Introducing ... the "Steel Webster"

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Sep 4, 2019
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North Carolina
My very first IC engine (actually, first engine of any kind) - based on the Webster design, but modified to suit personal preferences and materials on hand. A major difference, as suggested by the title, is that it is made (almost) entirely of steel. The only exceptions are the piston (cast iron), the cylinder fins (aluminum), the small end bearings and rocker arm bearings (brass), and the valve guides (bronze). Except for the plain bearings just mentioned, all other bearings are metric sized, flanged ball bearings (metric because they are cheap on eBay).

A major goal was to use materials on hand rather than buying - thus the use of steel throughout, as I have plenty of that but not a lot of aluminum, particularly in the sizes that would be needed. As it turned out, the only items purchased for this engine - not counting tooling, which I assure my wife does not count - were the ignition components (points, condenser, coil, spark plug), a package of needles to make the needle valve, and a couple of different sizes of flanged bearings (eBay specials, fortunately purchased before everything in China came to a stand-still). Everything else came out of my scrap bin. For the flywheel, I did have to weld up two smaller pieces of steel to get the blank.

I have put this in the Work In Progress thread ... but not sure this is the right place, because I am posting this mostly ex-post-facto. I began the build on November 16, 2019, and while there are still some things to be done (mounting the gas tank, for example), it did achieve its first run last night (or maybe it was early this morning!).

However, I have been taking detailed pictures along the way (with occasional lapses), and I would be interested in detailing the build a step at a time, explaining design choices (some of which do not match the good advice I read here!). Question is, would that be of interest to anyone? And if so, is this the right forum to put the build posts in? I await your feedback (please be gentle - remember that I am a newbie!), and even if the consensus is not to provide the detail, I will want to follow up (in whatever forum is appropriate) with some questions about how to fine-tune it - I don't really know what I'm listening for as I attempt to adjust the needle valve and throttle.

But for now, here is the YouTube video of its second run (I was so excited and surprised when it started up the first time, with almost no fiddling and adjusting, that I failed to get a video of it - and I promptly killed it when I tried adjusting the needle valve):

And a few graphics of the CAD design:

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awake !
I don't think the time to build and complete a project affects the "In Progress" name.
I'm not new or old, in the time (not long) I joined this forum, I realized this was the real place for model engine builders.
Congratulations and look forward to In Progress of your engine !
Congrats on a runner, it's always a great feeling the first time they fire up. This forum is the place for your build log, feel free to just continue this thread if you like.
Thanks Cogsy and Minh Thanh!

Cogsy, a follow-up question (directed to Cogsy, because I think I remember him giving guidance on copyright issues in previous threads, but of course happy to hear from anyone!): I have completely redrawn the plans as I have made my various modifications to the basic design. Is it okay for me to post them as I go through the build? While I will happily take credit (or blame) for the modifications I have made, I certainly would not want anyone to think that this is a completely original design; at the same time, I am vain enough to hope that my interpretation of the Webster might be of value to someone. :rolleyes:

I am not sure exactly what the copyright is on the Webster plans - public domain? Or ... ? Likewise, the Chuck Fellows carburetor, on which I based the design for the carburetor I used - public domain, or ... ??
Truthfully, I have no definite answer on either question as I don't know the copyright on either of them for sure. I think they're both in the public domain so it should be OK (with attribution) as they are certainly available quite freely. I doubt it would cause any issues so my guess would be it'd be fine to do so.
.........I am not sure exactly what the copyright is on the Webster plans - public domain? Or ... ? Likewise, the Chuck Fellows carburetor, on which I based the design for the carburetor I used - public domain, or ... ??

Joe Webster offered up his plans for this engine free on the internet about 10 yrs ago. Probably one of the best things to happen for this hobby as The Webster has been recommended to
newbie's by machinists as their intro build. You see many on Youtube with mods or as per plan and you see modelers continue afterwards..........thanks to Joe.

I agree with you. It would be nice to see other designers offer plans for free. A 4 in line that is basic and runs would be great. It allows you to gain confidence before moving on to more complex engines.


Andrew in Melbourne
Finally I'm getting a chance to start the build log - sorry it has taken so long. Work has been crazy busy as we have worked to adjust to the new paradigms enforced by the current pandemic!

The build log begins with the frame (the .pdf file is also included as a link):

Now, before we go any further, I plead for grace - I have not a single bit of training in drafting, so I am sure I have not laid this out or drawn it up in the best possible way. I would greatly appreciate [gentle and kind] pointers on how I could improve these drawings!

As I mentioned in the opening post, a significant part of what drove my interpretation of the Webster was use of materials on hand, which meant almost entirely steel. The frame is no exception; it began life as a couple of pieces of fairly heavy c-channel - which first had to be wire-brushed to remove the rust:


After chamfering the mating edges, these were clamped together ...


... tacked, and welded. Yes, it had been a while since I had done any TIG welding, and the results show the lack of practice:



To clean this up, I mostly used my restored Southbend 7" shaper - I really like using the shaper for squaring up parts, since I can let it run while I do something else:


I didnt get a picture of what happened next - I milled off the closed "top" and cut / milled the sides to give me the overall shape that I wanted. You can see that shape in the next picture below:


The picture above shows that not everything happened in logical sequence - as you can see, before I trimmed this end to be flat and to length, I had already made and added the bearing flanges - which was premature, as later I had to remove one of them to complete other parts of the frame and the ultimate assembly.

Not shown are the various operations I did to give me a flat inside surface where needed (rather than the angled and rough surface of the c-channel) - again, the shaper did the bulk of this work, but some of the setups were a little on the "just barely" side.

I don't have pictures of drilling the various holes in either side of the frame (yes, I hear that sigh of relief!) - and indeed I didn't drill them all at the same time, because I kept figuring out new holes that were needed as the design went along! But here is a picture of what is arguably the most important hole, the main bore in which the bearing flanges mount, which in turn hold the crankshaft:


Finally, a shot of an operation that actually occured after the first run, when I further tweaked the design to create a mount for the gas tank - this notch will accommodate a bit of tubing with a set screw in it, allowing it to clamp the rod that holds the gas tank mount at the desired height:



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Yes, the flywheel is steel - that episode is coming soon! I'll give you a hint: just as the frame featured welding, so did the flywheel ...

I didn't think to weigh the flywheel by itself, and at this point the engine has been stripped, cleaned, finalized with the last few tweaks, and re-assembled, with Loctite added to strategic points. Some of it is the "blue" type that can be removed, in case I have to disassemble again ... but it turns out that, at least with the design as I worked it out, this has to go together in a very specific order, and it is a bit of a pain. Okay, more than a bit of a pain.

All that to say, you've got me curious now about the weight of the flywheel, but I am not going to disassemble the engine to weigh it. What I will do, though, is weigh the whole engine - it is definitely chunky, but not all that heavy, I don't think.
Part 2 of the build log is very brief, but it turned out to be one of the better design decisions I made:

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The primary motivation for these bearing holders was to have enough "meat" to be able to mount two flange bearings on each side of the frame. The secondary motivation was that this approach would make it easy if I decided to change the diameter of the crankshaft - instead of reboring the frame, I could just make a couple of simple parts to hold a different set of bearings. As it turned out, I never did the latter; I used F6800 bearings, 10mm bore, with a 10mm (.394") crankshaft, and it worked out well.

Making these was quite simple - hardly worth taking pictures, so I only took a few:



I said this proved to be a valuable design decision - even though I never needed to change to a different size of bearings. Here's why: The relatively large bore in which these bearing flanges sit greatly eased the assembly of the crankshaft and the components that ride on it. I could partially assemble the crank shaft with the bearing flange, the crank gear, and the keys, and then slide the whole assembly in through the bore. Given the way I made the crank, with interrupted keyways, I don't know if I could have successfully assembled everything otherwise.


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Thanks Andrew, I'm enjoying this. I'm yet to build a combustion engine but when I do the Webster will be on my list.
Oh, by the way, I'm a draftsman and your drawings look fine to me - except for those funny dimensions """ :D.
Cheers John
Hi Picko,

The irony is that a lot of my design is metric, particularly any of the bits that ride in bearings, since I can get metric bearings far cheaper than inch-based bearings. (Or at least, I could, through eBay - don't know if how that supply chain is going to look going forward!) I also have a metric tap for M3x.5, but the smallest I have in inch taps is 6-32 - so a couple of the smallest screws in this design are M3x.5. I wish I could say that this reflects my international outlook ... but as with everything else in this design, it just represents laziness and cheapness - using what I have on hand or can get cheap!
Part 3 of the build log is the crankshaft:

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A few notes about the design - as you can see, I chose to go with a built-up crankshaft for my first time. I also chose to go with an interrupted keyway, but I'm not sure that was my most brilliant decision - as I alluded to in a previous post, this caused problems with assembly, since I couldn't slide the key along the keyway as I put the shaft through the bearings. One other note is the pin end, sized at a hair under 6mm so that the pin can ride in 6mm ID bearings used in the big end of the connecting rods. The length of the pin is a few thousands longer than the thickness of the big end with the bearings installed - this allows a small custom washer and a 3mm screw to fasten tightly to the end to hold the big end in place without binding up the bearings. (On final assembly, I added a dab of blue Loctite to this screw, but in the initial runs it did not seem inclined to loosen, somewhat to my surprise.)

I'm afraid I didn't take many pictures. Here is the main shaft underway:


And here is the pin in progress:


Cutting the keyway ...



A couple of things to note here. One is that I was, for the first time, using a 2mm endmill, smallest I've used to date. Why not use a 1/8" endmill? Part of the reason is that, originally, I was planning to make the keyway 3mm rather than 1/8", since the shaft itself is 10mm - keeping it in the metric family, so to speak. But I didn't have a ready source of 3mm keys, and I did have several 1/8" keys, so I switched to 1/8". Meanwhile, past experience suggests that endmills can cut just a bit larger than their diameter, so I prefer to use a smaller endmill and then shave the sides to size.

Something else that sharp-eyed readers might note in the picture above - you can see that the shaft is held in a 3/8" 5C collet. The use of the collet in the spin indexer was just a convenient way to grip this round part ... but wait; didn't I say the shaft was 10mm, .393" rather than .375"? No, 5C collets cannot expand that much! If you look back at the plans, you'll see that the end of the shaft, the part that goes into / connects with the web, is at 3/8" diameter, so the shaft is being held by that little stub in the 5C collet - but it is quite secure because I put a center in the other end, and as you can see, I am supporting that end.

Finally, a poor shot of the web end of the crankshaft after I assembled it - actually in place on the assembled engine, because for some reason* I neglected to take a picture of the finished crankshaft by itself:


*for some reason ... maybe embarrassment over the poor execution? In keeping with the spirit already established in the making of the frame, I decided to TIG weld the parts together. How did I do? Well ... the picture shows the results after cleaning it up as much as I could ... still not so great. But it works, so I'm calling that good for a first attempt!


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Part 4 of the build log gets into something that I think might be more interesting than some of the other parts - the flywheel. To be sure, the plans are quite simple:


However, the execution was - perhaps - unconventional.

I was looking for a flywheel with diameter of 3.75", at least .75" thick at the rim. I had on hand some pieces of 1" thick steel, 4" wide, but not a piece that was 4" long. So, having already established the pattern of using welding as a primary tool in this build, I prepared two pieces, 4 x 2 x 1" in size. Part of the preparation was setting each piece at a 60° angle in the mill vise and cutting bevels to facilitate a full-penetration weld:



To weld these together into what I hoped would be a solid 4 x 4 x 1" blank, I began by spacing the two pieces with a 1/8" gap to help with penetration, then tacked and ran a root pass on each side using TIG welding:




Not the best-looking root pass, but good penetration. I probably should have finished welding it up with TIG, but I was a bit concerned about the rods and argon that would be consumed, so I switched to stick welding with 7018 to provide quicker and less expensive build up - at least, in theory:


As the picture above shows, the results were so-so -- the 7018 is old, and not nearly as dry as it should be, so I struggled with porosity and inclusions here. When that occurred, I tried to grind it out and build up again. Maybe it would have been less time and trouble to have stayed with TIG throughout!

To be continued ...


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Continuing part 4 of the build log, the flywheel:

Once the blank was all welded up, I began preparing the blank, starting with a carbide-insert face mill in the Bridgeport:


In general, 7018 weld on mild steel machines reasonably nicely, but I had also filled in some gaps or defects with TIG. Normally, TIG welded mild steel machines beautifully, but if someone happens to dip the tungsten into the weld, it forms a small spot that is hard as a rock. I'm not saying that I did such a thing ... but I did feel the need to start out with carbide. :)

Once the surface was brought down nearly to level, I further prepared the blank using the shaper, getting the two faces flat and parallel:


Then I cut the corners off on the bandsaw to get a rough octagon (no pictures of that), mounted the blank in the 4-jaw chuck on the lathe with roughly half of the blank above the jaws, and began the roughing passes to get an oversized round blank:


In the picture above, note the centering mark that I had put in the blank to help get it roughly centered in the 4-jaw chuck.

Once one side was roughed in, I turned the piece over, switched back to the three jaw chuck, and mounted it up to the octagonal rim that remained on the other half of the blank. Now I could rough this other side, again leaving it oversized at this point (and also leaving just a tiny "rim" of the former octagon that had to wait for a later step). At this point, I began to do the finish turning on the exposed face:


Once the face was finished, I bored it to a nice, tight, but sliding fit on the 10mm crankshaft. In the picture below, the rim area is still oversized in diameter, but the inner hub and web are to final size::


Just after this picture was taken, I finalized the face portion of the rim as well, facing the rim down to the proper height above the web.

I removed the flywheel, switched to the 3-jaw chuck, and mounted some 1.125" diameter mild steel stock (scavenged long ago from some now-forgotten source). I turned a .9" long stub mandrel down to a nice sliding fit in the bore of the flywheel, with a flat face behind it (neglected to take a picture of that). Leaving this mandrel mounted so that it stayed perfectly true, I used Loctite to attach the flywheel to the mandrel and let it set up overnight. The first go round, I tried using the "blue" version that would be easier to remove, and I got as far as roughing out the inner hub and web, but ultimately it just couldn't take the torque, so I had to clean it up and do it again, this time using the "red" version. I held it firmly in place using the drill chuck in the tailstock while it set up overnight:


With the flywheel Loctited (is that a word??) to the mandrel, I could turn the rim to final diameter, including cutting off the little bit of octagonal "flange" that was left in previous steps:


To be further continued ...
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Further continuation of part 4 of the build log, the flywheel:

At this point, what is now the backside of the flywheel, up against the face of the mandrel, is fully finished, including the height of the both the inner hub and the rim relative to the web. Careful measurements were taken of the OD of the inner hub and the ID of the outer rim. Also, in the last bit of the previous post, we had finalized the overall OD of the flywheel.

Now to finish the exposed face to size. The rim area can be faced to achieve the desired .75" total thickness:


But the web is another matter - how to measure it? The movable anvil of the micrometer can go up into the inset area of the web, but not so for the fixed anvil.

The answer, of course, is to use a gauge block in the back side of the web, against which the fixed anvil can set; after measuring up into the inset area with the movable anvil, just subtract the size of the gauge block from the measurement, and hey presto! We get the current thickness of the web.

One small problem: I don't have any gauge blocks. (On my wish list, in case anyone was wondering what to get me for my next birthday ... :)) But the problem is not insurmountable; I just need to turn a piece of scrap so that it has parallel faces, measure it carefully, and use it as my gauge block. But another problem, not so small: my whole procedure depended on leaving the mandrel mounted in the 3-jaw so that it would stay true, and thus also the flywheel would stay true as I cut it. If I removed the mandrel to turn a piece of scrap, I'd lose my carefully planned precision.

This is where having a second lathe is invaluable. (Note to spouse: See? This really was a good purchase!) I turned a bit of scrap in my rebuilt 7x14 lathe, measured it carefully , and then used it to take the measurements of the web of the flywheel:




This allowed me to cut the web to final size, and once that was done, to finalize the ID of the rim and the OD of the inner hub. Voila! The turning is complete on the flywheel:


Now it is just a matter of cutting the keyway. To be continued one more time ...
The final continuation of part 4 of the build log, the flywheel. If you have stayed with this all the way through, you deserve a special treat; please help yourself to your beverage of choice and settle in for the final installment!

I cut the key way in the flywheel (and later on, in the cam gear and the ignition cam/starter spud) using the shaper. First, of course, I had to make a cutter. I tried a couple of approaches, but settled on a cutter ground from the remains of a 1/2" end mill:



Never, ever, ever would I throw away an end mill just because it is no longer usable as an end mill - heaven forbid that I waste all that HSS that is just waiting to be ground into something useful! (This is also meant as a note to my spouse, who seems to think I am a pack rat!)

I also had to make something that would let me mount this cutter in the shaper. Here is what I came up with:

As the picture shows, I cut a scrap piece of 1" thick mild steel to give me a "leg" that can go into the tool holder on the shaper, a body with a round hole to accept the cutter, and two cross holes that hold split-cotter clamps. (Only one of the latter is in use in, because I had to extend the cutter out further than I had first anticipated - but just the one held securely, with no fuss or muss.)

Here is the cutter in action, cutting the key way in the flywheel:


The cutter was ground to around .100" wide, rather than the full .125" needed for the key way. Part of that had to do with what was usable from the old endmill that formed the cutter blank, and part of it had to do with the thought that a narrower cutter would chatter less, and allow me to "sneak up" on the proper size, shaving down the flanks until the key just fit:


After cutting 4 key ways this way, though, I am wondering if I should have gone ahead and ground it to the desired final size - something different to try next time, I suppose. I have lots more broken 1/2" endmills. :)

Finally, the flywheel is done:


Well, almost done - I still had to hold the flywheel at a bit of an angle to drill and tap the hub for the set screws that screw down onto the key - one set screw on each side, placed over the key way. Fortunately unfortunately, I neglected to take a picture of my rather sketchy set up, but I did accomplish the task in the end. After breaking a tap. Which fortunately I was able to persuade out. (I did NOT want to have to go through all of that again to make a new flywheel!)

The good news is that the finished flywheel runs absolutely true. The even better news for you, patient reader, is that this part of the build log is finally complete!
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