Edwards Radial 5 build thread --- PHOTOS!

[Flyinfool]

That is exactly what happens with the radius, it acts like a ramp to get the snap ring expanding, and reducing the face area to hold it in place.

Not sure on the depth if there is room to square it up without being to deep.

 

[Alcap]

I was wondering if different size snap rings had different radius and came across this nice little chart , Im printing one for my reference https://www.boltproducts.com/documents/rotorclip/Shspred1.pdf

 

[JRaut]

That pin is never coming out.

Boy, I sure hope I'm wrong.

I'm hoping that I can (1) press out the current pin; (2) make a new pin using a Micro 100 grooving tool like this one; (3) press in the new pin.

If it has a center in it (or perhaps even not!), he can hold the other end in a 4 jaw and use a ground tool to clean that up.

Sure hope this type of setup won't be needed.... wouldn't be fun to dial all that in.

I was wondering if different size snap rings had different radius and came across this nice little chart , Im printing one for my reference https://www.boltproducts.com/documents/rotorclip/Shspred1.pdf

Nice reference. Much appreciated.


Anyone have any thoughts as to whether the Micro 100 grooving tool will be able to cut the Rockwell C60 hardened dowel pin?? Or am I just asking for trouble?

I'll try it out on a spare dowel pin before pressing out the current crankpin, just in case.

 

[JRaut]

Episode 10 || Successful Cylinder Barrels

Making these five cylinder barrels took a good deal of time, but all that time was well worth it in the end. There were plenty of ‘learning opportunities’ along the way (see Episode 8), but they turned out beautifully.

I tweaked my process a few times along the way, but the one I’m going to describe here is the final version, which I found to be the most expeditious and least prone to problems. As I’m writing these first couple sentences while thinking back and looking at my photos, I expect this write-up may be a bit boring. Well, sorry. Boring successes advance my project faster than exciting failures.

I first slabbed off a chunk of 7075 aluminum about 2-1/8” long. The barrels finish to 1.415” long overall, but I needed a bit to grab onto with my new-to-me 6-jaw chuck (!!).


No witchcraft here. Step-drilled up to a 1/2” hole down the center and used a boring bar with my compound slide set at 60* to accommodate a live center.


With my import live center in place, I turned down the OD to 1.735. The drawings call for 1.750, but I needed to take off a bit from my 1-3/4” stock. I could probably have gone to 1.745” or so instead, but (1) this is a non-critical dimension, and (2) I wanted to make all the barrels the same. 1.735” diameter would make initial centering of the extruded stock a bit less critical. I don’t have a DRO on my lathe, and am still trying to figure out a good way to accurately set distances and spacings along the Z axis. My current method is an extremely clunky combination of a 1” dial indicator on a crappy mag base, and a micrometer stop on my ways. Anyway, my micrometer stop has 1” of travel, which is enough for this job; I set it such that 0 on the micrometer stop equaled 1.600” from the face.


The drawings call for a series of four different ODs to be turned on the cylinder barrel. For reasons that will get into briefly a bit later, I turned only two of those ODs before removing the part (still mounted to the chuck) from the lathe. I turned those diameters using a parting tool. Perhaps not the ideal option, but it allowed me to get square shoulders on both the ‘left’ and ‘right’ side. If that makes sense. I used the micrometer stop to set the location of these cuts.


Now, over to the Bridgeport for some milling work. Similar to some of the folks on YouTube (Robin Renzetti, Stefan Gotteswinter, and perhaps others), I milled two flats on the backplate of my chuck so that I could easily grab it with my ‘vintage’ Kurt 6” vise. Here I first centered things up with my Indicol then drilled five 0.120”-diameter clearance holes to accommodate the #4-40 head bolts; the bolt pattern of course was the same as the bolt pattern on the crankcase.


Now we get to the point where we make this cylinder barrel look like its air-cooled self. I detailed in Episode 8 why I opted against doing this on the lathe, so I won’t repeat that here. Suffice it to say that I was getting very good results milling them with a slitting saw, so that’s what I did for all 5 of the ‘keepers’. I use a ‘CNC’ program to run the cutter in a circle around the cylinder to make each slit. I ran things at 10 inches per minute, and took two passes to get to the full depth of about 0.28”. It took about 1 hour of milling just to do the fins once I got things dialed in. Took longer for the barrels I did earlier in the process. Very, very messy job, but can’t argue with results. I would have done all this on a rotary table instead of using CNC, but didn’t have one at the time. (I’ve since bought an old Spanish-made 12” rotary table, but don’t have it on hand yet. I’m eagerly awaiting it’s arrival!!!)


Off the mill and back over at the lathe, I turned the final two diameters to size using the same parting blade. A bit hard to tell from these photos, but the smaller of the two diameters gets down just deeper than the through-holes for the cylinder bolts. The larger of those two diameters is about half-way into those bolt holes; this is the reason I moved over to the mill before turning the diameters. Wouldn’t have been able to drill the bolt holes otherwise.


Then I bored out the center. The drawings call for a bore diameter between 1.0615” and 1.0625”; I shot for the smaller end of that range. The actual value doesn’t matter much though, as each of these cylinder barrels will receive a cast-iron sleeve, the diameter of which I can tailor to suit. Regardless, I shot for 1.0615” on all 5 cylinders and ended up within a couple tenths in each case. I contemplated using a reamer to finish these bores, but I was getting a very good finish and had very little taper. That, and I didn’t have the right size reamer on hand (I had a 1” and a 1-1/8”, but not a 1-1/16”). If I had one, I’d have used it. Once bored, I cleaned everything up with a bit of emery cloth and parted each off about 0.020” longer than required.


The last step in the process was to get the overall lengths of the cylinder barrels down to the 1.415” specified in the drawings. This called for an expanding mandrel to hold the parted-off parts. I dug through my ‘scrap corner’ looking for a good candidate, and found a perfect chunk of Delrin. I wouldn’t normally have thought to use Delrin for this type of expanding mandrel (would normally use aluminum), but the piece was perfect for the job. Many of us have probably made these sorts of crude expanding mandrels over the years, so I won’t dwell on the details. Simply tapped hole in the middle, countersink at the outside, and carelessly split along its length with a wood saw. Tightening a flat-head screw expands it. The pre-expanded OD I turned it down to was about 0.001” under the typical cylinder bore.


I faced each cylinder barrel off to the same length, and voila! Perfecto!


Starting to look like a 5-cylinder radial, if I do say so myself! But there are a heck of a lot of parts yet to be made. So this is certainly still in the early stages of the journey.



TIME ON (SUCCESSFUL) CYLINDER BARRELS: 23 hours
CUMULATIVE TIME: 148 hours

(The astute among you will recognize that I seem to have glossed over the issue with the rounded groove in the crankpin of my crankshaft. I’m tabling that issue for now, but will return to it at some point.)

 

[JRaut]

Episode 11 || Master Rod and Link Assembly

Okay everyone, thanks for the patience. The machining for this subassembly has taken longer than any of the other subassemblies thus far, and resulted in a few more parts for my pile of ‘learning opportunities’. So let’s dive right in.

The master rod and link assembly is basically the subassembly which translates the up/down motion of the pistons into the rotary motion of the crankshaft. It’s generally comprised of a ‘master rod’ and four additional ‘link rods’ which are attached to it via dowel pins. The link pin retainer plate helps hold it all together.


Link Rods
I started with the link rods to get my feet wet before embarking on the master rod, which is significantly more complex a part to machine. The link rods are pretty straight forward: 6mm reamed hole in one end, 1/4” reamed hole in the other. The dimensions on the other features aren’t particularly critical, but it’s rather important to make them all the same for motor balance. I started by cutting out some 7075 Aluminum blanks by hand using a wood-cutting saw. Then over to the Bridgeport to square them all up to the same dimensions. Nothing critical here.


To cut the overall profile, I ‘wrote’ a little CNC program. When I say ‘wrote’, I basically hard-coded each and every key point into my DRO by hand and let the Bridgeport work out the rest. See previous posts for a little more information about my 2-axes EZ-Trak. I started with a 1/4” end mill for the outside profile, then a 1/8” ball-nose end mill for relieving the inside, then a series of drills and reamers to punch the holes in each end.


Do that 4 times and I had the ‘top sides’ of each of the link rods finished up. Notice all the chicken-scratch on the drawing sheet. Most/all of those notes were used for ‘writing’ my CNC program.


Now, I’ve never used soft jaws on my mill before. But I reckoned this would be the perfect opportunity to do so. I bought two sets of soft jaw blanks off eBay for something like $30 delivered. I considered making the blanks from scratch, but the material alone for two sets (four jaws) would be pushing $30 in small quantities. Anyway, similar to the overall outline of the link rods themselves, I wrote up a CNC program to mill out a home for the link rods, top-side-down, so that I could finish them off. Strictly speaking, I machined them to be over-constrained (I think that’s what the fixturing folks refer to it as), but so what. I was only doing 4 parts and milling some noncritical features.


One quick word of caution here. I ruined all four link rods while clamping them down in the soft jaws. The pockets I initially milled in the soft jaws only grabbed a very, very tiny sliver of the link rods. Combine that with some over-zealous clamping force and I squashed all of the reamed holes (some more than others). Didn’t notice until the last one. Anyway, it wasn’t a big deal to re-make those four link rods, so I just bit the bullet and redid them. I re-milled the soft jaws to grab a lot more meat the second time around. The completed link rods turned out great the second time around.


Master Rod
The master rod forms the heart of this subassembly, and resulted from a whole pile of different machining operations. Conventional mill work, CNC mill work, drilling, reaming, boring, more soft-jaw work, and even some action on my New-to-Me Rotary Table!!

I started with a chunk of 7075 plate and hand sawed out an appropriately sized piece. Same as the link rods, I squared everything up on the mill and prepared to CNC mill out the overall profile on the ‘top side’ of the part.


I blued it up and gave my program a test run at about 0.010” deep. Worked like a charm! Bottle cap for scale. And because Deschutes Fresh Squeezed IPA is delicious. Rinse and repeat to get down about 0.020” deeper than the finished part thickness.


A little bit more milling on the top side to finish off the basic profile.


Then some drilling, reaming, and boring to finish off the features from the top side.


I then milled out the soft jaws to fit. Clamped the part in the jaws, milled off the ‘hat’, and finished off the features on the bottom side. Easy peasy.


The last feature on the master rod that needed machining was the slot to accommodate the link rods. The slot is nominally 1/4” wide plus a few thou and extends all but 90 degrees around the part. It was a great excuse to use my brand new-to-me 12” rotary table! It performed admirably on its maiden voyage.


Link Pin Retainer
This is a funky bit of sheet metal. The plans call for ‘steel’ to be used. I bought a 0.040”-thick sheet of 316L stainless steel for making the intake/exhaust flanges, so that’s the plate I used for this retainer plate. Thing was a ***** to machine. And I won’t dwell on it because this post is getting too long already. Suffice it to say, I broke a couple end mills in the process because 316L is very difficult to machine. It work-hardens like nobody’s business.


Link Pins
The link pins are nothing more than 1/4” dowel pins with a slot machined into them to grab onto the Link Pin Retainer plate. I first tried using a Micro 100 carbide face grooving bar for the grooves. But after breaking off two of them on the hardened dowel pins, I opted to grind the groove in using a tool-post-mounted Dremel. Wasted about $40 in those two carbide bars; bummer. The Dremel wheel wore away pretty quickly, so I couldn’t rely on my dials to get a depth of cut. Just had to check the fit every once in a while until it was good. Nothing critical here. Used the same Dremel wheel to part it off once it was grooved.




Okay, here’s the completed subassembly! Looks like a little dancing fella.




Anyway, lots of work on this episode, but again lots of fun. And everything came out (just about) perfect!


TIME ON MASTER ROD AND LINK ASSEMBLY: 32 hours
CUMULATIVE TIME: 182 hours

 

[JRaut]

One thing I forgot to mention:

After reaming all the holes in the master and link rods, I found that my dowel pins were a bit too tight. I could force them in there, but not really the fit I was after for something that'd be spinning a few thousand RPMs. Likely due to the dowel pins being a couple tenths oversized, and the reamers reaming right on size.

I'm sure they would have worn in nicely, but I wanted to be proactive about it.

There were 2 hole sizes I needed to deal with, 6mm and 1/4". For both, I chucked up an extra length of dowel pin that I was actually going to use in the motor. After quickly zipping in some shallow grooves with my Dremel, I had a perfect reamer!

Gave it a squirt of WD40 and reamed out each hole to the exact size I needed. I removed almost zero material, but it was just enough. The result was a perfect sliding fit at all locations.

 

[savarin]

And I have learnt something here. Good one.

 

[JRaut]

I sorta borrowed that idea from Chris over at Clickspring on YouTube.

Apparently it’s an old clockmaker’s trick to make a custom D-bit reamer from a piece of of the shaft you actually intend to use.

So I copied the concept but just figured I’d try it out with some Dremel’d grooves. And it worked great for taking off a few tenths.

The part got quite warm, so I wouldn’t try to use it to take off more than a thou or so.

 

[JerryL770]

I know this is a little late but hopefully better late than never. I'm new here, an aeromodeller and also classic car buff so was interested to read this thread. When I came to mention of the difficulty and resulting mess made by trying to dissolve the broken off tap with allum, also as a Chemical Engineer I was intrigued to see if anyone came up with the answer. I have only skimmed through the thread so apologies if this solution has already been posted.

I needed an adaptor for a steering wheel wheel on my Facel Vega and my sone was able to turn one up for me at work but I had to tap blind holes for the wheel attachment. On the next to last I broke the tap. A propriatory remover was destroyed to no avail.

The answer is nitric acid. Acquire some by whatever means school labs are one possibility, it does not need much. Build a little dyke around the hole with the broken tap using plasticine or even bluetak. Fill with nitric acid and wait for bubbling to cease. Wash it out and refill, keep doing this till bubbling ceases on filling with fresh acid. The tap is gone and there is only a little staining of the aluminium around the hole.

HTH. Jerry

 

[JRaut]

Thanks for the good info, Jerry.

If still got my old crankcase with the tap still embedded. So maybe if I can get my hands on some nitric acid I can give it a whirl.

Any idea if any household products would do the trick as well, albeit slower? I haven’t tried googling around at all, but I don’t have any obvious connections for acquiring potent acids.