Another Whiplash gasser build.

[bradi]

Originally Posted by Doug Darby

As for he TT bolts that hold the TT end to the TT I had one back out and cause a bunch of ancillary damage so now when I get done loctiteing them I also put a small piece of Heat shrink around the bolts so they can't back out period....

Thats a great idea! I used ca on my tt bolts but I like the heat shrink idea.

[Azalin]

Nice build Jeremy.

[jharkin]

Originally Posted by Azalin

Nice build Jeremy.

Thanks Suat... shame it might end up being the last new build thread

[jharkin]

... a shot of how I laid out the generator components. Though not likely to be many future builders who need it for reference

[jharkin]

Ok, so when I built the heli I made use of the 14SGs telemetry capability to get headspeed at the Transmitter, using an SBS-01RM sensor Y-harnessed to the stator gator.

With the voltage trick this works great, but the limitation is that its reading motor RPM, just like the governor... so in situations you would really like to know true headspeed - during an auto for example - it isn't usable. Raja has been pushing me to switch this - and with good reason. So tonight I gave it a try.

Setting this up is not hard to do of course, we will just be using the magnet and hall pickup setup like a nitro, and between the GV1s and SBS I have 3 spare hall pickups.

The tricky part... where to put the magnet? Raja was thinking use a collar on the shaft. I ordered a 10mm MA collar but looking at it, its hardened steel and Id have to drill the circumference of it for the magnet and it could easily let go like a bullet. So I decided to try plan B - mount it in the main gear. This way I could face mount it and the centrifugal force would just be pressing the magnet against the side of the hole its in, not trying to fling it out.





Mounting the magnets was not hard. To maintain the strength of the gear and give a good location for the senor I decided to mount it on the bottom in the thickest part of a spoke, but not too close to the teeth. I pulled the shaft and removed the gear, then made up a jig for the drill press so I could mount two magnets identically spaced at 180 degrees. Using 2 magnets should hopefully maintain the balance of the gear.

I drilled a couple of shallow 3/16 holes, just deep enough for the magnets to sit flush, and secured them with 30 minute epoxy. I dont think epoxy (or any glue) really bonds well to delrin, so fingers crossed this works!

[jharkin]

Next up is to mount the sensors. Having a spare GV1 around (destined for my Helix build) was helpful so I could test which side of the magnet gave a reading and get the sensor located right.

Plan is to mount the sensor below the gear on the muffler side and then run the wire around the clutch and up to the front gyro plate where the SBS is.




So far so good. I put the maingear in temporarily with a spare mainshaft and spun it around as I checked the readings on the GV1. Im getting over 90% on both magnets so the location looks good. Im gooping it in place first (held to dry with some tape), and then once the glue is dry I will pull the gear, drill and add a small screw and lockout as a safety precaution.

I also picked this spot because if it ever did come loose and caught in the mmaingear it would get thrown out against the canopy and not dragged into the frame to potentially jam things up.




Once I get it all back together I'll switch the SBS over and we will be able to try it out on the TX. IF this works we will be able to watch headspeed during autos (with a helper of course) and might be able to do some cool things like set a low RPM alarm to warn you before blade scatter. I might even play around with the new voice telemetry function in the latest update.

[jharkin]

OK, so still not trusting those magnets just glued into delrin, and not wanting to risk stripping some irreplacable gears or causing a crash if it let go in flight, I devised a test. I bolted the gear to a spare mainshaft and chucked it into the drill press with the belt on the middle speed which is 1720rpm.

Wore goggles and put up a makeshift guard just in case it let go and shot that magnet like a BB, then gave it a spin...



And as it turns out, everything worked just fine. Magnets didnt go anywhere and there doesnt seem to be any vibration indicating its out of balance.

We shall see what happens in the heli....


Meanwhile I got the sensor gooped in, added one bolt for safety and routed the wire back up to the RX. I pulled the tank to make this easier and good thing since I found yet another wire/vibration issue (im having bad luck with wiring). I had run the power lead from the switch and the lead for LED headlight around the front of the tank and up under the battery tray plate to the gyro plate. Well, they where pinched against one of the aluminum frame spacers by the tank and the vibration was rubbing through the wire.Luckily they where wrapped so only the sheath was damaged. I'll have to re-route things again.

Anyway, its all wired up and ready for a test run.

[jharkin]

Well, got everything put back together, reset the gear ratio in the telemetry to 2.0 and spun the head by hand and we have a reading. project done, and we will now get headspeed readings during autos

[rbort]

The only thing I'm worried about is that you mentioned 3 posts up that you read 90 something percent on both magnets. You should read 90 something on one and 2 to 3 percent on the other. If not you have to flip the magnet otherwise you will get double the rpm readings.

Looking forward to some flipping autos with your machine to see what rpms I maneuver at

-=>Raja.

[jharkin]

Originally Posted by rbort

The only thing I'm worried about is that you mentioned 3 posts up that you read 90 something percent on both magnets. You should read 90 something on one and 2 to 3 percent on the other. If not you have to flip the magnet otherwise you will get double the rpm readings.

Looking forward to some flipping autos with your machine to see what rpms I maneuver at

-=>Raja.

Yes, I did mount both magnets the same way... The telemetry menu in the TX has a gear ratio option same as GV1 and it let me set it to 2.0 to account for the 2 magnets.