Webster Build

[simister]

Guys, I have just started to build the Webster. However, I notice that Brian and Longboy have used Viton O rings instead of normal steel rings. What is the reason that you have used O rings instead of steel?

Do the O rings give a better seal?

Also, does the aluminium flywheel have sufficient weight or is it better to go for cast? . I would prefer to use aluminium if it is heavy enough.

John

 

[Blogwitch]

John,
I can answer both of those questions for you simply.
If you are not going to be running your engine for long periods of time, say just to show people what you have made, then viton is perfectly acceptable. But, if you are going to have it running for hours on end, say at a show, then you are much better of fitting cast iron rings. It is just a case of longevity versus time used. The viton rings wear away much quicker than cast rings would.

What a flywheel does is to store energy produced by the piston/cylinder to enable it to turn over until the next power stroke.
The further away the outside mass of the flywheel is from it's centre of rotation, the more carry over it will have. So your question about using an aluminium flywheel, yes it might work, or it might not have enough inertia to carry over to the next power stroke.
There are ways to get around that problem, drill cross holes in the flywheel rim and either fill them with molten lead or even just Loctite in some steel slugs. Or, if you have room, you could make a steel tyre to go around the flywheel rim, both will have the same effect.

Slug type flywheel (not cross drilled as suggested)

Steel tyred

I hope this helps a little

John

 

[bazmak]

Certainly does blogwitch.Nice flywheels,nice workmanship.Congratulations

 

[simister]

Thanks for your advice.

Yes, I understand your points.

Do you get any better compression with the Viton O ring?

Would brass slugs on the flywheel give sufficient weight?

 

[Blogwitch]

John,
Viton, if using the correct compression figures for the o-ring to give a good seal, then it will seal perfectly straight away, whereas piston rings usually take a while to 'bed' in, but once bedded in, they will be there for years, whereas viton will wear and you will need to change them when the compression drops to a point the engine won't start. It is the old swings and roundabouts theory.

With regards to the brass or steel slugs. Because they will be heavier than aluminium, yes you will get a better turning force. It also depends on how many you use.
The one I showed with the slugs around the outside were only for a finger engine. Without the slugs, it was difficult to keep it running smoothly, once fitted, the whole machine became much more manageable and it worked a lot better.
If possible, I would always go for the steel tyre, and if done with brass spokes, the looks can't be beaten.

John

 

[simister]

John,

Thanks for your advice. I was going to do the brass slugs. However, I can see the steel tyre would be much heavier.

I already have the piston rings (Otto), but I noticed on Brian's posts that he used the Viton O ring. As this is my first IC engine, I was thinking that if I am a fraction out of tolerance with the piston fit, the Viton may be a little more forgiving than steel rings.

John

 

[Brian Rupnow]

After building 9 i.c. engines (which all run well), and fighting to get a proper seal numerous times with cast iron rings, I can firmly state that small diameter pistons with cast rings are a complete and utter pig of a thing to work with. The Viton ring will seal immediately, with no problems. Contrary to what some may say, I have run some of my engines all day at shows with no trouble from the viton rings. The only caveat when running a viton ring, is that you must run at least a 50:1 mix of two cycle or lubricating oil with the fuel, and the engine must not be allowed to overheat.---And--You don't want the cylinder bore to have the typical cross hatched finish that would be suitable for running cast iron rings, because the cross hatching holds minute quantities of oil to lubricate them. When running viton rings, lap the cylinder bore with 600 grit lapping paste and leave it shiny, otherwise it will chew up the viton ring quickly. On a couple of engines I have built for use with cast iron rings (and failed miserably to achieve compression) I have swapped the pistons out for pistons made for a viton ring and ran them. After half an hours running, the viton ring will be worn out, but the inside of the bore will be polished to such an extent that the next viton ring will last forever.---Brian

 

[Brian Rupnow]

Here is a Webster I built to the original plans (and with a viton o-ring). When I couldn't get it to idle slowly enough with the original aluminum flywheel, I made the largest diameter flywheel I could (without changing the bearing support pillars) from brass and made it as wide as I could by moving one of the bearing support pillars out to the maximum that the base would allow. Engine runs marvelously!!!
http://s307.photobucket.com/user/Br...LOWS CARB ON WEBSTER_zpsuvmz22jj.mp4.html?o=5

 

[simister]

HI Brian,

Thanks for your advice and I thought that the o-ring may be more forgiving than cast rings. Do you have a part number of the Viton o-ring that you used or it's dimensions?

The flywheel that you made with the brass slugs looks great.

I have been reading your posts with interest as I go through my build.


John

 

[simister]

Brian,

I didn't realise that you changed from the brass slugs to all brass. Still looks good.

 

[Brian Rupnow]

All of the o-rings I have used are a "nominal" 1/16" cross section. ---In reality they are .070" cross section. You only need one ring per piston, and the groove should be 0.057" deep x .093" wide. I don't have specific part numbers, and I can't remember what bore the Webster is, but if it has a 1" bore, ask the o-ring supplier for a ring that will have a 1" outer diameter. There is really a 3 part story to my Webster. First, I built it with an aluminum flywheel, as per the original drawings. (which, by the way, are excellent.) Then I wanted it to idle slower, so I drilled the aluminum flywheel and put the brass slugs into it, which helped a lot. Then I had a brain wave about putting a 3 ball governor onto it and turning it into a hit and miss engine, but for that I needed the truly huge flywheel. It "sort of" worked as a hit and miss, but not well enough to keep it that way. I took the 3 ball governor off, but left the huge flywheel.

 

[simister]

Brian,

A company here in Melbourne has suggested the following o-ring.

Viton Part Number BS-O18

Inside diameter .75"
Thickness .07"
Outside Diameter .89"

Temp Range +220 Centigrade.


How does this compare with what you used?

John

 

[simister]

HI Brian,

Our posts have crossed at the same time.

Thanks for that info. The supplier here is very helpful, so I will take the info down next week and have a chat to him.

Did you find that the flywheel with the brass slugs worked ok or should I go for more weight?

I was thinking of either going for Bright Steel, however it is a large diameter to machine. The other option which Blogwitch suggested was to make a steel tyre to go over the aluminium wheel.

John

 

[Brian Rupnow]

That o-ring information looks correct. The engine ran fine with just the brass slugs added to the flywheel. A steel or brass or cast iron "tire" added to the o.d. of the aluminum flywheel would be a great help.----Brian

 

[tms6401]

I am also watching this build. It is an interesting engine and all of the finished examples seem to run very well.

I might have a go at the cylinder and if that goes OK we will see.

I am following this thread with great interest.

Tom

 

[simister]

Thanks guys for your advice. This forum is a great help to newbies like myself.

I am sure there will be a lot more questions as I progress.

John

 

[simister]

Well, I have finally made a start. I have decided that I am going to use the Viton o-rings for the piston and the dealer for Viton is 5 minutes from my place. I have left the base plate as a rectangle and not done the cut out as shown in the drawings. I haven't rounded any of the edges of the cylinder block at this stage.

In the notes on the drawing it suggest .250 drill rod for the camshaft. Is it really necessary to use drill rod or could I use Bright Steel?

Here are some pics on where it is at the moment.

 

[tms6401]

I am not an expert by any means, but I would think that bright steel would work. Drill rod does have a smoother finish, and that might make some difference.

Tom

 

[Cogsy]

You can buy drill rod (or silversteel) from Bohler Metals or Blackwoods. It's not expensive and cuts nicely. I've just started using it for the first time and I'm a huge fan of it now.

 

[simister]

Thanks Tom and Al,

I have never used drill rod before but it sounds like it is worth using rather than bright steel particularly if it machines to a smoother finish.

I didn't realise that drill rod is silversteel.