VAF Forums

VAF Forums (http://www.vansairforce.com/community/index.php)
-   Traditional Aircraft Engines (http://www.vansairforce.com/community/forumdisplay.php?f=21)
-   -   Ground run shroud (http://www.vansairforce.com/community/showthread.php?t=86912)

RV8RIVETER 05-31-2012 04:00 PM

Ground run shroud
 
I have been planning on starting the break-in on the ground for many years. Now that I have actually experience doing it, I thought I would post this for anyone else thinking the same.

It was fairly simple to build. The hardest part is making the scalloped tabs that bend over and rivet to the top skin. Used the old ECi overhaul crews recommendation of 1 cubic foot of inlet area for each cylinder. The cable in the center I think now is overkill, but didn't want to take any chances. When bolted on it is rock solid.

Did my first break-in ground run this morning, 50 minutes 80% power. The shroud worked well, with the highest CHT htting 330 deg. I need to increase the size of the oil cooler inlet some as the oil max'd out at 250 deg. I used an extra Van's eyeball vent rear end and thought it may be too small, but wasn't sure how much pressure I was going to get.

I know there are those out there who like all the technical data, like me, (no offense Dan :) ) , but we are trying to get this plane to Oshkosh, so I am sorry there is no time to try and modify my engine plenum press box to take readings. If I have time after Mel has given the plane his OK, may try and get pressure data, because I would like to know. On the other hand there is the old, "it just works" way of thinking.









N427EF 05-31-2012 06:04 PM

Just curious?
 
It's quite a set up.
Out of curiosity, what are you hoping to gain from running your engine on the ground?
Your 8 looks like it's ready to fly, why not do the breakin in the air.
I am sure you have a good reason.

G3i Ignition 06-01-2012 06:25 AM

I like it, nice set-up. Extra time spent on options like this are well worth it. Piece of mind as well as safety.

RV8RIVETER 06-01-2012 07:07 AM

Quote:

Originally Posted by N427EF (Post 664664)
It's quite a set up.
Out of curiosity, what are you hoping to gain from running your engine on the ground?
Your 8 looks like it's ready to fly, why not do the breakin in the air.
I am sure you have a good reason.

Speaking for myself only, we all have our opinions and choices. I do not feel comfortable test flying a new plane AND a new engine, too much going on, cuts the safety margin. Also, my airpark has no good options if the engine quits on take-off, so it is good to know the engine is running well and has been run hard for the most critical part of the break-in. When it flys, we only have to concentrate on how it is flying.

SMO 06-01-2012 10:40 AM

I like it!
 
The constraints associated with doing a proper engine break in seem to me to be incompatible with flight testing activities, this has been a niggling concern in the back of my mind. I may do the same as you.

N427EF 06-01-2012 07:31 PM

All Good reasons!
 
You mention all good reasons for doing the ground tests.
How many hours are you planning on doing this?
Your concerns have been shared by many others before you, I have just never actually seen anybody do what you are doing.
I suppose if you keep your cylinder temps under control and keep the oil from cooking, your engine will break in just fine.
Hope you make it to Oshkosh, and good luck on your first flight.

jrs14855 06-01-2012 07:36 PM

ground run
 
The optimum for ground break in is a test club. Any of the engine shops that have test cell would probably discuss the test props.

RV8RIVETER 06-02-2012 07:42 AM

The only reason to have a test club is nobody wants a full size, very expensive, prop in their test cell. I guess another would be known hp, if you have a test club pitched so that you know it takes 180hp or 200hp to make full RPM then you have a poor mans dyno check. Other than that there is no difference.

According the test guru at ECi, they used this method for many years on all of their overhauls until they built their test cell. You can even see a picture in their engine break in pamphlet.

RV8RIVETER 06-02-2012 08:01 AM

Quote:

Originally Posted by N427EF (Post 664992)
How many hours are you planning on doing this?


Your concerns have been shared by many others before you, I have just never actually seen anybody do what you are doing.

The engine is running very well so while I orginally planned to try and get 4 hours, I think I will be happy with one more hour.


Yes, I remember a thread long ago where people said "you can't run it on the ground" and "pay the engine builder to do extra runs" ect.. Some nay sayers out there, some think it is way to complicated. It is not that much time to make, took me 2 days. And it shows, made from scraps and didn't want it pretty, just rigid. Based on my first numbers CHT cooling is better on the ground. The engine doesn't know the difference. The only down side is you had bettter be on good relations with your neighbors. :)

LarryT 06-03-2012 10:52 AM

Request for more info...
 
What engine RPM and MP were you using? Did you sweep the area around the aircraft pretty carefully? I prefer to be moving before I have my prop turning over 1800 RPM because it is quite easy to suck up a rock and ding it.

Your comment re noise got me wondering if this method with a fixed pitch prop would be louder because of higher engine/propeller speed.

Do you have approximate dimensions of your shroud or did you just eyeball it?

Looks like a good idea to me. I won't have many options for forced landings around W52 either (guess I could "drop in unexpectedly" on Jon at Parkside). I can hear the occasional plane take-off from W52 from my house, which is about 1 1/4 miles away. I know our airport owner has had noise complaints from neighbors. I think they are from low level overflights from aircraft making improper departures, but I expect that running at high power for an extended time period would meet with similar objections from the same people.

Larry T


All times are GMT -6. The time now is 11:33 AM.