Norvel 1/2A Engine Prep

Tell us what you do to get the best performance from your engines.

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sgilkey
Posts: 2351
Joined: Mon Mar 19, 2001 8:26 am

Norvel 1/2A Engine Prep

Post by sgilkey »

Those of us who ran Norvel 25s in other classes remember fondly that they are engines with, well, some foibles. Reliability is not generally the first word that comes to mind when folks talk about Norvel 25s. Great power, light weight, yes. Reliability- well, that depends. Some had good luck, others not so good.

Looking at the design of the 1/2A Norvel we see the same basic design concepts as on the 25s so we can expect some of the same foibles. The purpose of this thread is to show some prep done to a new norvel .061 which tries to address those foibles and make the engine run more reliably.

First, completely disassemble the engine and clean it out. Norvel says they ship the engine with some kind of preserving oil that should be flushed out. It's easier, I think, to disassemble and clean than just flush it out, plus I found some "freebies" when i took it apart. Here is some of the goop I got out of the crankshaft bore when I swabbed it.

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The main bearing was similarly goopy
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Supposedly the Norvel cyliner surface "absorbs" oil so the first break-in steps are to let oil soak into the cylinder overnight. On an assembled engine this is done by oiling it up and letting it set for awhile. Since I had the engine apart, i put the pis/cyl asm in a cup full of oil and let it soak for 24 hrs.
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The backplate on the engine is a screw-in affair. These backplates have been known to have air leaks. The pre-revlite engines have no o-ring seal, just like the 25s. The revlite engine has an o-ring. My oring looked questionable, with a booger hanging off it.
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I removed the oring and trimmed off the booger. Then for belt-and-suspenders i sealed the backplate with some hylomar (a non-hardening water pump sealant available at auto parts stores- RTV works just as well here, but makes a mess when you take it apart).
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A conventional electric starter can be used on 1/2As but it is awkward and prone to damage the engine if it is over-primed. 1/2A electric starters are much easier to use. However if you do not want to invest in such a starter, Norvel sells a spring starter similar to that seen on Cox engines. It is designed to fit in a small hole in the RH engine mounting flange. If your engine does not have the hole (some i have gotten do not) it is easily drilled.
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also seen in this photo is the thru-bolt that holds on the carb- this feature is found only on the Revlite versions. I removed the nut and applied some blue loctite. Also observe that, like the 25, the .061 uses a prop stud/bolt that threads into the end of the crankshaft, with a loose-fitting prop driver and shim washer on the end of the crank. over-prime the engine and hit it with the starter and ZING off flies the prop bolt, spinner, driver, shim washer, and prop, all in different directions, to hide in the grass. NOT conducive to starting on time. After each heat, remove the fuel line and crank your engine over to be sure it is clear of fuel. At the beginning of the next heat, put on the fuel line and glow heat, then choke the engine until the fuel gets to the carb. Then hit it with the starter. Chances are you will not get any kick-back. Also it helps to make sure you get the prop bolt snug, it is a 5mm hex and a nut driver works well to tighten it, better than a screwdriver.

The HS needle has no o-ring seal, I apply a piece of fuel tubing to seal the threads.
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The fuel tubing usually expands enough that the ratchet spring no longer works well. Rick Fraley taught me a neat fix, using a small zip tie to gently clamp the ratchet spring back into good contact with the needle. This is shown in the photo above.

Reinstall the pis/cyl to the engine. Norvel recommends a bunch of hand-cycles of the engine before initial start-up, as they are usually very tight at TDC. A good time to do this is before the head is reinstalled. I just made sure there was plenty of oil in there and cranked it over 500 times.

The engine comes with three head shims. usually one is installed and two are taped to the instructions. I pretty much default to one shim on 15-25% nitro fuel. However for break-in you may want to run two or three. There are differing theories out there on how to handle head spacing during break-in so go with your favorite theory. The head screws in and is tightened with a special wrench- norvel sells one, but the Cox wrench works too and since i have a jillion of them i just use my Cox wrenches.
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The shim can get crooked when you try to install it, it seems easiest to put the shim in the cylinder, then use the glow plug/button to press is down in place. make sure it is not cocked, as it will bend. when the shim and button are in place, apply the head/clamp and tighten. Check tightness often, especially during break-in.

When you remove the glow plug, the shim usually sticks to the bottom of the plug, which is nice (makes it easy to get out). If the shim is stuck in the top of the cylinder, resist the temptation to try to pick it out, you'll probably scratch it and ruin it. A blast of compressed air will usually lift it enough that you can coax it out.

Compared to the baseline of a Cox, the Norvel .061 is a smooth-running, powerful, reliable, and consistent engine. However it is no 25FX in terms of user-friendliness. Taking some of these simple steps will help make your engine run more reliably.
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boiler
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Post by boiler »

Thanks for the information Scott. I can use it to prevent a lot of frustration caused by inexperience.
sgilkey
Posts: 2351
Joined: Mon Mar 19, 2001 8:26 am

Post by sgilkey »

happened to buy a used Norvel 061 and was prepping it, compression was low and engine was covered in fuel residue, took off the head and found a classic example of misinstalled/crooked head shim. this is easy to do so be careful!
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Lee Liddle
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Post by Lee Liddle »

Scott, I just want to thank you for AAALLLLL of the great info that you are providing on the 1/2a`s. From the builds to the super flight testing that you and Brian did last weekend, you`ve done a great job. I`ll tapp into these threads over and over as I get my 1/2a stuff working. Thanks a bunch..... Lee
sgilkey
Posts: 2351
Joined: Mon Mar 19, 2001 8:26 am

Post by sgilkey »

Hey Lee, it goes both ways, I have been really enjoying all the e-combat stuff you have been posting so I've been learning a lot from your stuff, believe me! This tinkering is fun stuff for me anyway, it's why i never seem to get anything done, too busy puttering.
cipoll717
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Joined: Wed Jun 30, 2004 2:05 pm
Location: USA

Post by cipoll717 »

Wow, 500 hand cranks. Sounds like you've got good cranking endurance built up in your hand Scott!

A couple of tid-bits that I may add:

- ditto to what Scott said. Make sure you don't flood your engine. Only takes a drop or so, and this was especially problematic with bladders. And, yes, when flooded, the whole damn propnut assembly flys off in different directions, and it's not even worth looking for.

- use a glo-starter that has a good charge. A weak one will work fine for regular engines, but not these.. Also, sometimes, if the engine doesnt immediately fire up, try twitching the connector slightly to make better contact. This almost always works.

- invest in a 1/2a starter. i use the sullivan.

Other than that, these engines seem to run quite well. I never messed with any of the pre-run stuff Scott described, but will do so in the future.

MC
sgilkey
Posts: 2351
Joined: Mon Mar 19, 2001 8:26 am

Post by sgilkey »

Hammer, although VERY tempting, I am not going to cross swords with you over the 500 hand cranks thing. oh this is tough...

I'll just leave it at saying that 500 hand cranks does not take that long. there, I was good.
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