TorqueFest

Hi Guys

I recently received my telemetry kit for the spektrum in my LST. Having cooked two engines in that last year I felt that the real time temp monitor would be a great insurance policy for my new Nova 528. The RPM sensor should help with tuning (which has never been my best skill) and as I've recently changed from twin RX batts to a single 1400 unit, the voltage display should help me gauge how much life is left before I start another heat.

I had a look at everything in the box when it came and it soon dawned on me that the length of the leads were not designed for a large RC truck. You could lengthen some of them but there's already enough spaghetti & connectors around the place. There's no way that the standard temp and RPM sensor leads will reach from the radio box to the engine/flywheel. I didn't fancy leaving the Telemetry Module in the open and I've seen reports that the semi wrap around nature of the LST flywheel made it difficult for the RPM sensor mount to position the sensor to get a good reading off the flywheel.

So this is what I have come up with as an initial solution. I hope it will help any of you who are having problems making it fit neatly.

I figured the only sensible place for it was where the rear pair of servos are, as this allows all the neccessary leads to just about get where they need to go. Fortunately I've been FOC for some time now and I have a few old servos lying around waiting to discover their destiny. The Telemetry Module is about the same width as a servo so I couldn't just drop it straight into the hollowed out casing. So I cut out an oblong the same size as the profile of the module on each side of the servo body and this held the it nicely (I'll need to cover the sides to offer some water protection) and allowed enough space inside for the connectors and then the leads could come out the top hole (I'll try and seal this with something suitable when I know everything works properly). This appears to have worked surprisingly well.

The bigger problem was getting the RPM sensor in a position where it could read the flywheel or clutch bell and be located within reach of the lead's limited length. The stock sensor mounts do not easily work with the LST's small diameter flywheel so the clutch bell is the obvious alternative. I have a couple of sheets of lexan which I have previously used to bend and mould various items with the gentle help of a heat gun. There's not much space to play with and I wnated to use an existing screw for mounting a bracket.

I came up with this modified L bracket. The base is drilled for the CSK screw and then heated with the screw half screwed in. When hot enough I tighten the screw and the lexan moulds itself to the shape of the CSK. Then I heated again and used pliers (mainly to get a good square bend around the nose of the pliers) to make the bottom and return bends. The sensor has some protrusions on the back so I placed a spacer in between and then allowed the mounting screws to tap their own threads in to lexan (I started the holes with a bradawl just enough to get the screw started).

The lead from the telemetry module to the spektrum receiver uses the receiver's battery socket and the instructions don't tell you where to re route the battery lead. I've seen someone else say (and I've had this confirmed by Horizon) that the AUX socket can be used (or via a Y lead if this is already in use) although I've found that the red two pin connector is a little wider than the 3 pin ones and my battery connector does not want to go in easily. First job tomorrow is to chop it off and replace it with a three pin connector.

It seems quite neat so far. Hopefully tomorrow I'll get the electronics working and find out if the Telemetry is as "plug and play" as the original Spektrum was. If you use your reverse servo then obviously this would not be a complete solution but possibly something to work from if you're having installation problems.

One tip with heating Lexan is practice first to get a feel for exactly how much heat you need to bend it in a controlled manner. I've found that there is a narrow margin between Viagra and lettuce leaf.

Before anyone comments on the heavily worn gears I am expecting some TiNi's in the post any day now.

ProjectLST

Great Idea! I'll have to bookmark this until I find a decent price on the unit.

bentgear

Since the clutch bell is black you may have to use the silver colored tape to allow the sensor to get a reading, or remove all the bluing from the bell so its back to a metal color and add the black tape.

I have not tested the idea yet, but have been thinking about just adding a black spot to several adjacent flywheel serrations to see if that would give a good reading.

The heat, voltage and lap timing parts work pretty good.

Ed M.

TorqueFest

Thanks ProjectLST

bentgear - I had put a silver strip on the clutch bell (although in the pics it looks dark - due to inadequate lighting in the garage last night) but now that I've run it this morning I think I might try a black strip. The outside surface of the clutch bell seems to be quite smooth and slightly polished so that it might cause a certain amount of reflection anyway. It's colour and surface is probably similar to a combination of black and silver (a sort of slightly shiny gun metal). Plus I have had some historical rubbing between a homemade secondary gear cover and the last few mm of the bell resulting in an more polished strip at the gear end. I'll try a black strip this afternoon and see if this cures the problem. If not I may have to look at painting the bell with high temp black paint or polishing it as shiny as it will go.

In operation, the Temp and voltage displays work well but the RPM is intermittent, probably due to the above issue.

One thing I have noticed (and it is mentioned in the instructions) is that the voltage dips quite a bit when the servos are in heavy use. I have recently moved from twin RX batts to single and as I use two Airtronic 358s with 200 oz each I have a rather severe case. The low voltage vibration rumble can go off momentarily each time I do a tight 180 turn of tarmac. I may go back to a twin RX batt set up and/or lower the voltage rumble level.

The temperature sensor reading is impressively close to that measured at the glow plug. The hand held unit seems very easy to use and the display is easy to read at a glance when driving condition allow. I have used the optional post that allows the display to be fitted in the aerial socket on my KO EX-10.

"Q" Could someone recommend a high temperature black paint that would be suitable for the outside of the clutch bell. I would prefer not to use anything too heavy and ideally sprayable.

bentgear

TorqueFest, please keep us informed as you learn more. For black paint you might try engine block paint from the auto parts store or grill paint from the hardware store, both are high temp.

94358's would give a pretty good draw. My memory tells me I measured them at about 1 3/4 amps under heavy load but this was a few years ago. Still got some, may redo the test. Good servos. Mix in the use of a throttle servo at the same time and the amp draw goes up there. Thats a pretty long run of small gauge wire for at the amps when you figure where the battery is located. You may want to set the battery alarm donw at 4.5 volts or so. Just have to experiment with your settings.

A tip if you go with the lap counter. It will read thru a clear window, but if its dusty that window clouds over quickly blocking the infared signal. Cut a hole in the body and don't mount the sensor right next to it or it will just dust over anyway.

Ed M.

TorqueFest

bentgear - Thanks for the tip, I'll go to Halfords (our auto specialists) but might leave the job until the TiNi's come and do both jobs at once.

Good point about the lap timer. Our track gets very dusty in summer and would be useless within a lap or two. Good job my transponder is not IR.

benifur

My Feedback: (4)

To ellimenate the Y connector you cut the switch into the +/- leads on the Male/male wire they give you. I made a new switch up, added another male lead on the out side the signal bypasses the switch. It's a built in y now that leaves the Aux open for a PT.
Horizon says you can use any port for the batt.