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I purchased 3 Nelson engines, one is marked 29, the other 2 have no markings. How does one determine the displacement? I am assuming that the unmarked are .36 cu inch, but perhaps one is a .41?
<Dave, Lucky you, there are only 20 of the .29s in existence according to Doug Galbreath who built them.. For the other engines, pull the heads and measure them then mark them in a way you will remember which is who. All are the best there is in each class.. Thermals, Glenn strong>
Thanks for the info Glenn.
So I assume that the unmarked are either .36 or .41? Any other sizes? Is there much difference in power? Maybe just running them to see which is more powerful?? I hate taking engines apart that are already good runners. Will look more closely to see if there is a marking somewhere. Should have looked more closely at the models that they came off of to see if the models were marked.
Kind of the same problem with Cyclons, whether they are 049s or 061s. Do you need to measure those also? I know that two of my Cyclons are 049s, and two are 061s, but have never compared the power. Actually the 061s have not been run yet. Should put one on my 1/2A model to see if it speeds it up any more. It is already a streak at 240 sq inches with the 049!
Good to know that the 29 Nelson is rare. Will have to be careful with that one. How much power difference between the 29 and 41??
I can’t imagine that someone would build engines without marking displacement!! But I have seen many examples of that, but still can’t believe they could not have gotten that one last detail complete. Kind of like building a beautiful model, and then not putting your name on it.
Dave, You might try calling Doug Galbreath who might have better information about your engines. A simple measurement might be to measure the stroke through the glow plug hole with a depth guage if you have one or a piece of wire measuring it with a standard set of marks. If the strokes are the same ( they might be) look in the exhaust to see which one has the thinnest liner. Pulling the head is usually no big deal as they have metal gaskets/shims that go right back together. The Cyclon .061s are significantly stronger than the .049s In F1P we fly 400 sq in airplanes that weigh usually in excess of 10 ounces with .061s and they GO! Thermals, Glenn
So I called the original owner of the Nelsons, and found out that I do have a .36 and a .41. He mentioned that they had different thickness of head spacers. So then I find that they have the displacement scratched into the beam mounts, but the one with the higher head on it says .36, the one with the shorter head .41. So unless the shorter one (.41) is a larger bore and shorter stroke, it might seem like they are marked wrong? Might have to see if can get an answer from Doug Galbreath.
You would think that the one with the higher head would be the larger displacement.
I sent this picture to Doug Galbreath, but I think that it is figured out now. As seen from the picture, you can see that the cylinder liners show a thicker one for the .29, a thinner one for the one marked .41 on the left, and an in between thickness for the .36 on the right. For some reason the head is a little different for each one. Anxious to get one mounted to a model and powered up.
Doug Galbreath did verify that the engines are marked correctly, and they are the latest version. So I lucked out with a set of .29, .36, and .41. Says they should be considerably more powerful than a K&B 40 series 70. The picture should provide a means of identifying the engines, different head arrangement, and differences in the cylinder sleeve thickness. They each weigh 8.7 ounces compared to 8.0 for the K&B 40.
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