5 Cylinder radial (winter's project)

[gbritnell]

This morning I got started on the little right angle plate to hold the rockers for cutting the radius on the end. I put a .125 reamed hole in it and press fitted a 5-40 stud for holding the rockers. I also put a little boss on the valve end to keep the arm from possibly moving. I found a 10-24 tapped hole on my universal aluminum fixture block and mounted the angle plate. The first rocker got laid out with centerlines. Once the rotary table was indicated in I mounted the fixture block. In the second photo you will notice extra clamps mounted flush with the rotary table once I had the layout lines wiggled in and the clamps tightened I mounted the extra clamps against the sides of the fixture block. I have found that no matter how hard you try at setting up everything as perfectly as you can when you start cutting a radius it seems like that part is always shifted just a little. The extra clamps are used to adjust the fixture block. I make an initial cut and see if it looks like everything is even, if not I loosen one of the stop clamps, add what I think is the necessary shim, push the clamp back up against the fixture and tighten. I then take the shim out, loosen the fixture clamping bolts and push it against the now moved stop clamp and re-clamp. This way I can fine tune my cut so that the radius ends up perfectly centered on the square.
The first picture shows the angle plate mounted to the fixture plate. The second photo shows an overall view of the setup. The third picture shows a rocker arm mounted and ready to be cut. The fourth picture shows the radius spun on the rocker end. To get up against the body of the rocker arm with the cutter I slowly rotate the table and backing off until I see that I'm close. Once there I put a reference mark on the rotary table so that I can repeat for the other parts. It's better to stay a little away and file the piece rather than dig into the body and have an ugly looking gouge. I have so many hours in these things already I certainly don't want to start over with the whole process for just one or two arms.
gbritnell

 

[gbritnell]

So far so good. Ten rocker arms with no errors that can't be fixed with a file and some emery paper. Tomorrow the same fixture will be used to put the pockets in for the pushrods. Everything is still on center so I only have to remount the arms and do this final machining operation. From there it's just files and polishing.
gbritnell

 

[vcutajar]

George, can't wait to see it running.

I have found that no matter how hard you try at setting up everything as perfectly as you can when you start cutting a radius it seems like that part is always shifted just a little.

So it's not just me that gets that feeling.

Vince

 

[petertha]

George, when you do jig plate operations on the rotary table like this, do you have some alignment method that registers it concentric to the RT hole? Like a pin that goes through the plate into an MT? plug in the RT or something?

 

[gbritnell]

Hi Peter,
When I'm using a fixture plate such as I show I don't use any type of dowel pin. Each job has a unique setup situation so the fixture plate needs to be moved to center. Here's the way I would do it for putting a radius on the end of a connecting rod or link. Drill and tap your fixture plate for the mounting screw. Counterbore for a hollow dowel pin that would go in the rod or link. If the part is too small for a hollow bushing then drill, tap and counterbore for whatever screw you are going to use. Lets say you're going to use an 8-32 screw, drill and tap for that and then counterbore for the diameter of the screw. In this case it would be .164. Now turn up a screw with the proper shank diameter, manufactured screws are all undersize, some quite a bit, so they won't locate very accurately. Now setup your rotary table and indicate the spindle to the center of the rotary table. Set your handwheel dials or digitals to -0-. put your fixture plate on the table and get your clamps and heels set up. Now what I do is I have a rod with a 30* taper on it and I mount it in my spindle. I bring the spindle down until the tapered rod enters the counterbore on the fixture plate and then tighten up the clamps. I would say that by doing it this way you would be within .001 or so given spindle, and cutter runouts. The next thing I do before mounting the piece to be cut is indicate one side of the fixture plate that it parallel to the holes you put in it to hold your part. Rotate the rotary table to get a parallel setting to either X or Y. Now mark your rotary table or set the handwheel to -0-. The reason for this is in case you have to cut the sides of the rod parallel or even at an angle you have a -0- reference to go back to. Now mount your piece, move either axis the radius of the piece plus the radius of the cutter and spin your part. I always stay at least .005 away initially (.010 diameter) and mike my part. Like I mentioned, given cutter and holder runouts it's better to creep up on your finished dimension. Once there it should repeat fine.
By explaining everything I do I didn't mean to be condescending about it but sometimes it's better to give too much information rather than not enough.
George

 

[Mosey]

George,
Thank you for this explanation. It explains all of the details of the process that some of us(I) struggle with in terms that are simple and I am able to emulate. It is just the correct amount of information.
Your build narrative will serve me as the literal "how-to-do-it" text as I work on my engine build. Don't hesitate to give full explanations.
When you are finished, I am going to print out this build narrative and bind it as my shop manual.
Mosey

 

[gbritnell]

Well I ran into my first major snafu on this build. Everything was going along great and then I started assembling rods, pistons, cylinders and what have you only to find that as I was putting successive cylinders onto the crankcase the valve timing didn't match the piston position. Now I don't mean by a little I mean that they weren't even close. How could that be?

I pulled out the Morton drawings and went over the cam drive, mine is nothing like the Morton but the gear ratio is the same. I then went back to my Autocad layout drawing. When I start a project I have one drawing that is strictly for layout, meaning this is where all the parts and pieces get fit together and problems get resolved before the individual sheets get drawn. Hmm, everything looks good there. I better go to the crank and cam layout to see if I can spot something. Aha!! The darn cam is not in time with the crank because it's turning the wrong way. The crank turns one way and the cam turns the other. Shouldn't be a problem you say, lots of engines have that configuration. Well they do but it won't work for this engine. When I layed out the gear train I started with the crank gear, it turns counterclockwise from the front, the intermediate gear then turns clockwise. The intermediate gear is a double gear and the second gear drives the internal gear that is the cam ring. The problem is the cam gear turns the same way as the intermediate gear. One of those oh shucks moments but not quite that mild.

The next question is can it be fixed or should I just start a new engine, I do have all the cylinders and heads for one. I'd rather fix this one if I can.
Back to the drawing board. If I make new gears but 22 teeth instead of 25 teeth I can make idler gear that will correct my rotation problem. To make smaller gears I have to reduce the diameter of the crank from the gear forward to allow for the smaller gear. The crank went from .276 to .250. That solved that problem. Now all I have to do is disassemble everything, fixture up the crankcase and put in new holes, along with making the gears and shafts. The prop hub will have to be redesigned because I can't use a taper on the shaft, too small. Well I sorted that out. I'll put a small pin through the crankshaft and put a cross slot in the new prop hub. This will give a secure drive mechanism and positive stop when tightening the nut.

I got all the parts made and reassembled everything and it works just like it's supposed to. Now I can move on to making the intake runners. Hold on, the intake port is now the exhaust port and vise versa and the rear crankcase was machined for the other iteration. Darn and double darn. I can do one of two things here. I can try and bend the tubing with double bend in a tight arc, no I don't like that, or I can make a new rear crankcase. Well get out a piece of .75 aluminum plate and start whittling.
I finished all the machining today. I have about 7 hours in the new rear crankcase. Tomorrow I will do the finish work and then I can move on to the intake runners.

Well it was a good learning experience and I do like to machine things so once you get over the initial shock of 'what have I done' it wasn't so bad after all. It's not like I had to pay someone to do all the work.

Anyway dear friends I have attached the following pictures to show that it's really starting to look like it might work after all.
George

 

[steamer]

Nice catch George! The gremlins do find their way in don't they!

She looks beautiful! I especially enamored with your adjustable rocker arms. I've seen similar in big practice, and they look the part here.

:bow:

And Karma from me for showing the leadership how to deal with and solve a major problem!

Dave

 

[metalmad]

Absolutely Inspiring :bow:
Pete

 

[vcutajar]

I've experienced that situation many times. Sometimes it's fixable but other times it's not. Looking forward to see it run.
Vince

 

[Mosey]

In all seriousness, the mistakes are educational as well, as they show us how you work around a problem and fix it, instead of throwing something against the wall and quitting. Keep it coming and thanks.

 

[ref1ection]

Great work as usual George and especially like the trick using the extra clamps to adjust the fixture.

Ray

 

[petertha]

Hi George can you elaborate on these? Do they vary the pushrod length in order to adjust rocker/valve clearance gap? If so, what keeps them locked from unscrewing?

 

[gbritnell]

Hi Peter,
That's exactly what they do. The pushrods are .093 diameter and the threads are 1-72. There is a lock nut between the 2 parts. You simply adjust the pushrod length and then tighten the jamb nut. I have a similar setup on my Holt and they work great. It saves the extra weight of the larger rocker arm and the additional adjusting screw and nut. Naturally it only works on exposed pushrods.
George

 

[gbritnell]

After everything got straightened out it was time to make the intake pipes. I have bent several different sized tubings with my small tubing bender from brass to stainless and it has worked well. The tubing for this engine is type 304 stainless, .219 O.D. with a .015 wall thickness. When I bent the tubing for the V-twin I had to make another tubing bender as this one was designed for a maximum of about .25 diameter and the V-twin is .375.

The designed inner radius is .200. The reason for this radius was so the pipes would clear the fins. I had no idea if it was possible to get this size radius from this tubing. I made up the appropriate die and while I was at it I changed from a round follower, or whatever you call it, to a rectangular follower with a .1095 radius milled into it. This was what I used on the V-twin bender and it seemed to give more support.

I calculated the pipe length needed, plus a little for safety, and then filled it with Cerro alloy. I then clamped it into the bender collet, made my die and shoe adjustments and started bending. I got to about 50 degrees and the tubing split. Well that didn't work.

 

[gbritnell]

Not knowing how small of a radius this tubing would take I went from a .200 radius to a .280 radius and made up the new die.
I did find out that I didn't need as long of a piece of tubing so the next one was shortened up about .350.

The tubing was again placed into the spit collet with the proper amount of projection and clamped tightly. The die wheel was then moved up against the tubing and the post was tightened.

 

[gbritnell]

As I started to make the bend I noticed that the die post was moving. My original design only had the .219 diameter shoulder sitting against the bender with a 6-32 threaded post for tightening. I couldn't tighten it any more so a modification to the bender was in order. I took the tubing out and took the bending arm off of the base and milled a .375 x .062 slot along the original slot. I then made up a new post with a .375 shoulder on it. After reassembling I put the partially bent piece of tubing back in, adjusted the die and tightened the post. It felt much better with the change. The shoe was adjusted up against the tubing with the adjustment screws and the through bolt was tightened. I applied a little bit of oil on the tubing to help the shoe slide around the tubing.

 

[gbritnell]

The bender was clamped back in the vise and I started the bend again. This time everything held tight and it looked like the bend was going well. When I got to about 50 degrees I started to pucker but the pipe held and I went the full 90 degrees. As you can see the results are great.

I proceeded to fill the rest of the tubes with Cerro alloy and bent them up without incident. I must say that this is about the limit for this little bender. Although it did a good job it was just about at it's limit with this sized tubing.

 

[gbritnell]

The excess was trimmed from the tubes and they were fitted to the heads. They will get adjusted even more before silver soldering the flanges on. The vertical end of the pipe is a close fit into the crankcase so when it comes time for assembly a bit of sealer should seal things up nicely.

The last 2 pictures show the modifications to the bender, one was the revised post with the shoulder and the other was the rectangular shoe. I will make the changes to the drawing and post it for everyone who has requested the drawings or has already built one.

George

 

[steamer]

Beautiful work George as usual

I am always impressed by your work. It always shows thought , effort and preparation.

:bow:

Dave