Greetings all,
I know this is probably a long shot; but does anybody know the guys who did the Bear-H and Dart dio called “Bear Hunt” in this month’s issue? I’d soooooo love to see if I could get a look at how the props were done!
If Konstantin, Charles or Tory are lurking in the forums somewhere please message me directly so we can talk!
TIA
I got the new issue in the mail just yesterday and the “Bear Hunt” diorama was so cool that I immediately bought another issue of FSM to mail to my friend Juan in Hawaii.
I agree!!
I’m not too interested in building the rest ofthe diorama; but I do like the lights and motorizing the props! That is way cool! I’m wanting to have mine where someone can turn on each motor individually. I also would like to know how they have it where the props start off slow then gradually spin up to full speed!
[:D[
It sure reminded me of the lighting and motorization of the B-17 in this thread:
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Id definately like to know how they did counter-rotating props on the bear...mustve been a…um…a bear to do…[whstl]
Thanks for the kind words on the Bear Hunt. Charles Heyer is the brains behind the contra rotating gearboxes, I’ll see if I can get him to chime in here. As for how the slow start was done, that was in one of Konstantin’s microprocessors. I beleive he used some sort of pulse to get them moving slowly at first and then faster. I’ll see if I can get him to chime in as well.
Tory
Greetings RESlusher,
I built the 4 gearboxes that contra-rotate the Bear’s props. I learned to build the mechanism while working at Stevens Institute of Technology here in New Jersey. The one I worked with was rather large and was used to propel a 3’ long boat model. When approaching the Bear project I needed to miniaturize the pieces- the gearboxes are only 5/8" in diameter to fit into the Bear nacelles. They consist of 4 gears and a shaft within a tube. Again, to fit the system into the nacelles the gearbox most be connected to a very small motor. I used a #GM-18 motor from Solarbotics.com .The motor is connected to the shaft extending from the rear of the gearbox and thru the gearing the shaft extending out the front turns one way and the tube turns the opposite. I know that words don’t adequately describe them, but I think if you do an image search for “contra-rotating gearbox” you may find some descriptive drawings or cutaways.
When we bring our latest diorama to the IPMS convention in 2012, we will also bring along the BEAR HUNT as an entry in the non-judged “previous winners” catagory. I imagine once again there will be smiles and head scratching all around. GLUEPUDDLE
My friend showed me the issue today, and I too must offer my kudos. Seriously brilliant work.
Great issue, the Battle of the Bulge dio right in front of the Bear Hunt spread was phenomenal as well.
Saved this from a model I built years ago, might give you an idea
Hmm…interesting.
Thanks for posting…
Greeting again RESlusher,
You have asked some good questions; I’ll try to respond here: 1) The shaft turning inside the outer tube has a few thousanths of an inch clearance, and they are polished and are dissimilar materials so no heat is generated. 2)The gears (4 of them) are Delrin, a very slick and tough material. There was no need to use a lubricant, therefore. That combined with intermitent operation allowed the gearboxes to perform reliably for the three days of the convention. (I wish we had put a counter on the diorama to keep track of the number of “plays”; it would be interesting to know that number!)
I will attempt to post a couple of photos here–its been awhile since I did this. Forgive me if something strange (or nothing at all) appears here! [:S] Thanks for the interest guys. Charlie
Charlie,
Thanks for responding to my questions posed. I’m not an engineer nor, according to my wife, very mechanically inclined.
The idea of motorizing props on model aircraft has always held fascination for me. Others might disagree; but I believe it offers a certain amount of a “Wow! factor”. that’s addition to it’s increased technical difficulty.
I’m making a Bear-H with counter-rotating propellers my “Everest”. I’m not going to get there soon. I’ll have to work up to it; but I’ll get there.
Thanks for setting the bar for the rest of us.
The contra-rotating props ARE magical looking , and I was very pleased to be able to pull it off. It would have been nearly impossible without Tory’s magnificent Bear build and Konstentine’s superb slow start electronic controls. There have been several single engine aircraft with contra-rotating props, so perhaps one of those might be good to start with. By the way these props are CONTRA- rotating not COUNTER- rotating. Counter rotating props are like those on a P-38 where the two props turn in different directions for stability. Contra-rotating is when the two props are on the engine but turning in different directions. (I didn’t know this until I got into this project!)
Mount Everest has been concoured by others; now it’s your turn! Good luck with your quest.
Charlie