Updating old Schluters.....

Here’s one for Pete
Retro helicopters
Posts: 266
Joined: 16 Feb 2018, 06:19
Location: Varberg or Stockholm, Sweden

Re: Updating old Schluters.....

Post by Tobe » 03 Mar 2019, 17:37

Need to make a dive to my attic and pick the next project:
505 Falcon , mint condition, Super Heli Baby or Heli Star, in good used condition and decide if go electric instead of nitro!
You are an inspiration Pete.
Unfortunately I don't have more then a few remains of my first heli a Lark.
The Schluter Huey was my dream....

Posts: 183
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Updating old Schluters.....

Post by Pchristy » 21 May 2019, 14:36

Well, I managed to get the Cobra airborne at Ponty, but not without a struggle! In the hot, calm conditions, it didn't want to lift off until I increased the pitch on the blades to 8 degrees (the book says 4!).

I've been having a few issues with the motor setup since I put a higher kV motor in over the winter. Occasionally, just after lift off, there would be a loud CRACK - as if something in the transmission had broken - and it would flop back to the ground! It always seemed to happen on the same battery pack, so I was starting to blame that, but a long chat with Phil_G on Sunday suggested that the motor timing in the speed controller might be too advanced, resulting in an occasional "backfire". Apparently this is a well known phenomenon on electric bicycles!

This morning, I've retarded the timing in the speed controller from "medium" (the default) to "low". That has immediately liberated a lot more power - its now lifting off easily at 6 degrees of pitch. Due to space limitations in my garden (plus the size of the Cobra!), I haven't had chance to try a quick spool up yet, but so far, Phil's suggested fix seems to be working!

Many thanks, Phil!


Posts: 19
Joined: 21 Feb 2018, 02:01
Location: North Carolina

Re: Updating old Schluters.....

Post by pulserudder » 21 May 2019, 15:45

Pete, your posts got me digging about, and I actually found an old photo of my fixed pitch MFA Sport 500. Guessing 1990 or 1991. I was in my mid 20's and still had black hair. Must have been the first time I hovered her, as I see I am holding a two stick tranny. I switched to a single stick JR which was loads of fun and eventually moved on with Hirobo Shuttles and Kyosho Concept 30's.

Posts: 266
Joined: 16 Feb 2018, 06:19
Location: Varberg or Stockholm, Sweden

Re: Updating old Schluters.....

Post by Tobe » 27 Jun 2019, 21:46

This is for you Pete!

User avatar
Bo Edstrom
Posts: 23
Joined: 20 Sep 2018, 19:52
Location: Sweden

Re: Updating old Schluters.....

Post by Bo Edstrom » 27 Dec 2019, 22:21


Do You have eny more photos of interior of Your electric Huey Cobra, showing ESC and battery mounting?
Was the new electric motor with 580 Kv a better choice?

Have You made any special solution for cooling of motor, ESC and battery?
In Your Cobra how hot is the motor, ESC and battery after a flight that You showed in one of the videos above?

The connection on the shaft between gearbox and motor, the cylindrical piece You have on our Cobra - does it serve any more puprpouse then just a connection between gearbox shaft and motor shaft?
It seem big so I'm just wonder.

I have two Hegi Huey Cobra and I think I would like to convert one to electric.
One of them will be 50 years old in 2023, and it competed in first helicopter competitiuon in my country October 28 1973 and placed 2nd. It was no FAI rules then so the hosting club had to make the rules and flight Schedule for this occasion. I post a photo of this Cobra below.
I have read that the main difference between the Schluter Cobra and the Hegi Cobra was the gearbox on Schluter Cobra was in metal (and stamped Shluter on the side of the case) and the Hegi it is made of plactic. Other minor differences described here (in German):
https://www.schlueter-cobra.de/technics ... diff.shtml
Just load the URL in Goggle translator rom German to English if You need the test in English, I think this will do the trick:
https://translate.google.com/translate? ... diff.shtml


My Hegi Huey Cobra (built in 1972-73, by another person then me):

The engine (Veco 61) and gearbox in my Cobra:

The 13 helicopters that entered the very first helicopter competition in my country (Sweden), in October 23 1973 below. My Helicopter is in the second row behind the Kavan Jet Ranger that is marked "POLIS" (Police).

The winner of the helicopter competion below, his name is Ulf Johansson. As long as he was active flying RC helicopters he was one of the best pilots in our country, he flew Schluter helicopters. In photo below from the competition I do not know for sure if it is a Hegi or Schluter Huey Cobra he is flying but I think it is Hegi Cobra:

This is the brand of radio that was originally in my Cobra, that was used at the helicopter competition, the brand was OPPS and was made in Sweden (very expensive radio at that time, avaliable in 3-6 ch):

Posts: 183
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Updating old Schluters.....

Post by Pchristy » 14 Jan 2020, 16:26

Hi Bo,

Its probably about time I posted an update on here, as quite a lot has happened over the last few months - or at least, until the weather closed in! :evil:

To answer Bo's questions first: The coupling between the motor and gearbox was a flexible one, as I wasn't sure how accurately the alignment between the gearbox and motor had turned out. It eventually failed - probably due to the "backfire" I was getting from the motor, and was replaced by a solid, cylindrical, clamp-on coupling.

This video of the first attempts at flight show the battery mounting. It fits in the floor of the radio compartment:

The backfire eventually stripped a couple of gears in the gearbox! Yes, it was that violent! Luckily, and old flying buddy had some spares, which he donated to me, but I had to rebuild the gearbox yet again!

The backfire eventually turned out to be caused by the speed controller overheating in the fuselage! On a sunny summer day, even a cool one, the camouflage paint job was making the fuselage too hot to touch! As the speed controller was velcro'd to the fuselage side and there was little air circulation inside, the speed controller would suddenly get "out of sync" and create a massive "backfire".

My son suggested fitting a cooling fan to the esc, but I've now mounted it onto the aluminium chassis plate near the motor, and this seems to have solved the problem. It is still in its heatshrink wrap, but the heatsink is now pressed to the chassis, and this seems to have solved the problem.

The motor barely gets warm! Bearing in mind I'm getting 10 mins airtime out of a 5AH pack, which gives an average current of 30A max. The motor and speed controller are both rated at 80A, so neither is working very hard! Indeed, because they are so lightly loaded, I found it hard to believe that it was overheating to blame!

If I was going to do it again, I would be tempted to use a prop-adapter on the motor, and keep the clutch! I have a Hirobo Lama which keeps the clutch, and if you program in a slow motor start, it sounds just like a gas turbine starting up! Mind you, the Lama is flown on collective pitch, and the motor set to constant speed in flight - not really suitable for a fixed pitch set up! ;)

Turn the sound up!

I've now bought some new blades for the Cobra from Germany. The originals are not very straight, and difficult to keep in track!

Next up is to do the same modification to my DS-22! The HP 61 in that is well past its sell by date! This video was taken way back in 2002! That was before I realised that the engine doesn't like Nitro, and runs far better on straight fuel!

Tobe: That was very brave flying a Cobra that fast! All these old Schluters suffer from a runaway nose-dive if you exceed a certain speed! You can only recover from it by shutting the throttle, which then causes the nose to pitch up violently!

The original builder of my Cobra had this happen to him at a flying display back in the early 70s! He thought it was going in, so he shut the throttle, and the thing promptly stood on its tail! He hadn't been flying helicopters very long, and in attempting to recover it, crashed into the roof of a large marquee tent, doing significant damage to the tent! He had to pay for a sail-maker to repair the tent, as well as a new set of blades for the Cobra!

You can cure the nose-dive by setting the paddles at a positive angle - full-size Hillers have their paddles like this for the same reason. However it is difficult to get them both the same, and this can cause tracking issues! If you get the angle just right, the cyclic trim will not change with airspeed, but it is difficult to get just right!

I just live with it and keep the speed moderate! :)


Posts: 266
Joined: 16 Feb 2018, 06:19
Location: Varberg or Stockholm, Sweden

Re: Updating old Schluters.....

Post by Tobe » 16 Feb 2020, 16:49

Today I picked up, bought back my old Schluter Heli Boy that I sold 35 years ago from the same guy that bought it at the same price. The guy never flew it or cranked up the motor but kept it immaculate so now I have a dilemma! Shall I keep it IC and fly it with the original Kraft transmitter as helicopter radio is not needed as the mixing throttle/pitch is mechanical or shall I go electric and fly it with a modern radio?
I would in either case replace the old mechanical gyro with a faithful Futaba GY 401 with relative servo as my left hand is no longer up to speed.
FYI I still have the original fix pitch head option together with the collective pitch one so there I also have choice.
From my original collection of Schluter is only missing the Heli Baby now. I have the Mini Boy, Heli Boy with both training canopy as the Bell 222 fuselage and Heli Star. All are in flying condtion and original with IC engines...but I have installed proper rail gyros

Posts: 183
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Updating old Schluters.....

Post by Pchristy » 19 Feb 2020, 10:05

Nice one, Tobe! I sold my original Morleys to a fellow club member around 40 years ago. He put them in the attic and never touched them! On the rare occasions I see him, I ask to buy them back, but he's not selling!

If you look at my Charmouth video (first post at the top of this thread), you'll see my HeliBoy about 4'15" in. Its currently powered by a SuperTigre 45, which is fine for gentle circuits, but not enough for aerobatics! Since that video was taken, I've done quite a bit of work on "fine tuning" it, and it now flies very well. I fitted some more suitable paddles (heavier and bigger) which sorted the handling, and added a boom-stay, which allowed me to run a higher head-speed without it trying to shake itself to pieces!

Work is progressing (slowly) on the DS-22. I have a new chassis plate and a rebuilt gearbox complete. On of my flying buddies has a 3D CNC milling machine, so I'm hoping to persuade him to fabricate some proper motor mounts, rather than the bent aluminium I used on the Cobra!

I've also acquired another "Lark"! A Mk2 this time, and I'm intending to electrify it. I've got all the bits, just need some metal work doing! Watch this space....


Posts: 183
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Updating old Schluters.....

Post by Pchristy » 09 May 2020, 11:43

With the Lark now finished - pending the end of the lockdown - time to move on to another project, my Schluter DS-22!

When I electrified the Cobra, I made the motor mounts out of angled aluminiun from
ImageDSCF2146 by Peter Christy, on Flickr
ImageDSCF2145 by Peter Christy, on Flickr

This time, I got a friend with A CNC milling machine to make me a proper one!
ImageGeoff.DS-22_4 by Peter Christy, on Flickr
And a very nice job he's made of it! :)

First job is to strip the old mechanics out:
ImageDS-22.stripped by Peter Christy, on Flickr
I've hit one small snag already. The shaft adapter on the output shaft of the newly rebuilt gearbox is held in place by a pin which appears to be driven in by a press, or large hammer! Not easily removable! That means I can't swap the auto-rotation unit over. Mind you, the chances of carrying out a successful auto with it are approximately zero, I guess, but I thought it might protect the gearbox in case I get any "backfires" like I suffered with the Cobra!

Never mind!

I think this DS-22 may be the one that was originally built for the Radio Modeller review, back in 1974! The review was carried out by a friend of Dave Nieman's, and this model came from his Wembley shop. Here's trhe cover of the mag:
ImageDS-22_cover by Peter Christy, on Flickr
And if you look at the old video, higher up this thread, you will notice the similarity in colour schemes!

At the moment I'm awaiting delivery of some 3mm blind nuts to make fitting and removing the chassis easier. I wanted to do this with the Cobra, but the woodwork was too flakey! The DS-22 is in much better condition! I'm also awaiting a speed controller. I'm going to try one of the FrSky Neuron controllers, as it will provide a lot of telemetry about temperatures, current and voltage. I had a problem with the ESC in the Cobra overheating - despite running well within its limits - and the Neuron has a massively heat-sinked case!

Watch this space.....!


Posts: 108
Joined: 19 Jun 2019, 04:09

Re: Updating old Schluters.....

Post by bluejets » 10 May 2020, 02:16

I can't swap the auto-rotation unit over.

Aren't these fixed pitch ..??

Post Reply