Updating old Schluters.....

Here’s one for Pete
Retro helicopters
Posts: 173
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: 106
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: 173
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: 106
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! :)


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