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HomeAircraftHelicopterGasser Model RC HelicoptersOther › HWC Trex 700 / TRM VX231 RS Auxilliary Fuel Tank Installation
01-26-2012 05:50 PM  6 years agoPost 1
Doug Darby

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Dallas, Texas

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A wise old engine builder shared his wisdom with me long ago and said "All you guys are the same... You want the big Friggin fire but you don't want to put no wood on it!!!!"

which translated means that if you build an engine for more power, it will need more fuel (generally) to make gobs more power.

After I finished breaking in my new TRM VX 231 and got it set to spin about 13,200 RPM and make great consistant power I indeed did find that it consumed more "wood" (fuel).

The HWC 700 conversion comes with about a 10 oz tank that fits nicely in the frame. With my previous stock engine which was only balanced and ran very smooth at about 12,000 RPM I was able to fly it 10 minutes with a little left for good measure.

My new Power House will only allow me to fly 8 minutes and I wanted to get back to the 10 minute range. I looked at Header Tanks which are all about 2 oz and seemed like a good idea, but then I found a very nice sized Dubro (#404) 4 oz tank that fit perfectly between the frames and as I am not using the "electonics" tray that is above the main tank I decided to mount it there and add 4 oz to the capacity. I did not plumb it like a header tank but rather like an auxillary tank. (Thanks to Raja for the advice) I took the vent line off the main tank and ran it to the clunk line of the Aux tank. I then added a vent to the Aux tank. All the fuel flow to the carb is still running only through the Main tank, so If my plumbing or the tank does not function correctly it will simply fly off the main tank for 8 minutes. If it performs correctly as fuel is burned out of the main tank, it will "suck" fuel from the Aux tank into the Main tank and vent air into the Aux tank to keep the system at atmospheric pressure. I hope to get a chance to try it tomorrow when the weather improves. Here a a few photos of the tank and the install.

doug

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01-26-2012 07:10 PM  6 years agoPost 2
Carey Shurley

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Orlando, FL - USA

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good idea, if you look through the Spectra-G assembly manual it outlines the exact same procedure, although in that case the tanks are further apart.

the fact that they are stacked under the mainshaft should minimize the weight shift.

The turbine models use this approach as well although usually with 24 or 32oz tanks

no question the higher performance motors are flowing a lot of fuel

Proprietor - Gas Powered Helicopters

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01-26-2012 10:15 PM  6 years agoPost 3
fern

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Portugal

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this ideia cross my mind but, I wonder how it will work on inverted fly on low main tank level?

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01-27-2012 12:03 AM  6 years agoPost 4
rbort

rrProfessor

Franklin, MA - USA

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Looks really good Doug!
I'm sure alot of the century boys are going to like this idea

Hey as far as the inverted question from fern, its no different that it used to be without the extra tank. What should happen now is that the main should should remain 'mostly' full until the header tank is dry and then drain normally.

Flight report due tomorrow from Doug!

-=>Raja.

MA 1005 Hanson 280, 4225 flts
Spectra 27 3DMax, 3325 flts
Whiplash V1-2 Hanson 300, 1650 flts
Whiplash V2 Hanson 300, 504 flts

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01-27-2012 06:07 AM  6 years agoPost 5
Justin Stuart (RIP)

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Plano, Texas

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I see you've using one of those Dubro fuel filler valves. I've got the same valve mounted on the back of my Spectra. They are a nice little piece of equipment. But if you don't hold your hand on the valve tip when you're filling your tank, the valve tip can slip off and you will then squirt fuel all over the place. I learned that the hard way many years ago with a plank that had a Sullivan valve through the side of the fuselage. Of course that was with a high powered electric fuel pump (and I think everyone is using hand crank fuel pumps these days), but it could have been disastrous if it had sprayed in my eyes.

Avant RC
Scorpion Power Systems
Thunder Power RC
Kontronik Drives

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01-27-2012 12:41 PM  6 years agoPost 6
Doug Darby

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Dallas, Texas

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The valve has worked perfectly for about 100 flights and I do use an electric filler. So far the valve has stayed attached with no extra effort. Hope it continues.

doug

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02-20-2012 02:51 PM  6 years agoPost 7
Doug Darby

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Dallas, Texas

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Finally!
I finally got to fly my 700 with the Aux tank installed and it worked perfectly. Gave me an increase of 4 minutes minimum to get from 8 min back up to 12 minute flights. I still had one third left in my main tank at 12 minutes and the Aux tank was empty.

It worked fine in all orientations for any amount of time.

A nice upgrade for an HWC 700.

doug

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02-20-2012 05:09 PM  6 years agoPost 8
rbort

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Franklin, MA - USA

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Excellent Doug!
And enjoy it! I got the same dual tank setup in my fpv taylorcraft total 34oz fuel between two tanks and I flew it for 1 hour last week, landing with about 1/3 of the main 16oz tank remaining

-=>Raja.

MA 1005 Hanson 280, 4225 flts
Spectra 27 3DMax, 3325 flts
Whiplash V1-2 Hanson 300, 1650 flts
Whiplash V2 Hanson 300, 504 flts

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03-06-2012 11:38 AM  6 years agoPost 9
blade77

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N. Ireland

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Refuelling aux tank
When refuelling do you have to fill both tanks seperately or will the aux tank fill from the primary tank after it fills up?

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03-06-2012 03:27 PM  6 years agoPost 10
rbort

rrProfessor

Franklin, MA - USA

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Fuel
Primary tank will flood into the auxillary tank after its full.

Aux tank will flood out the vent when its full.

-=>Raja.

MA 1005 Hanson 280, 4225 flts
Spectra 27 3DMax, 3325 flts
Whiplash V1-2 Hanson 300, 1650 flts
Whiplash V2 Hanson 300, 504 flts

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03-06-2012 03:34 PM  6 years agoPost 11
spiderco

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Henderson, Nevada

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Raja,

Are using a felt clunk on both tanks or just on the auxiliary tank?

fly til its dry

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03-06-2012 03:39 PM  6 years agoPost 12
rbort

rrProfessor

Franklin, MA - USA

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Just the main tank
The auxillary tank is not as important, it will empty first and have a chance through the rest of the flight to suck in bubbles and the rest of the fuel over time from flips and such.

Remember that its backwards from nitro. The original tank is still the main tank. It just overflows into the aux extra tank. When you run, the vent of the main tank draws fuel from the aux tank to keep it full while the aux tank drains.

Do it exactly like I told Doug to do it above and it will work great for you. I have the same setup on my taylorcraft (can fly for 1 hour with reserve on 16oz main and 18oz aux) and have done it in the past on autonomous or aerial photo helis.

-=>Raja.

MA 1005 Hanson 280, 4225 flts
Spectra 27 3DMax, 3325 flts
Whiplash V1-2 Hanson 300, 1650 flts
Whiplash V2 Hanson 300, 504 flts

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03-06-2012 03:41 PM  6 years agoPost 13
spiderco

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Henderson, Nevada

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Thanks, I've got a spare header tank laying around for this. Extra flight times are always welcome.

fly til its dry

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03-06-2012 06:22 PM  6 years agoPost 14
blade77

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N. Ireland

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Yes thanks for the great info raja - I'm gonna rig this up on my heli too.

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01-12-2013 03:43 PM  5 years agoPost 15
Doug Darby

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Dallas, Texas

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Updated photos by request...
Here are the photos of the tank installed and plumbing...

doug

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01-14-2013 02:33 PM  5 years agoPost 16
marke

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hamburg NY USA

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Doug, thank you again for posting these-where do you have the vent go?

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01-15-2013 08:04 AM  5 years agoPost 17
Toddc72

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weed,ca-usa

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Doug

It looks like the filler is in between the tank and the feed line to the carb? Be careful on this setup. May not have an effect on a lower drawing of fuel in a heli but with us in the boats that is the worst place to put it. Problem is that is usually not made to have a suction pulled on it. What happens is it opens the valve and pulls air into the carb. Causing lean out. Have had tons of customers call with lean conditions only to find that they are running a quick fill in the feed line to the carb. By pass it and all is well. Just something to keep in mind.

Todd

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01-15-2013 02:00 PM  5 years agoPost 18
Doug Darby

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Dallas, Texas

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Marke,
The vent has a coil of fuel tube that is open to the atmosphere to allow air in as the fuel is consumed. It can be put anywhere and connect to nothing.

Todd. No issues yet with mine but its good to know so I can watch for it.
Thanks.

doug

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01-15-2013 02:46 PM  5 years agoPost 19
marke

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hamburg NY USA

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by chance will fuel leak out of the vent if inverted?

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01-17-2013 04:08 PM  5 years agoPost 20
Doug Darby

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Dallas, Texas

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With a couple of loops of tubing it will not... I run one loop on the vent line and never noticed a bit...

doug

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