Cirrus V8 rotary valve engine build 2x scale up

[davidyat]

Unfortunately, no. I was like a kid in a candy store. Go here, go there and just snapping pictures at random. Will do better next time.

 

[davidyat]

Grasshopper update. Well, I'm taking advice from my mentor, Ray. If you don't feel comfortable, don't machine it. I started to turn the crankshaft using a 0.125 parting tool. I didn't feel comfortable. No matter what I did, I didn't like the feel. So I bit the bullet and got a used Dumore Model 14-001 tool post grinder. Got a 0.250 grinding wheel. I needed to make a better holder for my purposes. The first bit of grinding did feel a whole lot better. It's going to be time consuming and tedious, but I don't think I'll mess up this one. I'm sure it will make a world of difference when I get to the rod journals.

 

[Cogsy]

1/8" is still a fairly large parting blade, though it likely would be ok if ground properly. I use a 0.093" (I think) blade with the end 'bifurcated' which means split in two with a small v ground in the centre. So it has small contact area and handles cutting side to side. I'm sure grinding will work out though, I just couldn't handle the noise for that long.

 

[davidyat]

SUCCESS!!!

Grasshopper here. I never thought this day would come. I now have a crankshaft! I started on a blank steel shaft. One of my 2 best friends was here visiting me from California. He owns a grinding shop where he uses Blanchard machines and double disc grinding. He was seeing my frustration with the steel. Since he has so much experience with grinding all kinds of metal, even Inconel, he suggested using 416 Stainless Steel. He said since the motor wasn't going to power anything, just run on compressed air for a few minutes, 416 SS would be so much easier to machine and would hold up to what I wanted it to do. So I got a blank. The pictures show I started by machining the ends down to 3/4 inch and the interior center areas also to 3/4 inch. I wanted to keep as much beef as I could during the machining process. Barry (Bazmak) gave me a lot of advice for machining. After the centers, I loaded the blank into the offset jigs. I started by using a 1/8 inch cut off tool to go in about 0.125 inch, move over about 0.200, go in again at 0.125. Then put in a 0.375 flat nose tool and went in 0.125. I wanted any surface I was grinding to be no more than 0.125. Two cuts with 0.125 (0.250) would result in the 0.375 only cutting 0.125 of surface area. AND TALK ABOUT SLOW. 60 rpm on the lathe, moving the cross slide in 1 to 1 1/2 thousandths per revolution. It's taken me 1 month to finish this crank. With it installed in the block, I can see that if my old eyeballs are correct, I'm going to have to adjust 10 thou here and 20 thou there to get everything to line up correctly width wise. One bank looks pretty good and the other side might have to be adjusted. I just want to thank all you experienced machinists and your advice to this novice. I'm learning a lot. I can't thank my mentor, Ray Clyde (a master machinist who also helped build the B-2 Stealth Bomber), Bill Birch(the Grinder) and Barry from down under.

P.S. After cleaning up the machining area, went and sat down on my front porch swing, and opened the most awesome tasting COLD beer I've had in a long time!!!

 

[davidyat]

Again thanks Barry for the advice on putting support between the rod journals for support.

 

[natalefr]

YEAH !

 

[bazmak]

Congrats,i think one of your problems was the initial cutter.It looks far too wide and would creat too much pressure
I initially started with a parting tool ground to a point and simply nibbled out the meat,gradually facing the sides
When i was almost there i used a lh and rh tool to finish the webs to size and the parting tool to finish the diameters
Took quite a while but the beauty of the turning fixture is you can remove /reset and nibble the eccentrics.Isnt it a good feeling
when you get there.Now dont drop it

 

[davidyat]

Barry,
Thanks again. You were so right on the cutter. It was way too big. I look back on the crank machining and even with all my mistakes on the first 3 and botching them up, I consider it a learning experience. I learned how NOT to machine a crankshaft. The lessons I learned on the 4th crank I think will stay with me a long time. I've built plastic and balsa models for over 65 years and thought I had the patience part down. NO, the crank taught me MORE patience. Now I'll be working on the cylinders. I still have to bore out the 3/4 inch hole for the pistons. I know there will be some adjustments needed to get everything into alignment. I think I'm going to take some time from the V-8 and mess around with the 1/4 Scale Myers/Rider-Ericsson that's almost completed. When I was at the NAMES show last April, I was told that making the displacer piston out of BBQ grate cleaner (a stone like material that's a lot lighter) would be a better approach. Will keep you updated.

Grasshopper

 

[davidyat]

Barry,

Grasshopper here. A question on the crankshaft. I've enclosed a picture of my progress so far. My question is, do I have to turn the middle 3 concentric's to 0.500 inch? I left them at 0.750 inch for beefing up the crank during the machining of the rod journals to 0.500 inch. I have sealed ball bearings with a 0.500 inch hole for the ends, which will be turned to 0.500 in to fit the ball bearings. I'm hesitant to machine the middle 3 to 0.500 inch. I haven't made the hole for the inner concentric brass bearing yet. I can bore the brass inner bearing to 0.750 inch and leave well enough alone. Or am I leaving too much mass for the air to turn the engine?
Thanks,
Grasshopper

 

[bazmak]

I cant remember the exact size but i did turn the 3 inside concentrics to a larger dia as they are not doing anything
and i thought it better to leave them heavier for strength.No fixed rules just do what looks/feels right
From memory 3/4" seems a bit large.If the big end eccs are 1/2" or so then i think i made the concentrics 5/8"

 

[davidyat]

Thanks, now to make some chips.

Grasshopper

 

[davidyat]

Barry,
I have installed the cylinders with the pistons and everything moves with no obvious problems. What would you suggest for max diameter of the bore of the cylinder. I have 6 to 7 with very good fit. Pull the rod and piston out of the cylinder and you get a good pop. On the 8th, the piston is 0.750 and the cylinder is 0.764. One question, I can make another piston if needed out of 7/8 brass rod and turn it down to 0.764. Think I need one? Next what is your suggestion for the springs that hold the ball bearings in the head? Length and compression load? My hole for that is 5/16. What did you use on yours and where did you get them. Today, I'm going over to a supply house and get toothed pulleys and belts. I want to get the pulleys before I bore the air rotary valve and a few belts of various lengths in case I would need an idler pulley.
Grasshopper

 

[bazmak]

Yes I would say there is no reason why you cannot make an oversize piston to suit cylinder 8 as long as they are clearly marked
I was very limited with commercial available springs and used the lightest I could get,however I think they are still too strong
If you read back thru the post Chuck Fellows also pointed this out.I think it is a case of suck it and see. I did not get mine running
with borrowed compressor so put it to one side for when I have my own compressor and more time to play.I got distracted with other projects
Keep up the good work

 

[davidyat]

Thanks Barry. I will go to McMaster Carr and I believe I can specify the wire diameter of the spring. Will look for a light one. I've just ordered my 2 to 1 toothed pulleys for the crank and sleeve valve. I will probably use an idler pulley to keep tension. I need to get the pulleys before I drill the 6 inch hole for the intake sleeve valve. I am also going to use a compression fitting into the block for the air intake tube. 3/16 fitting with a 1/8 pipe thread. This way I don't have to be EXACT in my length of the intake tube. I have a large brass block at the top of the head where I will silver solder the tube into.

 

[davidyat]

An update. I received the cogged belts and pulleys. I was able to bore the hole for the rotary valve in the engine block and pressed the brass bearing in by putting the block in the oven at 500 degrees and the brass bearing in the freezer.

Having a small nagging problem with the brass bearing and the rotary valve. When the steel valve is rotating about 500 rpm in the lathe, the engine block with the brass bearing pressed in, will pass freely. But when I stop the lathe, the steel valve will have a slight resistance when installed about half way. I've been lapping for 2 days and can't seem to solve this problem. I don't know if the brass or steel is slightly bent by a few thousandths causing this problem. Will try to put the steel valve in the lathe and see if it's out of round and by how much. Anyway, I have been able to put both cogged pulleys on the crank and valve and have no clearance problems. The cogged pulleys are 15 teeth on the crank and 30 teeth on the valve. You can see by the photos that a standard belt has too much slack. I did order a few over sized belts and you can see that I will figure out an idler pulley system to keep everything snug.

 

[davidyat]

Baz, Grasshopper here. I'm almost ready to bore for the rotary valve. I must be very tired. I'm trying to figure which end is which. In this picture of your turning of the crank, which journal is closest to the live center in the tail stock, A or D? If you stand the crank upright and look at the dimension page to get the orientation of B and C journal, is A at the top or bottom. Pretty much it doesn't make any difference to me, if one way is wrong, just turn the crank around. Thanks in advance.
Grasshopper

 

[davidyat]

Well, Grasshopper finished the Cirrus Compressed Air V-8. It's either an engine or a very expensive paper weight. When I hooked up the air, I got two apparent exhaust pops and nothing since. Won't run. I've listed some pictures of the finished engine and how I drilled the timing ports. I used an extra cylinder to make sure number #1 piston was at TDC. Installed timing wheel and went to work. Some of my thoughts as to why it won't run. Springs too strong in the head, air leaks, possible air ports not lining up (I did back off the timing holes to just be opening at TDC but

maybe not enough?), the cogged belt too tight (if loosened up too much, cogged belt will jump some teeth?) or other problems I haven't thought of. I will take time off to contemplate my next moves. Anyway, some pictures.

 

[stevehuckss396]

It is very common to have problems getting a fresh build to run. Stay with it and double check valve timing. Look for things that didn't get tightened. Make sure parts didn't move due to set screws slipping etc. Its probably something simple.

 

[davidyat]

Thanks, the first thing I'll do is double check the valve timing. Then the springs holding the ball bearings that keep air from backing up into the valve. I am concerned with the rather snugness of things when the cogged belt is snugged up with the idler gear. I can turn everything by hand but I do notice it's not as easy as when the belt is off and I turn the crank, then the rotary valve. Like I said, it's been almost a year and a half and I'm going to take some time to REALLY think about what I've done and look at things from a different perspective.
Grasshopper

 

[stevehuckss396]

If it seems a little snug and think it might be the crankshaft or camshaft, try putting it in the lathe and use the lathe to motor the assembly for a half hour making sure it is well lubricated. If that seems to loosen things up, give it another half hour. Getting it rotating freely will give you a huge advantage when trying to get it to run on it's own power.

To motor it put the crankshaft in the chuck and lightly tighten it. Move the toolpost over so the engine block cannot rotate. If possible support the other end of the crankshaft with a live center in the tailstock. Put the lathe in neutral and spin the chuck by hand and see if everything turns without hitting something it shouldn't. If good put the lathe in a slow speed like 150 RPM and turn it on. Just let the lathe spin it around for a while.