Review - Thottle Jockey Pro
last updated 4-5-2004

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1. Setup
Before I begin, I have to say that the support Paul of Model Avionics gives to his products is top notch! I have seen many times on forums where he quickly responds to questions about the Throttle Jockey. You do not see that very often at all were the designer is actively helping in the public forums. He is also very quick to respond to questions emailed to him. I think that says a lot about him and his products.

What is a governor? No, in this case it does not refer to a politician :) hahaha In our r/c hobby this refers to a device that monitors the engine speed and controls the throttle servo to maintain a set speed. So why is this important? In helicopters a constant head speed gives consistancy in performance. Also it is critical to peak tail performance. For every hundred rpm you loose on the head the tail will drop over twice that! So how does a governor work? In the case of the TJ Pro it uses a magnetic sensor that is placed under the engine fan. In the fan you mount a magnet that is included with the governor. As the fan turns the TJ Pro counts the number of times it passes the sensor per minute. This gives the rpm of the engine which is used to calculate the rpm of the rotor blades. The governor actively controls the throttle servo telling it to increase or decrease the throttle to maintain a constant head speed.

Okay, now we have got some of the basic questions out of the way so lets look at what you get and what you need. In the picture on the left you can see several items are included. The primary item is the governor itself (no that is not a CSM 560 Micro gyro, yes that is the same case). Also you get some extension servo wires to run from the TJ Pro to the receiver. The previous version had these cables soldered directly to the governor. I like the use of standard extension cables so if you damage a cable you can easily replace it. In with the roll of cables is the magnetic sensor. The kit also includes two magnetics, two zip ties, foam mounting tape, heat shrink tubing, 30 size mounting bracket, 60 size mounting bracket, and the instruction sheet. The only item you will need during installation is some CA glue. Optional items are a high point balancer, counter weight, and an extra channel on the radio.

The first thing you do for installation is install the magnet(s). If you do have the stock plastic Raptor 30/50 fan then you will notice two places on the underside of the fan specifically made for the magnets. For other fans you will have to drill your own holes. Before you glue the magnet(s) in place you have a couple of questions to answer. Do you have a high point balancer to check the fan? And if you do then do you want to use one magnet or two?
Step A: No high point balancer. The engine spins at more then 10,000 rpm when running and any off balance will create a lot of vibration which can cause tuning problems, gyro problems, and decrease the life span of some components. I highly recommend balancing the fan after you install the magnets. Now if you do not have a friend with a high point balancer then you will need to install both magnets to try to keep the balance equal. You need to install them opposite polarity of each other. First test fit the magnet in the hole, it should have a close fit. So mix up some 30 minute epoxy and put a small amount in the hole in the fan. Do not put a lot otherwise you will not be able to get the maget in all the way. TIP: If you drill a small through hole in the magnet hole then the excess glue can come out as you push the magnet in. After you have one magnet installed you need to find the side of the 2nd magnet with opposite polarity. Place the magnet against the first one you installed. Find the orientation that causes the magnets to push away from each other. Then install the 2nd magnet with this orientation.
Step B: You have a high point balancer. Find out if your fan is currently unbalanced. If you do then install the magnet opposite of the heavy side. TIP: Be aware that the threads in the fan hub can offset the cones of the high point balancer. Rotate the fan hub 90 degrees and test again. If you come up with the same results then the threads are not interfering with the test. If you have a 2 stroke engine and choose to install only one magnet (like I did), then you first need to determine the correct direction to install it.
Temporally hook up the governor. Unplug the throttle servo from the receiver. Take one of the extension cables and plug it into the throttle channel on the receiver. Connect the other end to the 'THR' plug on the governor. Next plug the sensor into the 'SNS' plug on the governor. Now hold one side of the magnet near the top of the sensor. This is the side with the slop (side facing the left of the picture shown here). When you have the correct side of the magnet facing the sensor you will see a red LED light up on the governor. Read the section in step A for tips on installing the magnet. Now check the balance of the fan. If the fan is not balanced you will need to do one of two things. Either install the second magnet or some other counterweight opposite of the heavy side. I chose to install a set screw in mine and keep the second magnet in case I needed to use the governor on another fan later on. If you do install the second magnet you have to make sure the polarity of the magnet is opposite of the other one. Now keep in mind this is unless this setup is installed on a four stroke engine. They run at half the speed and so both magnets need to be installed with the same polarity and exactly 180 degrees from each other.
Now that you have the magnet(s) installed and the fan is balanced then you need to determine which mounting bracket to use. On the Raptor 50/60 you use the larger of the two brackets. For the Raptor 30 you use the smaller one. Sit the sensor on the top of the bracket and gently bend the three legs down the side of the bracket. Make sure you get the slopped side of the sensor on the top. Place the heat shrink covering over the bracket and apply some heat to shrink it. I found the heat shrink that came in my kit was long enough that I cut it in two and just used half. Next with the sensor flatly mounted on the top of the bracket apply some CA glue at the corner between the bracket and the sensor.
In the picture on the right you can see the bracket is installed under the two engine mount bolts. Also notice the bracket is installed on the opposite side of the muffler. Position the bracket so that the sensor is inline with the magnet under the fan. Rotate the fan a full turn to confirm you do have clearance from the sensor. You do want the sensor close, but not so close that it hits something under the fan.
Next you need to finish installing the electronics. Start by finding a good location to mount the governor. In the picture on the left you can see that I mounted mine on top of the battery. This area on mine has a good degree of vibration dampening due to the way I use the weather stripping tape and rubberband. Some people mount the TJ Pro on the top of the servo tray just in front of the pitch arm. In the event of a crash this might be a bad location (crashes have variable damage so this is just something to think about). In the picture on the right you can see I routed the sensor wire up and over to the through hole at the back of the servo tray. This then came around the left side and over to the 'SNS' plug of the governor. From a previous step you should already have one extension cable from the throttle channel of the receiver to the 'THR' plug on the governor. Next connect the throttle servo to the 'SRV' plug. If you do not have a spare channel on your radio to control the governor (See Tip #1) then you will use the manual pot on the TJ Pro. However if you do have a spare channel then you can remotely turn the governor on/off as well as have a combination of head speeds. Note: If you have all the receiver plugs filled up and you need a place to connect a battery monitor then connect it to the 'ACC' jack on the TJ Pro.
The instructions that come with the TJ Pro step you through the radio setup of most of the popular radios so I won't duplicate this here.
At this stage you now have everything hooked up and you are ready for calibration. The instruction manual on page 3 covers this well so it would be best to refer to this for the steps. Where some people mess up here is with digital trim radios, you need to hold the throttle cut button/switch during the entire calibration process. The reason you hold the throttle cut during the TJ Pro calibration is to show it the entire range from engine off to engine full throttle. If you did not hold the throttle cut down then the TJ Pro would only see a range from 20% open to 100%.

Tip #1: If you have a six channel radio and channel 5 is used to control the gain of a gyro then there is another option. This is only for people that are good at building electronic projects. You can make a manual adjustment circuit for the gain plug on the gyro. <HERE> is one such circuit. Most of the time once you have the gain set for the gyro you do not need to adjust it anymore so a manual setting is not much of an inconvenience. You can then use the gyro function in the radio to set seperate head speeds for different flight modes.

Tip #2: For convenience you can change the length of the sensor wire to a couple of inches then use an extension cable to connect it to the TJ Pro. This will allow easy removal of the engine without having to undo the cable routing to get the engine out.

Product review: Throttle Jockey Pro by Model Avionics

First I do have to let you know my position on the use of governors in general. I think a governor is great on a well setup helicopter, however I too often see people use them to mask a poor setup. As an example in a non-governor setup if after flying two to three minutes you see the head speed is higher then you know the engine was set a little lean. With a governor you would not see this because it would lower the throttle to keep the head speed the same. Eventually the engine would get so hot that it dies in flight. A governor does not remove the need to have a properly tuned engine, you still need to do that yourself for now (there is an accessory jack for optional future devices). There are still signs you can watch for to know when you have a hot engine such as hearing pre-ignition (kinda like a metal pinging sound). Also when you do an auto the engine should drop to an idle quickly as well as when you land the engine should also drop to an idle quickly. If it takes more then five seconds or even stays high then the engine is hot.

Okay, so what were the results? Very good! I was impressed at how well it worked. Over a few weekends I would have my flying buddys tach my head speed while I performed a range of set maneuvers with the governor on versus governor off. It compared very well with my throttle curve/cyclic mix. Things like continuous flips my own mix would vary by only 10 rpm while the governor varied by 30. With continuous tic-tocs both my mix and the governor varied by 30. Then there were some combination maneuvers the governor would do a little better then my throttle curve/cyclic mix. One thing that was really nice is in a high dive or tail slide I did not have to manage the collective to keep the head speed from sky rocketing. It did much better then I could. Even with good management my head speed usually goes up a hundred or more rpm. With the TJ Pro it kept it locked in which I liked a lot. Also I have setup a lot of GV-1's for other people and the TJ Pro had better dynamic performance (more constant rpm during tricks). Also the setup was extremely easy. The GV-1 is not difficult but there are several steps you need to make sure you do.When I was setting up my TJ Pro I had everything hook up and ready for what I thought was going to take a few minutes for the calibration. Instead as I read the instruction is was basically just raise the throttle stick up then back down and you are done! How much easier could it have been! Another advantage the TJ Pro has is an accessory plug for future add-on's. It also has a high frame rate mode for Super servos like the 9253/9254/94757/8700. The GV-1 does have the advantage of a display unit to set the target rpm's and a voltage monitor, however I do not see this as a big feature. I would rather use a Gem2000 for the battery monitor and as for setting the head speed you can get an optical tachometer. You can use the optical tach to check other pilots head speed that way. Actually you do not even need a tach. Just adjust it higher or lower to make the helicopter feel the way you want for the type flying you do. The feel is what it is all about anyway, not if you are running exacty the same head speed as someone else.