Old Hirobo Bell 47

[pchristy]

I'm in the process of renovating an old Hirobo Bell 47. Actually, its in pretty good shape, and doesn't seem to need much doing. I'm replacing all the radio gear and Nicads, but have run into one problem.....

The engine is fitted with an electronic ignition system. At some point in its history, someone has fitted it with old style Sanwa connectors! I expected it to only need + and - volts, but it looks as if all three leads do something - but what?

Does anyone have a manual for one of these old style ignition systems?

I can probably back trace it and work it out, but in view of the difficulty in obtaining spares for these old machines, I'd rather have the pukka gen!

TIA,

--
Pete

[electricsceadu]

it might be worth giving dennis s an email as i'm sure he's had the mk1 hirobo bell 47
i know he never got around to painting the mk2 before it went to pastures new

[trillian]

I know someone that might have some material about that engine. I have not spoken to him in a while but I'll dig up his email.

[pchristy]

Update:

Well she took to the air for the first time in my hands yesterday (Saturday). We tried on Friday, but couldn't coax the engine into life! In the end it appears it just likes to be very rich to start with!

Once we'd sussed out the right procedure for starting it, it started pretty easily!

She seems to have plenty of power, despite some of the comments that have been posted about these old Hirobo engines, hovering easily at half throttle! I was surprised by how lively she was on the cyclic controls - I was expecting her to be quite slow! The tail rotor, in contrast, is very dead.

Now I've got everything in the ball-park, I need to readjust some of the linkages - too much throw on the throttle, for instance. I also need to do some cosmetic work. The crack in the bubble spread quite quickly with vibration, so that will need remedial action for a start.

But she flies! And that's the main thing!

--
Pete

[daren]

Come on Pete show us the pictures!!!

[pchristy]

I've got some video of it - no stills at the moment. I'll try and get it up on Youtube shortly, and put a link up.

--
Pete

[trillian]

Sorry to hear about the crack in the bubble. I don't recall any cracks when I had it.

That engine gets a bit finicky when it hasn't been run in a while but when it's hard to start it's usually a matter of not enough fuel getting in there. Sometimes it would start easier with the choke on.

Even though it's a heavy bird it has a such a large rotor disc area that it is suprising how easily it lifts off the deck.

[pchristy]

Hi Trillian!

Yes, there was a small crack on the port side, just over half way up. Even though we only flew it briefly in the hover, the vibration caused it to spread quite rapidly. However, I believe the new ones still use the same cabin parts so spares should be available. I also know someone who has quite a few spares for these tucked away - not sure if he's got a bubble, but I'll soon find out!

As a last resort, I've got a mate who makes vacuum mouldings, and might well be able to make me a replacement - so all is not lost!

I had to fit a new bubble on my little Morley Bell 47 a while back! The original had gone yellow and brittle with age! It literally fell to bits in my hand, so I'm used to dealing with problems like this!

I've uploaded the video to youtube, but it hasn't "appeared" yet - when it does, I'll post it here!

[pchristy]

Not sure how to embed YouTube videos in here, but here's a link:

[ame="http://www.youtube.com/watch?v=5OWjzcX79X0"]YouTube- Hirobo Bell 47[/ame]

WooHoo! It seems to have worked! How did I manage that.....?

BTW - that's NOT me flying it in the video! I'm far better looking, but was behind the camera......



--
Pete

[trillian]

Cool! It's alive!

Here's a few stills I took last year;

Kalt rc helicopters unofficial fan site

[pchristy]

Trillian - when was the last time you know that it flew?

--
Pete

[trillian]

Trillian - when was the last time you know that it flew?

--
Pete

Hmmm, it was spring of last year. Then I was planning on going through it and changing out a few things, putting in a 2.4ghz rx and I was still using the 35mhz setup I got with it and then having a think about painting it etc. but I realised I was doing good to get enough flying in with the smaller helis so it sat on my shelf here for most of the year.

Then starting it again nearly took my arm off, I literally pulled a muscle or something. For some reason the gassers just don't like sitting up but when they're run regularly they'll fire up straight away.

[pchristy]

Here's a couple of stills taken on Friday, when we couldn't get it to start:





I know what you mean about pulling your arm off! A few years back I had an Eagle gasser for a while. Once we'd got it sorted, it was great - but learning what it needed for a cold start nearly knackered both Mark and I!

This one was the same - but the technique seems to be 1) Ignition OFF 2) Close the choke 3) Pull it over until fuel is well and truly in the carb! 4) Choke open 5) Ignition ON 6) a couple of good pulls with the throttle just cracked open, and 7) BINGO!

I was quit surprised how quiet it was too! I recall my Eagle having quite a loud bark! And my old DS-22 is deafening - despite only having a 60 glow motor on board!!!

At the moment, I've removed all the cabin decorations. Once I've got all the links sorted to my satisfaction (new servos all round!), I'll start work on the cosmetics....!

Cheers,

--
Pete

[trillian]

Yeah, it's pretty civilised in terms of sound. I have a G23 engine with a similar looking square can muffler and it is quite loud. I was surprised how loud it was. I just put a Century pipe on it but then when trying to start it a while back a skid strut snapped in two. I got new skids (exhorbitantly priced Minair 'tuff struts') but have not got round to fitting them yet.

Regarding the starting situation, have you pulled the plug in there and had a look? I was going to do that but didn't have a replacement plug. If it gets too much carbon deposits the spark can start shorting to the nearest bit of carbon.

I made the mistake of letting the Predator sit for quite a while last year and paid the price when I took it out back in December, but now it starts right up very easily. Basically if you don't feel it kicking a bit then it's probably a matter of not enough fuel going in yet, second to that would be a weak spark.

I was quit surprised how quiet it was too! I recall my Eagle having quite a loud bark! And my old DS-22 is deafening - despite only having a 60 glow motor on board!!!

[pchristy]

Yes, I took the plug out yesterday morning before we went up to the field. Its in very good condition, but seemed a little wet.

I wasn't sure I'd got the wiring of the ignition right, but Mark reckoned he could hear it whistling (beyond my range these days, alas!) and there was definitely a spark at the plug when we pulled it over.

At first I assumed we'd flooded it, but shutting off the fuel didn't help, and the engine "felt" dry. So we took the plug out again, choked it, opened the throttle, and pulled it over without the plug until we saw mixture coming out of the plug hole. Then we replaced the plug, and she fired first pull!

It definitely likes to be very wet to start!

--
Pete