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[MOG8]

MH&B PB2 REVERSING GEAR
 am going to use  this MH&B PB2 on a steam launch, The reversing gear arm  has a swing of 90°, while a normal servo swing is about 60°.
The torque to be applied is quite considerable.
The servo link is at 90° direction to the engine reversing arm.
Has anyone ever tried to hook this engine reversing gear to a RC servo?
Thank you for sharing your experience, sketches, advices.

[kiwimodeller]

I have not used this engine but have had a similar problem with one of my boats. I bought quite a large and powerful servo from a mate which I believe was originally for retracting undercarriage on aircraft. It had a 90o travel and heaps of torque. I had to put in a 6volt receiver battery pack instead of the 4.8volt one but then it worked well. Most servos advertised these days have a spec sheet that will give you torque and travel degrees so you should be able to find something to suit. Hope this helps, Ian.

[MOG8]

Ian,
Thank you  for your advices.
I will try to find a suitable servo powerful enough.
I was also thinking of using one of my Graupner vintage servos which had a linear movement instead of the usual swinging arm  (or disk)rotating around a pivot.
Cheers,
Giovanni

[Aeronut4]

Use a long arm on the servo and a shorter arm on the engine.

[wideawake]

The Cheddar Gemini has a similar (smaller) tumbler reverse mechanism and mine operates OK with a standard servo.

Guy

[geoff p]

While we're on the subject, can anyone explain/describe how this reversing gear works, please?

Geoff

[MOG8]

Use a long arm on the servo and a shorter arm on the engine.

Thank you for your reply.
I have calculated that I need an quite a long arm (47,3 mm.) using the shortest available radius on the lever (18 mm.).
This will transform a 60° swing into a 90° degrees swing.
Giovanni

[MOG8]

While we're on the subject, can anyone explain/describe how this reversing gear works, please?

Geoff
[/quote]

The reversing arm and its toothed sector engages into an O-ring and disk fixed on the eccentric shaft.
Swinging the lever 90° the eccentric shaft (parallel to the crankshaft and geared 1:1 to this) rotates of the same amount as the lever, changing the advance valves events, as it happens with a slip eccentric gear.

[HS93 (RIP)]

I use these when I can, they protect the servo from striped gears. the gears alter the timing to get reverse.


http://demonpowerproducts.co.uk/product_info.php?products_id=284
Peter

[geoff p]

What a shame, HS93, it would appear that Demonpowerproducts' website doesn't respond to us expats.  Whilst Google seems to think the site was updated '7 hours ago', all I can get from it is "Forbidden blah blah to access this server" - from even their home page.
Geoff

[HS93 (RIP)]

try

http://shop.ebay.co.uk/i.html?LH_AvailTo=3&_nkw=kimbrough+servo&_arm=1&_armm=63&_dmd=2&_ruu=http://shop.ebay.co.uk/i.html%3F_nkw%3Dkimbrough%2Bservo%26_arr%3D1%26_dmd%3D2&_rdc=1

Peter

[mogogear]

What a shame, HS93, it would appear that Demonpowerproducts' website doesn't respond to us expats.  Whilst Google seems to think the site was updated '7 hours ago', all I can get from it is "Forbidden blah blah to access this server" - from even their home page.
Geoff

Working Ok for me right now..??

[Underpressure]

I use these when I can, they protect the servo from striped gears. the gears alter the timing to get reverse.


http://demonpowerproducts.co.uk/product_info.php?products_id=284
Peter

Once a car racer, always a car racer 

[dave301bounty]

Used a servo ,off a yacht was powerfull ,the sail servo .this was on Stevensons type reverse gear .it worked ,after some small adjustments ,then a proper job was made .the servo was an old,ish futaba .but there we are .

[MOG8]

HI all,
thank you for all advices received.
I have bought a metal gear 15 Kg. torque servo with a 60° arm swing. Multiplying the lever I succeeded  having a 90° rotation and moving the steam engine reversing lever.
The 1,5 mm. steel rod bends a little under the effort!

[kno3]

Care to show us the launch you're building?

[MOG8]

Care to show us the launch you're building?

MH&B OPAL WITH MH&B STEAM PLANT: VERT. BOILER+PB2

[Bernhard]

Hi...What a great launch and boiler,,,please some photos of the opal...do they still make the launch and boiler?
Regards Bernhard

[kno3]

That's a beautiful steam plant. Looks quite compact too. How much does it weigh?

[MOG8]

Hi...What a great launch and boiler,,,please some photos of the opal...do they still make the launch and boiler?
Regards Bernhard

he OPAL Kit, not present in current production, can be made upon request by Brian Marten (he will be glad if I encourage some of you, but please mention me, his Italian customer, as I owe him a little favour)) and I bought mine last year.
I know that he can sell the flanged parts of the vertical boiler for a DIY construction of it.
This is my Opal in construction with a Caton engine and a custom made vertical copper boiler.

[MOG8]

That's a beautiful steam plant. Looks quite compact too. How much does it weigh?

This is a feather-weight steam plant, mainly due to the particular boiler construction (if you want I will go into details).
Engine  361gr.
Boiler (fully fitted less wood lagging): 844 gr.
Boiler funnel: 47 gr.
Boiler gas burner: 50 gr.
Separator & Gas tank: 137 gr.
Assorted copper pipes: 27 gr.
Total: 1466 gr.


From Brian Marten:
"The Opal is a light displacement launch. Here are the weights of the original steam plant;

Boiler - 960 gms
Engine - 420 gms
Separator tank - 80 gms
Gas tank - 100 gms
Pipework - 40 gms

These are all dry weights. There is no reserve buoyancy in the model. The nearest suitable complete unit that I know of is the Cheddar Models 'Pintail' with vertical.boiler.

Regards

Brian Marten"
OPAL with Caton and custom made vertical boiler

[HS93 (RIP)]

have you seen an Opal on the water ? the boiler is very light for the Opal, when i got my boat I spoke to Brian about other boilers as I had a few spare and he explained that to make it sail it needs one of the same hight and weight, if you notice any of there boats they are very carfully balanced there was a post about a Topaz not so long ago that was a bit low in the water and I think that was the adding of a gas valve, they can look lively from side to side with the correct boiler.
but they are a beautiful kit.

this is one of mine at the start of refurb. they are not copper by the way

Peter

[kno3]

This is a feather-weight steam plant, mainly due to the particular boiler construction (if you want I will go into details).

Yes please go into details.
At 1,5 kg the steam plant is a reasonable weight. Just for comparison, I consider Cheddar plants heavy.
For the next plant I'm assembling my target is to stay under 1,5 kg if possible.

[benjaml1]

Digressing....

Many many years ago I watched a television series called "Victory at Sea"... In the lead in there was a battleship/heavy cruiser ploughing through the waves. Bow submerged, then stern down with the wave cascading down the foredeck.... Some of you may remember ?......  It stirred my loins it did...
Sooo.... I went about motorizing an Airfix model of HMS Hood...  Hood was a strange ship, with the refits the additional armour would give her little freeboard aft, so I trimmed her well....
Upon launching I became very dissappointed, scale speed of about 120 knots & that ploughing effect was similar to a fishing float with 3 lead shot weights.... Undaunted at the tender age of 10 years old I thought  "Ballast"... Casting lead pigs using a bakelite 3 pin plug as a mold ( remember them ?) I re-launched HMS Hood only to see it sink ( blast the low freeboard ) for the very last time....
At 10 years old I learned, if I wanted a model boat to look realistic on the water I have to make it heavy....Very heavy... OH ! Have lots of freeboard to boot... 

[HS93 (RIP)]

thats it they are Nickel steel boilers with a copper top cover.

Peter