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[pugwash]

He won't be the only one who enjoys it.  Great bit of film for somebody who is building one of these.
They diont make newsreels like this anymore, mores the pity.
Geoff

[Perkasaman2]

It's a good one Geoff.   

[SinWin]

I must say! That was most interesting. Thank you so much for sharing!

There has not been very much progress in the last weeks. I'm currently working on two film projects in addition to a miniature ROV.

However, I managed to change the batteries in the MTB the other day. It rides much higher in the water, and there is something odd with the balance: for some reason it leans to the starboard, but I think I will just counterbalance it, and leave it as it is, and see what happens.

As one can see, there is a "slight" difference in size between the batteries I had, and the ones I have now!

[SinWin]

Things are happening, although slowly.

Since one of the ESCs decided to blow, I have to buy a new one. Since they are rather expensive from my local dealer, I had to wait until I could afford yet another one. I searched ebay the other day, however, and found the exact same ESC from a German dealer at under half the price. I bought that, and am currently waiting for it to ship.

Apart from that, I used my little pool and balanced the boat with the new batteries. It will need half a kg of lead on one side to be properly balanced, but there will be some weight saving after all!

[SinWin]

I've been thinking a long time about having exhaust fumes coming from the real exhaust ports, those that were above the water, anyway. However, I don't know how much smoke came from these engines? And if, how visible was it, do you think?

I came across this "high output smoker" made for RC tanks the other day, and wondered about installing it in the MTB. http://www.rccommand.com/Whats_new.php

It is possible to run it on 12 V, and it will last for one hour, they say.

[Perkasaman2]

Hi Sindre, the 2 stroke Deltics were definately  'smokers' on startup. Twin Deltics were used to power several of our diesel/electric locomotives and they were very big smokers on first startup when the engines were cold, especially during winter:

 http://www.youtube.com/watch?v=c4sQqtaJKWw&feature=related

http://www.youtube.com/watch?v=pv_cGG56QA4&feature=related

http://www.youtube.com/watch?v=CG91fYHcm-k&NR=1

The large locomotives and Nasty/Tjeld both used twin 'blown' versions of the Deltic - enjoy their soundtrack on the loco clips above. Once they were warmed up the whistle and roar of the twin Napiers on full power was unique/dramatic and less smoky.  

The smaller British Dark class mtb/mgb also used twin Deltics but they were not 'blown', however, black soot deposits on their rear hull sides was definately a problem, so the rear half of the hull was painted black to make the soot staining from their side mounted exhausts less noticeable.

Your Tjeld would demonstrate 'clagging' in Norway and  sound amazing 'thrashing' up a fiord at 50 knots.  

[SinWin]

Woah, that is some serious smoke! (And sounds, for that matter!) But if they were not "smokers" during normal operation, I guess a smoke generator would be out of place?

[Perkasaman2]

In the colder climate of Norway they would smoke continuously as the exhaust condensed/chilled......................... order a smoke unit and add extra style to a very loud sound unit for a really authentic Deltic duet. The soot is excess fuel which is partially combusted/expelled in certain running conditions, and the white smoke is unburnt fuel during cold startup and condensation while running at normal temperature. The smoke is of coarse lost/mixed in the spray and left in the wake as the boat's speed increases. 

[SinWin]

Hmm.. It is becoming more and more tempting to buy one! If it can be argued that they really did produce smoke also while running, I guess it would be pretty cool to have exhaust fumes coming from the real exhaust ports! A sound unit could be cool, too, I agree, but in some ways I think the sound (not that it's much) of the electric motors is cool enough 

[Perkasaman2]

Your motors are a personal favourite of mine and I'm wondering if one can be persuaded or tweaked to whistle and roar like a blown Deltic............. Hmmmm.        (The inbuilt cooling fan on the rear of the armature may have potential  . )

[SinWin]

He he he 

I can see why you like them, though - pure, raw power. But, may I ask what the difference between blown and not blown is when speaking of the Deltic?

[Perkasaman2]

Deltics were originally intended for marine use and designed for extended or continuous  high speed running. The turbo charged ( blown ) version was capable of 3700 bhp. Even higher outputs were possible but the engine was governed to 1800  rpm in order to extend it's service life and reliability.
The rail locomotive version was unblown (without a turbo charger) and de-rated to 1650 for use in rail locomotives, singly or in pairs to generate electricity for their electric motor drivetrain.

[SinWin]

Aha, I see! Thanks a lot for the info! I think I'll order one of those smoke generators after all. I really can't resist! (Who can?) Just have to wait until the 12th, which is payday!


I'm having great trouble with one of the channels on my sender, the left hand on/off-switch on top of the sender unit won't toggle anything. I tried the channel with different equipment attached, and I have changed the receiver (yes, the entire unit), but still no sign of functionality. I have checked the programming of the unit as well. I guess it's down to hardware failure, then?

[Perkasaman2]

Hi Sindre, which TX - make/model are you enjoying?

[SinWin]

It is a Graupner MX-12. I'm thinking I could use one of the switches for the smoke generator, if I buy it.

[SinWin]

I received the new speed controller a few days ago, and yesterday I got the chance to change it. What I did not get a chance to test was the boat on the water, as I used the daylight for trying to get my helicopter in the air. (It did, eventually, before I crashed it into a hedge after a few seconds in the air. It was either that or some electric cables....)

Anyway. Having fiddled for a long time to get the old controller OUT, I fiddled for some time to get the new controller IN. I have not yet fitted the fuse holders I got from Action RC, but I will!

As one can see there is limited space for me trying to get hold of the controllers in their position.


But I managed it eventually, and mounted the new controller differently, in a more convenient spot for maintenance, if not for cooling.


The new speed controller is of the same type as the old one, but appears to be of some new and more fancy model: it has auto set up, which is a feature I really like.

Perhaps I'll get a chance to test the boat on Saturday, we'll see.

[pompebled]

Hi SirWin,

I just stumbled upon your build thread and I have a few remarks.

Before I say something, please understand I'm only trying to help, not putting you down, but you've made a number of newbie mistakes...

1) The propshaft angle is much too steep, this is one of the reasons you fried a number of ESC's last year, a MTB is basically a fast electric speedboat, or at least it can be, when it is set-up right.
(In the fast electric department I have a lot of experience, as I'm running my boats in competition for the better part of a decade now and my fast scale boats benefit from that experience.)
The propshaft angle needs to be as shallow as possible, the way your's are set-up, a lot of the thrust is angled down, lifting the rear end of the boat.

I watched your first video and I was amazed how 'wet' it ran, with the bow pressed down into the water pushing big masses of water to both sides. (when I saw the pictures of the propshaft, it was obvious why this happened.)
This may look impressive, but puts a heavy strain on the motors; you were 'lucky' to do the first runs on Lead acid batteries, which cannot deliver the current that the motors draw under these conditions.

(I've been running 700 motors on 12 cells NiMH in the past and they do draw up to 40A getting out of the hole; once the boat is on the plane, the current drops to an average of 20-25A)
I assume you have two Graupner Best.-Nr. 3308 motors; if you look at the specs, the current the motor draws when blocked to a standstill is 75A! So it's no wonder your ESC fried under the constant load of those big props trying to lift up the boat.

Basically you're overloading the drive train big time, and when you're using a powersource that really can deliver the current (like Lipo's), the motors will fry.
When you're 'abusing' the motors, like everyone does in fast electric boats, you need to watercool them, both can and brushtabs, or you'll be buying motors for ever...

To get the propshaft angle right, you'll need long (very long) propshafts, so the motors sit way forward in the hull allowing for a shallow propshaft angle.

2) The propshafts need to be supported, both outside the hull and inside, specially when using rubber couplers, the vibration can rip the propshaft right out of the hull if it's not properly supported.

3) The motors need to be mounted on a bulkhead, using the M4 threaded holes on the front of the motor.
This also gives you room for can cooling.

If you want to keep running large props, these motors are on the edge for such a large hull, two 800 motors would have been a better choice, as they don't have to work so hard and draw less current.
Watercooled (can- and brushtab cooling) they will just get handwarm.

I'm building a slightly smaller (110 cm) Italian MTB, which is going to be powered by a fanmotor from a car, made watercooled and slimmed down (it's a heavy motor), source: the scrapheap, costs next to nothing and has the torque to turn a big prop with very modest ampdraw.

I'll add some pictures of the things I mentioned, to give you an idea of how it can be done.

Regards, Jan.

[pompebled]

Pictures.
This is the boat I'm building, notice the propshaft angle.

For my model I will use an even longer shaft to get the angle even more shallow, as the water is not scaled down, the propangle has a big impacy on the running attitude.
More to come.

Regards, Jan.

[pompebled]

And more pictures:

Here's a motormount:

With a 700 motor flanged onto it:

From left to right: Graupner 1700 Ultra, 800 motor, copier motor, fan motor.

And the fan motor with the full jacket and brushcooling:


A 700 motor with can and brushtab cooling:


The long shaft for my M.A.S., the motor is going to be at bulkhead no.5:


Regards, Jan.

[SinWin]

Thanks a lot for all your pictures and hints! I take no offence from it, I'm glad for all the help I can get. I do sincerely hope that the lightened weight of the boat will do something good, though, for reading your suggestions I see a whole rebuild!

I guess I could change the shaft angle, although it would mean cutting out a large portion of the hull, because I've glued them rather extensively. When it comes to support for the shafts, they are supported on the outside, but not on the inside. Also, changing the motor mount would be quite a job. Oh dear! I see the mounts you show in the pictures are very elegant - I've never found things like that in the shops I've visited. Where do you get those?


As far as I can remember, I bought the longest shafts I could find in the shop, according to recommendations given by the people who sold me the hull. I might still have mounted them wrong, but this was as shallow angle as I thought I could go - but I guess you're right in that it could have been shallower.

But do you suggest even bigger motors? Wow. I would have thought a pair of 700s would do fine.

So, summing up you suggest:
- shallower angle on the shafts
- water cooled motors

And, perhaps:
- smaller propellers(?)
- larger motors


Again, thank you for your comments!

[pompebled]

Hi SirWin,

The motorflange propshaft are mainly used in raceboats, where alligning the motor and propshaft can be trickym due to space limitations.
Available here:
http://www.gundert.de/ka33.htm
Gundert also makes these on demand if what you need isn’t listed, such as a longer one, with a 4 mm shaft and multiple support bearing due to prevent the shaft from whipping.

If you have access to a lathe, or have a machineshop nearby, I have the drawings of such a coupling bell on my harddrive, the measurements can be adapted to your wishes, let me know if you want it.
You can make your own.

Removing a brass propshaft isn’t difficult, when you’ve used epoxy resin to glue it in.
Apply heat to the stuffing tube and the epoxy will get soft, allowing you to pull it out, or alter the angle.
With the latter, adding a bit of glassclotht and epoxy will seal the hull again.

I have a tutorial on my harddisk for the cancooling, with pictures, pm me your emailadress if you want it.

A pair of 700 should do the job in your boat, but you'll have little reserve in terms of thermal overhead due to the relative high current, this should improve once you have a better propshaft angle and fitting props for the motorsize.

Mind you, making the motors watercooled is intended to keep the windings and the magnets cool and should not be used as an excuse to overload the motor in terms of voltage and propsize, as they will burn up, regardless of the watercooling...
So, if the 700 motors turn out to be too small for the task, bigger motors are in order.

Regards, Jan.

[SinWin]

Hm, perhaps I can try and adjust the angle, if heat is the only thing that is needed. I could use the same motor mount that I have today, only modified: if I cut off a portion of the wooden beam, I could just use that to fasten some new motor mounts to it. That way the motors will run cooler as well (more air around them). Perhaps that would be sufficient both with regards to cooling and angle?

I do have access to a small 'workshop', the only thing I need to get hold of is the metal, and if so I guess I could make some simple mounts myself. I would think the main thing is to lift the motors so that they stand up from the "ground"?

I really hoped to avoid water cooling, because I'm afraid of leaks and such, but I don't know. Perhaps I'll have to do it.

When it comes to propellers, do you have any suggestions? I have two 45 mm propellers as of today, Raboesch type "C" (as can be seen to the left here) - they are perhaps a little too big?

In the same photo I guess you can see well enough that the angle of the shafts can be a lot shallower.

Again, thanks a lot for your replies!

[pompebled]

Hi Sinwin,

Making the angle more shallow will make a huge difference in how the boat will run, lowering the ampdraw.

I would make a new motormount in the form of a bulkhead where the motors can be bolted onto, leaving room for can- and brushtab cooling.

With the cooling in place, the motorcan should sit just clear of the bottom of the hull one millimeter will suffice, more will make the angle bigger.

Installing watercooling in- and outlets in a polyester hull is very easy and very waterproof, if done right.
All my fast boats have watercooled motors (and ESC if required), none of them leak.

On a 700 motor, driving a subsurface propellor, I have not gone bigger than 40 – 42mm, if the prop is high pitched.
With a low pitched prop the diameter can be 45-48 mm but not much bigger or the motor will start to draw a lot of current.

As it’s a fast boat I wouldn’t bother too much with scale props, you can mount them for when the boat is at display, for running the boat I prefer the more efficient two bladed props.
Graupner has a nice selection.

Low pitch serie:

http://www.graupner.de/de/products/1be70983-07b5-4873-80ae-f2ebea0d8f72/451.3/product.aspx

High pitch serie:

http://www.graupner.de/de/products/1be70983-07b5-4873-80ae-f2ebea0d8f72/455.5/product.aspx

Surface drive props 2318 serie:

http://www.graupner.de/de/products/1be70983-07b5-4873-80ae-f2ebea0d8f72/2318.40,5/product.aspx

The 2318.xx series are surface drive props with high pitch which actually perform really wel in a subsurface drive, but be aware of the fact that the blade surface it big and too big a diameter will fry your motor, ESC, battery, due to excessive ampdraw, so start small!

If you make the propshaft angle smaller, make sure a 45 mm will just clear the hull (1-1,5mm), you won’t use such a big prop in a high pitched version, so this amount of cleareance will do.

Regards, Jan.

[Perkasaman2]

Hi Sindre, I do agree with pomplebled re. the need for much shallower angles on the prop shafts to improve efficiency and it would probably be well worth removing a suitable area of deck to allow the lowering and repositioning of your motors. I would buy a pair of alloy motor mounts to suit the turbo 700 motors and bolt them in position through the bottom of the hull but mounted on baseplates. It's worth remembering that prop thrust is linear and this hull is'nt a helicopter - planing requires only forward thrust. The bow will lift correctly as speed increases - true to the design of the hull. The present steep angled shafts have increased drag and obstruct water flow to the props. A much more horizontal alignment, using much longer shafts will reduce these problems and maximise thrust. I have used 45X props on these motors and cooling was not needed when running on 12 volts (twin 12v 7amp/hr sla's wired to deliver 14 amps).

[SinWin]

Smart! I'll have to get hold of a heat gun - will that be sufficient to make the epoxy weak and bendable?

The shafts I have now are 450 mm in length - would I really need even longer ones?

I think I'll start with removing the motors, cutting out the wooden beam they are resting on and then seeing how low I can mount the motors. Then I'll adjust the shafts accordingly.