Blade Runner - Murrells Models

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Blade Runner


I decided to purchase the Kyosho Blade Runner kit after looking at the current boats kits on offer by the various manufactures, this one appealed to me because of it's hull design - see pictures - the surface drive system which is steer able, motor gearbox (which will allow me to tune the motor and prop better). Also after reading 'Fast Electric Powerboats' by Paul Williams, published by Traplet Publications (ISBN 1 90037102 2) this hull design seemed the best (excluding a hydro or similar)

10/01/02 Purchased kit from Howes Models along with a Hitec mini servo HS85BB for the steering. I already have a spare set of 27Mhz Radio gear and an old buggy speed controller which I will change for a proper unit once I am happy with the boat and have decided which motor I am going to use in place of the original unit.

12/01/02 Optional tune up parts purchased to improve the performance of the boat, two ballraces for the final prop shaft and a thrust bearing as well. Bought from Ripmax.
Kyosho part numbers = 94948 and 94949

14/01/02 Whilst fitting the radio gear I found out that the buggy speed controller is faulty so I will either have to use my spare plane controller (no reverse but has soft start, uses full stick travel, which will be difficult to use with a standard throttle stick on my transmitter), buy one or make my own.

15/01/02 To increase the water cooling for the motor I've fitted the next size up silicone tube, rather that the supplied size, this also means that I can remove the metal joining tubes from the hull inlet and outlet along with their grommets because the slightly larger tube fits the existing holes in the hull and seals itself - may have to put a smear of silicon sealant around the tube just to stop it moving due to vibration etc.

20/01/02 Finished assembling the surface drive unit, the propshaft is fully ballraced but the vertical steering shaft still runs on the plain bearings as supplied, may change these in the future if the bearings start to corrode. I sealed the propshaft in the hull with some silicone sealant after fitting the motor.

26/01/02 Installing the motor after running it in, run it for 10 minutes on 4volts with an aeroplane prop attached to the gearbox shaft, then clean out any brush dust using some motor cleaning fluid. Mount the water cooling coils on motor but don't cover the holes in the motor casing, screw motor in to hull - note that the angle of the prop shaft affects the angle of the propeller shaft.

03/02/02 The hull comes with a block of polystyrene glued in to the bow, I thought that this would not be enough buoyancy to stop the model from sinking if the hull flooded, so I cut some more polystyrene to shape and glued it to either side of the existing block.

27/04/02 Had to design and make a servo reverser so that the boat would steer in the correct direction as the small steering servo would only fit in the radio compartment one way around.
05/06/02 Also bought a water cooled speed controller off of Ebay

For it's maiden voyage I will attach a pop bottle to the top hatch with sticky backed velcro, just in case ! bottle is attached to the front of the hull with some string. If the boat sinks the bottle rips off of the velcro and supports the boat.

Motor upgrade - comparing the original 540 motor and gearbox with the Graupner Speed 700BB Turbo (9.6v version)

Speed 700 showing the home made motor mount and the water cooling coils. Testing will show whether the coils will keep this size of motor cool enough.

Speed 700 fitted to the boat, had to make a new prop shaft joint because the motor output shaft is a larger diameter than the original 540's.

22/03/03 Motor loading - The original motor was geared down so that it could turn the original plastic prop. With the larger more powerful motor it can turn the prop without having to be geared, this means that I get no losses in the gearbox so the boat should be more efficient. To load the motor more I have bought the Kyosho prop upgrade, which is a very light weight three bladed prop (Diameter 37mm Pitch 1.4) Testing will show how this affects the boats/motors performance. Had to wait ages for this too arrive via Ripmax, cost £30 inc postage - was it worth it ?

25/04/03 I am surprised that the 3 bladed prop made by Octura (X437/3) needed so much moulding flash removed, it would not even fit on to the dog drive until I remove some of blade, now that I have modified the prop it's probably out of balance - I will have to make up a jig to check it.

20/06/04 There are two pictures of the boat running with it's original two bladed prop. When I fitted the three bladed prop the boat would not run fast enough to plane - more investigation needed to find out what's going wrong.

2/04/15 Technology has moved on a long way in 11 years since I last worked on this boat, so I have purchased a brushless motor and will power it using 2550mAh 40C Li-Po and a 60A speed controller on 2.4Ghz.

I have fitted the motor into the original gear box with some minor modifications to the mounting holes.

PRODUCT ID: 3900-2848SL
2848SL 3900kv Brushless Inrunner (WaterCooled)
Kv: 3900rpm/v  Diameter: 31mm  Length: 60mm
Shaft diameter: 3.17mm   Weight: 153g  
Battery: 2-3S 3,000mAh+

Kit contents

2848SL Brushless motor
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