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Bell 47 Crash

Old 08-16-2008, 10:06 AM
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pa18135
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Default Bell 47 Crash

Hi M.Goldstein, Last winter I built a brand new Hirobo Bell 47G Gas engine 24c.c ( see picture on my Gallery) I flew it for the first time last week it is a very stable helicopter and easy to fly.When I flew it last time as I was hovering at about 15 foot height,without any warning the UNIT fell on the ground. I brook it for may be $600. Now I have few questions for you.My radio is a FUTABA 7CHP the Receiver is aFP-R 127DF .The Receiver was fixed under the seat in the cockpit. The antenna was free under the UNIT. Q. #1 Is this receiver compatible for this Big Machine? Q#2 Could my receiver to close from the engine and was overheated by the engine?My last Q.I ordered a new radio Futaba 2.4 GHz will it resolve the problem? Thanks and Best Regards Claude
Old 08-18-2008, 09:46 AM
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Default RE: Bell 47 Crash

He has been at IRCHA all week so bear with them, and his name is Dan.

1. It should be but gassers are prone to producing ignition noise and I would think a PCM reciever would be better, and a 2.4 better still. I also think that 2.4 isn't a substitute for proper radio installation and these kits have been around for a while before 2.4 was available.

I doubt over heating was the issue but you never know unless you do some temp testing.
Old 08-18-2008, 07:11 PM
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Default RE: Bell 47 Crash

Hi Andy,thanks for all your info. I will continue to investigate.I just received my new 2.4 GHz Radio as soon as I will receive the rest of my Heli.Parts.I`ll make another flight test and you will be the first to know how it behaves. Thanks Claude
Old 08-19-2008, 09:29 AM
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Default RE: Bell 47 Crash

Claude,

I concur with Andy's suggestions.

There are numerous factors that could have contributed to your crash.

By installing the 2.4 system you should virtually eliminate the possibility of radio interference being a cause of a crash and you can also program the fail-safe function as well.

Other potential failure contributors could be your power system, fuel mixture or other mechanical failure.

Let us know how you make out when you get it back in the air.

take care,
Old 08-19-2008, 11:20 AM
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Default RE: Bell 47 Crash

Hi Dan,Very happy to hear from you and Handy, It is better for my moral.I have a few more questions for all of you. What would be the best place for my antenna? I know I have to fixe them 90° apart.Should I fixe booth of them in the cockpit or booth of them beneath the cabin or one inside horizontally and the other pointing toward the ground under the cockpit ? Thanks Claude
Old 08-19-2008, 11:35 AM
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Default RE: Bell 47 Crash

either way, the receiver isn't very picky.
Old 10-29-2008, 07:08 AM
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Default RE: Bell 47 Crash

Hi Dan and Andy,I would like to be more specific about my crash.It was not caused by an engine failure or by a mechanical problem.The real cause was the receiver antenna.After refuelling I lifted the Unit and my feet was on the antenna broking it inside the cabin.This caused a Range problem. I fixed the Helicopter three weeks ago and I installed a 2.4 GHZ radio.Now I am back in the air it flies like a new one without any interference and I still love it.Thanks a lot to you Dan and andy for your help and support. Claude
Old 10-29-2008, 10:12 AM
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Default RE: Bell 47 Crash

Glad you got it sorted
Old 12-06-2009, 04:31 PM
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Default RE: Bell 47 Crash

Hi Clude, Andy and Dan,

I just got an old Hirobo Bell 47G unfinished from someone who never ever get her in the air and i am now restoring it. Mostly hangar damage.
However, this is myfirst time with a gasser hence I want to be safe. I have flown both electric and nitro heli but i know gasser is different.

i hope you guys can help me to get into my first gasser? First of all, i dont have the manual. may I know if any of you cna help with the manual? especially the gasser engine operation manual. I saw there is an electronic box connected to the engine, this is obviously an extra bit compared to my nitro. not gyro, not receiver, not servo. my guess is ti is something to do with the timing of the park plug?

i think it is a 23cc hirobo engine , so can i cross reference that with other brand (car) 23cc engine operating manual?


thanksin advance for your help!

Lawrence
Old 12-06-2009, 04:32 PM
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Default RE: Bell 47 Crash

also guys, a simple one, are the fuel tank and fuel line for petrol need to be specific and not the common nitro fueld system? any special material request? thanks

Lawrence
Old 12-06-2009, 09:40 PM
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Default RE: Bell 47 Crash

Lawrence,you need DUBRO TYGON GAS TUBING DU-BRO STOCK #554 and a GAS Conversion STOPPER in the Tank Made By DU-BRO # 400 It will help. Claude
Old 12-07-2009, 11:43 AM
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Default RE: Bell 47 Crash

Hi Claude,

thanks for the fast reply. I have a look at your gallery, it is a NICE heli! Well done.

opening the cabin revealed a 6V nicad connected to the ignition box. May i ask if i need to use separate 6V battery to the ignition system and antoehr pack for the receiver/servo?

Thanks.

Cheers.

PS:I have sent an email to hirobo and see if they come back to me with the manual.

Lawrence
Old 12-07-2009, 06:45 PM
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Default RE: Bell 47 Crash

Hi Lawrence,my engine is probably different than yours.On mine I do not need any battery connected on my ignition to make it run.Here is a few pictures of the engine.Hope it will help you. Best Regards CLAUDE
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Old 12-08-2009, 03:59 AM
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Default RE: Bell 47 Crash

Hi Claude,

Thanks for the photos and info.

I have tried to look on the engine to see if i can find any model number etc but couldn't.

I have taken some pictures of it in the heli itself. the one with the 'black box' is the ignition box i suspect. there are 2 pairs of wire connected from the box to the engine.

I saw the box was connected to a 6 V nicad so I suspect I can do the same with a fresh power pack, remaining 6V.

Hope I can get some help from here, if any gurus here can help me identify the engine.

Thanks!

Lawrence
Old 12-08-2009, 04:03 AM
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Default RE: Bell 47 Crash

Photos, sorry I know it is still look like a mess but it is up for a full restoration!
1. heli from front
2. engine from left view
3. engine from right view
4.heli front look with bubble canopy
5. ignition box
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Old 12-19-2009, 02:16 PM
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Default RE: Bell 47 Crash

Hey folks,

I tried to start the engine today but it wont keep running. i think the fuel is not reaching the engine as the engine only start on the prime fuel. i opened up the walbro carburetor and the diaphram seems stiff from age. I think I need to change all the gasket of the carburetor due to its age and hardening.

I have ordered a cheap weed eater engine (30cc) new hoping that i can just replace the entire carburetor to the engine and see how it goes. hopefully it will be powerful enough to hover. meanwhile, at least thsi shown that the 6V ignition system (external battery pack to the ignition box) is working.

also, i am searching for the main blades. may I know what is the lenght of blade this heli needs? 79 or 80 cm? anyone knows a good place for a great deal to get these rare sized blades or is there any other heli using this size so i cna use it directly?


thanks.,

Lawrence
Old 12-19-2009, 02:20 PM
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Default RE: Bell 47 Crash

also guys,

by any chance anyone knows the weight and power (HP) of the tas 24cc engine?

Cheers

Lawrence
Old 12-19-2009, 04:26 PM
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Default RE: Bell 47 Crash

Hi Lawrence,the Main Blades that you need for your helico.if you choose a wooden Blades they are 790MM long and there is one paire in MontrĂ©al Canada at UDISCO Send an E-Mail to MARC the address is [email protected] If you prefer a Carbon Fiber Blades they are 800MM long NHP RAZOR PRO You can buy them in California USA the e-mail adress is WWW.HELI-WORLD.COM Hoping it will Help. Claude Q.
Old 12-19-2009, 04:32 PM
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Default RE: Bell 47 Crash

Hi Claude,

Thank you for your help and info. I will try to search within UK if any shop carrys those. I am hoping to get the fiber blades. May I also ask if your blades are wooden/ fiber , semy symetrical or symetrical? sorry for asking so many questions at once cos I want the get the right ones. cheers and many thanks.

Lawrence
Old 12-19-2009, 04:33 PM
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Default RE: Bell 47 Crash

Hey Lawrence, Wooden Blades 790 MM Parts #0404-769 Claude
Old 12-19-2009, 04:48 PM
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My Blades are made of wood and SEMI-SYMMETRICAL If you Buy Those you will have to make good WEIGHT & BALANCE ROTORTECH 810 would be another good option they are Ready to Fix they`re very nice but they are very expensives Claude
Old 12-20-2009, 04:07 AM
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Default RE: Bell 47 Crash

The model for walbro carburetor WALBRO WT-486-1 CARBURETOR http://www.lawnmowerpros.com/detail.asp?id=WT-486-1

You can find out from here http://www.fraser-ker.com/neasham/Model_E_Stage_6.htm
Old 12-21-2009, 10:17 AM
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Default RE: Bell 47 Crash

Thanks for the info Claude and yacsf.

I will keep you guys posted about my progress. Waiting for carburetor repair kit and the 30cc cheap engine to come in. hope either the repaired original carburetor or the carburetor from the cheap engine let the engine run smooth. then i have to made a decision on the blades.


Progress might be held back due to the current cold weather in London, it just started to snow again 10 minutes ago.

Cheers guys.


Lawrence
Old 01-04-2010, 09:06 AM
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Default RE: Bell 47 Crash

Hey guys,


Some updates on my progress. I have the Walbro gasket repair kit came in before the 30cc engine so i have replaced all gasket expecially the diaphram. I started it and it was running really WELL!
however, it was running without main blades but at lest the throttle response seems fine. I did not rev it up, just from idle to maybe 20% throttle stick as it was almost unloaded with just the fly bar on the rotor head. At least i am happy and have it running!!! Thanks for the helps guys!

I also started to make a a pair of wooden blades. I know it has to be properly balanced and strong enough so i have spent quite some man-hours on them. i made them 80cm so can be cut down to 79cm later if needed. they are sanded to shape now and ready to be heat shrink-ed. My plan is to test the engine power with my wooden blades. Once i see it is powerful enough to hover, then i will purchase a pair of proper fiber blades. Because I read some folks saying that the older hirobo engine is underpowered even for normal flying hence dont want to spend a fortune on blades at early stage. I also cut down a pair of fibfer glass trex 450 main blades from 325mm to 130 mm to use as the tail rotor blades.

so once the main blades are ready to be used, i will try to fit it onto the head with 5mm bolts and have a try at the field, of course, if weather permits. I will find a place with no one around for safety.

Will update when more progress coming. just too cold to be outdoor for too long nowadays.

Cheers.

Lawrence
Old 01-04-2010, 09:07 AM
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Default RE: Bell 47 Crash

Happy 2010 to you guys as well!
Safe and happy flying for all!


Best Wishes from London
Lawrence

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