Webster Build

[Brian Rupnow]

When I built my Webster, it was my first internal combustion engine. I found it VERY scary to drill a hole thru the extended hub on the flywheel and thru the crankshaft.--What if I got it wrong??? Fortunately I followed the instructions exactly, and everything come out okay----but it was quite unnerving. Longboy is right in what he is saying.--If you look on page #27 of this link, you will see that I actually built a fixture to ensure that everything was positioned correctly before I drilled the hole. There is also a detail drawing of the fixture I made and used.-Brian
http://www.homemodelenginemachinist.com/showthread.php?t=7687&page=27

 

[simister]

OK, Thanks guys. The roll pin seems to be the way to go. Correct me if I am wrong, so, I should not drill the hub/shaft until the final assembly so I can get the timing adjusted correctly?

Brian, how did you manage to drill the extended hub of the flywheel, given that it is very close to the wheel itself. Kquiggle suggested a drill rod extension, which seems like a good idea. I would be interested in any other ideas that may work.

John

 

[Brian Rupnow]

OK, Thanks guys. The roll pin seems to be the way to go. Correct me if I am wrong, so, I should not drill the hub/shaft until the final assembly so I can get the timing adjusted correctly?

Brian, how did you manage to drill the extended hub of the flywheel, given that it is very close to the wheel itself. Kquiggle suggested a drill rod extension, which seems like a good idea. I would be interested in any other ideas that may work.

John

Simister--Look in the link I posted. it's all in there. I used the "longest skinniest drill-bit in the world".---Brian

 

[simister]

Thanks Brian, Yes, got it now. Also, the design for holding the flywheel looks like the go for accurate drilling.
John

 

[Longboy]

OK, Thanks guys. The roll pin seems to be the way to go. Correct me if I am wrong, so, I should not drill the hub/shaft until the final assembly so I can get the timing adjusted correctly?
John

The timing gear ( my engine) is independent of the flywheel on crankshaft so its placement has no effect setting the timing. What I would do is drill for a 3/32nd roll pin in flywheel hub. Mock up your crank with all components (crank throw, timing gear, flywheel, points cam trigger and starter drive) in the frame bearings. Then you can slide shift the flywheel between the timing gear and ignition side bearing in frame to your satisfaction. With a transfer punch thru the drilled hub, mark the crank to drill for the pin then. Upon final assembly you know where the flywheel's fixed position is and you can still get a hex key down to the timing gear to set timing too. I used purchased timing gears with set screwed hubs for my Webster.

 

[simister]

The timing gear ( my engine) is independent of the flywheel on crankshaft so its placement has no effect setting the timing. What I would do is drill for a 3/32nd roll pin in flywheel hub. Mock up your crank with all components (crank throw, timing gear, flywheel, points cam trigger and starter drive) in the frame bearings. Then you can slide shift the flywheel between the timing gear and ignition side bearing in frame to your satisfaction. With a transfer punch thru the drilled hub, mark the crank to drill for the pin then. Upon final assembly you know where the flywheel's fixed position is and you can still get a hex key down to the timing gear to set timing too. I used purchased timing gears with set screwed hubs for my Webster.

The only problem is that I have loctitited the drive gear to the flywheel. My drive gear did not come with a set screw. I am not sure if I can do what you suggested, now that the drive gear is fixed to the flywheel.

John

 

[Longboy]

That Loctite bond can be broken with heat and separated from the flywheel again. Looking at the Webster plans, if you are using the SDP gear per plan, I see has a .188 hub length.....that's enough to drill and tap for a #6 set screw.

 

[simister]

I think there is enough room for a set screw. Ok, sounds good - I will separate and drill it. This method seems to allow more adjustment and little more forgiving than fixing the flywheel/drive gear to the shaft.

 

[Swifty]

If there was no boss on the gear for a set screw, you could always put a small one in a tooth gap. Just make sure that the screw doesn't protrude into the tooth gap. We're only making models with very little load on the gears, so a screw in the teeth will not make any difference.

Paul.

 

[simister]

Thanks Paul. I think there will be enough room on the boss for the set screw.

 

[Longboy]

Also John,with hub less spur gears, you can make a press fit hub with set screw. If you find it impossible to drill your flywheel hub for a pin because it doesn't extend out far enough.... the same solution. You can bore the existing flywheel hub to receive.... let say a 5/8 in. Dia. brass or CR round with a flange to seat square in your flywheel. When installed, you would chuck the flywheel up in the lathe to run true , then you drill/ ream the replacement hub to crankshaft diameter. On my new "SUPER H" twin, an overhanging crank engine, the flywheel is CR steel round with a pressed in hub drilled for a roll pin.

 

[simister]

Ok, that is a good tip. However, I think I will have enough meat on the flywheel hub to drill and fit the roll pin. I will be removing the drive gear and setting it up on the weekend. I will post the result when done.

Thanks for all your advice.

John

 

[simister]

I removed the drive gear from the flywheel. After applying some heat it came away easily. I didn't have enough room on the hub of the drive gear to drill a hole for a set screw. So I drilled through the teeth gap as suggested and tapped for a grub set screw. This sits below the teeth and the gear runs smoothly.

Next is to drill and fit the roll pin to the flywheel.

John

 

[Swifty]

Glad you found a solution, members tossing ideas around is great.

Paul.

 

[simister]

I have now set the drive gear up independent of the flywheel. Here is a photo of the flywheel before I removed the drive gear. Now to start on the valve block.
John

 

[simister]

I have finally got back into the shop to do some more work on the Webster. I have completed the valve block and it seems to be working ok. The engine so far seems to have good compression, however, I have nothing to compare with, so I am not sure. When I try to spin the flywheel it bounces back quite vigorously. If I squirt some compressed air in through the inlet port it throws the piston back with a lot of force.

As this is my first attempt I am not sure what to expect. Although I am happy with the compression, and on the surface it appears that it will be quite sufficient. However, when I insert compressed air into the inlet port there is some seepage of air through the closed exhaust port/valve. It is also the same if I inject air through the exhaust port - the inlet port has seepage.

I have re done these valves and inserts twice to try an eliminate any leakage, but I still get some. Am I expecting too much for this to be a complete air tight seal?

I have not completed the tappet at this stage.

John

 

[bmac2]

Hi John
I’ve read 100’s of threads on IC engines but I’ve only built 1 so I’m no expert. What I can say about mine, and what I’ve read is that it is almost imposable to get the valves in these small engines to seal completely before they run. My Webster had what I thought was good compression and the valves where seating as good as I felt they were going to get but the difference after the first couple of pops was very noticeable. Please note I’m saying “pops” not minutes of run time.
It sounds like you have a good solid build there and I’m sure it’s well on its way for making smoke and noise. Thm:

 

[simister]

Thanks Bob, Well, that's encouraging. It seems to have a fair amount of compression. I am looking forward to some smoke and noise, but I have a way to go yet.

John

 

[gus]

John,

No worries. The Webster is a very forgiving engine to build. The outboard valve block was a bit strange to me but as long as you lap the valves and seats properly, the engine will start but will need some timing adjustment.A good indication is when you get some pops and smoky exhaust,you are about there. Some plus and minus tuning will get your engine up and running. No worry about engine not starting and run on day 1 or day 2. On day3 mine decided to start and run. A good job on the carb is required. I cheated and bought an OS Carb. Subsequently I did master the black art of making good carbs and tuning. Good Luck . Now worries. The Nemett Lynx was a bit tough to make and get going. Rupnow Hit&Miss engine was hard to get the hitting and missing. Good Luck. Now doing the Howell V-2 Engine. Will take another 2 more months minimum to to complete. Very Unforgiving.

 

[gus]

John,
Your engine looks good and sure beat mine.