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Home✈️Aircraft🚁HelicopterThunder TigerOther › OOPs melted shroud is it important?
07-19-2006 01:51 PM  14 years ago
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DRUMMER

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Dover, UK

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OOPs melted shroud is it important?
Having a great Rap 90 session today having just learnt how to loop and getting a few in.. Second tank of fuel downwind on the first circuit when the head speed starts to drop and the engine is a coughing like a dog eating a chicken bone... sort of auto'd in and more luck than judgement she sat nicely [but quietly] in some long grass spinning down. Inspection revealed the os 90 viperhead has started to melt the plastic around the head/plug area. Both plugs are a light tan colour.

Do you think this is the cause of the stoppage or an obvious symptom of overheating, therefore the cause? Also importantly, have i now knackered the plastic or can it be removed and cooling left to the viperhead heatsink capabilities?

The engine appeared to be running rich with a nice smoke trail and until this showed no other symptoms. The one thing i did change between flights was just upped the idle 1 throttle curve by a few percent to ensure no bogging when looping.It is a very hot day here in the UK [ 37*]

Any help as always appreciated.
drummer:confused

'if your face, fits then wear it...'
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07-19-2006 02:22 PM  14 years ago
AnnihilaT

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The Netherlands

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Im new to engines but sounds like a lean run to me or something else which caused the engine to overheat. You using 30% nitro? If not you should be in this heat. Helps with power and more importantly keeping the engine COOL



A day without sunshine is like, well, night.
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07-20-2006 10:02 AM  14 years ago
DRUMMER

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Dover, UK

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Thank MFIS, I am using 20% nitro fuel and have plenty of smoke.

Could really use some advice about the melted plastic situation if anyone has some advice please?

regards
drummer
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07-20-2006 11:37 AM  14 years ago
RockDoc

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Middlesbrough, England

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I had the plastic insert in the cooling shroud stick and melt itself to my Viperhead. I had to pull the engine out with the plastic attached to it. If it is the same just clean it up and file off some of the screw mounting posts on the back of the plastic shroud extension for some clearance above the head and re-fit everything. Should be OK after that.

Hope that makes some sense!

D.
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07-20-2006 01:27 PM  14 years ago
DRUMMER

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Dover, UK

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Hi RockDoc,

thanks for the reply. The plastic piece surrounding the actual glow plug area is the bit that has melted and fused itself to the head. I have managed to eventually remove the engine but most of that plastic area is no longer there. Do you think I can fly without this plastic once the engine is checked out or should i engineer [read bodge!] a replacement piece of plastic for that area??

once engine was out found all the head bolts were loosened so that was the cause...

regards
drummer
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07-20-2006 01:30 PM  14 years ago
Pete Niotis

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Grand Haven MI, USA

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Drummer, I loved how you described the engine symptoms
"head speed starts to drop and the engine is a coughing like a dog eating a chicken bone."
To clear this up, you do not use the plastic baffle in the fan shroud when using OS motors, that baffle is used when installing TT,YS or Webra motors. For reference, check the manual on page 13 section (1-2-5 Cooling Fan Casing Subassembly)
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07-20-2006 06:40 PM  14 years ago
DRUMMER

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Dover, UK

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Hi Pete,
thanks for your reply and help.

I'd better start by stating i am using a converted rap 60 to 90 conversion the 60 manual does not give any detail about optional baffles? In fact I am not sure what that is?

Is it the 'cooling fan casing sub assembly' which comes in two halves and on the front has a solid piece of plastic with a 'U' shaped slot to fit around the glow plug? If we are talking about the same piece this is not removable in the 60. Except that now I have melted it and it is missing... IS this the baffle you refer to and /or can I still fly with this missing or will it not be efficient cooling over the head?

Hope that makes sense?
regards
drummer
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07-20-2006 06:44 PM  14 years ago
Pete Niotis

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Grand Haven MI, USA

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yeah drummer that piece of plastic plate with the U shape for the glowplug is what they refer to as the baffle in the 90 manual and does not need to be there for the "OS90" so you might as well finish removing whatever is left of it with a dremmel.

no problem!
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07-20-2006 06:47 PM  14 years ago
Wa11banger

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Huntsville, Al

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DRUMMER,

You used the original fan shroud from the older 60? If so you do not have a baffle piece to add or take away, the baffle as being called is a small piece of plastic that is flat and rectangle in shape it has the same "U" cut out of it like the shroud does but it is held into the inside of the shroud with two screws. In this case you melted the front of of the fan shroud and it is very important for proper cooling. So I would say if its melted to the point of missing you will have to replace it. Here is the kicker, Once upon a time there was a 60 version of the shroud and servo tray and a 90 version of the shroud and a servo tray.. Neither tray or shroud could be used with the other. So now that there is mostly only the one new 60/90 shroud carried in stores or at vendors web sites I am not sure you wont have to buy a new servo tray as well when you replace the shroud. If you go to ACE hobbies online and download the manual in PDF format you will see the little baffle piece they are talking about and it will come with the new shroud..

Hope this was of some help, and to clarify yes you need this part of the shroud covering at least a good portion of your head to offer up sufficient cooling

Rick
Proud member of the Quick UK, Duralite Flight Systems, V-Blade, & KBDD team
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07-20-2006 07:20 PM  14 years ago
DRUMMER

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Dover, UK

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Hi Guys,

Thanks for all your inputs but now i am baffled by the baffle
question I have just finished dremmeling the last of the baffle away and am covered in black bits. I could with my usual ingenuity no doubt build a replacement baffle and install it. [As my os 91 touched the olds baffle I could give it a little more room]
but only want to do this if definately needed for cooling?

Does it say why to remove baffle for OS engines. ie is it cooling related or because of size constraints?


Keep the ideas,comments and abuse coming boys..I need all the help I can get!

drummer
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07-20-2006 07:29 PM  14 years ago
Wa11banger

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Huntsville, Al

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Ok last question was there two areas with the "U" shape in the stock fan shroud? If so and you removed the inner most area... then you are ok as long as you have the outer one still covering the head.. If in fact you know have nothing covering the most portion of the head it needs to be built up to provide proper cooling again..

Rick
Proud member of the Quick UK, Duralite Flight Systems, V-Blade, & KBDD team
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07-20-2006 07:35 PM  14 years ago
DRUMMER

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Dover, UK

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Thanks Rick,

I have comletely and quite neatly removed ALL the old 'baffle' [said with Dr Evil fingers \/...\/ ] In that case i will spend the time rebuilding a 'baffle' \/....\/ to enhance said cooling. No doubt safe in the knowledge that after all the extra work i shall probably stuff it in on my next loop!


thaks & regards
drummer
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07-20-2006 07:47 PM  14 years ago
Wa11banger

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Huntsville, Al

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hehe ok that clears up a lot for us and you. The "baffle" as it has been called here, is a secondary piece you add to the lower portion of the shroud to accomodate shorter engines like the YS, Webra, and TT as stated above. it is in essence a short 2" duplicate of the lower portion of the fan schroud that bolts into your existing shroud to in a sense move it closer to the shorter engines.. To keep the airflow closer to those type of engines so to speak. so what you dremeled out was the fan shroud The "baffle" is a part as described above that came out later than your version of the R60 and was included in most R90 kits.. I wish you luck on your reconstructive surgery..

BTW if you do stuff it in the near future and it needs replacing, I recommend just getting the new R60/90 fan shroud and servo tray and doing it all at once then so you don't get frustrated later They have changed several part numbers since your original manual was printed.

Rick
Proud member of the Quick UK, Duralite Flight Systems, V-Blade, & KBDD team
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