Right angle drive units “SRAD” steerable right angle drive

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Recently been given a boardroom model of a pusher tug and associated barge which had been built to demonstrate to potential buyers the design and use of twin z drives [SRAD ?] for a contract to the Pakistan River Steamers Ltd company, East Pakistan. The model is balsa construction and scale is about 1/48 (1/4" to the foot).

The model drives are of German manufacture.

The motors operate but the propellers do not turn. Disassembling the units reveals the problem. The propeller end of the vertical drive shaft had a fixed on obloid plastic block which should locate into the motor side of the vertical drive shaft which has a tubular end and internally shaped to accept the obloid. The problem is the obloid slides along the shaft and a magnifying glass shows both obloids on both shafts to be cracked so not gripping the metal shaft.

Here's the motor side of the coupling

and here's the propeller side of the coupling

The plastic obloid is apparent about the central silver disc (the metal shaft).

How would this be rectified? That is suggestions please. I can gain access to either part of the shaft and consider perhaps soldering a blob on the propeller shaft then filing to shape. I still need to ensure that the motor end is secure to its shaft.

Has anyone any information on this type of Z drive, I'm assuming it to be of German make. The motors are labelled thus :-

The obscure top left reads WE ST and the red lever is a polarity change over slide which I've seen on early German motors before.

And here's my hand holding a complete unit, very nicely made and just ripe for a 3D print copy once I know a bit more about them.

Thank for any tips on possible repairs, I'll apologise now for delays in replying as I'm on my way to UK and will have varying access to the site over the next week.

Thanks for your time, aye Kimmo

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Z drive and suggestions for repair please

[Colin BishopModerator @colinbishop34627]

Kim,

The motors are almost certainly early Marx ones, probably Monoperm or Monoperm Supers which date back to the mid 60s/early 70s. You can see from the 1966 advert here that some of them have the transparent back covers shown in your photos.

**LINK**

At that time they were being mated with the Bongo Z drive shown bottom left in the advert

I have an old Ripmax catalogue going back to then but your drives are not listed, perhaps they were not available in the UK. Certainly the plastic housings look very similar to the mouldings which were used for the add on gearboxes of the time.

So far no luck with an online search!

Colin

Edited By Colin Bishop on 26/11/2022 17:54:43

[Tony HadleyParticipant @tonyhadley]

Colin is right, they were 'Bongo' Z drive units. Found this on a Swiss site about the old Marx motors. The unit on the next to bottom row.

**LINK**

Vic Smeed designed 'Moonsong' around this unit, back in 1964. When the late Dave Milbourn built this model, he reverted to conventional motor/prop with a kort nozzle.

Last post in page 1 of this thread was Dave's research –

**LINK**

Page 23 of the same thread shows the model as built. –

**LINK**

 

Edited By Tony Hadley on 26/11/2022 18:19:30

[Colin BishopModerator @colinbishop34627]

Well done Tony, great find!

I guess Kim will have to try and find a way of bodging the units back into working order. Maybe it would be possible to weld the cracks shut with a hot soldering iron. For metal to metal, if solder doesn't do the job then maybe JB Weld might help. When looking online I found suggestions that this type of unit is not always mechanically robust and can't cope with high revs. In other words, the original unit was maybe a bit of a bodge! That's German engineering for you!

Colin

[Richard SimpsonParticipant @richardsimpson88330]

Drill right through and pin them? Tricky as you are going through plastic first then the shaft but carefull setting up and very gentle drilling with a new drill should go through square. Then pin and glue.

Obviously pin perpendicular to the crack.

[Tony HadleyParticipant @tonyhadley]

Thank You Colin, hope your paddler is progressing nicely.

I found this on the 'Bongo' drive units in the November 1962 Model Maker magazine.

[Colin BishopModerator @colinbishop34627]

Thank You Colin, hope your paddler is progressing nicely.

Thanks Tony. Yes, Paddler progressing OK slowly but weather has delayed pond trials although I am confident!

Adding more fittings at the moment.

Colin

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Thanks all, very good info for me.
When I get back I’ll open up both arts and attempt the repairs

thanks Kimmo

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Hello again, back home in the cold!

Right, update for those interested, and again thanks for the searches made and the material produced. I prised apart the drive assembly for one unit very carefully and luckily age was on my side as the glue used broke apart easily. The two halves are slightly different, one having ledges to hold the shafts the other capping plates to keep the shafts in place. No grease inside but this unit had a feather jammed into the inner part of the propeller drum.

Hers's the assembly as opened.

Examination revealed more damaged parts, splits in the plastic parts which were pressed onto the shafts. They include the drive locating lug, bevel gear on the propeller shaft and that on the drive shaft though the later two were quite solid and not slipping when pressure applied by hand.

Glue is not going to be a solution, neither will pinning all these bits. Looking at the second unit similar splits were also present in the coupling lug and the bevel on the propeller shaft. So how to move forward?

Now the luck comes in…. A trip to the model shop (yes we still have one local) for some small brass screws when I spotted the adjacent shop had 3D printed items in the window. Popped in and yes, they dealt in some items 3D printed but from re-cycled materials, like lemon and orange peel, and used coffee granules. Interesting but not helpful until the owner mentioned the new shop 5 doors down from him. They do 3D printing he said.

Well hurried there and YES eureka!!!!! Not only was the shop set up with 3D printers operating and spool upon spool of material all about, these chaps were fully into back engineering and making bespoke items for anybody.

Went back with the drive units. No problem, they could easily replicate the drive gears, in a much stronger UV activated polymer, in fact could do the whole assembly at the same scale or whatever. Initial cost to create the files for just the gears and plug estimated at £30 with production cost of £5 per set (plug, and two bevels). He's working on them right now, when I left yesterday he was hoping to complete for today.

Anyone want a Bongo unit? Just kidding…. or are we?

Aye, Kimmo

[Colin BishopModerator @colinbishop34627]

That's amazing Kim. Those units are actually quite neat but I do seem to recall that they did not wear too well so updated versions could be of a lot of interest. I'm sure Ashley can see some possibilities.

Colin

[ashley needhamParticipant @ashleyneedham69188]

Possibilities Colin, but, when you can just hang a 28mm motor underneath bumper style?

Ashley

[Colin BishopModerator @colinbishop34627]

Ashley, I've always been brought up proper and told to keep the water outside of my inner workings……

Too old to change now, anyway, running an electric motor submerged just aint natural. No good will come of it, mark my words.

And if the good Lord had meant us to swim he would have given us gills…

Colin

[Kimosubby ShipyardsParticipant @kimosubbyshipyards]

Hi Ashley, nearly came along two Sundays back for a visit but ended up further up river at Walton.

Anyway, I agree with you, there are some good looking cheap units that can be slung beneath the hull, they still require steering and I'm certainly tempted to get a couple for my great grandsons refurbished bespoke tugboat. The latest units to take my eye were fluorescent green and just over £20 the pair. Post from China.of course.

And yes Colin, if the bits can be made "better" then the Bongo drive, for smaller lighter craft, then there will certainly be a local demand here for them. I've already lined up a fleet of small slipper boats, saves me making similar units with the motors mounted vertically above the drive shaft. And with 3D printing there's nothing to stop scaling up for bigger craft, 6mm shafts and 60mm props.

We'll see what can be achieved soon, unfortunately I have other shopping to do apparently?

Aye, Kimmo

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