5 Cylinder radial (winter's project)

[gbritnell]

As promised here is an update to running the radial.

I had time this morning so I took the radial out to the garage and hooked everything up. Put some fuel in it, cranked it over a few times by hand to clear any oil and hooked up the starter motor.
After a couple of seconds of spinning it started to pop. As I adjusted the needle valve it got closer and closer. Finally it kept running, and on all five cylinders. After about 5-6 seconds one of the clamps started to come loose so I quickly switched of the ignition and reset the clamps.

Another spin with the starter and it fired right up. A little fine tuning with the needle and it was running, albeit at about half throttle. I had adjusted the barrel stop in the carb to let it run a little faster, and it was. I let it run for about 2 minutes and ran in to get the camera and set it up for a video.

Set up the camera, picked up the starter, gave it a crank, fired right up and then came to an instant and inglorious halt. I tried to turn the prop but it was jammed up tight.

Put away the camera, unhooked everything and headed to the shop.

After unbolting the prop, rear frame, carb, oil lines, inlet pipes and motor mounts I started taking the engine apart. It didn't take long to find one of the problems. After removing the rear crankcase cover and looking at the slave crank I could see a nice circular gouge in it. Reason: one of the rod wrist pins had backed out and jammed up tight against the slave crank disc.
Everything else looked good at this point but rather than have it this far apart and put it back together only to have something else go wrong I decided to take the cylinders off, pull the master rod and check out the bores and such.
I forgot to mention. The prop hub is driven by a cross pin (.078 dia.). When I first pulled the spinner and prop off I could see the drive pin was bent on both sides of the crankshaft, it's drill rod mind you. The engine had stopped so instantly that if bent the drive pin into a lazy S shape. I had to grind one side off so I could pull it out the other side. The crankshaft stayed true it just elongated the hole a little.

The bores all look good and everything turns over nice and smooth so I'll start putting it back together. I just have to come up with a way of locking the crank wrist pins in place. I'm thinking of drilling and tapping at right angles through the master rod at each pin location and Loctiting a small set screw into it. There's not much room for anything else.

At least I know that it runs.
gbritnell

 

[steamer]

Oh man, sorry to hear that George. I'm sure the good doctor will put her right though

Congrats on the run!....Can't wait till she's fixed!

Dave

 

[ozzie46]

Great news on it running :bow: :bow: :bow: :bow:, but sorry to hear about the rod pin. :wall: :wall: I know you will fix it.

Ron

 

[metalmad]

Thank goodness so little damage was done, but its a good thing that a weakness was found and will now be removed.
There can be no doubt that you will sort it. :bow: :bow:
Pete

 

[Don1966]

George I am glad to see that there was little damage done to such a superb built and that you have it sorted out. I just had a small mishap with my engine and I know how disappointing that can be. I have enjoyed following you thread. :bow: I look forward to seeing it running.

Best Regards Don

 

[vcutajar]

George

I am sorry to hear about the mishap but glad it's not something serious. Looking forward to see the video.

Vince

 

[NickG]

Looks like I've found this too late but glad I did ... amazing work again George, can't wait to hear it.
:bow:

 

[rmoore45]

Just checking on this build and wondering when there's going to be a video of it running. I have watched this build from its beginning and am patiently waiting on a it to be finished. Maybe I missed it?

 

[gbritnell]

I didn't have much luck getting it to run on 5 cylinders consistently and with all the summer activities I really didn't have a lot of time to spend on it. About 6 weeks ago I got back into the shop making some miniature steam engines. With those out of the way I'm getting back into the radial. When I built it I used 1 piston ring ala the Morton but I think that might be part of my problem. Although the compression is good the seal is just not good enough to keep the oil out so I'm going to make all new pistons that will have 2 rings per piston. Hopefully that should take care of the excess oiling.
With that the whole engine has to come apart. When I first built it I used stainless steel 2-56 socket head screws to hold the cylinders down. I found that the stainless ones don't have a very good hex in them and after several tightening cycles the hex becomes rounded so I'm going to replace all of the cylinder base screws with regular black oxide steel screws. They won't look as nice but the hexes are much better.
Another issue is the weight of the propeller. It doesn't have enough centrifugal weight to allow the engine to run slowly. The prop is 11 inches in diameter but has no mass because it's plastic. I haven't figured out what I'm going to do about that yet.
I'll keep you posted and will get a video out as soon as possible.

 

[Admiral_dk]

Hi George

A 11x5 is a rather small prop for a Four-Stroke engine your size. Plastic props are the heaviest according to makers sites and wood is the lightest (I thought is was the other way round).

 

[petertha]

...I used stainless steel 2-56 socket head screws to hold the cylinders down. I found that the stainless ones don't have a very good hex in them and after several tightening cycles the hex becomes rounded so I'm going to replace all of the cylinder base screws with regular black oxide steel screws. They won't look as nice but the hexes are much better.

Interesting you should mention this. I ordered some 2-56 stainless socket cap screws recently in progressive lengths. If memory serves, some length sizes were USA, others/majority were offshore (likely filling in-between sizes?) Anyway, some of the offshore hex's looked stamped & did not fit hex key well. But it wasn't consistent either, some were ok. Guess they have 'bad Mondays' too

I cannot get small sizes like that from KBC (Canada) but for example, 6-32 black oxide are $4.86/100 (import) vs.$21.30 (holo-krome brand). So I usually go with clones even though the thread fits seem to vary a bit & the hex's round out much easier. Anyway, just mentioning FYI. It may have less to do with stainless vs black than import vs N-Am.

Hope to see your engine breathing fire one day soon!