Raptor 60               Raptor 30

This is an idea created by Simon Hardman from the ACE Hobby forum 'Raptormansimon'.   

All credit for this idea goes to him and it won't be long before I get down to 'Halfords' to  get hold of one to and try it out for myself........................What an excellent idea.  All the explanations below are taken directly from Simons post and lastly thankyou to Simon for letting me publish it on my site. Thanks !!!

Hi again, I have been testing my latest version of my rpm display using a cycle speedo (Model VDO Cytec08). This has a very neat magnet that fits to the bottom bolt, just remove the 4mm locknut and bolt replace with the magnet in the ROUND hole where the bolt head went add a little locktite to threads.

Magnet at the bottom of Auto unit

You need to remove approx 2mm from the end of the magnets threaded section to allow the bolt to thread into it fully as without doing so the thread stops against the shoulder of the bolt.  You also need to open up the  hole in the red gear slightly to allow the magnet to slide in without stressing the plastic.  This is just on one side of course so it sits against the shoulder.  The magnet and holder now from the nut as it has a threded section in the centre.  Use plenty of loctite !!!

During testing the heli showed no signs of increased vibration due to the magnet being used instead of the nut.

Replace bolt from the other side. You will need to make the bolt 2-3mm shorter as it hits the back of the magnet and will not tighten enough. The sensor is taken out of its plastic holder and stuck to a small square of Carbon Fibre sheet I had handy.

Sensor

Stick ideally with the thick double sided tape used with your gyro mounting, this is important as the vibration on the sensor can give false readings. This is then also stuck to the side from in between the two bolts that hold the bottom bearing on the main shaft.

The Unit is attached to the tail boom using the supplied fixings.

Display

Set the wheel diameter to 1667mm and that's it.

Accurate rpm readings can be checked in real time by just hovering near to and reading the top display, or set the unit to remember the MAX speed and you can check it when you land.  You can see my last flights max rpm was 1843.0rpm yes down to a 10th of a rpm!  The larger digit shows the current rpm which here is showing 80 rpm. display's up to 3 digits so 153 is equal to 1530rpm. It also has an Average rpm calculation during the flight which was 1284.5 rpm

It also has a neat timer that will record the flight time from first rotor turn to stop. It will also give the distance the tip has travelled which during 22mins of flying it covered 48.3km (roughly).

The Raptor 30 is slightly different in the placement of the sensor and magnet are different, the same 1667 reading is used and all the functions are the same.  

The sensor is placed on the left side frame just above the main gear and stuck using double sided tape, remember to clean the frame thoroughly with some sort of alcohol to remove any oil or mould residue. (See the picture below) Also ensure that on full negative pitch the aileron link does not interfere with the magnet.

The magnet I had trouble with, I first intended to drill the 3mm jesus bolt out to 4mm and thread the magnet on the end the same as the 60.  I had trouble drilling through the auto bearing sleeve as its hardened steel, I then basically stuck the magnet using double sided tape to the top of the main gear.

I was concerned about vibration however the magnet is so light I haven't noticed any unddue vibrations at all.  I may use a counterweight opposite just to stop the niggling doubt.  Another option is to use a smaller, lighter rare earth magnet that the scale guys use on door closures. This should do the job adequately and save messing around with counter weights.

Everything you need comes with the unit as standard All for £16.99 from your bike shop, a lot cheaper than the new optical unit from x-cell which in the UK is about £100.   It has been checked against one of these units and is as accurate.

Finally if you can't get hold of one  and would like to try I am willing to buy one and ship it for the cost of the speedo plus shipping (£23) approximately $35 USD which is a lot cheaper than a tach.  Email me, payment accepted by PayPal to the same address heliweb@ntlworld.com

Here is another tach fitment sent in by Dwayne form the Ace Forum.

For some detail on my install:
I used the SigmaSport 600.

The magnet is a tube type cylinder looking magnet that is in a plastic case.  Remove from case with a knife.  I used a dremel to route out a place to put the magnet into the mail gear.  After roughing everything up with sandpaper and cleaning with alcohol I epoxied it into the groove I made.  I
also made a space on the gear for a small piece of lead weight about the size of a hole punched out piece of paper.  Same thing for mounting that. Final balance was done on a high point by drilling small holes half way through the gear.

The pickup is zip tied on a piece of carbon pushrod I had laying around. This was the best way I could think of at the time and whatever gets it over the magnet is ok.  The computer is mounted to the tail boom with the supplied hardware.  You can see a crack in the crystal of the computer on a few pictures.  That was due to transportation and not operation.  :)

My top headspeed of last flight is clearly visible in a few pics, 1929, woo hoo.  Gotta get that down to about 1800-1850.   It's those decents in idleup2.  Wish I had a governor.

The wheel diameter is set up like all the others, 1667.  This unit cost me $17.00us and it has all the functions you would want including speed, total distance, clock, odometer, total flight time, and top speed (the most useful one).  It also has a top kph of 250 and updates fast, so you could use it up to 2500rpms!!  I checked it against a Miniature Aircraft SkyTach and it was dead on.

Drop me a line if you have any questions,   Dwayne