USS SHARK SSN-591: Refit Log 2016-09-22

[QuarterMaster]

Lessons learned from the 2016 Groton Fun Run.

1-After accounting for the mass of the additional 12V 7.5Ah SLA, and it's addition of CSF, I discover I was actually quite close to the original foam requirement. and I had left too much out.

2-2.4 GHZ worked GREAT.

3-WAAAY overpowered as evidenced by the sheared dogbone, as well as it becoming overpowered beyond "3" clicks on the TX throttle stick.


So,

A-Minor addition of CSF.

B-Program the ESC for EXTREMELY soft start (Acceleration Level 1) to minimize impact on the drive train.

C- Two inline 3:1 Gear reduction units, 9:1 reduction from Motor to Screw.

Sea trials this Sunday

Anyone recognize the 2nd gear reduction?? My SRP in action!

First Gear Reduction unit on aft Bulkhead:


2nd Gear Reduction unit on shaft support bulkhead.

[crueby]

If by any chance that was one of the white plastic Dumas dogbones, I would put part of the blame on the dogbone itself. A year or so ago the nylon Dumas dogbone in a little tugboat I have finally wore out after about 30 years of use. No problem, bought another one and put it in. It lasted about 30 feet of travel at medium throttle before the lugs snapped off it. That was with an old Dumas 6v electric motor, which could never be called a speed or power demon. Seems that the current generation of their parts are being molded very poorly. So, back in the shop with a bar of high strength nylon I obtained, and made my own replacement - fine ever since.

Okay, rant over, sorry for the distraction!

[JWLaRue]

3-WAAAY overpowered as evidenced by the sheared dogbone, as well as it becoming overpowered beyond "3" clicks on the TX throttle stick.

....and that's why I do not use Dubro dogbones. Too fragile. Use a more robust universal like the ones from SDP and it will not be a problem, nor will you need to program the ESC for a 'soft start' in order to protect the drive train. (you may want the 'soft start' for other reasons, of course)

-Jeff

[JWLaRue]

Ed,

A suggestion: Instead of chaining gear reductions why not simply remove all of the gear reductions and go direct drive by replacing your motor with one that has a lower top RPM? Right now that's adding a lot of friction resistance to your drive train. You will also get much better low RPM performance out of it as well?

I've been running all of my r/c subs direct drive for several years now...and am much happier with performance. It also gives me longer run times.

-Jeff

p.s. that 2nd drive reduction looks like a Merriman set of parts?

[bigdave]

Jeff
What in the hell is soft start?
If they don't jump out of the water right away something is very wrong! BD

[QuarterMaster]

If by any chance that was one of the white plastic Dumas dogbones, I would put part of the blame on the dogbone itself. A year or so ago the nylon Dumas dogbone in a little tugboat I have finally wore out after about 30 years of use. No problem, bought another one and put it in. It lasted about 30 feet of travel at medium throttle before the lugs snapped off it. That was with an old Dumas 6v electric motor, which could never be called a speed or power demon. Seems that the current generation of their parts are being molded very poorly. So, back in the shop with a bar of high strength nylon I obtained, and made my own replacement - fine ever since.

Okay, rant over, sorry for the distraction!

One of the newer ones, obviously a different casting material. That white stuff I see that's so prevalent now. The older ones were definitely a translucent nylon material. Regardless, I always snipped the pins off and retrofitted the with a brass rod after drilling through the "ball".

This one sheared at the narrow section, just aft of the "ball" part. Obvious quality issue.

From henceforth I'm making the from 3/16 brass stock. Easy enough.

[eckloss]

jeff, specifically what motors are you using in your boats for direct drive?

[QuarterMaster]

Ed,

A suggestion: Instead of chaining gear reductions why not simply remove all of the gear reductions and go direct drive by replacing your motor with one that has a lower top RPM? Right now that's adding a lot of friction resistance to your drive train. You will also get much better low RPM performance out of it as well?

I've been running all of my r/c subs direct drive for several years now...and am much happier with performance. It also gives me longer run times.

-Jeff

Easier at this point to add, at least to have time to continue to run this season.
When I was running the D & E 3.5, she would lose control at about a 2/3rds bell, that had 12V SPEED 600 w/3:1 Reduction. I'm swinging a 3-1/4 Solid brass prop. Now just at three clicks, ALL-STOP to WARP speed. So I figure I'll try 9:1 and see if I finally get range THROUGHOUT my throttle stick. The soft start is more of an experiment now anyway. I don't think this throttles down to stop before it reverses. Like the way the old SubTech Throttles did, or was it FMA? I had the FMA in the WTC3.5.

p.s. that 2nd drive reduction looks like a Merriman set of parts?

You win the Golden Ticket Jeff!!

[QuarterMaster]

Jeff
What in the hell is soft start?
If they don't jump out of the water right away something is very wrong! BD

If I try that Dave, she just rolls violently to port and heads into a steep dive!

[JWLaRue]

Yea, the 'soft start' is usually meant to eliminate the sudden, strong reverse torque that can otherwise occur when rapidly going from (full) forward to (full) reverse....or vice versa. I've not seen it implemented as a shallower throttle curve. I've used the capability of the Multiplex transmitters to make those adjustments.

So BD...no worries, you can still have your subs do their flying fish routine!

-Jeff

[JWLaRue]

jeff, specifically what motors are you using in your boats for direct drive?

Erich,

I use Mabuchi motors....the same ones that OTW sources for their dive modules. Alternatively, Graupner motors. In either case, you need to be sure that the max RPM is not one of those 20K speed demons!

-Jeff

[crueby]

Jeff
What in the hell is soft start?
If they don't jump out of the water right away something is very wrong! BD

That is why we keep tennis racquets handy when Dave puts his sub in the water, to whack them back in!

[bigdave]

What you want is a motor like this.
High turn made for Rock Crawlers.
Great for direct drive in a sub. Lots of torque. BD