Brodak .40 Threads?

Searching the board for threads with useful basic info on the Brodak .40: weight, power, workmanship, things to watch for, etc etc, I get thousands of hits, even using "and" logic.

Has anyone saved especially useful threads on this topic?

Thanks,
Kim Mortimore
Alameda Aeronuts

>
>Searching the board for threads with useful basic info on
>the Brodak .40: weight, power, workmanship, things to watch
>for, etc etc, I get thousands of hits, even using "and"
>logic.
>
>Has anyone saved especially useful threads on this topic?
>
>Thanks,
>Kim Mortimore
>Alameda Aeronuts

That does not surprise me. Worse, select the wrong ones and you'll never buy one of these engines. Hit others and an even dozen engines won't seem to be enough.

As to your last sentence, No. But you could...

For what it's worth:
Weight is about 7 oz, a little more with a tongue muffler, an ounce or more heavier with the stock unit.
Power is significantly greater than almost any stock Fox 35 and more than any stock OS35S that I have owned anyway. The engine is somewhat of a drop in replacement for the 35S-same bolt hole pattern and shaft length, same bolt hole pattern as 35/40 FP, 40/46 LA but shorter shaft. Brodak says for stunters to 43-44 oz and this matches my experience though they should fly heavier, draggier airplane in perfect conditions.
Workmanship is very good, though some individual engines have apparently slipped through quality control from time to time. Brodak replaces or corrects with no questions asked.
Break in exactly according to instructions. They are very easy to flood, seem to reach their best performace after an hour or so's time and are very user friendly. Powermaster 10-22 seems to work well as does an APC 10.5 X 4.5 or APC 10X5 on Nobler and Oriental sized airplanes used in a breaking run. Others have used them with an 11X4 in a steady wet 2 cycle run. The Noblers and Orientals will need 65 feet or so of lines to keep lap times around 5.0to 5.2 with the APC 10.5 X 4.5.
Great out of the box stunt engine for the price.

As a follow-up on the workmanship "issue". I have seen no problems with the last two batches that I have gotten. Matter of fact, I haven't had any peoblems with any that I have had. Several people mentioned on the first round that the liners on the engines that they received were slightly off, or that the prop nut was tight, but that was only on a few of the engines, and beyond that I really don't know of any issues. The first stock mufflers were too draggy, but then they copied the OS on that line. The last two batches have a larger stinger opening so they are less restrictive (and the engines are thus able to develop more of their useful power.)

As mentioned, this is a good out of the box stock engine. It has the weight of a Fox 35, but much better power. And you can replace the 1.9 ounce stock muffler with a .3 ounce tongue muffler to have it very near the weight of the open exhaust engine that many of the classic ships were designed around.

Jim P mentions props and this last summer I watched Will Reeb's beautiful Olympic with Brodak 40 quite closely. It was the first time I had seen one of these engines run to what I regard as a high standard, and Bob Smiley also had a fresh B40 out that responded quite nicely to various adjustments and increased run time.

However, Will's engine would sometimes just kinda give up on him right when he really needed all the power he could get. Entrance to four-leaf clover, for example. It was a little confusing, as the engine gave off what can only be described as an odd sound. During the latter stages of one flight I actually slipped on a pair of Mickey Mouse ear protectors just so I could watch the model without confusing clues from engine exhaust note.

Proving that I have no right to kibitz, I told Will all I knew about what was happening. He didn't seem to have noticed, presumably as it only went into Goofy Mode a few times each flight, and he was concentrating on the model, not the engine.

I forgot about it, although I did notice that later on in the afternoon there was no apparent problem. Will volunteered that all he had done was to go from an APC 10-6 to APC 10-5.

Why a current 40 wouldn't pull the larger prop is beyond me; but the change was very much for the better, is most certainly worth trying.

The B40 should run in a strong 4 cycle on any of the common props- 10/6. 10/5, 11/4, 11/5.

some of them had/have low compression and will sometimes go into a rough, ragged 2 cycle that sounds like a 4 stroke run and has less power. If you have this problem, either send it back for a new head, or you can try getting the head fit to .010 head clearance.

>The B40 should run in a strong 4 cycle on any of the common
>props- 10/6. 10/5, 11/4, 11/5.
>
>some of them had/have low compression and will sometimes go
>into a rough, ragged 2 cycle that sounds like a 4 stroke
>run and has less power. If you have this problem, either
>send it back for a new head, or you can try getting the head
>fit to .010 head clearance.

Hmmm, Phil may have nailed it. His description above as to the sound from Will's engine is pretty close and is why I used pretty effective ear protection, as I was never sure exactly what the engine was doing, wanted to see the effects, not hear them. Too many times we let--or I think we do--the ear contradict what our eyes are telling us.

I'll get Will right on it...

>some of them had/have low compression and will sometimes go
>into a rough, ragged 2 cycle that sounds like a 4 stroke
>run and has less power. If you have this problem, either
>send it back for a new head, or you can try getting the head
>fit to .010 head clearance.

Phil,

Are you saying that this ragged run is caused by not enough head clearance?

Kim Mortimore
Alameda Aeronuts

It's too much head clearance/too low compression. I got one of the first engines John sold. It ran OK, but would have this tendency to go into a rough sounding four stroke. Eventually Tom Hampshire was flying with us and recognized the problem immediately. He recommended setting the head clearance to .010 by trimming the head. It helped greatly. The motor no longer has the power loss when it goes into a 2 stroke.

Apparently the builder kind of went overboard on going for low compression. I had to take .065 off the head to get the deck height right.

As Lou points out, this can also be a problem of tolerances ganging up, so it can happen to any randomly assembled engine. If you have this problem, I'd try checking the head first. It is the easiest fix. This engine is so conservatively timed I can't imagine the other tolerances having a huge effect on how it runs. Having the sleeve timing off a couple of degrees will have an effect to be sure, but a head that is off 1/16 of an inch probably overwhelms everything else.

>The B40 should run in a strong 4 cycle on any of the common
>props- 10/6. 10/5, 11/4, 11/5.
>
>some of them had/have low compression and will sometimes go
>into a rough, ragged 2 cycle that sounds like a 4 stroke
>run and has less power. If you have this problem, either
>send it back for a new head, or you can try getting the head
>fit to .010 head clearance.

I have a feeling this isn't a head problem, Phil, but a deck height problem which will affect compression, etc. This happens with every mass produced engine when the tolerances get accumulative. Very seldom will a manufacturer work from the middle as in +-1. They don't want to take a chance with the piston hitting the head. So it is usually 0 to +2 or some such. Then if you get +2 of this and +2 of that and +2 of something else, the thing gets way out of whack. I have seen a number of FP engines that were 6 to 8 thousandths high. I had one engine that was 17 thousandths high. Only once have I seen one low and it was 2 thousandths low. (High deck height means low compression. Low deck height means high compression.)

The LA engines, the Magnums, the Thunder Tigers, the Foxes, all have the same situation where deck heights can vary from engine to engine. A simple and dirty solution is to change head shims to restore compression. You can still have the timing off a couple of degrees as a result, however, so the best solution is to drop the sleeve in the case. I have never seen a problem with the head itself, however, as any variance here would be very minor.

My next question, if this was the case on a couple of engines, was it in one of the early runs?

I have done quick checks on the engines I have gotten lately and have not seen any problems at all with these.

Oh, by the way, 10 thousandths for the head clearance also seems a bit low. Are you sure about that figure?

I think Tom said 10 thous, but maybe it was 12. The head has a pretty big bowl in it, it's around 75% of the bore, which is a large combustion chamber(low compression). So there isn't much of a squish band, and it's angled too boot.