ZB-1, ZB-2: Scratch Build Cylinder design for limited Production by Zero Bubble.

[Davidh]

Hello Everyone,

That's a really good question, I currently have no idea about the RPM. Initial tests show that it will have plenty of grunt to get the boat around the pool. As for the "Silberpfeil" I agree, cool looking cars.especially the W125 "Rekordwagen." As for serial numbers, you know what yours will be...

The end caps are now at a point where they are pretty much done. They have had endless coats of spray putty and undercoat primer. It is time to start creation of the Silicon molds. I spent a bit of time going over the surface finish of each part, mainly the end cap and also the outer gearbox housing. Once again the save time and because I am molding a round object I will once again use the PVC pipe as the round mold wall. This saves so much time not making the box mold base that I usually create. I decided to create the outer gearbox housing first. Smaller piece and easily secured to a base of MDF and then held down with play-doh.



I just need to add plenty of play-doh and seal the inside especially the holes. I usually have the play-doh rise up to about halfway of any given hole so that the mold will have detail of both ends of the holes to be cast. After marking around the base and then taking the part out. I could then drill the required register holes around the sides of the part between the part and the wall. I also made space for where the air vents would eventually be cut.



The Blue area to the top left is where the pouring sprue will be located. The lines are the air vents between register holes. Have not places play-doh in place yet. Once that is done then a layer of silicon around the rim of the PVC should secure the hole unit and make sure that not silicon leaks.



Ready to be poured. A shot of Stoner part release even though silicon sticks to nothing else.



I didn't have enough white pigment to add to my pot of black to make a nice shade of grey that I was after. So as a result It was really dark grey. Bubbles rising to the surface and popping.



After a couple of hours I came back and the silicon had hardened. As a result could easily pull away from the base and the PVC pipe. Then after pulling out the master I could clean up and run some scissors around the outside of the mold and any excess along the sprue and vents. The Ply-doh dries out after contact with Oxygen and silicon. it is still usefull however not as Ideal as the soft stuff that comes out of the tub initially...



Repeat the process from the other side. Scrape out any left over play-doh and residual left over stuff. No need for Play-doh here. Rub up with Lanolin and slide the PVC pipe over the mould and spray with release agent. Press the master in position and pour.



Then you have two parts. Some excess silicon has made its way around the rim of the holes. This is simply run off with a knife. The white around the rim is the silicon from the base of the PVC pipe mixing with the silicon of the mold. I also have to run a knife around the rim of the base of the molds as the edges of the parts would otherwise come out a bit jagged.






First part out of the mold. The sprue tree has not been cut off the part yet. The air vents have been quite effective. There are no bubbles around the furthest edges of the parts.
I am happy with the result.




David H

[JHapprich]

Cannot see all the pictures, only the last 3

[Davidh]

[Davidh]

Hello all,

Lul in Christmas day proceedings. Its 9 pm here and everyone has gone home. It's been cool for summer only about 20 degrees and rain. Anyway I decided to get on with this post and complete the pics that did'nt seem to come up last time. So as can be seen the last installment was the outer casing molds have been completed and the first parts have come out.






I am happy with the quality of the parts. Now it is onto the development of the main end cap. Once again I used the PVC pipe method to create a round mold. I just needed to cut out areas around the bast to fit the extended profile of the surface that mates onto the front housing. This would mean cutting into the existing base that I used for a previous end cap design.

I then went through the same process of mounting the end cap in position. Using Play-doh to fill in gaps and holes and pushing around the sides to fill. The end cap has the inside facing upwards. I placed a small amount of play-doh inside the horizontal holes inside the support arms that come out of the end of the end cap. This ensures that no silicon joins up from either side creating a joint that would make it really hard to get piece out. This is unlikely as the air bubbles would'nt be able to escape and would cause the silicon to stop short. Then taking a piece of PVC and using some silicon to press it down on the base. Once done I could then pour the silicon.
Once done this was the result.



The second mold is easier than the first. All I had to do was massage the mold with lanolin and place the master back in the mold. Then place the PVC pipe over the top and repeat process.



Once this mold is created I can then cut the sprue and air vents leading to the outside and create the first parts.



A new end cap mean't the creation of a new holding fixture for the lathe. This has to be created for each end cap in order to machine it to a precise fit for each end piece of lexan.

Next week.

David H

[Davidh]

Hi all,

As David Merriman and Bob Martin have mentioned, each end cap needs to be machined to a specific piece of Lexan. As soon as I bought my second piece of Lexan this was confirmed to me. Even though both were 76 mm OD they both weren't quite 76mm OD. So pick an end of Lexan and machine cast end cap to that diameter. I have to say I have become reasonably proficient at this. I have yet to under machine a cap and have to throw it away when the O rings simply don't compress enough..

So once again I created a wooden fixture for the lather to machine down the radial flange of the end cap to fit.This simply bolts to the Face plate of my lathe and after spending sometime with a dial gauge checking for centricity (yes , I made that word up and It's awesome) I can start machining down the radial flange to be a snug fit with piece of Lexan I have chosen.



Fixture shown without the bolts for the end cap. Below complete and ready to put on the lathe.



Then machining does't take long as I usually only need to take off a small amount.



First one "O" ring groove cut. then press fit over the lexan and check that it's not ridiculously tight. Then machine that Groove a little more if need be. then repeat process with second groove. There have been times where an air bubble has created a cavity right in the middle of the flange. This has called for the grooves to cut not in their original locations. This has sometime mean't that I have had to cut into the front face a little further to create a groove not compromised by the cavity.



I have still to work out how to get the air bubbles out of the dead end that is the support arms coming out the back.



Once the flange and grooves have been machined the end cap can be taken off and checked with the lexan. You do want to make sure the fit is what you want before taking it off the fixture as re-centering it can't quite guarantee that it will be exactly aligned like before.



Here the Oil-lite flanged bushes have been placed as the backstop for the shafts and the rest of the gearbox can be assembled from here. This principally means machining and creating the two drive shafts and gears. I have to drill a small 2mm hole through the 6mm stainless steel shaft. This is a pain. I have cobalt drills running at low speed but it is still a drama. Anyone got any good tips for this one? This dome so that a small locking pin can go through the gear and the shaft to lock and stop the gear from slipping. The pinion gear is attached to the motor and the 2.3mm screws are securing it to the back of the end cap.




Here all the components are in place. The 6 mm shafts have been assembled and the silicon sealant has been run around the rim to seal the unit final assembly under the outer housing.



All that needs doing is the assembly of the outer seals around the two 6 mm shafts and then testing and fingers crossed. I don't think the one shown below would work too well. Might leak.



David H

[He Who Shall Not Be Named]

Glue a piece of #200 grit sandpaper to the face of that bulkhead holding fixture and it will help to prevent the work from sliding around as you start in on the lathe work.

And I love the cut-away of the motor bulkhead with attached bearing-seal cup. Most informative.

Excellent work, pal!

David

[JHapprich]

Concerning drilling: i use standard (black) bits that received a much pointier edge on the grinding stone, say 45 degrees plus wd40.

[Scott T]

What if you mold in a centered hole part way through the casting, then use it for aligning on your turn fixture.

Drill holes

[Davidh]

Hello all,

Thanks Scott, Jorg and David. I will be taking the advice on board.

Entering the final stages of this Build as this is the final assembly of the last of the three end cap configurations. Now it is down to the assembly and testing of the ZB-1/2 unit. From here it is really just the
assembly and fitting together of the 6 mm seal. Now that I have my whiz-bang new Sieg SX1P Milling machine I can mount the outer casing of the ZB-1/2 and run the milling bit over it to get flat the two flat surfaces for the seals. This will help with alignment of the seals and shafts.

As mentioned before I have had a hard time getting to ascertain the precise amount of friction that should be present with the 6 mm shaft and the corresponding 6 mm cup seal. When placed over the shaft these cup seals seem to be quite a press fit and have a fair bit of friction. I was concerned that it would be too much for the motor and would draw too any amps. So up until recently I had been taking the shaft down ever so slightly to about 5.98 mm or so just to loosen the friction on the shaft. However with the way my motors have been going they don't suffer from a lack of Torque. I asked this question last week of David when I dropped in on the Free Dive tribe ( Kookaburras in the background, I didn't set that up) and he mentioned that I shouldn't touch the shaft and try machining it down, I'm not that good a machinist So I will make a test seal without touching the shaft and see how the motor handles it.



Here we have the results of a year's labour. The ZB-2 on the left is the direct drive two motor and two shafts. The ZB-1/2 is the single motor, twin shaft and my favourite. I actually prefer it to the ZB-2 and thios is mainly due to manufucturing considerations. Then there is the ZB-1. These units featured below have the prototype grey and brown silicon, I now use a nice clear one that doesn't look messy. I am still doing some fine tuning to the designs and trying to streamline the manufacture process, trying to verify shortcuts that will lead to time savings and actually a better product that is more reliable.



This is what will be included in the units.



As you know the front end cap is the same across all units.



For me this pretty much wraps up this Project , I'm sure there may be the odd tidbit here and there as things come up. It will be interesting to see how these units fare out there. I will now probably transfer a lot of my energies to production and the development of the WW1 U-Boat SM U-23 class. I would like to thank HWSNBN, Jorg, Scott T , Gantu, Trout, Subhuman, Rick T, for all your help and advice. Greatly appreciated.


David H.