Skeeter Jr.

[Barney Bahle]

Are there any small helicopters based on the Rotax 915 engine?

Dynali uses the 912.

 

[bryancobb]

Just tracked. Bolts left Honolulu about 4 hours ago.

This A.M. local EST they are in

02/23/2022 9:42 P.M.

On the Way Import Scan Botany, Australia

 

[HobbyCAD]

Nice, the job is waiting for them .....

 

[HobbyCAD]

Dragged out the project, giving it "full bore" to now get it all done.

Today completed the install of the reluctor wheel and the hall effect sensor brackets. Redesigned the clutch front bearing inner retainer to hold the reluctor wheels. The outer retainer holds the hall effect sensors. One sensor is for the engine tacho signal, the other is for the governor signal. Two different frequency ranges required, hence the need for 2 rows of reluctor teeth.

This setup allows my Yamaha engine to use the stock Mini-500's Westach dual engine/rotor tacho indicator to indicate engine RPM. The setup simulates the same Ducati style signal from the engine.

Note the governor drive actuator lower down in the picture.

Thanks to Bryan Cobb for assisting with the purchase of a longer bolt from McMaster Carr and shipping it to me in Oz. Here you need to purchase the entire box of 100. Bryan also drilled the hole into the bolt head. To finish this job off, need to figure out how to retain the safety locking wire.
More to follow soon.

 

[btd1982]

Looks good and look forward to more updates

 

[HobbyCAD]

Whilst I'm contemplating how to safety wire the main clutch bolt, I started to close off some other loose end. When the project nears completion, you discover a myriad of these "loose ends". As the saying goes, the final 10% takes another 90% of effort!

I tackled the throttle cable today. The stock Yamaha cable is not long enough, so I sourced some cable termination "goodies", and this time, a THANK YOU shout-out to Steve White, aka De Fault, whom I traded my Bensen B-80 plans library to, for a spare Yamaha throttle cable and original oil filter. These items are not available in Oz, so he sent me the items from Canada. With all the spares, and a longer outer jacket, I made up a custom length cable assembly, retaining the original engine and frame end fittings.

An issue I came up with, I interpreted one must be able to gain full throttle twist travel, without needing to lift the collective. But then there is the correlator action that is added to the travel when you do lift the collective lever. You can then run into the issue that with correlator action plus full throttle twist, the cable travel bottoms out. I had to come up with some over-travel solution, so finding inspiration from some tent guy ropes I have, I constructed a small safety spring that gives the same over-travel as the correlator travel. I'm adding this to the throttle cable circuit.

Looking for the correct crimping tool, to crimp the stainless ball onto the wire rope.

Cheers, Francois.

 

[bugflyer]

Whilst I'm contemplating how to safety wire the main clutch bolt, I started to close off some other loose end. When the project nears completion, you discover a myriad of these "loose ends". As the saying goes, the final 10% takes another 90% of effort!

I tackled the throttle cable today. The stock Yamaha cable is not long enough, so I sourced some cable termination "goodies", and this time, a THANK YOU shout-out to Steve White, aka De Fault, whom I traded my Bensen B-80 plans library to, for a spare Yamaha throttle cable and original oil filter. These items are not available in Oz, so he sent me the items from Canada. With all the spares, and a longer outer jacket, I made up a custom length cable assembly, retaining the original engine and frame end fittings.

An issue I came up with, I interpreted one must be able to gain full throttle twist travel, without needing to lift the collective. But then there is the correlator action that is added to the travel when you do lift the collective lever. You can then run into the issue that with correlator action plus full throttle twist, the cable travel bottoms out. I had to come up with some over-travel solution, so finding inspiration from some tent guy ropes I have, I constructed a small safety spring that gives the same over-travel as the correlator travel. I'm adding this to the throttle cable circuit.

Looking for the correct crimping tool, to crimp the stainless ball onto the wire rope.

Cheers, Francois.

For terminating wire rope there are barrel-shaped ends that tighten with a set screw. Smaller size is used on bike cables...maybe some for motorcycles may be larger.

smiles,
Charles

 

[HobbyCAD]

And for the final loose end tied up for today, I finished off the sintered bronze sliders that fit into the tail rotor pitch slider. They have to be as close as damnit to the desired dimension, to have just about zero slop in the system. I ended up having to make six, before I had two that worked just fine. So that's another loose end done and dusted.

Tomorrow, weather permitting, I'll tackle the final assembly of all that goes onto and into the tailboom. Then it's on to final setup of the main transmission internals.

Cheers, Francois

 

[HobbyCAD]

Hi Charles, I'm a bit hesitant to use such a low-tech solution. I do not think one could clamp up the barrel safely. My life is going to depend on that cable working all the time, or it's unexpected auto's for me.

I made up some test crimps today, and hung a 60lb weight off it. I then bounced the hanging weight up and down a couple of times, the crimp did not let go. I would say there is no way I'll be loading the cable up more than 60lbs by hand twisting the throttle, so I think I have a soluition in-hand.
Thanks for offering some advice, Cheers, Francois.

For terminating wire rope there are barrel-shaped ends that tighten with a set screw. Smaller size is used on bike cables...maybe some for motorcycles may be larger.

smiles,
Charles

 

[MikeBoyette]

We always used the little brass throttle ends at the twist grip with silver solder to ensure it didn’t come off. Over the years I can only remember one failing and it was caught before total failure.

 

[Vance]

I recall a friend with a helicopter on floats that was doing auto rotations with a power recovery who pulled the end of of the cable off and had a landing that required repairs before being flown again.

 

[MikeBoyette]

I recall a friend with a helicopter on floats that was doing auto rotations with a power recovery who pulled the end of of the cable and had a landing that required repairs before being flown again.

I too remember that.

 

[HobbyCAD]

Vance, exactly what would give me sleepless nights. On the throttle end, I used the larger brass barrel ends with a small hole through it. I then drilled a recess pocket in the one end. Next I put a smaller brass barrel onto the wire rope, and crimped in on with considerable force, in fact, I stuck it under my press. I then filed that crimped on end down to fit into the recess pocket in the larger barrel. After threading the wire rope through the hole, and with the small crimped end seated into the pocket, I soldered the pocket closed. I pull tested it to 60lbs. Let's hope it stays secure in there.

Cheers, Francois.

I recall a friend with a helicopter on floats that was doing auto rotations with a power recovery who pulled the end of of the cable and had a landing that required repairs before being flown again.

 

[Vance]

Vance, exactly what would give me sleepless nights. On the throttle end, I used the larger brass barrel ends with a small hole through it. I then drilled a recess pocket in the one end. Next I put a smaller brass barrel onto the wire rope, and crimped in on with considerable force, in fact, I stuck it under my press. I then filed that crimped on end down to fit into the recess pocket in the larger barrel. After threading the wire rope through the hole, and with the small crimped end seated into the pocket, I soldered the pocket closed. I pull tested it to 60lbs. Let's hope it stays secure in there.

Cheers, Francois.

It reads like you are doing well Francois.

My experience with motorcycles suggests it is best to have the stop at the control so the cable doesn't become the stop.

In your case that would be at the twist control on the collective rather than at the carburetor.

 

[HobbyCAD]

Vance, makes perfect sense, but I have an extra layer to contend with, being the throttle correlator. I currently do have the throttle twist control travel limited to slightly less than the throttle body travel, so this control alone will never load up the cable joints. But when I lift the collective, it adds a little throttle as well, so I now run into the situation where if I set up the max travel to be twist plus correlator, when the collective is down, I cannot twist the throttle up to max. Do I need this, maybe not, I hope some experts chime in here. Am I being over pedantic to expect possibly needing to go full throttle, at low collective? My initial thoughts were "No", but what if I require the engine to spool back up fast before I load up the pitch, would full throttle not be the best way to do it? Return comments on this will be appreciated.

This is why I put in the over-travel spring setup, to allow 99% full travel by twist only, and when raising the collective from that point, the spring allows me the over-travel. BTW, the spring is set to be slightly more stiff than the throttle action required, and it's travel is more than what the correlator can add, so I still do not end up with a situation of a solidly bound up cable.

Your always wise advise and comments are highly appreciated.

Cheers, Francois

It reads like you are doing well Francois.

My experience with motorcycles suggests it is best to have the stop at the control so the cable doesn't become the stop.

In your case that would be at the twist control on the collective rather than at the carburetor.

 

[Vance]

Vance, makes perfect sense, but I have an extra layer to contend with, being the throttle correlator. I currently do have the throttle twist control travel limited to slightly less than the throttle body travel, so this control alone will never load up the cable joints. But when I lift the collective, it adds a little throttle as well, so I now run into the situation where if I set up the max travel to be twist plus correlator, when the collective is down, I cannot twist the throttle up to max. Do I need this, maybe not, I hope some experts chime in here. Am I being over pedantic to expect possibly needing to go full throttle, at low collective? My initial thoughts were "No", but what if I require the engine to spool back up fast before I load up the pitch, would full throttle not be the best way to do it? Return comments on this will be appreciated.

This is why I put in the over-travel spring setup, to allow 99% full travel by twist only, and when raising the collective from that point, the spring allows me the over-travel. BTW, the spring is set to be slightly more stiff than the throttle action required, and it's travel is more than what the correlator can add, so I still do not end up with a situation of a solidly bound up cable.

Your always wise advise and comments are highly appreciated.

Cheers, Francois

You welcome Francois; my helicopter experience is limited.

The correlator was part of the problem in my friend's mishap.

I admire your tenacity and thoroughness.

Thank you for taking us along on your wonderful adventure.

 

[HobbyCAD]

Thanks Vance, for your kind words.

Fitted the spring capsule into the circuit today. Works in principal, but the spring requires too much pre-load before it actually starts to open the throttle. The too low a spring preload also does allow the throttle to return to idle every time, if you gently lower the throttle down. Needs a bit of tweaking.

Heading off out of town for a week, will again tackle the issue next weekend.

Cheers, Francois

You welcome Francois; my helicopter experience is limited.

The correlator was part of the problem in my friend's mishap.

I admire your tenacity and thoroughness.

Thank you for taking us along on your wonderful adventure.

 

[HobbyCAD]

I find that when it comes to the human factors part of CAD design, it's just not possible to get the correct "feel" for it from your CAD models. Even animating the actions, you cannot feel how it's going to feel in your hands. So to get my throttle collective correlator ratio correct, I CNC routered out 6 different ratios. They are a press-fit onto the shaft, so by interchanging them and sliding them up and down the shaft, I should be able to get the correct feel and ratio. By feel I mean, to use a comfortable amount of wrist twist, to give the correct mechanical travel at the throttle body end. Too much twist and you need to double take, move your hand grip onto the collective shaft in order to get enough turn out of it, too little twist and the throttle is too sensitive.

More later...... Cheers, Francois.

 

[btd1982]

I find that when it comes to the human factors part of CAD design, it's just not possible to get the correct "feel" for it from your CAD models. Even animating the actions, you cannot feel how it's going to feel in your hands. So to get my throttle collective correlator ratio correct, I CNC routered out 6 different ratios. They are a press-fit onto the shaft, so by interchanging them and sliding them up and down the shaft, I should be able to get the correct feel and ratio. By feel I mean, to use a comfortable amount of wrist twist, to give the correct mechanical travel at the throttle body end. Too much twist and you need to double take, move your hand grip onto the collective shaft in order to get enough turn out of it, too little twist and the throttle is too sensitive.

More later...... Cheers, Francois.

Absolutely right, sometimes you have to just make it and see what it feels like. I had to do this multiple times on my coax. Yes you can draw it on cad but there's no substitute for real conditions. You may alter it again after 5 minutes of flight as muscle fatigue can play a part for example. Wish I had a CNC router to make parts, maybe one day.
How long is your to do list before any rotor run ups can take place ?

 

[HobbyCAD]

How long is your to do list before any rotor run ups can take place ?

btd1982, once I have the correlator sorted, I finally crimp on the cable end fitting, and the throttle circuit is done. Next job is to install the governor hall effect sensor, when it arrives in the next day or 2. Then clutch mounting setup is finally done. Re-install the seat and restraint harness, I'm then done nose to behind the seat. Next I jump back to the tail boom, I need to lock in the tail driveshaft bearings. Once done, I re-assemble all the tail sub-assemblies (the tail transition, tail blades, vertical and horizontal stabilizer) back onto the tail boom, and re-attach it to the airframe. Before I can attach it to the transmission, I need to sort out the outstanding main transmission items, being the bearing preloads and gear meshing pattern. Last part to fabricate will be getting hold of some blue spring steel sheets, and have a sandwiched drive plate set waterjet cut. I wish to have a drive set that could handle some in-plane flex. With this done, I need to re-assemble the sub-assemblies onto the top of the mast, and finally, statically balance the main and tail blades. At this point, I'm ready to start dynamic track and balancing.

Cheers, Francois