Victor III

[bwi 971]

While awaiting the arrival of the O-rings, I assume the come by pigeony, I designed a gearbox for the pump. This design keeps everything compact, ensuring that the motor's outline fits snugly within the pump's perimeter. A bearing was installed on the pump side, and Teflon washers were utilized to provide clearance between the moving and stationary parts. These washers, originally 1mm thick, were sanded down to 0.5mm for. Despite its small size, the gearbox is provided with openings to facilitate assembly. Additionally, Locktite was applied to the set screws of the gears.











Grtz,
Bart

[bwi 971]

The O-ring has arrived and fits perfectly. There were no leaks during the test run. Results at 3500 rpm show a flow rate of 1.2 liters per minute or 40.6 fluid ounces per minute.



Grtz,
Bart

[He Who Shall Not Be Named]

That is one well designed, kick-ass little gear pump, pal. Well done sir! The GPM is outstanding. Much backflow when stopped and the backside has a significant pressure over the front end?

Consider going commercial with this thing, Bart.

You European's are an amazing bunch.

David

[trout]

Bart, that rocks. Solid design ideas!
I could use something like this in my 1/144 Seawolf sub.

[bwi 971]

That is one well designed, kick-ass little gear pump, pal. Well done sir! The GPM is outstanding. Much backflow when stopped and the backside has a significant pressure over the front end?

Consider going commercial with this thing, Bart.

You European's are an amazing bunch.

David

Backflow, yes as expected. I hope I can eliminate this by raising the suction/discharge line to the ballast tank above the water level in surfaced condition; otherwise, I have to use a solenoid (preferably not). Regarding pressure, it required quite some effort to stop the flow by applying pressure with my finger on the discharge. I can't do it without taking a small shower.

Grtz,
Bart

[bwi 971]

Bart, that rocks. Solid design ideas!
I could use something like this in my 1/144 Seawolf sub.

It can still be made smaller too, imo. The gearpump and its downsides like the backflow, it just somthing that I need to try.
Grtz,
Bart

[bwi 971]

The WTC pushrod seals are also ongoing. I wanted to use bellows, so I tried to manufacture them myself; however, all attempts failed. The bushings in the endcap are 8mm while the pushrods will be 2mm.

The first method I tried involved using flexible resin. Although they looked good, the flexibility was not as expected, even though the wall thickness is only 0.5mm. They can be squeezed between two fingers, but it would challenge the servos. The fatigue test was not good; they broke after being bent a few times."





Then I came up with the idea to cast them out of silicone rubber (mold making rubber). I made a two-part mold with a core. The first attempt failed because the rubber deep inside the mold refused to cure. In subsequent attempts, I placed the mold in an oven with the idea of aiding the curing process, but that didn't work either. From the pictures, it can be seen that deeper in the mold, the curing of the silicone stopped. In my opinion, this was due to the lack of silicone mass to facilitate curing. At the bottom of the mold, the silicone is cured, as the body mass is higher.



Then I decided to use O-rings. The bushings in the endcap would come with threads, and an endcap would be used to secure and squeeze the O-ring. Initially, I went for a fine 0.5mm pitch thread. That did not work out, as the threads did not align properly and were damaged when forced.







I abandoned the idea of using a fine thread and instead applied a pitch of 1.25mm. The standard thread did not work, so I started applying a larger clearance between the endcap and the bushing. Both bushings and endcaps were marked with the applied clearance to keep them identified. An additional clearance of 0.05mm seems to hit the sweet spot.

Difference between the 0.5mm and 1.25mm pitch



Different attempts one fail and two wins.





Again o-rings are on order to carry out some testing.

Grtz,
Bart

[He Who Shall Not Be Named]

The WTC pushrod seals are also ongoing. I wanted to use bellows, so I tried to manufacture them myself; however, all attempts failed. The bushings in the endcap are 8mm while the pushrods will be 2mm.

The first method I tried involved using flexible resin. Although they looked good, the flexibility was not as expected, even though the wall thickness is only 0.5mm. They can be squeezed between two fingers, but it would challenge the servos. The fatigue test was not good; they broke after being bent a few times."





Then I came up with the idea to cast them out of silicone rubber (mold making rubber). I made a two-part mold with a core. The first attempt failed because the rubber deep inside the mold refused to cure. In subsequent attempts, I placed the mold in an oven with the idea of aiding the curing process, but that didn't work either. From the pictures, it can be seen that deeper in the mold, the curing of the silicone stopped. In my opinion, this was due to the lack of silicone mass to facilitate curing. At the bottom of the mold, the silicone is cured, as the body mass is higher.



Then I decided to use O-rings. The bushings in the endcap would come with threads, and an endcap would be used to secure and squeeze the O-ring. Initially, I went for a fine 0.5mm pitch thread. That did not work out, as the threads did not align properly and were damaged when forced.







I abandoned the idea of using a fine thread and instead applied a pitch of 1.25mm. The standard thread did not work, so I started applying a larger clearance between the endcap and the bushing. Both bushings and endcaps were marked with the applied clearance to keep them identified. An additional clearance of 0.05mm seems to hit the sweet spot.

Difference between the 0.5mm and 1.25mm pitch



Different attempts one fail and two wins.





Again o-rings are on order to carry out some testing.

Grtz,
Bart

Now switch from O-rings to X-rings, and you have a winner. Good work there, sir -- we're all looking over your shoulder with rapt attention.

[bwi 971]

Now switch from O-rings to X-rings, and you have a winner. Good work there, sir -- we're all looking over your shoulder with rapt attention.

I had a look and at this side of the pond they are realy expencive....16 x the cost of the equivalend o-ring.
As replcement will be easy I will stick to the o-rings.

Grtz,
Bart

[bwi 971]

The end caps of the ballast tank are ready... Perhaps my reasoning behind making a custom water pump did not make sense. Routing the tubing inside is tricky, as the minimum bending radius of the tubing is relatively large. The last picture shows that both the discharge and suction of the pump and the lines integrated in the intermediate cap are in line. This was my aim; this way, no bending of the tubes is required. It will only require a small straight piece of tubing.











Grtz,
Bart

[JHapprich]

Neat! End product or master pre-casting?

Jörg

[redboat219]

The end caps of the ballast tank are ready... Perhaps my reasoning behind making a custom water pump did not make sense. Routing the tubing inside is tricky, as the minimum bending radius of the tubing is relatively large. The last picture shows that both the discharge and suction of the pump and the lines integrated in the intermediate cap are in line. This was my aim; this way, no bending of the tubes is required. It will only require a small straight piece of tubing.











Grtz,
Bart

Having no access to a 3D resin printer. I, would have done the piping by hand. Annealing brass tubing with a torch then eye balling the bends.

[bwi 971]

Neat! End product or master pre-casting?

Jörg

End product, did the prototyping in PLA to verrify all was ok.
Grtz,
Bart

[bwi 971]

Having no access to a 3D resin printer. I, would have done the piping by hand. Annealing brass tubing with a torch then eye balling the bends.

I would have done the same, now its 3D CAD, estimate the tolerances/clearances, add supports, slicing and hope for the best.

Grtz,
Bart

[bwi 971]

I noticed that the holes in the motor endcap are too large to accommodate an M3 thread. Instead of redoing the endcap, I decided to enlarge them to 3.5mm and fabricate M3 threaded inserts, and press/glue them in place. Eight pieces need to be fabricated.

In the endcap, the M3 bolt just drops into the hole (one of the inserds alongside).



The existing holes were opened up to 3mm; they just miss the inner edge (left 3,5mm, right 3mm).



Bushings are fabricated from 10mm aluminum rod that I had lying around.













Grtz,
Bart