Yet Another Webster Begins

[CFLBob]

https://www.homemodelenginemachinist.com/threads/scottys-webster.32160/
Not a super detailed build thread but there are pics. My frame rails were a little thinner than the plan so I made my bushings and spacers to fit.

Very useful. My brain works better seeing pictures than engineering drawings.

 

[CFLBob]

Quick Traxxas Carburetor question. Is there a preferred in/out? It seems like looking into it along the big axis, it's symmetrical. I can see the lever close the air pathway, and the fuel is independent.

I started messing with ideas for an adapter down to the size of the port the Webster carburetor would attach. Started testing it and it got stuck.

This would be the fuel/air mix going into the engine on the left and the air intake on the right. The fuel intake is on the far side of that tube on the upper left.

Does it matter?

 

[scottyp]

That is how that carb is designed. I made my adapter out of brass with a loose sliding fit and tried to use the o ring as the seal. My carb had screws on the side of the barrel and i used them to secure the carb to the adapter. Look at the first couple of pics in my thread.

 

[Brian Rupnow]

Yes it matters, and yes, you have it right.---Brian

 

[CFLBob]

Thanks, Scotty, Brian.

I'm making progress, slowly, but there aren't many things remaining before I try to start this up.

 

[CFLBob]

I found a mistake in my counterweight. Apparently I didn't ream the hole the crankshaft goes into, so even though I tried Red LocTite and spent days waiting for it to cure, it broke. Twice. I had enough time to order some 680 LocTite last weekend and get it delivered while waiting for the joints to cure.

Today I thought instead of making the counterweight over, I'd enlarge the hole and make a bushing for it. I made the hole the counterweight 3/8" (reamed to size) and then bored the bushing to 5/16 for the crankshaft.

This is everything before assembly. I mounted the bushing with the 680, and will polish the shaft a bit more to make sure the scratches don't bind as I try to put the crankshaft in place.

 

[coulsea]

Adding a bush has made the assembly even weaker. pin it and it should be ok

 

[CFLBob]

Adding a bush has made the assembly even weaker. pin it and it should be ok

Could you explain how the bushing makes it weaker?

Do you mean to pin it through the bushing and shaft, drilling in from the side through the centerline of the thickness of that circular sector?

 

[coulsea]

it now has two joints instead of one. I would pin from one of the angled sides (shortest distance) through the bush and shaft and at least 1/8 into the other side.

 

[CFLBob]

Thanks.

 

[L98fiero]

it now has two joints instead of one. I would pin from one of the angled sides (shortest distance) through the bush and shaft and at least 1/8 into the other side.

Maybe it's overkill but I'd lose the bronze bushing, replace it with a pressed in steel bushing and then pin it

 

[CFLBob]

Maybe it's overkill but I'd lose the bronze bushing, replace it with a pressed in steel bushing and then pin it

Well, it's a pressed in bronze bearing now.

 

[CFLBob]

With the pressed in bronze bearing, I've gotten farther than I've ever gotten

I did this primarily to size the spacers on the crankshaft, left and right. The washer on the right (ignition cam side) is .031 thick.

Now for my dumb question of the day. How do you put these things together and take them apart again? I can't do it with hand strength alone.

I can't get this apart, and the only way I could press it together was to use an 18" Bessey-type woodworking clamp and a cap over the right end of the shaft. I have no idea how to get the crankshaft out of those parts.

I need to take it apart because the flywheel isn't tight enough on the shaft. While it all runs fine if I spin the flywheel when it's hooked up like this, if I put resistance on anything, the shaft spins in the flywheel or in the bronze bushing on the crankshaft throw. I'm concerned the piston will cause enough resistance that the timing will get knocked out. I'm going to peen the shaft in a few places so that the next time I put it together it will be twice as hard to put together. At that point, it might never be taken apart again.

 

[scottyp]

First, what parts had the tight fit that needed pressing together? At this point the only crankshaft related parts that should be stuck together are the crankshaft itself and the gear to the flywheel. The crankshaft assembly should be able to slide out to the left fairly easily (looking at the rear of the engine in your pic). The ignition cam should be a sliding fit, it is held in place with a setscrew later when it's timing is set.

Second, carefully read this from the plans and get your head wrapped around it before you drill for pins:
"Exhaust valve timing is set by rotating the crankshaft
counter-clockwise (as viewed from the cam side) until it is about 15 - 30 before
it's outward most stroke. It is then held in place while the flywheel is rotated C.C. until
the cam just starts to lift the exhaust valve off of it's seat. Clamp, lock, & secure everything
in place and drill the two roll pin holes as shown on the next sheet. If set properly, the
exhaust valve will close a few degrees before TDC."

Good luck - the timing will eventually make sense.

Also, maybe mark you gears with some white paint dots so you know where they need to be rotated when reassembling things, that will save a bit of frustration.

-Starting to look like an engine!

 

[werowance]

on the flywheel it was just a sliding fit on mine, then once I had everything done I drilled and put in a roll pin as per plans. I did have to use a long reach drill to do it but that was pretty much the last step after everything was test fit.

 

[CFLBob]

First, what parts had the tight fit that needed pressing together? At this point the only crankshaft related parts that should be stuck together are the crankshaft itself and the gear to the flywheel. The crankshaft assembly should be able to slide out to the left fairly easily (looking at the rear of the engine in your pic). The ignition cam should be a sliding fit, it is held in place with a setscrew later when it's timing is set.

Thanks, Scotty. The parts that are the tightest are the ones that are supposed to be: the crankshaft in the ball bearings. Pushing it through the second bearing (right in this picture) was what took the Bessey clone clamp (from Harbor Freight). I had let my head get ahead of reviewing the plans yet again. I've had the ignition cam on and off with its setscrew, that's not a concern.

on the flywheel it was just a sliding fit on mine

That's what I have and what I was concerned about. I need to RTFP again until they sink in better.

Bob

 

[minh-thanh]

CFLBob !

You can use the hammer and a wooden (it helps not to damage the outer part of the crankshaft )
Or you can use the woodworking clamp to remove it.

 

[scottyp]

OK, I did not have ball bearings in mind. Carry on.

 

[CFLBob]

It took a while to get here due to tools on hand, but I have the flywheel pinned to the shaft.

The crankshaft throw that's a sector of a circle had me a little mentally barfed up for a while. Finally a little careful drawing in CAD got me how to align the throw to get the 15 degrees before TDC that the drawing says to work with. Naturally, I didn't do this check until after I had made it the wrong way, so that it was 30 degrees before TDC. I had to drill a second set of holes in the crankshaft to pin it properly.

I have one of those digital angle gauges that I used to set the "downhill angle" on that to 8 degrees.

My plastic gas tank from Tower Hobbies should be here tomorrow. I'll need to get dimensions and plan a little stand for that. And I need to learn how to set up my electronic ignition.

I think all I need to buy is a set of points and some Glow Fuel.

Edit to add: I keep forgetting I need some gasket sheeting to make the head gasket. Does anyone know if the kind of cardboard used as the back on a note pad would work?

 

[BaronJ]

Hi Bob, Guys,

Yes it will work, though you would be better off with the proper material. I've used a synthetic material with success.