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[hemayann]

  i was wonder has anyone made a gear box (for'd back and nutrual) for a nirtro or petrol motor eg. wipper snipper motor
im building a big model displacement hull and i want it to be like the real thing engine mounts and exhaust through the deck

[Proteus]

depending on the size of engine look at HPI model cars they do one that does not req the engine to stop.

Proteus

[andyn]

This has been said on the model boats forum, I'll say here what I said there. It's a waste of time, why would you even want to go backwards with an IC boat anyway? What's the point? It is possible yes, but would more than likely stall the engine every time. Marine engines for the most part don't like running slowly, especially the bigger ones. Besides just about every IC boat hull you can buy will not like going in reverse, it will dive in over backwards and flood. Adding to this, you'll probably do untold damage to the engine, and if running a flexi drive, it'll unwind it and you won't get anywhere... Don't waste your time trying.

[omra85]

As you said that you're building a "displacement" hull, the grim scenario Andy has portrayed would not necessarily apply 
Instead of trying to do the job of reversing with a gearbox, how about using a variable-pitch prop. I've seen drawings but have never had the chance to examine one 'in the flesh' but I'm sure they have been used with steam engines in the past.  The obvious question would be - how would it stand up to the higher revs and greater torque of an IC engine?
Another idea would be to use one of those impellor thingys with a scoop at the back to direct the water down and forwards - that might keep the stern up at the same time as giving you reverse.
That's one advantage elecric has over IC, they go in reverse.
You can get a clutch for a strimmer motor which seem to work quite well, but as to the gearbox ... ???
Danny
 

[John W E]

hi there another option which may be feesible for reversing an IC engine is a Kitchener Rudder - it would have to be built fairly strongly, when you think about the thrust from a modern day IC engine - food for thought.

The Kitchen Rudder is the familiar name for "Kitchen's Patent Reversing Rudders", a combination rudder and directional propulsion delivery system for relatively slow speed displacement boats which was invented in the early 20th century.

aye
john

[Proteus]

this is the unit.  some people use them on non reversing steam plants as well

Proteus


http://www.hpieurope.com/piw.php?lang=en&partNo=87039

[andyn]

Firstly, it will impossible to line that Savage unit up, so it will just wibrate it to pieces, and secondly, to select reverse gear you 'simply hold full brake for three seconds', in which time you will have cut the engine if your throttle is set up as it should be according to OMRA rules...

[Proteus]

Firstly, it will impossible to line that Savage unit up, so it will just wibrate it to pieces, and secondly, to select reverse gear you 'simply hold full brake for three seconds', in which time you will have cut the engine if your throttle is set up as it should be according to OMRA rules...

first Why will it be imposable to line up.? and why will it shake to bits , and is he going to race it in OMRA ?

Proteus

[andyn]

Probably not going to race it no, but the rules that clubs follow state that engines must be able to be shut down via the radio.

To line it up, you would need to mount it firmly in perfect alignment to the shaft and engine, if it is even a fraction of a millimeter out it will vibrate. Second vibration point, the engine will vibrate in it's mount, at low speed engines move more in their mounts due to the lower frequency. This will try and take the reversing unit with it, which of course it cannot do, so you will break a shaft or connector or worse do in the bearings in the engine. So you will either break part of the engine / reverser, or crack the hull around the shaft.

You are more than welcome to try if you like, don't blame me though if you waste your money ending up breaking things. Proteus you are more than welcome to come have a look at Wiki park at how much one of these engines vibrates.

[Proteus]

I did off shore over forty five years ago when it was wavemasters and sea queens and did fast ic for a long time also rc cars back in the PB days and some modern stuff and yes they vibrate but so do cars that is why they use a drive shaft to it with joints on both ends , people have always had the ability to stop n engine usual via the trim , lets be honest you don't like the idea of a gear box but it is for  hemayann I am posting the info.

there is a very nice ic tug that uses a generator to run an electric motor as per the full size boat Ill try and find the link, it works very well by the looks of things, depending on the size of motor you are using RABOESCH did a variable pitch prop for IC up to about 3.5cc , they come up on ebay every so often I got a couple a few years ago , they are a bit bulky if you go down one of these routs think about water cooling and an electric pump for when you are manovering.
what type of boat where you thinking of

Proteus

[bogstandard]

Proteus,

I gave away a brand new Raboesch unit only recently, and I am sure it said that it could handle up to 10cc. The blade size when put into motion would definitely be a little large for a 3.5cc. But the necessary sliding coupling that was designed for it would need to be made a lot more substantial, it would disintegrate in seconds if used for an ic engine.

I have some drawings for a crash gearbox that was designed for use with a larger model steam engine to obtain reverse if that is any use.

The easiest way for reversing, would be to set the engine up driving thru a simple plate gearbox (1 to 1 if wanted), and put in a tumbler reverse as used on a lathe. Instant reverse of the shaft direction with no gear crunching. This is a tumbler reverse being made for a lathe, but could very easily be reduced down in size to fit in a model. The only downside is that the engine would need to be offset to the shaft centreline.

http://bedair.org/Tumble/Tumble.html

Hope this helps


Bogs

[hemayann]

i dont care how many servos it takes but maybe getting a rc car engine and putting a 2 to1 reduction on it then find some little gear box, i heard though a bloke at a model shop said thats rc cars with nitro motors have them

[derekwarner]

Oh dear...... ...I suggest this newer member...hemayann

"I dont care how many servos it takes"


Takes a back seat for a few days & reflects   on his  comments ........& then digests a few of the many helpful postings  by other long term experienced members ....Derek

[andyn]

If you setup your boat for the right sized prop in low gear, then when it shifts into high gear it will be under propped and slow down, because it will just be spinning the prop very fast and not getting any power into it. However if you setup your boat for the right sized prop in the higher gear, in the low gear it will be over propped and stall the engine, or at least increase the wear on all parts in the drivetrain, which in the end will make your gearbox fall apart.

Why do you think noone else does this? I think it's because everyone else realises it won't work.

[Proteus]

If you setup your boat for the right sized prop in low gear, then when it shifts into high gear it will be under propped and slow down, because it will just be spinning the prop very fast and not getting any power into it. However if you setup your boat for the right sized prop in the higher gear, in the low gear it will be over propped and stall the engine, or at least increase the wear on all parts in the drivetrain, which in the end will make your gearbox fall apart.

Why do you think noone else does this? I think it's because everyone else realises it won't work.

Read the original post He want to make a SCALE boat and does not mind if it is geared, he says nothing about two speed box but wants reverse, so a car box will work no problem unless you have had Personal experience to the contrary.

Proteus

[Shipmate60]

Andy,
Why do you decide it is impossible?
Most of the ships sailing the seas are, yes, IC with a gearbox.
If the IC Engine is geared down you then have 3 choices, reversing gearbox, kitchener gear or CP Prop.
The easiest to produce is the CP Prop and has been produced commercially.

Bob

[andyn]

Why do you decide it is impossible?
Most of the ships sailing the seas are, yes, IC with a gearbox.

I don't, the people who have tried already did.

How many of those ships are pulling an absolute minimum of 2000rpm up to around 44,000?

[malcolmfrary]

I don't, the people who have tried already did.

How many of those ships are pulling an absolute minimum of 2000rpm up to around 44,000?

Of course, we should refer to the original question from the first post -

im building a big model displacement hull and i want it to be like the real thing engine mounts and exhaust through the deck

which implies a larger, probably slower revving engine than an out and out racing set-up, rather than answering a different question.

[andyn]

which implies a larger, probably slower revving engine than an out and out racing set-up, rather than answering a different question.

Which would still be 2000 - 12,000 rpm.

[knoby]

i have seen 2 scale models with ic engines in them. 1 was a tug, but i cant remember any details, the other was a large trawler that had a 4 cylinder ohv engine ( a sea lion i think) The trawler was seen at maidstones moat park in the late 70's. used a centrefugal clutch &, I believe, some sort of a tumbler gear box ( as bogs suggested).

If i was looking for information, I'd try the Society of Model and Experimental Engineers. there are several ic powered locos that use various types of gearbox, my guess is if anyone knows it will be these guys

just my thoughts
cheers Glenn.

[Proteus]

Look on e-bay for a OS 40 ohv marine engine, they rev nice and slow if req don't sound like a strangled cat are easy starting, etc or if you feel flush look for an old Gannet they where a nice slow revving petrol engine, but expensive these days.

Proteus

[rmaddock]

How about a Voith Schneider Propeller......probably impossible to do but wouldn't it be fun?

http://en.wikipedia.org/wiki/Voith-Schneider  


...STOP PRESS....

Actually, now that I look further, Graupner actually make model ones.....search for Voith on their web pages 

http://www.graupner.de/en/

[longshanks]

Just a thought for this green, politically correct world we live in.

hemayann have you checked your area for sailing water? Ponds that allow IC engines are few and far between these days

[andygh]

Oh dear...... ...I suggest this newer member...hemayann

"I dont care how many servos it takes"


Takes a back seat for a few days & reflects     on his  comments ........& then digests a few of the many helpful postings   by other long term experienced members ....Derek

Eh? 

[andyn]

How about a Voith Schneider Propeller

Won't take an IC engine...