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Old 12-15-2012, 04:40 AM   #1
jc23cl
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Talking I need some help.....I have Gas (Goblin Style)

Hi all,

I have had a week off and finally got time to finish of a project I have been working on.

I have almost finished but need a little help.

If anyone has an accurate weight of a G270RC standard or VX TT version with clutch I would really appreciate it ; ). I already have Goblin/s so all other parts are sorted.

I am finalising the tank size and position and this info would go a long way to getting the COG as close to Ideal as possible.

Anyway here are some screen shots if anyones interested, as always happy to take constructive critisism or suggestions.














Thanks again guys, and any help would be very much appreciated.

Joey.
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Old 12-15-2012, 07:44 AM   #2
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WOW that looks great, here is a link, all of the Zenoahs on the link are very similar in weight, only the bore size changes

http://www.zenoah.net/files/Zenoah/G...OBBYG290RC.pdf

A few observations:
Looks like you drew in a RJX muffler, they are heavy and are not the most powerful, consider using a Century V2, lighter and more powerful.

The starter is very close to the ground, may need to use higher LG to keep the drivetrain from getting damaged in a hard landings.

If you want more power. Quickdraw has a tuned pipe.

Not sure on your gearing but for 3D it is critical to get the engine into the right RPM range. For a Toxic 270 with a V2 plan on idle 1 at 13,500 and idle 2 in the low 14,000's engine RPM's at your desired head speed. For the Quickdraw, plan on low 15,000 range
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Old 12-15-2012, 08:44 AM   #3
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Wow. This is the most interesting gasser project without a doubt. Could you be the owner of HeliX? : )

BTW the stock 270RC weighs w/o clutch and muffler 2.1 kg. (according to the manual)
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Old 12-15-2012, 11:05 AM   #4
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Woaw... very nice project. Just a suggestion, don't the goblin are tail heavy? so flipping the motor 180 forward will help with CG ?

I'm into a similar project but again Align based, however with the latest electric V3 DFC and adjustable motor mount for pinion change.

An old RC format CY23cc engine weight at 1550g on my scale w/o clutch & muffler, larger displacement weight about the same.

You can add 150g for the original clutch assembly or go as low as 75g for an Lauterbachker 4 shoes teflon.
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Old 12-15-2012, 06:07 PM   #5
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Hi all, thanks for the enthusiasm and suggestions. (didn't expect it).

I'll post a quick reply now but will send some more Info tonight.

fastflyer20 - Thanks for your comments.

I have modelled in the Hatori, I had this on my last Helibug and absolutely loved it, at least comparing it to the RJX it came with.

The Century V2 is absolutely an option ! Do you know the weight of one off hand ? I'll do some research for sizes and weights off the Internet. I'll get back to you on this.

Yes the CAD shows the pull starter very close to the ground, I'll pump the skids if required.
What clearance do you think we should aim for ?

Thanks for the Gearing suggestions, I should be able to find the right pulley for the planned T, although I haven't done the calc yet. ( Certainly a virtue of SABs very clever modular transmission approach ).

Azalin - Thanks for the enthusiasm.

I am not the Helix owner ( love his work though ), having said this I'd love someone to prototype the frames and bits for me...hint,hint Mr Helix.

Thanks for the weight Info, I i'll post something tonight to be more specific.

martin_ - Thank you, sounds like you are a kindred designer as well ; )

Yes the Goblins are tail heavy, but I am battling the thoughts off getting the heat out of a very closed canopy. I fear that if the motor faces forward I may compromise electronics (heat wise). Opinion/experiences welcome.

Also if the motor faces forward the tank will have to go at the back, it will look good but will add to the tail weight being aft the main shaft.

I think at this stage I should be able to counter tail weight with 2S LIPO, tank and throttle servo placement. "fingers crossed".

Thanks for the clutch suggestions, have you got experience with the "fancier" clutches, are they still ok for Heli applications. I would certainly welcome opinions, the weight saving would
be a bonus !

Anyway thanks again all, and please be patient with the responses, I'm in OZ and don't get to replies until morning ; )

Regards Joey.
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Old 12-15-2012, 06:42 PM   #6
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Sorry, the drawing looked like an RJX. The V2 muffler weight is 8.2 oz, Carey has a very nice post with measurements and weights. Hatori's are quiet and very well made.
http://helifreak.com/showthread.php?t=317770

Completely agree on rear cylinder for heat removal, big issue on helis running RC format engines with cylinders facing the front during Summer heat (including early reports on the Helix).

Skid height is subjective depending on the LG strength, flex and pilots ability to land softly . But I would think 1" minimum.

Stock Zenoah clutches are holding up well in the Whiplash, you can always upgrade later. Helis are much easier on clutches than RC cars.

You have done lots of work with the RC engine, but just a thought, the PUH is lighter. You will need a fan and fan cover, plus they are harder to mount, etc. The Century Radikal 30 has a very good cooling system for the PUH. The Radikal cooling forces the heat down so having the cylinder facing forward is not an issue.

Hard to go wrong with a Toxic 270.

The Whip and HB use an additional bottom plate tying the engine fan cover to the frame sides, not sure if you were planning on that.

Keep up the good work!
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Old 12-15-2012, 07:31 PM   #7
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Thanks fastflyer20,

All good Info, and exactly the feedback I need ; )

I have thought of the PUH, the cooling shroud is not an insurmountable constraint as I can adapt an existing component at for the moment anyway.

From what I have read and viewed (Smacktalk) and alike, the consensus is RC format.

I personally think the PUH will be nicer from a packaging, aesthetic point of view but would love to hear the opinions of the Gurus in this area.....Carey and Al wink, wink.

The concept so far represents at least for me the main obstacle to the conversion, that is maintaining the "modular" transmission design approach that the Goblin does soooo well.

The screen shots show how the motor, clutch and pinion assembly can remain as a synchronous unit while still able to swap pinions and - quickly re-adjust belt tension.
This "unit" will still require side frames, that will house gas tank, throttle servo and what ever
suggestions the community(you guys) can come up with ; )

It will be literally the last thing designed once all these elements are in place (3D model space).

Thanks again, and keep those comments coming.

Warmest regards Joey.
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Old 12-16-2012, 03:34 AM   #8
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Hey all,

Here are some pics against actual Goblin at 1:1.

As highlighted the pull start looks to be at around 10mm from the ground, this can be accomodated with relocation of the landing gear bracket onto the Zenoah frame plate.

It also looks as the canopy may need to come forward 10mm, having said this I've calculated a 32 tooth pinion which is much larger than the standard. Even though this is not a standard Goblin part I have already sourced it.

VX270TT @ 13500 RPM x (32/204) = 2117 HS - Aftermarket Pulley
VX270TT @ 13500 RPM x (30/204) = 1985 HS - Aftermarket Pulley
VX270TT @ 13500 RPM x (28/204) = 1852 HS - Aftermarket Pulley
VX270TT @ 13500 RPM x (26/204) = 1720 HS - Largest Standard SAB Pulley

The consequence of this is that the motor assembly will get closer to the main shaft, I'm not sure if the standard motor belt will cut it, I'll do some more detail in this area over the next few days.

Here are some pics.








Thanks guys, until next post ; )
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Old 12-16-2012, 04:01 AM   #9
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subbed.

Sent from my phone using Tapatalk2...otherwise i would of sent it from my home PC.
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Old 12-16-2012, 10:33 AM   #10
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Default Gasser Concept...

Jc23cl..

You got an interesting conversion goin on here. As with the work you have done as far, looks like it will work out fine. I know you mentioned the canopy would need to move foward some 10mm, though you are using the 700 as platform. Have you looked into the new 770 size Gob ? Maybe the best ticket for your planed application with some room to spare.
I saw the new 770 getting build at my LHS ( PiroFlip.com ) on Friday and looks pretty roo
my...

Looks like I need to start saving up for the Gov. ...hehe

Keep up the awesome job ....

Frgy28
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Old 12-16-2012, 11:55 AM   #11
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I wonder if stock landing pipes/skids would be able to handle ~12lbs?
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Old 12-16-2012, 02:10 PM   #12
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Interesting.
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Old 12-16-2012, 08:40 PM   #13
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I see that it's a very enclosed canopy, not a good idea to make it with the cylinder facing forward, but is the heat will really escape better with the cylinder at the rear? For sure the tail belt will took alot of heat.
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Old 12-17-2012, 03:57 AM   #14
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Hey all,

As mentioned next design hurdle was the motor pulley.

It would of been a good thing if we could use the original motor belt, given that I need to go for a 30 tooth pulley. Looks ok.

I have laid out the PCD's of the variuos pinions and found that going from a 22 tooth right up to 32 tooth results in a 6+mm change.

This pushes the motor assembly and clutch 6mm toward the shaft, not such a bad thing as I gain much needed canopy clearance.

Also now that I have been forced to make the pinion aftermarket I have beefed the clutch bell shaft to 8mm. This makes me feel much better compared to the original 6mm.

There is also a side benifit of using the bigger 30-32 tooth pinion, heaps of meat for a large M4 or M5 set screw to bite on the clutch bell shafts flat. Also much greater rap around compared with the smaller 22 tooth. (not that I think anyone has reported belt slip yet, but hey couldnt hurt).

Anyway, next installment of screen shots.







Before I forget - martin

I reckon there is about 30mm b/w the top of the motor and the bottom of the tail pulley, air gap is pretty good but I reckon I'll design in a deflector to force the air out sideways towards the pipe. You may notice the little hole on the plastic shroud in the above shots, this I believe is the common deflector mount hole.

FRGY28- Thanks for the suggestion, I dont have access to the 770 but if I can make it work for the 700 it should definately be ok for the 770. I wonder whether the Zenoah is upto the big 770 ? Its still all theoretical even for the 700 at this stage

FastRunner - I too get a little concerned about the standard landing gear, I'm guessing at this stage I'll put beefier reinforcment plates than the stock ones. Larger, longer and probably 3mm thick since I'm using 3mm carbon on the motor/clutch side plates anyway.

We'll see

O.K. I think thats all, until the next Installment.

Keep those comments coming, I'll kick myself if I miss something that someone with a younger keener eye can spot now

Regards Joey.
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Old 12-17-2012, 04:49 AM   #15
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Very very cool project. Hats off for taking this on. Best of luck to you sir!
Matt.

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Old 12-17-2012, 04:58 AM   #16
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Quote:
Originally Posted by brewer00psd View Post
Very very cool project. Hats off for taking this on. Best of luck to you sir!
Matt.

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Cheers mate, yeh go gassers !

I keep getting the feeling after all the heavy lifting ( CAD + Design ) something small will trip me up lol. Lets see.

I reckon the Goblin will look cool with that big shiny pipe hanging out the side ; )
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Old 12-17-2012, 05:37 AM   #17
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If you can figure this out! I am buying a goblins and making it a gasser. Personally love nitro / gas engines helis and if there is a gas goblin... What's better than that!

Nice job !
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Old 12-17-2012, 07:40 AM   #18
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Darn it. I did say this weekend that the only way I would own a Goblin is if they made a gas version. Looks Great so far!!
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Old 12-17-2012, 11:59 AM   #19
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That is an interesting conversion. I see you have put some time into this. I am just asking, but have you considered the CRRC case instead of a PUH? The case it smaller and lighter and 'may'help . Any builder would be able to adapt his porting to it on his top end of the motor.. and weight matters.


-Cody
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Old 12-18-2012, 02:26 AM   #20
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Quote:
Originally Posted by Dr_Fibinotchi View Post
That is an interesting conversion. I see you have put some time into this. I am just asking, but have you considered the CRRC case instead of a PUH? The case it smaller and lighter and 'may'help . Any builder would be able to adapt his porting to it on his top end of the motor.. and weight matters.


-Cody
Hey Doc,

I did consider the PU and the CRRC but after a little discussion and some quick layouts it was going to make the modular transmission concept difficult. With the RC format bottom fan it has allowed less compromises. Thanks for the suggestion though ; )

As an update I have been kindly asked to look at the possibility for a top start option, this will be tricky but shall give it a red hot go !

Thanks all again for the encouragement, and until next post.

Joey.
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