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[Martin (Admin)]

 
or .... https://www.ebay.com/itm/355588326442 
or .... eBay item number:355367341102

[1967Brutus]

That is one of the great questions of life...

And unfortunately, the "why" will never be explained. All we can do is walk along ALL hopeful wrong paths until we have the one that is not wrong...

I know about these telescopic shafts. There is one downside, they are to the best of my knowledge not availlable in the length that I need... Otherwise I would have ordered one long ago.

What I need is one that has a safe extendable length under load of 24 cm.
I have not yet seen them longer than 22 cm...
They are usually intended for Crawlers, so probably not that suitable for heavy loads.
Which is a real shame, since these splines look like they would slide excellently under load...

[1967Brutus]

A friend of mine made a copy of the coupling=cup out of hardened tool steel.


This evening I took the boat out for nearly to the minute exact 1 hour of sailing (I believe the runhour counter said 1 hr 1 minute). Where the brass cup severely worn away in less than 2 hours, the new cup did not show ANY detectable wear or wallowing-out after this hour.

Of course, pitch, now not being hindered by those horrible notches, responded quite a bit better (but still needs some work to improve controllability, because there's quite a bit of hysteresis) and all in all, I just had a nice evening of absolutely troublefree operation.
Engine started immediately, kept running, and seems to run better every outing...
The warm weather of the last few days was noticable in that in general the entire system consistently ran 2~3 degrees hotter than 2 weeks ago. It means that probably I need to increase cooling capacity a bit/ Most likely I will simply replace the existing 3 mm ID tubes for 4 mm ID. That will increase effective surface by about 30%, and dwell time (time the water spends in those cooling tubes, dissipating heat) by about 75%.

The cooling fan works wonders, and all in all, I am happy with the set-up.

https://www.youtube.com/watch?v=apmv7IJsEKM


https://www.youtube.com/watch?v=_6-f_VWYC54

[1967Brutus]

The engine by now has about 4 hr 20 minutes of "in-water" runtime.
I kept myself busy with tryihg to get the governor to work, but 3 things stood in the way. ome down, 2 to go.
One issue was that the throttle servo mount was rather flexible. this hs severe impact on precision of control. THat has been fixed.
Did not solve the governor issues.
on the to-do list are stil the issue of carburation, on this scale and for this purpose and fuel type, there simply are NO suitable carbs availlable. That is going to be a real chore.
The last thing is that this governor is very fast, and difficult to "tame".
The idea is, that I will fit a servo-slowdown in order to make it move so slow that the engine will follow without overshooting.

BUT...
In the meantime I got myself a digital dynamometer, and with that I managed to measure bollard pull.
She pulls in current shape and form about 1,9 kilo, and that is by all standards quite impressive...

[1967Brutus]

After some consideration, I have decided to try a reduction gear for the following reason:
The more RPM the prop turns, the more difficult the pitch adjusting mechanism moves, due to the centrifugal forces acting on the blade roots.
The engine won't run below approx 1500 RPM, and this RPM allready makes the pitch mechanism move "notchy".
Now if I could reduce that prop RPM, pitch will move more freely and controllability of the boat improves.'


Since I have basically 100% freedom of programming in the Taranis, my thought was as follows: I can utilize the centre half of the stick movement for pitch control at minimum RPM, from neutral to max in both directions. This should allow for fine control of thrust, and thus a good manouverability.
At stickdeflection above half, I can hold pitch as fixed in max position, and start adding RPM.

The downside is a higher engine RPM when towing, taking away a bit of the sound and "feel" of the boat, but that is going to be used only when actually towing so probably less important.

I ordered a planetary gear, as that does not change the alignment of the shaftline.

The only suitable gearbox I could find (5 mm in, 5 mm out) has a reduction ratio of 1:3.7, meaning at idling engine (appr 1500 RPM) prop RPM will be appr 400 RPM.

I have no idea what kind of engine RPM will still be acceptable WRT sound, but probably 3000~3500 and that should result in around 800~950 on the prop.
With a bit of luck, I can use a higher max pitch value, so I should not loose too much static pull.

It's a long road, but slowly I'll be getting there...

[1967Brutus]

Slight delay, I thought I had placed a valid order for a gearbox, but somehow, payment never happened, so no gearbox yet...
With a bit of luck, 2 weeks from now...

[Martin (Admin)]

 
         

[1967Brutus]

         

It gets worse, I repeatedly tried ordering yesterday, none of them "caught", and I am pretty bummed about that.

But the good news is, I also ordered NOT using PayPal but just my own banking service, and that one went through, even received a confirmation from AliExpress, so fingers crossed...

[1967Brutus]

Meanwhile, received confirmation that a reduction gear with my name on it, has left China...

[1967Brutus]

Still no gearbox...


But a nice meeting in horrible hot weather (32 deg C), the boat functioning as flawless as the rather stubborn pitch control allowed, no engineroom temperature issues (ventilating the engineroom with 32 deg C outside air apparently still is sufficient), no signs of overheating (highest cooling water temp 81 deg after a few minutes dead in the water with running engine), and a first (not too heavy) tow...
All in all close to 55 minutes of runtime consuming about 150 ml of fuel.

Towing, due to the not yet perfect pitch control needs to be done a bit careful, but the towing bit seems to be in a very usable spot: straight line course stability is basically as good as it gets, wider turns under power (when the towing wire is pointing other than straight aft and excerts a listing force) not causing any issues either.

The other two boats (gas powered cabin boat and the steamer) also each did about 1 hr of runtime, also flawless.
All in all a very lovely day if it would not have been zo awfully hot. Pretty exhausted...

[Martin (Admin)]

A different 'Gasoline powered Tugboat' !
 Seen about 20 years ago at Deans Marine ...
 




 

[1967Brutus]

WOW! That looks metal built?

Judging by the greasenipple on that propshaft tunnel, the window wiper mechanism being used as a rudder actuator, and what looks like some sort of Briggs&Stratton-like stationary engine engine, that thing must be HUGE...

Would love to see more about that.

[Martin (Admin)]

Found one more photo.
Sorry, the photos are all I know about it ..... anyone else?

[1967Brutus]

   Damn! That's BIG....

[SteamboatPhil]

Good grief how much bigger will it be with the superstructure 

[1967Brutus]

Personally, I would not fit a superstructure.... I would fit a seat...

[1967Brutus]

Meanwhile....

my gearbox has arrived!

Nicely made item, servicable, nothing complicated, BUT... The pinion gear, which I ordered for 5 mm shaft diameter, seems to be a press fit item, it does not have a setting screw, which is pretty weird, because the construction of the box itself would offer PLENTY of room for that. But alas, it is what it is, beggars can't be choosers, it is 5 mm and that is what is important.




A bit of a downside is that the output shaft, which I believed ALSO to be 5 mm, isn't, it is 8 mm. No biggie, the coupler that I have offers sufficient material to allow it to be drilled out.




One other thing that needs to be tackled is the flywheel adapter plate, which needs to be turned down a bit, in order to offer sufficient reach to get the pinion into the ring of satellite gears.

The 5 mm sticky-outtie part needs to be a bit more sticky-outier, so I called my lathe-kwondo Sensei, we're gonna fix that this evening.

The nice thing about planetary gears, is that they have no lateral forces, and the gear engagement being symetrically divided over its circumference, they tend to be a bit self-centering, only requiring a mount that mainly needs to be able to handle the torque, and halfway decent centered.
So installing that gearbox only requires a reasonably light bulkhead with slotted boltholes.

It really should not be a too complicated installation. Wednessday the workweek starts again, only one week this turn, so next week it should maybe take me 2 or 3 days to get the installation fixed.

[1967Brutus]

At the end of the tinker-session of this evening:



The coupler has been fitted on the output shaft. Probably a tiny burr at the threaded hole for the grubscrew, it did not want to slide home despite the bore being reamed to dimension. But I did not want to tap it home with a hammer, because that could damage the ball bearing.

The pinion was heated to appr 100 deg C, while the flywheel-adapter was cooled to around freezing, and I applied LoXeal 85-21.
Despite the temperature difference it took considerable force to hammer the pinion home.

Too late for turning down the adapter now (lathes make considerable noise when it is quiet in the evening). That will be tomorrow morning, first order of the day, and the last thing before returning to work.
Next week I hope to finish the installation before the weekend.

[Martin (Admin)]

Planetary or epicyclic .... are they both the same thing?

 What ratio?   ( Edit "1:3.7" .... Doh! )
 

[1967Brutus]

Planetary or epicyclic .... are they both the same thing?

Yup, different name, same thing.


1:3,7 was the lowest ratio I could find with these shaft diametres. It is apparently pretty difficult to construct 1:3, and the only ones I could find with that ratio had 3,17 mm shafts.
For constructive reasons I needed a gearbox with the shafts in line with each other, because initially I installed the engine as a direct drive with a straight shaft line.

I could design a 2 stage 1:2 or such, that would have its shafts more or less in line, but I do not have the means to build it and I could not find anything suitable and ready-made on AliExpress.
It would also have been much less compact, and constructive precautions would be needed to prevent lateral forces on the crankshaft output end.

So I will have to accept a much lower prop RPM and possibly a lower bollard pull. Upside is much lower forces on the conrods and big ends.

One of the downsides of the rather high RPM in direct drive, aside from the notchy pitch control, is that in neutral, due to the blades being curved, the prop causes a rather strong water movement when stopped in the water. This not only generates a considerable propwalk (the boat turning to SB on the spot continuously) but it also greatly increases the tendency to cavitate when reverse is ordered.

A boat spinning clockwise when stopped, is no good when the towing wire is connected to a tow...

[1967Brutus]

The last operations this leave period, in a week we can continue, but for now,,,

I had THIS:



but this would not provide the reach to allow the pinion to engage with the (I learned a new word ) epicyclic gears.

So I fired up the trusty old Ferm piece of crap masquerading as a lathe, and ended up with this:



The hub was turned down from 30 mm to 13 mm, over a lenght of 6 mm, so now this is possible:



Now off to work tomorrow, and I'll see you guys with more updates next week after Wednessday.

[derekwarner]

Burt....considering their size and actual loading, what type of grease lubrication is recommended for these speed reducers?........


From an earlier image, the speed reducer appears to have a ZZ [metal shield] for the output shaft bearing, which is interesting. I would have thought LLU  [plastic shields] would have been chosen due to cost minimization??


Looking forward to hearing in the improvements in propeller pitch control from this modification


Derek

[1967Brutus]

Burt....considering their size and actual loading, what type of grease lubrication is recommended for these speed reducers?........


From an earlier image, the speed reducer appears to have a ZZ [metal shield] for the output shaft bearing, which is interesting. I would have thought LLU  [plastic shields] would have been chosen due to cost minimization??


Looking forward to hearing in the improvements in propeller pitch control from this modification


Derek

Given the size, load and expected speeds (I intend to keep RPM at or below 3K for the engine, MAYBE 4K, and I doubt power will be over 100W) I would say that for the gearteeth, a simple EP2 grease should do it.
I am however in doubt whether that grease will keep the pins and plain bearings in the epicyclic gears lubricated.
Right now, I am leaning towards a heavy duty gear oil like Epona 150 or maybe 220, hoping that the agitation will make it reach those pins

The gearbox, as received, appears to have been supplied a marginal amount of grease of questionable origins and quality. I have no idea how well that would hold up in use, and I tend to not really wanting to find out.

As for the type of shields, I have always operated under the assumption that metal shields were cheaper than plastic or rubber ones...

I am pretty eager to find out whether or how much improvement this will give as well, but I am fairly sure it will.

[1967Brutus]

Got home from work today around noon, meaning I have 2,5 days to get that gearbox installed before the weekend, when there is some RC boating to do.


The gearbox came with a very marginal filling of grease of which I had zero faith that it would ever migrate through the box to lubricate the spinny bits. Especially the bearings of the epicyclic wheels worry me a bit.
Better greases are availlable, but the downside of grease is that in order to replace it, the gearbox needs dismantling and solvent-cleaning.

So I decided to "waterproof" it, and use an oil filling. If I would drill a drainport, I can replace the oil without dismantling.

There is not much volume availlable, and since I simply LIKE doing stuff differently, I did the following:

I drilled a tiny hole all the way through into the bottom of the outer gear ring, and fitted a bent tube into that hole. This hole is located in the path of the epicyclic gear wheels, and I expect each passing of a gear, to push a tiny bit of oil into that hole, creating kind of a pumping action.
A 2nd hole is drilled 90 degrees offset to the first one, but also offset to exit in the plane of the rotating gear carrier.. With a bit of luck, this creates a circulation, where the epicyclic wheels push with each passing a tiny bit of oil in an external line directing oil towards the gear carrier.




The pic unfortunately is rotated clockwise 90 deg, the left side of the pic in reality is "bottom"

EDIT: and dang.... Not only did I manage to seal up that gearbox, the oil circulation actually works... A lot slower than I hoped, but never mind that... it circulates, and that's what's important!
I have Epona Z, a heavy duty gear oil, in three viscosity classes, 100, 150 and 220. If 220 turns out running hot, I guess I'll try the lower viscosities.

[1967Brutus]

EDIT: and dang.... Not only did I manage to seal up that gearbox, the oil circulation actually works... A lot slower than I hoped, but never mind that... it circulates, and that's what's important!
I have Epona Z, a heavy duty gear oil, in three viscosity classes, 100, 150 and 220. If 220 turns out running hot, I guess I'll try the lower viscosities.

To be honest, it is not even THAT slow... I hooked up the gearbox to a cordless drill to spin it with some velocity, and it turns out, there is some frothing of the oil, making the flow pretty good visible, and If I have to estimate (based on tube ID and flow velocity) about 1 ml/min, which sounds like "not a lot", but it means a circulation time of appr 2 minutes, because there's only 2 ml of oil in the gearbox. And at least, circulation means the oil REALLY gets everywhere.

As a nice side effect, since there is no way of looking INSIDE the gearbox, the transparent piece of tubing allows for at least a visual indication (colour) of the oil quality.

Next step: Hauling the engine out.