Help please: propshaft-uj-stuffing box

[steveuk]

Hi. I want to ask for your help in deciding the following...

I am putting all the internal pieces together in my WTC. I have the tube, stuffing boxes, UJ's, motors, and shafts.

My question is How do you put them all together, Bearing in mind my WTC is a Removeable tube ?

I can see the propshaft will have to end with a UJ which can be disengaged when the WTC is removed. So what does the other end of this UJ fix to? - The motor spindle is not long enough to reach through the end cap and stuffing box. So presumably another length of propshaft will have to extend from the external UJ in through the stuffing box and then be connected to the motor via another UJ on the inside???
Does this sound right - Two sets of UJ, one inside the WTC and one Outside?

I think I am a bit lost.. my last method was a fixed pressure hull so I only needed One UJ connecting the motor to the shaft which then went down a greased shaft.

Any light you can shed will be much appreciated.

[tabledancer]

I am probably not reading

I am probably not reading this problem of yours rite or just to dumb,but why not do it the simple way and put an extension shaft on your motor to get outside the endcap/seal,then attach your u-joint end to the dogbone for the prop shaft.
TD

[anonymous]

Thats whats I would have

Thats whats I would have said, just extent you motor shaft by the right amount using a brass tube or similar.

[steveuk]

Thanks for your advice.
Y'know

Thanks for your advice.
Y'know ..I was thinking of exactly this. So is this what you all do? It's just I haven't seen it close up for myself.

My one worry was that if the motor spindle were extended it would have to be pretty well centred. If the extension spins eccentricly there would be lots of vibration, wasted power, and might even wear the O ring in the stuffing box.

I guess if I had a decent lathe I could make such a thing.

Maybe I'm worrying too much about the engineering tolerances needed for this job...

[crazy ivan]

Check out this thread under

Check out this thread under the New Product Announcements forum]Dogbone extension[/url]

It might be just what you need for the external section.



Edited By Crazy Ivan on 1134093629

[tabledancer]

I used the kit that

I used the kit that CI wanted you to look at.My drive shafts or dog bones whatever you want to call them are 4 in. long,no problems.
TD

[anonymous]

You sure that you don't

You sure that you don't want to gear down the motor?
It is quite common to use something like a 3 to 1 reduction ratio to reduce the current drawn by the motor.
If you do that changes the drive shaft problem that you have - to putting a gear or pulley on the motor. Turning the motor around (drive shaft pointing forward) can reduce the space needed - see next comment.

In any event, try to reduce the length of internal shaft in the WTC it is just useless space

[anonymous]

Another point.
You an estimate

Another point.
You an estimate the current drawn by running the motor with your chosen prop in direct drive with the prop in a bucket of water or the "home test tank".

If the current drawn(in amps) is getting at all close to the capacity of your battery (in amp - hours) you should consider a reduction gear or pulley or belt.

[steveuk]

Thanks for the input guys.

I

Thanks for the input guys.

I thought I'd show you a pic so you can see what the deal is.
As you can see the motor spindles need extending to span through the end cap and stuffing box's.
(How come you don't all have the same problems, am I doing something very different to the normal way?? )

I also put a pic of the size of props. These are 30mm and I am using RE380 motors. The motors don't feel strong and torquey so I don't think thay are the really fast type. Hopefully these won't need to be geared. But I'd like to hear your opinions on this ..what do you think?

[anonymous]

mmm - it is quite

mmm - it is quite difficult to say what current you will draw. Those props are quite large with quite a pitch.

I assume that you are scratch building this and it is not a kit. If so I would measure the current to save yourself a lot of possible revamping later.

The method I described will give you an idea and should not take more than a few minutes to do. (You will need an multimeter with at least a 5A range or a panel meter)
Hold the propshaft with one hand and the motor with the other. The water will get whipped up!

[anonymous]

I just went away to

I just went away to look if it is still there.

Have a look at the Electronize web site under motors. This will give you some useful data for their motors.

www.electronize.co.uk

[Guest]

Most 380 size motors tend

[color=#000000]Most 380 size motors tend to rev around 15-17k, so you'll probably need 2-2.5]

[steveuk]

Cripes, you are right! ..I've

[color=#000000]Cripes, you are right! ..I've just done a crude load test holding the motor/propshaft assembly in the kitchen sink.

At the start the motor was pulling 8 Amps! Then I stuck the stuffing box under the water to get the o ring wet and it dropped down to 6 Amps (or maybe the load dropped because the water had turned into a swirling whirlpool!!). Well the 2 batteries I have will give a combined total of 6.8 Amp Hrs. But there are two motors ,shafts etc so the current pull would be 12A. That wouldn't give much play time.

So I guess I will have to gear them down, just as you say. Now I need to find some gears. I think I'll try for nearer the 2.5]

[Guest]

Graupner do some reasonable gearboxes

Graupner do some reasonable gearboxes for those size of motors, and you can fiddle with the ratios a bit too.

All gearboxes tend to whine a bit, helical gears are nice and quiet, but expensive.

Belt drive is the ultimate, but now you are getting expensive.

Could be cheaper to purchase a couple of new motors!

[anonymous]

Also try the GWS gearboxes,

Also try the GWS gearboxes, they come with and without motors, plenty of ratios and sizes (and only about £5-£9) a go). Using them in my Revell VIIc convertion.