Tweet
I love running mine like that, the challange of not flipping over
-
-
MAJOR MELT DOWN
Headed out to the lake Monday evening and arrived in time to charge up a few sets of batteries and make a couple runs before the sun set. The lake was nice and calm so I was looking forward to some WOT run time.
First run went pretty well, managed to record my best speed to date of 79.1 kph (49 mph) but death wobble was very much present at high speeds, I'm certain it is what is preventing me from breaking the 50 mph mark.
The boat handled, IMO, exactly the same without the turn fins installed as it did before I removed them, so I'm convinced they are really only cosmetic on this hull. I'm not suggesting pulling them off for no reason, but if you damage one, or don't like the look of them, try removing them to determine for yourself if you think they do anything on this hull.
The temps were a bit higher than normal after the run at 35 - 39 *C (95-102 *F) on Batteries, Motor, and ESC. Not problematic, but because they were higher than normal I double checked everything, including the stuffing tube, and everything seemed pretty consistent. I chalked the rise in temps to lots of WOT running.
I popped in a fresh set of batteries, and less than two minutes into the run the boat made a funny noise and stopped dead.
When I opened the hatch the smoke rolled out and I'm thinking I've blown the motor or ESC, but it smelled like melted plastic, not electronics.
Turned out I twisted up another flex cable (third one between two boats) and seriously overheated the stuffing tube (warped it)
Melted Stuffing Tube Clamp: The glob of spun plastic looks fairly solid in the picture but it is spun plastic strands, like cotton candy.
The clamp was fused together with the tray, had a tough time getting them apart. Also fused right onto the stuffing tube.
The Stuffing Tube Guide is Also Melted
Details on Damage to the Stuffing Tube and Flex
This Gives an Idea of the Area Where the Damage Occurred
I believe the binding was starting on the first run, causing the temps to increase a bit, then failed during the second run.
I don't see much in the Eagle Tree Data to suggest a problem, amp draw was pretty normal compared to previous runs, although my battery voltage did sag very quickly toward the end of the run.
This does confirm my 79 kph top speed. GPS Green - Amps Red - Voltage Blue
KevinComment
-
After twisting up another flex cable and taking out the stuffing tube and component tray with it on my Red Spartan, I decided to try running the Blue Spartan without the liner, and with the stock .150 cable.
It was like a completely different boat. Accelerated better, and seemed more stable as well with less torque roll, BUT, I can't confirm the stability and torque roll just yet because the water was too rough to go wide open throttle for more than a second or two. But it certainly seemed more stable in the rough water.
Still had a good coat of grease on the flex cable after two back to back runs, although the end nearest the collet was looking pretty much wiped clean but the lower 2/3 or 1/2 including the stub shaft had good grease on it.
I'm going to run without the liner in the stuffing tube for the next while to see how it pans out in the long run.
Temps on the batteries, motor, ESC, and stuffing tube were all between 22 - 25 *C (72 - 77 *F).
My boat is going to be shelved until I can get a new component tray, and some flex shafts from Jeff. Thank goodness for the venerable SV27, rock solid and ever reliable.
KevinComment
-
Wow that is crazy.Did your stuffing tube still have the original teflon liner in it before it melted it or was it a newer liner?
Please keep us posted on your latest spartan adventures....
Comment
-
How square is your 1/4" bore into the bushing on your strut? in the picture it doesnt look square, but I take lots of pictures and know that is very probably an illusion. I looked close at the drive line on mine, and decided to trim the brass tube only slightly longer than the original, and not insert it in the strut, and instead am relying on the grommet to seal out water and the associated vacuum effect.. Im just wondering if a little strut movement would be enough to add some resistance to the cable where it is sunk in the rear bushing..
Alternately, could it be the teflon liner spinning in the tube, heating to molten in places, and binding the cable? I wonder if it got hotter at the rear bracket because that area is more insulated, and the whole thing started from that?
Or I could be completely wrong.. just things that come to mind.. its interesting, I know you have all quality components in the drive line, did you notice any S bend like what WVGeo is talking about in his build thread?en hobbies & more.Comment
-
The stuffing tube and flex cable lined up pretty well. I also checked the "movement" at the clamp end with the tube high and low in the rear guide as per GeoVW72 (George) observation. I'm not saying George isn't on to something, but I didn't think the amount of movement at the clamp was significant enough to cause any real problems.
At this time, I'm leaning toward the idea that the tolerances are just too tight with the liner in the tube on this set up. Running 1600kv (stock) or 1700kv (my setup) on 6S is giving you 35 - 37K unloaded RPM, on a large hull, and a good size prop. I think there is enough torque twist on the .150 cable that it is scraping the inside of the liner, then it starts to abrade and/or rotate the liner causing heat.
In the case of this failure, if you look at the detail picture, and the picture showing the approx. areas the damage took place relative to the flex cable and tube. It would appear the cable started to scour the liner near the rear guide and then start to bind, then the shaft started to twist and bind even more. You can see the heat discoloration on the flex cable where it twisted. At this point the liner would have been spinning rapidly and would have been pinched tight against the inside of the tube causing enough heat to melt the plastic component tray.
The sequence of events is really just a guess, but that is my interpretation.
I'm going to try running liner free, at least until my new cables from Jeff arrive to see what happens. The problem may still manifest itself, at which point, back to the drawing board, but my initial observation trying no liner, was favorable.
Kevin
Note: I don't think the teflon liner is actually melting. Teflon has a melting point of around 600 *F and I don't think things are getting that hot. That said, the liner may be a teflon blend/composite of some type and could have a lower melting point.Comment
-
We had a great weekend at the lake. Had a chance to run most of our boats several times. The exception being my Red Spartan, I'm still waiting on parts after melting the component tray.
We got in 5-6 flawless runs with my daughters Blue Spartan. It was encouraging to do multiple runs with no issues. We were running with the liner removed from the stuffing tube and the drive line temps were consistent at around 22 - 23 *C (72-75 *F)
Then we "decided" it was time to prove out the question of which is stronger; plastic or fiberglass. My daughter made a wrong turn in front of my SV27 just as I was coming back on plane out of a corner, and I T-boned her Spartan.
The results:
Spartan 0 - SV27 1
Spartan suffered a good hole in the hull
The SV27 suffered some very nasty paint transfer
KevinComment
-
Another quick video
Comment
-
wOW...well I have to say it looks like fun but cables won't long with hopping at those rpms but what the hell...have fun, fun, fun. :0Comment
-
yeah, but oddly enough, apart from the first cable that snapped less than two minutes into the maiden voyage, the (stock) cable in this Spartan has lasted the longest and is still going strong. (running without the liner in the stuffing tube)
Our cable problems seem to be related more to binding and overheating than running in rough water.
KevinComment
-
I really wonder if these liners are PTFE/teflon or some type ofother mix. There are tons of different makes of that stuff. Only recently have we seen some of those china boats having these problems.
So you snapped the 150 I sent you but the stock is holding....had to be a liner issue or alignment.Comment
-
I agree.
I was running Octura liner so quality should not have been an issue.
I am leaning toward the theory that that the flex cable is twisting enough under load that it gets too tight in the stuffing tube with the liner installed. Removing the liner gives the flex cable some "room to breath".
Since running without the liners we have had zero problems with drive line heat or broken cables. That is not to say we won't, we have maybe a dozen runs in at most without the liners, but so far this is our best reliability. Time will tell.
As soon as I pulled the liners it was like we were running different boats, faster and more responsive on the throttle.
Keep in mind, we are pushing our boats a bit beyond "normal" running. T180 ESC and 3674 1700kv running 6S with a Prather 220 prop. That has to be putting some strain on the drive line. I'm really considering dropping back to a P215, the boat is too jittery at WOT anyway. A bit less speed would be fine for how we run, and that will help unload things a bit.
KevinComment
-
why do you guys drive the boats from in the water?Comment
-
Just works good for us.
Not sure if you can see it in the video or not, but there is a buoy about 300 - 350 feet offshore. the water doesn't get more than chest deep until you get out past the buoy.
There are docks and boat lifts along the shore so we need to get out past those for good visibility.
Sooner or later you have to go retrieve a boat, so we just wear chest waders and stand in the water just past the boat lifts, and if we flip we just walk out to retrieve the boat. Just easier than jumping up and down off the dock.
KevinComment
-
....and its fun!Comment
Comment