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Thank you all a lot for the responses. I'll try to clarify some points. 1. btrueblood, the boiling of the coolant is the root cause I thought about, but can't proof that. The water is not under pressure and I'm not familiar with the techniques of pressuring the water. May you kindly tell more...

Hello, I have two stroke water cooled engine and from time to time there are cooling issues with it. Here some relevant information: - Configuration - boxer two cylinders about 120 cc total displacement - The engine max. power - 11 HP - Working speed - 6500 RPM (constant, 1000 RPM below the...

Hello, I need a solution for wireless telemetry data transmitting with following requirements: 1. Input and output terminals are RS-485 half duplex 2. Data rate: ASCII 10 bytes, up to 500 samples per second 3. Transmitting range: up to 50 meters 4. Voltage supply: 7.4 or 3.7 volts (nominal) 5...

First we've checked the helicopter with unmodified blades and didn't discover any vibrations, after that we replaced them with the modified set and than the vibrations started. I didn't measure frequencies. The helicopter is a light unmanned experimental one. The material is an epoxy that cured...

The rotor head is a teetering one with elastomer dumpers, no underslung, precone of 2.25 deg. The blade moves freely about lead-leg hinge.

Hi SparWeb, Thank you for the response. The blades are the original: I've injected the epoxy into the original blades. I compared the chord wise CG by hanging the blades one next to other on the same axle and observed that they are aligned. Moment of inertia I measured by swinging the blades...

Dear friends, My helicopter with a teetering rotor and two composite blades is not stable enough and has very bad autorotation characteristics. To improve these properties I decided to add mass to the blades by injecting epoxy to the tips. Total addition of the weight was 28%, but in the terms...

Thank you FeX32. The first article is seemed to be most suitable for my needs

Thank you electricpete, I mean torsional resonance analysis of the entire system. Is there some analitical or thumb rule way to roughly estimate this fequency? if not, what the solution will be? Thanks.

Dear Engineers, I'd like to perform an estimation of the gear transmission eigenfrequency. Does somebody know about some useful algorithm for such analysis or a standalone program? Thank you. Dima

Dear Engineers, I'd like to perform an estimation of the gear transmission eigenfrequency. Does somebody know about some useful analytical algorithm for such analysis or a standalone program? Thank you. Dima

Thank you Terry. I'll post the question on the NASTRAN forum, but as the solution, NASTRAN, I believe, may be very expensive for me. I thought to find some analytical algorithm to estimate a rough values of eigenfrequency and than according to the result to decide if I need to perform more...

Dear Engineers, I'd like to perform an estimation of the gear transmission eigenfrequency. Does somebody know about some useful algorithm for such analysis or a standalone program? Thank you. Dima

Thank you desertfox, this is what I looked for. I just believe that the drawing there is a third angle projection.

Hi, In the calculation of forces (in the MitCalc) in helical bevel gear pair [20/46 teeth pinion/gear, 20° pressure angle, 30° helical angle, Module 2, transferred power 15 kW, pinion speed 6200 RPM] I get a negative axial force for the pinion. This means that the force is pulling the pinion...

I have good news. We understood and solved the problem. As you noted the problem had a gyroscopic nature and to solve it, we increased the mass and the size of the flybar and this change led to dramatic improvement of the heli's behavior. Thanks to everybody.

I agree with you about the advancing and retreating blades, but the point is that the helicopter rolls to the side of greater lift (to the side of the advancing blade). The helicopter is a model.

I have encountered a strange problem when our small rotorcraft (2 meters rotor diameter, rotates clockwise when looking from the top) is hovering while an oncoming wind (about 10 knots) is blowing onto the platform. The craft begins to roll counterclockwise (if looking at the craft from the tail...

Hello, I'm looking for supplier of clutch/brake liner materials. I would like to purchase a roll of woven-cotton lining, 0.9"-1" width, 1/8" thickness, but other kind of flexible liner is acceptable. Image of a sample is attached Thanks.

Try this: MODERN HELICOPTER DESIGN by Dr. Eric Hollmann and M. Hollmann from http://www.aircraftdesigns.com/books.html