Yet Another Webster Begins

[CFLBob]

You know that saying, once you see something you can't un-see it? The flywheel reminded me of the '70s Saturday Night Live puppet, "Mr. Bill".



Now I see that puppet every time I see the flywheel.

 

[Shaun free]

D2 steel is a semi stainless air hardening tool steel. It is designed to be an abrasive resistant steel.If you are causing enough heat machining it it will harden and be harder than your HSS. You will be better off using carbide and cutting deep and fast than slow and thin.

 

[CFLBob]

D2 steel is a semi stainless air hardening tool steel. It is designed to be an abrasive resistant steel.If you are causing enough heat machining it it will harden and be harder than your HSS. You will be better off using carbide and cutting deep and fast than slow and thin.

Exactly what I experienced. If I turned .005" (radius), the chips came off with hardly any color change; maybe a light amber color. If I cut .010, they came off deep blue and brittle.

My lathe just didn't have the power to cut it as deep and fast as it "wanted". It's only one HP.

 

[CFLBob]

Brian, Werowance or someone who has done one of these.

I'm making the crankshaft on sheet 5, and knocking off the little parts there. I made the "Crankshaft Spacer" from a piece of half inch 4130 I had. I got a length of 5/16 rod for the shaft from SDP (the place I got the gears from), cut it to length, faced and made the ends pretty. I haven't cut the 1.250 x 0.500 x 0.25 thick bar. Does the Crankshaft Spacer go in the half inch hole in that bar? Is that silver soldered in place?

I'm trying to understand what I'm reading in the build threads about the crank shaft and counter weight web. That goes on the end of the shaft that's shown with nothing on it, right? I'm having a hard time seeing how this goes together, if there's something on both ends. Silver soldered on both ends.

I started on this part:

and then noticed that it's optional. I gather these are for the crankshaft in the two side plates, right? I bought ball bearings for those spots.

 

[Brian Rupnow]

Bob--the spacer is exactly that.--a spacer. It doesn't attach to anything. It fits between the small gear on the crankshaft and the left hand sideplate on the engine. For answer to most of your questions see posts #47 thru 51, post #98, 264, and 306 on the following thread.
https://www.homemodelenginemachinist.com/threads/anybody-want-to-guess.7687/

 

[werowance]

on my spacer, I didn't even follow the plans because after the gear press in, slightly thicker fly wheel etc the spacer would have been to thick. I left that for near last things to do. once I had everthing somewhat assembled and could rotate and such. (flywheel not pinned at this time) then I measured and cut a spacer to take up the dead space between the gear on the flywheel hub and the bearing on crank support. I just used feeler gauges to get the right thickness. I really don't think its overly critical (but do put one in) because the points cam and the crank web/throw on the other side keep things in place. and I just used a piece of scrap brass for mine.

then next are you going to use bronze bearings instead of roller bearings? for some reason I thought you were going with rollers? if so the part you have pictured is not required. I got mine on ebay. not the cheapest bearings but I do prefer rollers if possible.

 

[CFLBob]

then next are you going to use bronze bearings instead of roller bearings? for some reason I thought you were going with rollers? if so the part you have pictured is not required. I got mine on ebay. not the cheapest bearings but I do prefer rollers if possible.

You remember it right. I bought ball bearings. The ones called out on sheet 21.

 

[werowance]

on the crank throw counter balance, here is how I did mine. I cut a disk 1.75 because the plans call for a radius of .875 on the tip of the crank throw. I drilled the center hole and silver brazed it to my crank shaft. I then mounted it in my rotary table with er32 chuck mounted to it. I centered it with my mill head and then tramed it to drill the rod pin hole. I then trammed it over and cut the 2 sides leaving a counter balance at the bottom. - pictures will probably explain that better. I didn't make a bolt on counter balance or anything. and the plans don't call for a counter balance but is a nice feature I think. the counter balance section starts right at the center line of the center hole drilled for the crank shaft. the rod pin or shaft that the rod connects to on mine is larger than the drawings because I used roller bearings on that as well. 2 little tiny rc bearings pressed into the rod. unfortunately I had to use brass bushing on the rod / piston wrist pin side of things because I couldn't find roller bearings small enough on that end.

first pic is the disk brazed to the shaft - not my best brazing job either.

next 2 pics are after its finished

third pic is what the plans called for

 

[werowance]

rod showing the ball bearings - and I believe I keep saying roller bearings but that's just a bad habbit. they are really ball bearings so if you see me say roller - I mean ball. the blue side of the rod are the 2 ball bearrings.

 

[CFLBob]

It's hard to describe how messed up I was.

Let me show you:

There's a raised area on the shaft side of the that piece you made into a counterweight, in the red oval. It's .031 thick. There's a rim on the bearing that's also .031 thick (on the right). So I thought that's where that bearing went. If you don't look closely, the diameters match. The bearing is 0.500" diameter except for that lip.

The end views of that piece match. You posted the view looking at the shaft from the far side, let me post the view looking down the shaft at that piece.

We see the 0.313 is the shaft seen end on. That 0.500 circle, (.031 tall) is a mystery, though. Again, I thought it was that optional bearing, but that's 0.563" diameter. The lack of hidden lines in the side view wipes that out, too. It's just a raised area on the crankshaft side of that piece.

And I was looking at the crankpin grease cup on sheet 13 of the drawing to go in the top hole of that piece, where you have a threaded rod. I don't even see where that comes from. I mean, did you change dimensions on whatever that drives?

 

[werowance]

on that raised bit (.031 shim), here is how I handled that - and also how I originally planned to do it but didnt. when brazing mine, I had extra silver braze on the back side. I turned that lump back down to be the .031 shim.
the plans do show it as a cut part of the whole crank throw but a washer will suffice just fine. and is easier to adjust thinner or make wider as necessary.

what I originally planned on doing is simply making a shim (small washer) out of brass to adjust with if need be. and also if needed a shim (washer) on the rod dowel since I used ball bearings I didn't need that oiler cup on the rod dowel so that helped also. the roller bearings for the rod are not even mentioned in the plans as an option. that was just something I changed myself. made life a lot easier. I can get you the rc car bearings part number I used if you need or want them.

now also on that .031 shim (washer) - the thing to be carefull about is that you want the shim to contact the inside race of the bearings and not the outside race, so all you need is just something there to prevent the crank web from rubbing the outside race which is stationary and thus will score and mar.

 

[werowance]

And I was looking at the crankpin grease cup on sheet 13 of the drawing to go in the top hole of that piece, where you have a threaded rod. I don't even see where that comes from. I mean, did you change dimensions on whatever that drives?

on that part the crank pin is solid because I didn't do a grease cup - used ball bearings. here are the ball bearings I used - copy and paste from my ebay order. came in a pack of three, only 2 are needed installed side by side. Team Associated 8682 Bearings, .250 x .375 x .1 inches RC10F6

now looking back on my earlier post I said the crank rod pin was bigger, its actually smaller. .250 to fit the inside of those ball bearings. the outside of the ball bearings fit the rod as per plans. then on the other side of the rod you will still have to use bronze or brass bush.

 

[werowance]

sorry for all the replies, but here is another way I deviated. making the crank throw and brazing it to the crank shaft - the tip of the shaft that would normally go in the throw - I made it smaller and also drilled the hole in the throw smaller as well. this way I could reliably keep the throw in the correct position when brazing it. the crank shaft did not protrude all the way through the throw so that I could puddle a little silver braze in the recess. I did the same process for the rod dowel going on the throw. also beveled the sharp edges on the throw and the rod where silver braze would go so it could "get in the cracks" so to speak... a rough quick / exadurated drawing of what I'm talking about below

 

[CFLBob]

Had some time this afternoon to finish the gear/flywheel assembly.

It was a snug fit until I took a high spot by turning with a metal file. I think it's maybe a .0015 fit. I think it's red Loctite time.

 

[werowance]

nice, what material is your gear?

 

[CFLBob]

I didn't make it. I bought it from Stock Drive Products, number on the drawings. It's steel of some sort, it felt machined pretty much like 1018.

 

[werowance]

well, that should be a long wearing gear. great job on the flywheel.

 

[CFLBob]

Thanks. I checked my powder and don't have anything like that neat black wrinkle you used. I need to order some. First, I need to get that flywheel finished better and shined up.

 

[CFLBob]

Bob--the spacer is exactly that.--a spacer. It doesn't attach to anything. It fits between the small gear on the crankshaft and the left hand sideplate on the engine. For answer to most of your questions see posts #47 thru 51, post #98, 264, and 306 on the following thread.
https://www.homemodelenginemachinist.com/threads/anybody-want-to-guess.7687/

Brian - hoping replying to you pings this so you know this is here.

I was talking with a friend about this, while trying to decide if I use your triangular sector or werowance's semi-circle, and he asked me one of those questions that makes you go hmmm.

Instead of adding weight to balance the system, what about drilling out holes in the rim of the flywheel to reduce its weight? Something like this, 3/8 holes in the thick part of the rim. I've never seen it done. I know something about computing the moment of inertia and that's what matters, but I don't know how to design this and figure out how many holes, for instance.

Any thoughts?

 

[Brian Rupnow]

You can do it that way, but in my opinion it makes an ugly flywheel. And if you get it wrong, there is no way to fix it. I recommend doing the same as Werowance and myself, because we know it works. There is a scientific way to calculate the mass of the counterweight, but it is fairly complex and you don't have a gram scale to do it anyways.