Brodak .049 MK II

My curiosity got the best of me and I picked up a brand new Brodak .049 MK II off of ebay, which I received yesterday. I had not been able to find any reviews of this engine on-line with actual RPMs or anything, so I thought I'd post my results.

The specifications from the instruction sheet read as follows...
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Bore - .400 in.
Stroke - .395 in.
Displacement - .049 cu in.
Useful RPM range - 12,000 to 18,000 RPM. depending on fuel and prop.
Weight - 1.7 ounces.
Schnurle ported.

Construction - die case, alloy steel crankshaft, AAC piston and cylinder, plastic backplate, long reach plug.

Fuel - 10% to 20% nitro, 22% oil (1/2 castor, 1/2 synthetic)

Prop - Brodak 5x3 to 6x4
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Out of the box, there is a pinch at TDC, although not as severe as on a never been run Norvel I have. After break in and test runs it turns over smoothly.

The instructions recommend running three rich tanks of fuel, allowing it to cool down in between. Then they say to peak the engine out and then back it off a bit for the next three tanks. They recommend 5% to 10% nitro for the break in runs.

I went with 10% nitro and ran about 10 half ounce tanks of fuel through it last night, going from very rich on the first few tanks and slowly leaning it out each tank until I was getting 14,500 RPM on the last couple of runs using an APC 5.7 x 3 prop. I ended the session feeling a little disappointed. This morning I continued the bench runs using Sig 25% nitro fuel, which is my normal 1/2a fuel. I ran another 8 tanks or so and managed to sneak up on 16,000 RPMs a couple of times. Backing the needle off a little allowed me to run an entire tank in the 15,700 RPM range. I tried switching to a Master Airscrew 5x3 prop (cut down from 6 x 3) and the performance was pretty much the same. The engine runs were very consistent. For comparison, I've got an old Cox Tee-Dee .051 that will turn a Cox 6x3 prop at 17,000 RPM on the same fuel, although the runs aren't quite as consistent.

It looks like it'll make a decent sport engine.

Here's a pic with some other engines for comparisson.
Cox Babe Bee - Cox Tee-Dee - Brodak MK II - Norvel Big Mig .061



Jim

Edit - Mine weighs 2 ounces as pictured (with prop and plug) as does the Babe Bee. The Tee-Dee comes in at 1.8 ounces, and the Norvel is 2.1.

I just measured my Cox Surestart at 2.0 ozs.

I'd give that engine a chance to break-in some more.

I believe, you've bought one of the first engines. The later ones run much better.

Jim,

Good report!

Did you weigh the Norvel with muffler, or without?

Bill

>Jim,
>
>Good report!
>
>Did you weigh the Norvel with muffler, or without?
>
>Bill

That weight was as pictured, with the muffler and the propeller on. I was too lazy to take the props off.
I've got a little profile Mustang built for the Brodak motor (Fox called them motors didn't he?) and if my bellcrank and fuel tank ever get delivered I'll fly it and give a report on how it goes.

Jim

I noticed the instructions said 3 very rich runs. I personally believe this is incorrect for the ABC/AAC engines. If the engine is too rich the cylinder does not heat up enough and the pinch at the top really grabs and puts a lot of stain on the rod and egg shapes the con rod. Maybe the smaller engines are different but Ive seen too many ABC engines ruined this way. Picco got a bad name for awhile because of this as the rods would get torn up right away as the piston fit was really tight from the factory. Some companies just didn't update their instructions.

Just my experience.

Bruce

>I noticed the instructions said 3 very rich runs. I
>personally believe this is incorrect for the ABC/AAC engines.
>If the engine is too rich the cylinder does not heat up enough
>and the pinch at the top really grabs and puts a lot of stain
>on the rod and egg shapes the con rod. Maybe the smaller
>engines are different but Ive seen too many ABC engines ruined
>this way. Picco got a bad name for awhile because of this as
>the rods would get torn up right away as the piston fit was
>really tight from the factory. Some companies just didn't
>update their instructions.
>
>Just my experience.
>
>Bruce

That was my understanding for ABC engines, but I wasn't sure about AAC so I followed the instructions. Probably did more harm than good. I've got about 6 flights on the engine so far and it runs well with the APC 5.7x3 prop. I flew it with a Master Airscrew 6x3 (because I broke the APC) and it wasn't so great. I'll post more information once I've got a few more flights on it.

Jim

**Update**

I've got a few dozen flights on the engine now and it has no bad habits. I get very consistant runs with a uniflow tank. It's not the most powerful engine, maybe comparable to a strong Babe Bee.
For comparison, I removed it from the plane it's been in and replaced it with a Tee Dee (pictured in the original post) and flew it tonight. The difference was something along the lines of "holy cow!"

Jim