Engel piston - convert from 540 to 380 motor?

[JWLaRue]

...like the title says, has anyone done a conversion of motor sizes for the Engel piston?

-tnx,

Jeff

[bigdave]

Yes
DonO and I did.
It was years ago on his Shark (Skipjack) cylinder.
I think it required a different gear. I will ask Don.
Yo! Don! BD

[JWLaRue]

BD,

That will be much appreciated.

I was thinking that a different pinion gear would be required. I'm also thinking through how the smaller sized can of the 380 motor gets mounted. It doesn't look like the same mounting points on the piston endocarp would work.

-Jeff

[bigdave]

If I remember the pinion gear is smaller.
It needs the higher ratio to power the piston.
Cycle time is a bit longer but it draws less current than the 540.
Plus it fits in a smaller tube.
I thought Engel made an adapter kit at one time.

[JWLaRue]

An adapter kit would be great. I was looking at the Engel site earlier today, but didn't see one....time to look again.

-Jeff

[Guest]

I did this conversion over a year ago on a pair of 750ml tanks I was given and put some notes in the SCR fox schedule. My tanks were 6 volt tanks, and I replaced the 540 motors with 12 volt 385 motors. I retained the same gear ratio, but purchased new brass pinions from hobbyking, which only cost about a pound per pinion- the engel gears are 0.5m, BTW.

I made up some new motor mounts from brass. Conversion took about an hour per tank, and cost about five pounds per tank with the new motors being the chief expense. Halved the current draw, but speed was the same, and the new motors are plenty powerful enough.

Norbert Bruggen supplies a kit which makes the conversion a bolt together affair, and isn't that expensive. I just like to fiddle about!

You can see the kit on page 39 of Norberts catalogue, priced at euro 12.50.

http://www.modelluboot.de/Anleitungen/Katalog_ModellUbootSpezialitaeten_2012.pdf

[Guest]

Found the bit I wrote, which was in the September 2014 SCR.

Yours truly was fortunate enough to have a pair of new and unused Engel tanks given to him. They had been handed to a model shop owner by a customer. The store owner knew of my interest in model submarines and kept them aside, but didn’t really know what they were for. The original owner was apparently going to throw them away!!
The tanks were 6-volt 750ml versions. These are fitted with large 540 motors, which tend to be a little thirsty, especially when the tanks load up under pressure.

As I prefer 12 volts systems, I decided to convert them. Norbert Brüggen supplies a conversion kit for these tanks, and it’s fairly reasonably priced at about 12 euros. However, I seem to enjoy making life difficult for myself and having spotted some motors going cheap on eBay, I decided to have a go myself.
A pair of motors were duly ordered at a cost of £6 for the pair. I then fashioned some replacement motor brackets from brass sheet, and silver soldered some 4ba bolts into the bracket which bolted into the tank aluminium endcap. The motor was bolted in with M2.5 countersunk bolts, replacing the original M3 bolts. Two new 14 tooth 0.5 module brass pinions were ordered from Hobby King, as the originals were too big. The 385 motor has a smaller shaft size than the 540 style motor. The new pinions are held onto the motor with a grub screw fixing instead of the original press fit pinions. That makes life easier if I ever have to change the motor in the future.

The conversion took about an hour per tank and was fairly straightforward costing about £10 for both units. The new motors use about half the power for equivalent speed and weigh under half that of the old 540’s taking up a lot less room -- definitely a plus when trying to cram these in to the tight confines of a dive module.

[JWLaRue]

Andy,

Many thanks for digging up your Fox piece on the motor conversion....exactly what I was trying to find.

-Jeff

[Guest]

Norberts conversion will result in the motor taking up a bit more room radially than my conversion did. With my conversion you can get the tanks inside a 94mm I/D diameter (100mm O/D) cylinder. Something to bear in mind if you are doing the conversion to save on space.

The 385's I used are rated for about 10000RPM at 12 volts, which is about the same as the 540's I took out, they still have more than sufficient power, in fact I think you could comfortably get away with smaller motors, as the tanks could be extended to about 75% full before stalling. They pull a lot of current at that stage, but it's far beyond pressures they would normally need to work at.

[JWLaRue]

I was just looking at Norbert's conversion and saw that as well. I'm going to need to look closely at how to do this as I want to fit it into a 3.5-inch OD (ID = 3.25-inch or 82.55mm) cylinder.

Also, is this the gear that you ordered:

http://www.hobbyking.com/hobbyking/store/__11214__Pinion_Gear_3_17mm_0_5M_14T_1pc_.html

-Jeff

[Guest]

No, that pinion has a 3.17mm (1/8") bore for a 540 motor. I used these, which have the 2.3mm (3/32") bore for a 380/385- http://www.hobbyking.com/hobbyking/s..._14T_1pc_.html


I will take some measurements of my modified tanks to see if they will go into a cylinder that size, but it will be very tight if it does.

I take it you have the tank(s) already, if you're goign to buy them, do be aware Ron Perrott does a 90mm diameter WTC with twin piston tanks for a very competitive price.

[Guest]

I measured one of the tanks, and you would really need 83mm, and even then the motor would be resting on the cylinder wall.

I think you should still be able to do the conversion, but it will need a bit more work to mount the motor,as you will have to drill new holes in the endcap, or make a special bracket to offset the motor, and mount it so it is tucked in closer to the centre of the tank.

A second alternative is to remove two of the gear stages, and drive the main gear directly with a pinion, using an inline gearbox on a small motor. You can purchase these very inexpensively off ebay. Ultimately you're looking for a spindle speed of about 600RPM to maintain Engel's quoted rate.

[Guest]

A third alternative is to purchase the different middle gearwheel used in 12 Engel 12v 380 tanks and also the 14 tooth 2.3mm pinion (Engel supply this too, but it's a press fit). Engel may also sell you the motor mounting hardware, but this would be easy to make or adapt yourself I think.

As the drawings show, the tank will then fit easily, it just costs a bit more.

http://www.engel-modellbau.eu/catalog/product_info.php?products_id=1367

http://www.engel-modellbau.eu/catalog/product_info.php?products_id=969

[JWLaRue]

Thanks (again) Andy for the additional information.

You are correct, I already have the piston....so making it work (vs. buying anew one) would be the priority. Since Engel does offer pistons with 380-sized motors that are known to fit within a 3.5-inch OD cylinder, I'll find a way to make it work.

-Jeff