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Author Topic: To build a K Class submarine  (Read 10441 times)

bobk

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Re: To build a K Class submarine
« Reply #105 on: March 02, 2012, 07:42:21 PM »

Not intending to upset anyone, but on Tuesday I was this close to scrapping the sub driver and completing the boat as a surface runner  -  with all the detail, including funnels. 
I can build boats, and have a ring binder bulging with downloaded ‘instructions’ and FAQ’s on the SD25.

By getting an assembled sub driver I had naively thought I could install the electrics and commission it, that the main design process would begin in adapting it to the hull and the control linkages.  After many months I established this is not the case.  Submarine expertise appears assumed and info most often thins out at the end caps. 
For me the WTC is still most of development and build work.

First area for rework is the motor compartment.
L.H. photo is from the PDF manuals,   R.H. is as supplied.
    
So different, the manual becomes what I have in my hands.  It appears I have to cut the lugs off the 4 micro servos, sticking them in with double sided mounting pads, then make an extension tray to mount the Rx and snort pump.

From photos kindly posted recently I can see that the brass ‘U’ couplers supplied should be fitted direct onto the motor shafts, but to do so requires the help of someone with a lathe.  I only expected to have to rework the prop shaft ends.  One recent posted photo showed the plastic ‘dog bones’ cut down drilled and tapped to suit the shaft.  Great idea.  Thank you.

I only ‘found out’ about magnetic couplings last week, hence my concerns as to how I was going to get the WTC out.  Unless I can source these I will buy some micro rare earth magnets and try my hand at resin casting. 

This is going to be a long build, but I will get there.

Fitting the main tube on hull bulkheads is not a problem.  Interlocking bulkheads on the hull top with locating lugs along the joins.  Non technical, just model-making.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Today I hopped in the car and came home with an Engel Type 212A, 
IMO essential to see understand and work with many design and operation aspects that are still not as clear as they ought to be by now.

Call it a development prototype for the K.
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Re: To build a K Class submarine
« Reply #106 on: March 02, 2012, 09:01:45 PM »

Dave has made some mods to the sub drivers since you purchased yours, and I think that includes resin castings to enable the servos to be mounted in with their lugs intact. Might be worth having a word with him to see if you can tune up your sub driver. He also does magnetic couplers (called kli-cons), but they look easy enough to DIY too.

Good choice on the 212.

merriman

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Re: To build a K Class submarine
« Reply #107 on: March 02, 2012, 09:46:58 PM »

Ineed, the design has matured a bit since your unit was produced. If you would address your specific questions about the current situation, your situation with the SD in hand, I'll address them in adiquate detail to get your through this.

I am are currently going through the entire SD line and are writing up-to-date instructions to accompany the product.

David
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bobk

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Re: To build a K Class submarine
« Reply #108 on: March 03, 2012, 12:21:39 AM »

David.  I would hugely appreciate that.  Your photos were very helpful.  Thank you.

The quality of parts, especially resin castings, are excellent, and I understand that continuous improvement can quickly outpace documentation.  The PDF’s I had been pointed to are the Seaview implementation, and almost entirely just of the SD assembly.

This unit is ultra compact.  If cutting the servo lugs off is what I should do, then OK.  I was unsure. 

What would really help me most at this point is a basic generic block wiring diagram showing which leads go to where, I only had wiring connection info with the ADF2 angle driver and snort pump.  Are front and rear dive planes on separate servo’s or combined?  Do planes work in the same direction or opposed?  Motors rudder and planes are on the Tx sticks, but should gas bottle and snort be from sliders or on/off switches?

Is Rx wired from main battery (I assume 6V), or separate battery pack.  Is there a recommended battery, weight being critical. 

I got the recommended WFLY FT06-A, which was an amazing price for a 6 ch 40Mhz system, but I was not able to obtain the later required Sombra Labs TL-8 receiver as they don’t make a European 40Mhz version.  I have just bought a Robbe/Futaba F14 six channel 40Mhz system to replace the WFLY which I hope will be suitable.

Do Caswell stock magnetic couplings?  I have been unable so far to find any over here.  If not I can make them.
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merriman

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Re: To build a K Class submarine
« Reply #109 on: March 03, 2012, 02:08:49 AM »

David.  I would hugely appreciate that.  Your photos were very helpful.  Thank you.

The quality of parts, especially resin castings, are excellent, and I understand that continuous improvement can quickly outpace documentation.  The PDF’s I had been pointed to are the Seaview implementation, and almost entirely just of the SD assembly.

This unit is ultra compact.  If cutting the servo lugs off is what I should do, then OK.  I was unsure. 

What would really help me most at this point is a basic generic block wiring diagram showing which leads go to where, I only had wiring connection info with the ADF2 angle driver and snort pump.  Are front and rear dive planes on separate servo’s or combined?  Do planes work in the same direction or opposed?  Motors rudder and planes are on the Tx sticks, but should gas bottle and snort be from sliders or on/off switches?

Is Rx wired from main battery (I assume 6V), or separate battery pack.  Is there a recommended battery, weight being critical. 

I got the recommended WFLY FT06-A, which was an amazing price for a 6 ch 40Mhz system, but I was not able to obtain the later required Sombra Labs TL-8 receiver as they don’t make a European 40Mhz version.  I have just bought a Robbe/Futaba F14 six channel 40Mhz system to replace the WFLY which I hope will be suitable.

Do Caswell stock magnetic couplings?  I have been unable so far to find any over here.  If not I can make them.


Bob,

I've provided below some shots that will help guide you as you install the devices on the foundations attached to your motor-bulkhead. Note that almost every item in the after dry-space is semi-permanently attached, in one way or another to the motor-bulkhead; when the motor bulkhead is installed/removed from the cylinder, the entire assembly moves as a unit. The only make up to the cylinder being the two power cables from the battery-switch harness, and the lead from the ballast sub-system servo -- other than those two items, all propulsion and control hardware is mounted to the motor-bulkhead.

The below block diagram illustrates for you how the leads between the various devices connect to one another. Note that the receiver is the nexus point for most of what is going on in the SD; it is through the receiver bus -- fed from the ESC's BEC -- that the required five-volts is distributed to the other devices that make up the system.

Never connect the stern planes and the bow planes on the same linkage. Those two sets of control surfaces do two different things: The bow planes contribute little angular moment to the submarine, but they do push the vehicle up and down -- they are used for depth control. If you're inclined to employ an ADF, that device is placed between the receiver and the bow plane servo.

The stern planes of a submarine contribute mostly a pitching moment to the vehicle (the phenomenon of 'Chinese planes' aside for this discussion), so they are employed to set/maintain/alter the boats pitch angle, the 'bubble'. Just as helicopters require some artificial stabilization and damping about the yaw axis, a submerged submarine needs autonomous control of the pitch angle. You stick the angle-keeping device (in our case, the angle-keeping leg of the consolidated ADF device) between the receiver and the stern plane servo.

Don't mix, mechanically or through the transmitter, the stern planes and bow planes.

Here's the assignment of stick/switch/knob transmitter controls to the functions aboard your model submarine:
ch-1   rudder (right stick, left/right motion)
ch-2   bow planes (right stick, up/down motion)
ch-3   throttle (left stick, up/down motion)
ch-4   gas ballast sub-system (left stick, left/right motion)
ch-5   low pressure blower/snort
ch-6   stern planes




Here's the arrangement of the devices aboard a 2.5 SD. Once thing I would change: I would put the fuse between the battery and the input side of the ESC.



You're biggest challenge is running the 1/16" brass pushrods through the motor bulkhead watertight seals. Here you get some appreciation on how creative you need to get when bending these things to make up to their respective servo bell-cranks without binding, or getting in the way of the centrally located receiver




Just some of the tools I use when bending servo pushrods to shape.



Note that the central area over the cast resin servo foundation is open, ready to accept the systems receiver.



The Kli-Con magnetic couplers -- that interface between the SD pushrods, and the control surface pushrods -- shown here. Yes, they are stocked by Caswell Inc. Note the Dumas couplers (3/16" bore) attached to the two motor output shafts. The two 3/32" tubes atop receive external hoses that lead to the ballast tank and the induction intake up in the sail -- a portion of the LPB/snort ballast sub-system.



While tweaking the bends in the pushrods to achieve minimum binding I made good use of a 'servo-setter' device. Or, you can hook up the receiver and battery, and twiddle the sticks from the transmitter as you work to reduce the drag between pushrods and watertight seal gland.



I prefer to attach the servos with RTV adhesive/sealant. This holds them fast within the cast resin foundation, put will part if you need to yank the servos out of there.





Just some of the devices that attache to the motor-bulkhead foundations. Receiver, ADF (angle-keeper and fail-safe circuits on one board), and ESC. Not pictured is the LPB pump-motor and its attached MPC (motor pump controller), and Lipo-Guard (commands a blow before the Lithium-polymer batter voltage drops below the critical (destructive) level.



Bottom aluminum sheet foundation. This is where the LPB and its attached MPC are mounted with servo tape.



An outfitted 2.5 SD. The ADF is servo-taped to the side of a servo. The Lipo-Guard is so mounted on the other side. Note that the receiver fits between the servos, atop the cast resin servo foundation. The ESC attaches to the forward face of the device bulkhead.


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Subculture

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Re: To build a K Class submarine
« Reply #110 on: March 03, 2012, 10:56:08 AM »

I got the recommended WFLY FT06-A, which was an amazing price for a 6 ch 40Mhz system, but I was not able to obtain the later required Sombra Labs TL-8 receiver as they don’t make a European 40Mhz version.  I have just bought a Robbe/Futaba F14 six channel 40Mhz system to replace the WFLY which I hope will be suitable.

You didn't need to purchase a complete new set, Bob. The WFLY 40mhz TX would work with any 40mhz receiver- the Sombra labs is popular in the U.S because it has a slew of nice features, but you can find the same range of features in 40mhz from other brands.

A cheap receiver is the Corona brand, more expensive receivers from Schulze and Multiplex are excellent performers. You do need a small receiver for your boat- just not enough space for the larger types.

bobk

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Re: To build a K Class submarine
« Reply #111 on: March 03, 2012, 12:45:10 PM »

Wow Dave, that’s what I call some mega design improvements, new layout, and incredibly is even more compact.
The connection diagram was especially useful.  I now understand how the electrics are set up.  I have set your text and full size photos in my DTP and is printed at the front of my ring binder.  Thank you.  I will call Caswell Inc next week re Kli-Cons and battery etc.

I intend using the tall aft radio mast for the snort, making it extra tall to begin with.

Subculture:   Ooops, I thought Rx and Tx units were manufacturer specific and had to be paired.   Getting the F-14 showed my determination to get this build up and working. 
If I had waited a day and seen the new Rx and ESC mounting positions . . .  !
No, the F-14 Rx will not fit in there, but would fit the other side of the aluminium plate as in the older ‘Seaview’ photos I was going by.  I will look up the other Rx types you mentioned for size and spec.
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Re: To build a K Class submarine
« Reply #112 on: March 03, 2012, 02:17:19 PM »

There can be some incompatibilities among one or two sets- some use negative shift PPM, others use positive shift. Most computer sets enable you to alter that, but the F14 or WFLY rig won't.

If you use something like a Schulze receiver, they work with either, but manufacturer specific receivers can sometimes be fussy.

I remember someone once telling me my Fleet TX wouldn't work with anything other than Fleet RX's, which was complete fiction.

The Corona, Schulze and Multiplex RX's are very compact. Multiplex and Corona tend to be synthesized, so no crystal needed.

bobk

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Re: To build a K Class submarine
« Reply #113 on: March 05, 2012, 08:39:04 PM »

Progress today !   A local engineering company machined the brass drive couplings for me, which now fit snugly on the motor shafts.  I have shortened one end lug each on the four servos and fitted them to the resin frame. 

More good news : -   Four sets of Kli-Con magnetic couplers are on their way to me from Caswell Inc.   Thank you Caswell !   

Thank you Dave, your latest design info has made all the difference.  With the old info I had, I hope you will understand and forgive me for getting confused.

I am now underway    :}  :-)  :-))

Sourcing a suitable receiver that both works with the Robbe-Futaba F-14 and small enough to fit in the space is taking longer than expected.  The Corona RP6D1 and Schulze Alpha-5.40w both might fit the bill, although the later seems hard to source in the UK.  I will need a separate battery pack for this as the 3000 mAh litho polymers specified are 11.1V.  The LiPo battery and LiPo Guard I will also have to source here as LiPo’s cannot be shipped overseas from the States.
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Re: To build a K Class submarine
« Reply #114 on: March 05, 2012, 08:48:19 PM »

The Schulze will have the edge on quality. The Corona is difficult to beat on value. I use Corona 2.4ghz kit, and it's great. I have one of their little 8-channel 40mhz dual conversion synthesized receivers too, but haven't tested it in a submarine yet. Works great in other models.

Why do you need a separate battery? You're using an ESC which has a built in BEC, that regulates the 11.1 volts down to 5 volts for the receiver and servos.

I get Lipos from Hobbyking shipped from China.  I've been happy with the performance of them. 3000mAH will give you long sailing times.

bobk

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Re: To build a K Class submarine
« Reply #115 on: March 05, 2012, 09:05:10 PM »

Why do you need a separate battery? You're using an ESC which has a built in BEC, that regulates the 11.1 volts down to 5 volts for the receiver and servos.

I didn't know that, having previously used 6V lead acid & 6V NiCad batteries in surface warships.  Using an Mtroniks Sub 10 Esc on the K.

I am a bit nervous of Lipo's, having seen one go up !   
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Re: To build a K Class submarine
« Reply #116 on: March 05, 2012, 09:35:36 PM »

I'd advise fitting a fuse. Some people are against fuses, because they consider them to be a potential route of failure. Well I work in an electrical based discipline, and everything is fused, and we don't get nuisance blowing- correctly rated fuses only blow when something is seriously wrong, which is what you want. I'd sooner have a boat dead in the water than an on-board electrical fire any day. After all a 3S 3A lipo pack is easily capable of delivering best part of a kilowatt or more.

Some electronic boards e.g. a lot of the engel piston tank controllers, don't need a fuse fitting, as they build a fuse into the PCB board in the form of a smaller copper track. AFAIK Engel are the only company that do this however.

I've been using lithium batteries for about ten years now, and they're without a doubt my favourite battery technology. What I will say is that I think it's important to balance charge the packs.
« Last Edit: March 05, 2012, 09:38:25 PM by Subculture »
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Bob K

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Re: To build a K Class submarine
« Reply #117 on: April 05, 2012, 11:31:21 AM »

The K has been on hold for a few weeks waiting for various parts.  The special Lipo-Guard from Caswell was held up in UK Customs for three weeks, but has now arrived. 

The LiPo battery I could not source from Caswell as they can't ship LiPo's overseas, so I purchased what I thought was a similar spec here.  Unfortunately it is about 3/4 inch too long for the battery compartment.  Another 'spare' to put into back stock.  I will need to search again for a 3000mAh 3s (11.1V) but this time try a 25C spec as that should be more compact.

I managed to source a small Multiplex IPD Receiver, but even this is a bit too large for the small space between the servos and the inside of the clear tube.  I might try taking it out of its case as a few mm may do the trick.  Pity I can't use the WFLY 40Mhz receiver & Tx I bought with the original system.  That fits nicely.
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Re: To build a K Class submarine
« Reply #118 on: April 05, 2012, 11:55:34 AM »

Why can't you use the WFLY system?

Hobbyking are good for lipos, they do a very wide range in different C ratings, and the prices are good. Don't over look other capacities either, for instance these 4000mAh packs are very short and stubby, unlike the 3000mAH packs which are long and slim.

http://hobbyking.com/hobbyking/store/__11612__Turnigy_4000mAh_3S_20C_Lipo_pack_Perfect_for_QRF400_.html

http://hobbyking.com/hobbyking/store/__8851__ZIPPY_Flightmax_3000mAh_3S1P_20C_.html

Bob K

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Re: To build a K Class submarine
« Reply #119 on: April 05, 2012, 12:08:40 PM »

Why can't you use the WFLY system?

I was advised from the States not to use the WFLY Rx in this application. The Sombra-Labs SL-6 is their recommended Rx, but unfortunately these are not made in a UK compatible 40Mhz version.  So, I ended up replacing the WFLY system with a Robbe Futaba F-14 6 ch, but have been trying to source a smaller Rx for it.  I may end up using the WFLY system anyway, the Rx is very compact and it fits.  Not sure what the preceived problem with it is.

I will check out those Lipo links you kindly gave, now I know more about what I am looking for.  ie:  Best 11.1V spec that will dimenionally fit in the battery compartment.  Weight may be a factor, but I will have to fit one to find out.
« Last Edit: April 05, 2012, 12:12:12 PM by Bob K »
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Re: To build a K Class submarine
« Reply #120 on: April 05, 2012, 12:30:00 PM »

Thanks for those links, especially the first one.  I have now ordered the Turnigy 4000mAh 3S 20C Lipo pack.  Amazingly compact, will definately fit inside the 2.5" OD tube, and a higher mAh rating then the one I have that is too big, plus cheaper.  The other linked LioPo was a touch too long.
Prices in US$ put me off at first knowing the States do not allow air shipping of Litho's, but I believe this is from Hong Kong.
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Re: To build a K Class submarine
« Reply #121 on: April 05, 2012, 01:45:17 PM »

The Sombra Labs is better at rejecting interference, as it's dual conversion and features pulse conditioning. Multiplex offers similar features, and the Schulze receivers are very good, but single conversion and non-synthesized.

If the Wfly fits, try it, it may work just fine. It may also work with your F14 if they're both on the same frequency.

Yes the stuff comes from China. No problems with shipping, the battery should arrive within ten days or so.

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Re: To build a K Class submarine
« Reply #122 on: April 05, 2012, 04:39:27 PM »

Do to the tight packaging of other electronic devices within the after dry-space of that SubDriver, you'll find that the WFly receiver simply does not have the noise-rejection ability to cope with that very noisy environment. It'll work fine with a strong carrier, but the moment you turn off the transmitter (signal loss), the ambient electronic arcing and sparking going on in there will swamp the WFly receiver, and the servo will simply go insane! Very unlikely to get a valid fail-safe condition with all that going on.

Andy's suggestions are valid -- based on his high knowledge and experience base. Listen to the man.

David










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Bob K

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Re: To build a K Class submarine
« Reply #123 on: April 05, 2012, 05:42:01 PM »

Thank you David.  I have bought a small Multiplex IPD receiver, but it is still 1/8" too wide and 1/8" too thick to fit in the space.  A pity Sombra Labs do not do a 40Mhz version for UK use.   I will try to find a Schulze Rx in 40Mhz, which Andy had also suggested.
« Last Edit: April 05, 2012, 05:44:22 PM by Bob K »
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Re: To build a K Class submarine
« Reply #124 on: April 06, 2012, 11:17:06 AM »

Removing the case and wrapping in heatshrink may give you the required clearance for your multiplex receiver.

The Sombra receiver is extremely compact for an 8-channel model, dimensions are listed as 37mm x 20mm x 12mm

Schulze receivers work extremely well, but are a little bigger, and looking at Dave's pictures I don't think you'll have enough room. The 8-channel Delta model is 53mm x 21,5mm x 13,5 mm

They do a smaller 5-channel model 37mm x 20,5mm x 9 mm, and that will definitely fit in the space provided.

The Schulze receivers are a bit tricky to get in 40mhz here in the UK, however Engel stock them , and you should receive your purchase within a a couple of days if you order from them. You can use standard Futaba crystals in Schulze receivers.

Another alternative you could consider. This Corona receiver is bargain basement, the resolution isn't as good as the Schulze or Sombra receiver (no big deal on subs), and I've heard from other sources that the range is not quite as good as more expensive brands. But it's synthesized, so no crystals needed and smaller than the Sombra, so it will definitely fit. I've used their 2.4ghz kit and have found that works extremely well. Price is difficult to beat.

http://www.hobbyking.com/hobbyking/store/__6440__Corona_Synthesized_Dual_Conv_Receiver_9Ch_40Mhz.html

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Re: To build a K Class submarine
« Reply #125 on: April 06, 2012, 12:40:05 PM »

Andy you are a Star !    :-))
I know there are times when you must think I seem to attract problems like a neodymium magnet.

OK.  I have a 40Mhz Multiplex Micro-IPD Rx here, got it through Westbourne.  My error in not checking dimensions first.  Measures 55.3 x 30.3 x 16.2.  Just tried it without the case, but it's still too tight even before heat-shrink.  Good idea though.

For Reference the 8 channel Sombra Labs Rx is 37 x 20 x 12.  I could maybe ‘squeeze’ in 50 x 26 x 12 max.
The Shulze Delta dimensions you quote would be too big, but the 5 channel would (37 x 21.5 x 9).  Ideally, with 4 servos + gas ballast + snort I would have liked 6 channels minimum.

The Corona sounds interesting, especially as its synthesised (no Xtal), and 9 channel, plus connector pins are on the end like the Sombra.  At 36.0 x 18.7 x 8.2 that would fit nicely.  Thanks for the link !
I assume I could use that with either my WFLY Tx or my new Futaba F-14, both are 40 Mhz.

With David’s appreciated explanation of probable interference if using the WFLY Rx as it is in very close proximity to motors and ESC etc, might it be advisable to mount the Corona Rx well forward of the ESC instead to reduce possible interference?  There is approx 85mm between the ESC and the gas switch on the next O-ringed bulkhead.    Although I do love David’s new ultra-compact electrics layout.
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Re: To build a K Class submarine
« Reply #126 on: April 06, 2012, 03:06:26 PM »

Bob,

Sorry that the current installation geometry is giving you such a problem with receiver choice and placement. When I designed the system, I only had the Sombra receivers (the SL-6 and SL-8) in mind -- not bothering to think at all that Aroosh had not provided receivers compatible on the more common European bands. Damn!

Give the WFly receiver a shot, but my experience with those things has not been a happy one.

David
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Re: To build a K Class submarine
« Reply #127 on: April 06, 2012, 03:11:01 PM »

I didn't know neodymium magnets attract problems, iron filings yes, problems no.

It should be no problem with either of those radios, although I can't say for definate with the WFLY radio, as I don't have one of those. I have used this receiver with my FC16 and my trusty old Fleet Omega 7 and it worked perfectly with both. So your good to go with the F14.

It's best practice to keep the receiver as far away from the ESC and motors as is physically possible- easier said than done in subs though, especially the small ones.

I would set things up as shown, then start tinkering if things aren't behaving well.

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Re: To build a K Class submarine
« Reply #128 on: April 06, 2012, 04:59:56 PM »

Thank you both.

No complaints on buying the 40Mhz WFLY system, at only US$89 (£56), it was about the same price as a 2.4Ghz Planet T5 here.  Just a pity about the Rx in this application, and that Sombra don't do a 40Mhz version. 

I have ordered the Corona that Andy recommended, no point in taking addtional risks over a hap'th of tar, and will wire it up with lead lengths that can mount either in the standard position or flip over to mount close to the forward end of the compartment.

When (and I don't mean 'if') this all works nicely I am sure it will encourage others to go down the SD25 sub-driver route.
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Bob K

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Re: To build a K Class submarine
« Reply #129 on: April 10, 2012, 09:16:45 AM »

Could be a long delay.  Last week I ordered a special LiPo battery and Corona receiver from HobbyKing in Hong Kong. A rapid series of confirming emails about payment received and items being packaged for dispatch.  Today they send me a confirmation that the items have been dispatched, but . . . 
"YOUR ORDER MAY TAKE UP TO 45 DAYS TO ARRIVE.".  !!!!

Whilst I accept the possibility of being held for up to three weeks in Customs, like the US LiPo-Guard recently, I sincerely hope that six and a half weeks max delivery quoted is not typical.  I was hoping for just another week to restart building. 
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Re: To build a K Class submarine
« Reply #130 on: April 10, 2012, 09:30:31 AM »

I've ordered from them lots of time. Never had to wait more than fortnight for the goods to show at this end provided the items were in stock when you ordered them. The fact that they've said your order is dispatched is a good sign.

Bob K

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Re: To build a K Class submarine
« Reply #131 on: April 10, 2012, 09:49:32 AM »

Fingers crossed Andy  O0    This is in R&D, but I'm keen to get going.
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HMS Skirmisher (1905), HMS Amazon (1908), K9 (1915), Type 212A (2002), HMS Polyphemus (1881)

Bob K

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Re: To build a K Class submarine
« Reply #132 on: April 26, 2012, 07:55:09 PM »

Some progress on this long build saga !

On 10 April I ordered a Corona RP8D1 receiver plus a Turnigy 4000 mAh Lipo battery from Hobbyking in Hong Kong, only to be emailed on dispatch to allow 45 days for delivery. Well, they finally arrived, with a time span more indicative of ocean freight. 

Good news is that the Corona Receiver just fits into the very tight space between the servos, motors and ESC.  This will be my fifth receiver bought for this build, and the final option remaining to get an Rx that would meet the high spec and noise resistance required.  Previous purchases have been the original WFLY, two Robbe/Futaba’s, and a Multiplex Micro-IPD.

The battery is proving to be more challenging.  The Turnigy ordered, based on dimensions quoted online, turned out to be too tight a fit for the sub-driver tube.  I had allowed for my estimate of the slight corner radius based on other batteries I have, but it came almost square cornered.  This LiPo now joins the one I bought from Westbourne that appeared to match the US spec but was far too large.  My ‘spares’ shelf is growing.  Turnigy single-in-line LiPo’s tend to be too long unless reducing to very small mAh.

Today a club member recommended the Component Shop, saying how good their customer service was when asking unusual questions.  Their advice was spot on.  A five minute call describing the spec I was seeking, and that it had to fit inside a 60 mm ID tube in a space 130 mm long.  He even measured the diagonal for me.  I now have a 2800 mAh S1 25C that will fit the space ordered due to arrive within 48 hours.

Best part was they even asked what type of connector I wanted, and it is coming fitted with that.
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HMS Skirmisher (1905), HMS Amazon (1908), K9 (1915), Type 212A (2002), HMS Polyphemus (1881)

Bob K

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Re: To build a K Class submarine
« Reply #133 on: April 26, 2012, 08:39:08 PM »

Silly Question?

Going "LiPo" still causes me concerns, especialy for underwater use.  Looking online I can get standard 9.6V NiMh packs of almost identical mAh capacity that are almost identical in size to this 11.1V Lipo.    In this case why use a LiPo at all?  An NiMh can be charged in situ, operated with a magnetic switch obviating lake-side dismantling, and is unlikely to catch fire if it gets wet or upset.

I have a 2800 mAh NiMh running twin motors in my destroyer that happily sails for hours on a charge
« Last Edit: April 26, 2012, 08:42:30 PM by Bob K »
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Re: To build a K Class submarine
« Reply #134 on: April 26, 2012, 09:11:28 PM »

Sorry to hear the battery was too big. Always worthwhile making a simple cardboard template of the pack and double checking to see it will fit in easily.

Lipo offers greater energy density than NimH, and can generally deliver a lot more current. Also, although the packs may be similar in size, I would expect the NiMH pack to weight a lot more, so this could upset the balance of your boat- note I said could, not will.

Bob K

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Re: To build a K Class submarine
« Reply #135 on: April 26, 2012, 09:36:37 PM »

Thanks Andy.  It was my estimate on the corner radii added to the H x W x D dimensions given, I knew it would be a close.  Sadly too close to fit.  Pity, it is a nice 4,000 mAh pack.

If you recommend I stick with the LiPo then I will do that.  I am not sure what the design weight should be, but at least with a slightly smaller pack I can add ballast if necessary.  This is all R&D after all.   Hopefully starting assembly and wiring very soon, with pictures or course.
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Re: To build a K Class submarine
« Reply #136 on: April 26, 2012, 11:41:58 PM »


http://hobbyking.com/hobbyking/store/__11612__Turnigy_4000mAh_3S_20C_Lipo_pack_Perfect_for_QRF400_.html

Thanks for the tip on this.......I would love this in my Gato! I will file this for future use (after my current LiPo die off).
Cheers,
Tom
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Re: To build a K Class submarine
« Reply #137 on: April 27, 2012, 10:26:27 AM »

Unfortunately a bit too chubby for the 2.5" subdriver.

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Re: To build a K Class submarine
« Reply #138 on: April 27, 2012, 06:46:55 PM »

Oh, I was just looking at the depth (length). Guess I should have looked at all the dimensions! Thanks for the heads up!
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Bob K

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Re: To build a K Class submarine
« Reply #139 on: April 28, 2012, 11:15:40 AM »

Highly impressed with www.component-shop.co.uk.  New LiPo ordered late Thursday.  Arrived this morning.
Fits inside the 60 mm ID tube nicely.

Question:  I assume the 4 pin Lipo socket on the battery (R/Bu/Y/Bk) is used purely for monitoring whilst charging ?
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HMS Skirmisher (1905), HMS Amazon (1908), K9 (1915), Type 212A (2002), HMS Polyphemus (1881)
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