9 Cylinder Radial Build using Cox Sure Start 049's - Page 6 - RC Groups
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Oct 18, 2011, 11:27 PM
Dieselized User
gkamysz's Avatar
It should help stir things up a bit. At the RPM it's turning, there wouldn't be any significant pressure even for a properly designed impeller. To make pressure it would have to be properly designed and spinning at over 100,000 RPM.

I wouldn't worry about the direction either.

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Oct 19, 2011, 12:28 AM
Registered User
boingk's Avatar
Bingo. Another reason to check out the commercial aircraft 'chargers - they are usually geared affairs and run at very high rpm.

Just so long as there is something there to give the air/fuel mix a good old swirl you should be right.

Cheers - boingk
Oct 19, 2011, 12:50 PM
Double Naught Spy
iamplanecrazy2's Avatar
Aw shucks fellas, ya mean it ain't supercharged!

Seriously, thanks for the information gentlemen.
Oct 20, 2011, 01:29 AM
Registered User
boingk's Avatar
You might also want to think about the area the vane takes up as this will limit your voerall intake area. One way around this is to use a simple piece of flat bar as the mixer, thin edge towards front and flat edge to direction of rotation. It'd be a reasonably simple affair to either weld, braze or otherwise insert it into the crank.

- boingk
Oct 25, 2011, 07:39 PM
Double Naught Spy
iamplanecrazy2's Avatar

Progress on the prop shaft housing!

A bit of progress was made on the prop shaft. The World Series has kept me
out of the shop a bit. Go Rangers!

The next step was to get the radii cut in the shaft housing. My method was
quite crude and didn't provide the prettiest results but it did work. I simply
drilled two holes in a 1/4" steel plate, one for the prop shaft and one 21/32"
which works as a guide for the bit when cutting the housing. I attached the
housing to the steel plate with the prop shaft and with the drill press just passed the bit through
the 21/32" hole and let it cut the bit of housing that was hanging over in the
opening. I used a paper marked with lines at 40 degree increments as a
guide and would loosen the nut on the shaft so the housing would rotate to
the next cut. Pretty lame description but here are some photos that I hope
will make it clear.

Got ahead of myself again and took these photos after other work was done.
At the time I cut the radii there were no
holes in the base of the housing and the housing was sitting flat on the steel
plate (locator pins are holding it up in the photo). Snugging the nut up really
held the housing tight and there was no trouble with the bit trying to make
it spin. The bit was new and cut well. Problem was it kept eating at the hole
in the plate and by the time I made all 9 radii it wasn't doing as well.

Here is how the housing was placed. I just rotated the housing and centered
the radii on the line. Bit enters opposite side.

Here is how it was situated when cutting. You can see the housing through
the hole. Locator pins that were added after this part was done are what is
holding the housing off of the steel plate.

Next I drilled the holes for the housing's mounting screws and locator pins.
There are 3 pins and 6 screws. Pins are 1/16" X 3/8" split pins, screws are
2-56 X 1/2" filister head. To drill the holes I put the prop shaft through the
back plate, slid on the housing and lined the peaks of the radii on the housing
up with the 9 inner intake tube holes on the back plate. All holes were first
drilled 1/16". I used a compass to scribe a circle in the back plate using the
hole in the prop shaft for center point. First put shaft in housing and with
compass determined where to locate the circle for the screws. With shaft
on back plate I scribed the circle. I then simply center punched the hole
locations on the circle and started drilling. It proved to be very accurate.

Here is the housing after drilling and with locator pins in place.

Had to counter sink the mounting screws or the heads would hit the 8cc
tank/manifold. First enlarged the hole to 3/32", then used a 5/32" bit to
start the countersinking. Drilled until point of bit reached desired depth.
Cut the bottom of the hole flat with a 5/32" bit that I ground flat. It
worked great. I did put the flat tipped bit in the hole before turning on
the drill press. Set depth of cut for this step.
Here is the flat tipped bit.

Here is the back plate with the screws in the countersunk holes. Notice the holes
with red marks? Those are the holes for the locator pins. I didn't think to
mark them until after I had enlarged one to 3/32". I bushed it with a piece
of brass tubing. Sure made me sick to have done that! That is what happens
when you get in a hurry and don't think ahead.

Here is the back plate part way onto the housing's locator pins.

Here is the housing on the backplate with the engines setting in place around it.

Finally, a look at what the gear set up looks like! Will be using socket head cap screws to attach the small gears.

More to come!
Oct 25, 2011, 11:30 PM
Registered User
RknRusty's Avatar
That's a great piece of work, Planecrazy, especially since you don't have a super-fancy shop like most people that tackle projects like this. I'm in awe of anyone who can take so many measurements and not botch one key one. That's me, I can conceive of fabulous contraptions but the numbers on my rulers move around when I'm not looking... I swear.

I've been avoiding asking about this for days because I'm afraid it's stupid, but here goes. How much do you think it's going to weigh; are you considering power to weight at all? I mean, this just going to be a bench mounted showpiece, right? If it's been mentioned before, I missed it.
This has been a most enjoyable build.

Are you an A&M football fan? They're moving to the SEC, which is the home of my favorite teams.
Good luck to Texas from South Carolina.

Oct 26, 2011, 09:43 PM
UAS Pilot - FAA# *******HRK
CryHavoc's Avatar

I haven't said anything but have been lurking in complete shock and awe at what you're accomplishing with simple shop tools and imagination. To me this is worthy of much more praise than somebody with years of machining experience and thousands of dollars of equipment most of us will never have. Heck, with those guys you EXPECT these kinds of projects.

No pressure but like everybody else I can not wait to see it run. Good or bad, just to see it pop will be cool. Really interested to see how you handle the firing order.

Oct 26, 2011, 10:18 PM
Registered User


Awesome dude ! You have heart no doubt in my mind. Good luck on build.
Oct 27, 2011, 04:08 AM
Double Naught Spy
iamplanecrazy2's Avatar
Many thanks for the compliments fellas. I aim to see this thing through!
The best part of this project has been sharing it here and I hope to see
someone else give building one a shot.

I have been checking the weight Rusty and it looks like the finished weight
is going to be 1 lb 8 oz. If it will run I'm thinking the power to weight ratio
will be adequate to actually power a model. Don't know that I would have the
nerve to put it in the air though.

Had a great day in the shop today. It is getting real close to being ready for a
test run!

First thing I did was clean up the prop shaft housing. It was just too ugly!

I first put it to the bench grinder and knocked off most of what was left of the webbing.
Then used a file to smooth it off and finally finished it up by
chucking it up in the drill press and polishing with wet/dry paper from 320
to 600 grit then a final polishing with steel wool. It sure looks better!

Again I didn't get photos as work progressed but this is how I secured the
housing to use the file on it.

Here it is chucked up in the drill press. I cut the wet/dry paper into narrow
strips and just let the housing turn on it as I moved the paper back-n-forth
and up-n-down.

I cleaned up the radii a bit with the file also. It no longer looks like a Super
Tigre part.

Next I started on the clamp that holds the cases down. Another spinner back
plate was used for it and the engines back plate was used as a guide for
drilling all of the holes as the centers are all the same. Used a cheapy hole
saw to cut out the center hole but had to enlarge it with a grinding stone on
the drill press. This project has taught me what a woderful metal aluminum
is. It is so easy to work with! I've found that most any tool with a good edge
on it will cut it easily. I'd have never pulled this off with steel.

To cut off the outer part I just drilled holes in between and cut the bit of material left over with a pair of snips.

Here is the scrap part.

And here is the finished part after a bit of sanding on the edges. Also had to
put a radius on the bottom side to accommodate the radius on the cases.
Use a grinding stone on the drill press for that and did it before cutting the
part out. On that point all of the holes on both plates were chamferred with
an Exacto knife. I was lucky I never cut myself doing that.

Had to put it together to see if it was going to fit. To my amazement it did
without needing any trimming!

The gears mesh well but they could be a bit tighter. I will be making an
attempt at elongating the holes in the back plate so the cases can move in
a bit more. Would like to get the gears meshed so that gap is the thickness
of a sheet of paper.

With the clamp and all the screws snugged up the cases are mounted rock
solid. I don't thing anything will be moving about. Here all pistons are set
to TDC. Moving one of the small gears back-n-forth easily moves all off the
cranks. By golly! this thing just might work!

I didn't put the manifold on this time around. Still need to drill the back plate
so the prop shaft with pass through and contact the bearing in the housing.

The spinner will make a nice cover. Wish I had one that wasn't notched for
the prop. It will need to be notched for the little gears as well as the cylinders.
Oct 27, 2011, 07:48 AM
Jack of all master of none
splinterz25's Avatar
planecrazy you are doing such a fine job with this project I know you will be replacing those slotted screws w/ cap head screws? so all of the cylinders will fire at once? all the best w/ your test run.

Oct 27, 2011, 07:57 AM
Registered User
earlwb's Avatar
That is looking spectacular IamPlaneCrazy. You are doing a bang up job on your build.
I love it.
Oct 27, 2011, 08:50 AM
Two left thumbs
Regarding the spinner, I think Bob Brown or Tru-Turn will make one with whatever cutouts you want. Can't hurt to email them both and find out.
Oct 28, 2011, 06:13 AM
Double Naught Spy
iamplanecrazy2's Avatar
Originally Posted by splinterz25
planecrazy you are doing such a fine job with this project I know you will be replacing those slotted screws w/ cap head screws? so all of the cylinders will fire at once? all the best w/ your test run.

Thank you Bruce. For the first run I'm planning on setting it up so all cylinders fire at once.

I bought some 1 1/2" 5-40 cap screws from Fastenal last
week. Bought them long so there would be a shoulder on the screw. Needed
a snug fit on the gear hole and the shoulder on these screws is perfect though
I wish it were a bit longer. I have shortened one of the cap screws and will
be using a tip I learned from one of Bob's (Twin-Stack here on RCG) posts in
another thread here to shorten the rest. Here is a link to the thread, it is
post #1272 on page 85:


Originally Posted by Twin-Stack
Every so often, I need to slightly shorten some small bolts. As an example, I recently purchased an old 2nd hand engine with butchered head bolts. When I purchased some nice new ones, they were about 2 mm too long, and its a fiddly job grinding them down one by one, so here's what to do. Find some single thickness corrugated cardboard and cut a strip off, the same width as your bolts need to be long. Screw the bolts into the channels in the cardboard, so's it looks like an ammunition belt. Clamp this between two bits of soft wood (not balsa - I use soft pine about 1/8 in. thick) in your vise, taking care to line the top edge of the cardboard strip up with the top edges of the wood. The bolts are then easily filed down individually and no damage will occur to the threads. BOB
PS forgot to mention that the vise can be tightened up until both bits of wood touch.
Oct 28, 2011, 06:22 AM
Double Naught Spy
iamplanecrazy2's Avatar
Originally Posted by earlwb
That is looking spectacular IamPlaneCrazy. You are doing a bang up job on your build.
I love it.
Many thanks Earl! Are you going to the swapmeet in Manor (by Austin) tomorrow?
Here is a link to info if you haven't heard about it.
Oct 28, 2011, 06:24 AM
Double Naught Spy
iamplanecrazy2's Avatar
Originally Posted by GeoffinIN
Regarding the spinner, I think Bob Brown or Tru-Turn will make one with whatever cutouts you want. Can't hurt to email them both and find out.
Many thanks for the tip, will definitely give emailing them a try.

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