7PXR Failsafe Mystery-thoughts/advice

[Grimracer]

I would take the time to update it.. the video will get you past it..

If you have any questions.. please ask here.. or.. PM me or email.. [email protected] or call or text 715-450-9889

Grim

 

[P THOMAS]

My max speed on the fataba gps reads higher then the boat speed ,

I never see the top speed as I run, just current speed. it displays top speed in the center dial. on the telem gps screen you can touch that top speed and it will reset to current speed then see if it hits that same top speed again.

 

[Jason O'Brien]

I would take the time to update it.. the video will get you past it..

If you have any questions.. please ask here.. or.. PM me or email.. [email protected] or call or text 715-450-9889

Grim

Grim, are you referring to the Tx, Rx, or GPS? I have updated the Tx to the latest. Any idea if the GPS itself has firmware???

 

[Jason O'Brien]

One of the guys on IW was running a 7 or 10PX with GPS at the recent Cinci TT and he ran without issues including a measurement of 100mph on the GPS. I have run many many passes at 140mph+ with a 4PX and a R324SBS receiver without any issues. I do have the 400mm antenna's on almost all my SAW boats. Are you running the standard antenna or a longer one?

I can only suspect there is a resonance that occurs near 98mph in the boat which causes the receiver to fault. I would suggest moving position of the receiver within the boat as an easy test.

Tyler...when you say "resonance," do you mean Rf resonance, as in matching, or a harmonic of, the Rx/Tx comm frequency, or do you mean the boat's chassis is resonating, i.e. vibrating, and screwing with the Rx's oscillator?

I think you asked for a picture of my radio box. Antenna goes vertical just aft of where the foam ends, so I have a decent amount of it going straight up. This is the "new foam," With the 7PXR it was the same, just made the "GPS hole" a little larger to accept the SkyRC unit. The Rx and GPS have foam on all sides. Battery has foam on 3 sides, then a piece of adhesive foam on its back (the side facing the right side of the tub).

I'm going to test this weekend. I'll run separate tests with/without the GPS connected and same for the power switch, then I'll report back.

Thanks again for everyone's help!!!

 

[Grimracer]

Hum.. now I am confused.... LOL.. but thats easy for me...

Keep us posted.

Grim

 

[RaceMechaniX]

Jason,

I had a very odd issue in my carbon F-Hydro TT boat where it would kill the mixture servo and only the mixture servo. The throttle servo right beside it was never affected. This was a Promodeler servo that I use in many boats for the same function with no issues. Since the mixture servo is under no significant loads I was stumped, however after the third servo died I had to do some sleuthing. Turns out in all three servo's it killed the potentiometer and the only explanation I could come with was vibration. Promodeler confirmed the suspicion. The servo was rubber mounted and in a plastic frame however it would only last 1-2 runs before it went out of control. I have since switched to Hitec servo's for both mixture and throttle in that boat and 20+ runs with no issues. I mention all this just to point out vibration and resonance can happen and it's very difficult to pinpoint. Even when you are doing your best to cushion the hardware it can still be problematic. Your radio box looks quite well organized and cushioned, but if the problem persists I would try an even softer foam to change the cushioning. Pics are of my radio box with the Promodeler vs Hitec servo's. The receiver sits in a 3D printed cushioned mount on the sidewall.

 

[Grimracer]

EPP Foam is not a great choice.. truth is foam rubber is really the best..

Grim

 

[Grimracer]

I have used this in products before.. Its the best i have ever used.. not super cheap tho..

just food for thought. McMaster-Carr

I also make a RX cover from wet suit material.. (laser cut and sew.. I will have to post a pic)

Grim

 

[Mike Cathey]

75 mhz was good..I really never had a bunch of issues with them.. but.. some years ago I use to travel around racing 1/8scale On-Road cars.. Futaba Magnum Senior truth be told..lol I was in South Dakota racing in the Midwest series.. good racing.. I was on the back straight the car had just shifted into 2nd.. and yep.. a guy with the matching Frequency turned on.. (I had the clip)... cost me a beautiful 100 dollar carbon chassis and the fun of packing up with a broken car and driving home with the cost of a few overnight stays and gas, and food.. and.. well you know.. that old chesnut.... (YES THEY HAD AN IMPOUND)

I HAVE NEVER had that happen again... not using 2.4..

END OF STORY... and PEROID.. that to me IS THE POWER OF 2.4...

Grim..

P.S. I was good too.. TQed just about every race I was in... but never won a main.. (no duration..(45min mains) story of my life!!!!LOL)

You just never knew with the 75's what might hit you. Where we race at Marysville Washington is known as twin lakes because it's two lakes separated by probably 150' of woods, brush and an access road. One of our guys lost the radio in his boat and it hit a log on the beach at Mach 10 wiping it out. The culprit? A kid in the lake next door with a cheapo hobby shop electric boat (so no one heard it) that was operating on the same frequency.

 

[Mike Hughes]

You just never knew with the 75's what might hit you. Where we race at Marysville Washington is known as twin lakes because it's two lakes separated by probably 150' of woods, brush and an access road. One of our guys lost the radio in his boat and it hit a log on the beach at Mach 10 wiping it out. The culprit? A kid in the lake next door with a cheapo hobby shop electric boat (so no one heard it) that was operating on the same frequency.

That is why I always ran the PCM radios. Nothing ever hits a square wave signal. Sold all my old stuff to Tom Folley. It was great. But I like being able to turn on my radio anytime I liked with no worries. Made it easy to race cars at the track since no one ever had your channel.
Mike

 

[Tom Foley]

That is why I always ran the PCM radios. Nothing ever hits a square wave signal. Sold all my old stuff to Tom Folley. It was great. But I like being able to turn on my radio anytime I liked with no worries. Made it easy to race cars at the track since no one ever had your channel.
Mike

I have since switched everything over to 2.4 because of the bull crap rule eliminating 85 mghz in D 3 racing in 2024 . I almost said f... it and quit racing but I enjoy the pain too much lol . I have an issue with one boat that had killed 2 Hitec.225 MG servos in a row in a matter of a few minutes. Radio is set properly for analog servos . I have installed two full size std servos now we will see what happens. Could a receiver kill 2 servos ? 6.6 volt Life battery.

 

[John Beardslee]

I have since switched everything over to 2.4 because of the bull crap rule eliminating it in D 3 racing in 2024 . I almost said f... it and quit racing but I enjoy the pain too much lol . I have an issue with one boat that had killed 2 Hitec.225 MG servos in a row in a matter of a few minutes. Radio is set properly for analog servos . I have installed two full size std servos now we will see what happens. Could a receiver kill 2 servos ? 6.6 volt Life battery.

Not likely. Most times it’s a twist in the case even using grommets or a bind in the linkage and end point bottoming out. I’ve gone back to full size servos on everything except the 20 boats. I smoked 2 micros on the 20 throttle before I realized I hadn’t reset the fail safe. I quite often turn the transmitter off first which engages the fail safe and in this case the boat was out in the water and I didn’t realize what had happened until it did it twice to brand new micro servos.

 

[bsmtboy2]

I agree with the harmonics issue, at 98 mph, there is hull harmonics that are playing havoc on your reciever, take the gps out and run it, then get one of those gps units from herzog racing that has its own power supply.......problem should be solved. Vibrations at speed can cause all sorts of issues you wont see unless your running balls out. I think there is a voltage drop due to the gps system and vibrations at speed.........boat goes into failsafe mode.

 

[Tom Foley]

Not likely. Most times it’s a twist in the case even using grommets or a bind in the linkage and end point bottoming out. I’ve gone back to full size servos on everything except the 20 boats. I smoked 2 micros on the 20 throttle before I realized I hadn’t reset the fail safe. I quite often turn the transmitter off first which engages the fail safe and in this case the boat was out in the water and I didn’t realize what had happened until it did it twice to brand new micro servos.

So turning the boat off first is a potential problem?

 

[Daniel's Racing]

So turning the boat off first is a potential problem?

No you always turn rec off first. Trans on, rec on> rec off, trans off

He just made a boo boo.

He didn't but shut trans off first. Well of course that would be loss of signal and activate any failsafes you had set. If they were over travelling mechanically it toasts the weak servos very quickly.

When you set your failsafes make sure they are not binding on the limits at all. If it flips it could be in failsafe a while before it gets picked up.

 

[Jason O'Brien]

Okay, we can close this one!!! Went well above 100mph last night with the Futaba GPS on my 7PXR without losing the flame. A lot of you had great advice, so don't throw stuff at me, but I *think* Tyler was the first person to mention vibration, then Rich Jones mentioned the switch. I had not done anything with the switch when I was having the issue, but I replaced it after reading his post. It felt silly while I was doing it, but dang, everything else was either swapped or new.

I suspect some harmonic, approaching 100mph, was bouncing the contacts in my first switch. It was one of those waterproof toggle deals. I went back to a dirty old generic "R/C rx switch" I found in a parts bin. Not Sure if there's any correlation, but I did notice a "rx status" dropout in the logs a few times when I was originally diagnosing it. I could see where bouncing contacts would cause that if the sample rate was fast enough???

I wish I knew a little more about what the logs were telling me. They have the potential to be an amazing forensic tool. Anyway, thanks again for all of your help!!!

 

[RaceMechaniX]

Great to hear Jason!

 

[Grimracer]

Awesome news!

 

[Tom Foley]

Glad you got it sorted out!

 

[Mike Hughes]

So it was a power issue. Awesome your got it. Sometimes you jsut have to change everything to figure it out. Had that on a gas boat. The carb iso block looked great, but it was leaking at full song and surging motor. We had changed everything else up to that point. Only thing left.
Mike