Webra fuel pressure regulator Order No. 3712 - RC Universe

Webra fuel pressure regulator Order No. 3712If a high-performance motor is employed in a model helicopter, it isnormally virtually impossible to set up a regulated fuel supply. TheWebra pressure regulator solves this problem by ensuring that thecarburettor is fed an adequate quantity of fuel commensurate withany throttle barrel opening. This is achieved by pressurising the fueltankby means of a connection to the motor’s crankcase (backplate).This means that fuel is supplied at adequate pressure to the pressureregulator, which in turn passes it on to the carburettor underregulated flow conditions. The pressure regulator itself is also connectedto the silencer, and it is silencer pressure which controls thefuel regulation process, i.e. the quantity of fuel supplied to the carburettorvaries according to motor speed: carburettor closed - less fuel;carburettor open - maximum fuel supply. The unit can be attached tothe motor lugs using the mount supplied.The Webra fuel regulator is proof against methanol and easy to maintain. It is not suitable for petrol!Assembly1. The first step is to set up a pressure connection between the motor's crankcase and the fueltank,once you have ascertained that the tank itself is suitable, i.e. is strong enough to withstand the increasedinternal pressure (0,4 to 0,5 bar). This selection describes the method of assembling thepressure line connections and completing the fuel feed connection:a) A pressure nipple has to be installed in the crankcasebackplate. First remove the backplate from the motor.Mark the centre of the backplate and drill a 3.2 mm Ø holeat this point (Fig. 1). An M4 thread now has to be cut inthis hole using a tap. Carefully remove all rough edgesfrom the threaded hole (metal particles must not be allowedto get inside the crankcase - potential motor damage!),then screw the pressure nipple (supplied in the set)in the hole in the backplate from the outside. Set the nippleflush with the inside of the backplate (Fig. 2), then tightenthe nut (7 mm A/F) to secure the nipple. A drop of metaladhesive (Loctite thread-lock fluid or similar) can also beapplied for extra security. Clean the backplate carefully,then re-install it in the crankcase. Make sure the backplateis positioned correctly!Fig. 1Fig. 2b) Connect the backplate pressure nipple to the one-wayvalve, and the valve to the fueltank pressure nipple.Please note that the maximum length of the tube betweenthe backplate pressure nipple and the one-way valve is 10cm (Fig. 3).Fig. 3c) Note that the one-way valve must be the right way round:the direction of pressure flow is indicated by the arrow “>”,which must point towards the fueltank (Fig. 3).1

2. The recommended method of mounting thepressure regulator is to use the mountingplate supplied (Fig. 4), which can be securedon top of one motor lug using the standard retainingscrews. The example illustrates onepossible option for which there is space inmost model helicopters. This method ofmounting ensures that the pressure regulatoris located in the immediate vicinity of the carburettor.The shorter the link to the carburettor,the more reliable the system! The pressureregulator itself is attached to the mountingplate by fitting the pressure regulator nozzlethrough the slot, and tightening the retainingnut over the shakeproof washer. Place thepressure regulator housing in the desired positionbefore tightening the nut fully. The outletnipple on the pressure regulator (marked“OUT”) can now be connected to the carburettorfeed nipple by means of a length of fueltubing.Fig. 4Mounting plate3. Connect the fueltank to the inlet nipple on thepressure regulator (marked “IN”) (Fig. 4). Wealways recommend that you use a fuel filter; ifyou prefer to install one outside the pressurefueltank, then it should be fitted in this fuelline.4. The next step is to connect the pressure regulatorto the silencer using another length offuel tubing. The nipple for this is located onthe rear face of the pressure regulator; connectthis to the pressure outlet nipple on thesilencer or tuned pipe (Fig. 5). The pressureline should be as short as possible; do notmake it any longer than physically necessaryto complete the connection.Fig. 5For the pressure and fuel feed lines it is important to use silicone fuel tubing with an internal diameter of2 mm or larger. Once you have completed all the connections, please check each one and ensure that it issecured properly. It is a good idea to secure the pressure lines on the nipples using hose clips.Do check that the fueltank does not leak, i.e. is completely sealed. The system can only work effectively ifthe tank and the filler valve are effectively sealed.Starting the motorPressure needs to be built up before you start the motor. This is done by sealing the outlet of the silencer ortuned pipe with a finger for a few moments while you fire up the motor. Release the outlet pipe immediatelythe motor starts. When the motor is running, you will find that the carburettor needs to be adjusted; this isinevitable due to the change in fuel supply conditions.2

Fault-findingIt is important to check the pressure system from time to time. Leaks in the pressure lines may cause a lossof pressure, which will interfere with the operation of the regulatory system; escaped fuel may indicate apressure leak.If you notice a change in the operation of the regulator, the cause could also be particles of dirt in the regulatorysystem, carried by the fuel:a) Check for soiling in the pressure line from the silencer (or tuned pipe) to the pressure regulator;b) Check for soiling (oil residue, dirt particles) in the pressure line from the backplate pressure nipple to thefueltank, and also in the one-way valve.c) Check for dirt particles inside the pressure regulator, or the inlet valve of the pressure regulator.Cleaning the system: first remove the pressure regulator from its mounting, then carefully undo the fourhousing screws and separate the top and bottom sections. Check for dirt particles between the membraneand the housing section and remove them - but please be careful: when re-assembling the parts ensurethat the small peg on the valve piston faces the inlet valve, and that the small bulge of the pressure membranerests against the valve piston. Check for soiling also in the inlet valve of the pressure regulator: unscrewthe pressure nipple marked “OUT”; you will find a compression spring and a valve ball behind it.Please be careful handling these parts, as they must be re-assembled exactly in their original position.The one-way valve is screwed together tightly, but can be opened by unscrewing the knurled section of thehousing. Once again, please be careful, as there is a small compression spring and a valve plate inside thehousing. Clean the parts, then re-assemble them and re-install the valve the right way round (arrow mark).All pressure lines can be washed out using normal glow fuel.We hope that you are satisfied with our product, and enjoy using it.WEBRA Modellmotoren GmbH & Co. KGA-2551 Enzesfeld / AustriaOverall view of the system connections3

DRUCKREGLERPRESSURE REGULATOROrder No. 3712Artikel Nr. 3712/06 /05 /01/06 /02/05/043712/23./201 ./201./202/201102Replacement partsOrder No.Pressure regulator housing 3712 /01Pressure regulator membrane 3712 /02Nipple set 3712 /04Screw / nut set 3712 /05Regulator valve set 3712 /06One-way valve 3712 /20One-way valve housing 3712 /201One-way valve set 3712 /202Mounting plate 3712 /23Pressure nipple + nut 11024