/

 

[kquiggle]

Thanks John - always looking for new suppliers, but Down Under is a bit of a stretch for me - I should have noted your location.

 

[simister]

I am in the midst of machining the cast iron fly wheel. I am not sure how it is secured to the crankshaft. I was going to put a set screw in the hub but I am having difficulty getting the short drill bit into position, because of the width of the chuck. Any clues on this would be a help.

John

 

[kquiggle]

John - roll pins.

The following is from the last page of the plans (sorry for the all-caps, it's from the original - underline by me):

EXHAUST VALVE TIMING IS SET BY ROTATING
CRANKSHAFT COUNTERCLOCKWISE TO ABOUT 15
BEFORE BOTTOM DEAD CENTER. ROTATE FLYWHEEL (AND
CAM GEAR) UNTIL THE EXHAUST VALVE JUST STARTS
TO LIFT, AS SHOWN. CLAMP / LOCK IN PLACE,
THEN DRILL FOR, AND INSTALL ROLL PINS.
​

However, I have read other builds where set screws were used, as you are planning. I am thinking of using set screws myself for my build, and I may also install them at a slight angle to the vertical to enable access for drilling. Another option is to make a long-reach drill bit by installing a drill bit in a longer piece of rod (and a similar long-reach tap to go with it).

I have seen other builds where the angled set screw idea is used but I have not read any discussion as to whether this method has any drawbacks or not.

If I decide to go with setscrews, I will install two at a 90° angle to each other, and maybe mill a couple of small flats as well if I see any slippage.

 

[Longboy]

Set screws are marginal for flywheel to crank security in a gas engine. The constant hammering of the power stroke of single cylinder engines rocks the flywheel ( the heaviest item mounted) back and forth on the crankshaft where the cup points of a pair of set screws just doesn't have the contact area to resist. Another reason.... set screws will gall the crankshaft if loose at the edge of the set screw flats in crankshaft when trying to "cure" the loose problem. If you ever have to remove the flywheel for servicing or troubleshooting the engine you can scar the hub bore to the point where flywheel never runs true and wobbles from now on upon reassembly. Roll pin or keyway the flywheel here.Thm: