Customized TD .049

I have seen fins removed from engines for two other reasons.

1. So that the engine runs hotter.
2. The opposite - so that a heatsink can be fitted. The heatsink is nothing more than bigger fins.

The fins were removed to fit into the body which went on the speed pan. Similar to cutting off the exhaust stack to fit it into the body. Ken

It sure is neat. You should run it and see what it tachs out to. It will draw with the KK just fine on the bench.

Hope you can get more info on it.

Ron

I got some modified 1702 heads like you show in a batch of parts from a Texas 1/2 A speed racer's son. I thought they were to alter the glow plug heat range to adjust for different percentages of Nitro Methane in the speed fuel. I could be very wrong but the chamber sides were also cut back to increase the compression ratio.
Also in another batch of stuff from him I got some orange KK speed props with some modified to be almost like toothpicks.
The oddest thing was a KK prop cut to fit into a brass one blade prop hub !!

I was too late because the engines he had were all gone. Don't know if they were TD or Reed valve either.... The Dad apparently knew how to make Cox engines go fast...

66 Malibu wrote:....The oddest thing was a KK prop cut to fit into a brass one blade prop hub !!t...

Those one blade props are strange aren't they. They really work though.
Rusty

More nitro means more power, but also a richer running engine. A richer running engine means better cooling, less cooling fins needed.

Truth is with a TD, you can't run it on fuel to make it hot enough. I've run them on 70% nitro  with no problems aside from certain failures within the engine. These same failures can occur using mild fuels.  It all comes down to fit of piston sleeve and head clearance. The biggest problem is the crank shedding apart. I have 3 cranks here that have been heat treated and lightened. These cranks were used for that kind of running. I was seeing high 24k-25 on the ground. I figured about mid 26 when the engine unloaded. Many times though the engine would fail, either the ball socket or the crank as mentioned. It was a frustrating attempt. This finally led me to give up due to Norvel's and Stel's engines running at 24-26 all day long without even pushing them. I have one proto speed 1/2A that's still Tee Dee powered. I bring it out now and then for fun. Our group attends another club in the fall where they have 3 speed guys that are quite old now. 2 of them don't fly so we fly for them.  One unfortunately is partially deaf and his eyesight is rapidly declining. That gentleman has helped me through the years and is just a book of knowledge to the speed community. He showed me how to rework props and repitch them correctly. One thing he's always said in regards to a two bladed prop is that if one prop blade isn't quite the same pitch as the other it still may work. His theory was that the over pitched prop blade opposing the other will still bite into clean air which is the theory behind the single bladed prop.Ken

I've never seen a single bladed prop. By "single blade"... does that mean it still has two blades.. but only one having pitch? From a balance standpoint.. I don't see how it could work otherwise.

The one bladed prop unit that I have has a KK orange prop sawed in half just enough to have the prop mounting hole intact. Then it is installed in the brass hub which of course the prop mounting hole also. The hub has a large "bump" opposite the prop to counter balance the one blade.
The prop began as a KK Orange LH 5.4 X 5 per the markings and has been heavily profiled and lightened.
I would expect very high revs with very light load on the engine.
Again, It may have been for reed valve engines only but there were LH TD cranks available also.

Roddie here's a pic of a single bladed carbon fiber prop. There's a hub made of brass with a counter weight on the opposing side. The theory is that the single blade prop is not only less resistance and load, but it's always grabbing clean air. I have a Tee Dee that utilized this prop which has a custom cylinder for a tuned pipe. Props like this however will not take a ground strike and when it does, the end result is failure and a shaft run. Something I really try to avoid but it happens. The Tee Dee usually blows up. Ken

Ken Cook wrote:              Roddie here's a pic of a single bladed carbon fiber prop. There's a hub made of brass with a counter weight on the opposing side. The theory is that the single blade prop is not only less resistance and load, but it's always grabbing clean air. I have a Tee Dee that utilized this prop which has a custom cylinder for a tuned pipe. Props like this however will not take a ground strike and when it does, the end result is failure and a shaft run. Something I really try to avoid but it happens. The Tee Dee usually blows up. Ken

Wow.. that's a new one on me... and a "shaft-run"... yea.. I guess that would be real bad!

Thanks Ken

fyi, I've seen full size goodyear racers use single blade props.

FWIW I have used SBF ( Single bladed folder ) props on Rossi 15s flying F1C. This one came from Mario Rocca in Italy.

They work very well, and as was suggested having only one blade it's always in clean air.

Of course modern F1Cs now often use triple or even four bladed props..........So who knows?

I have a pic here but am too dumb to work out how to put it on this fine site.