Propellor shaft set up

[Michael BordParticipant @michaelbord10152]

Hi,

When installing the prop shaft on my (first r/c) boat, I put a washer between the prop lock nut and the end of the prop tube. Thought this would take the thrust from the prop while running. Any advice as to how much clearance/play the prop shaft should have? Guess it shouldn't be tight, but shouldn't put strain on motor bearings either?

Prop shaft greased and no water gets in via shaft.

Regards,

Michael

[Michael BordParticipant @michaelbord10152]

[Colin BishopModerator @colinbishop34627]

Yes, quite right Michael. Clearance should be minimal, just enough to allow the shaft to rotate freely. best way to do it is to screw it up until tight and then ease off by a quarter turn at a time until the shaft is free. The washer will help give a watertight seal when going ahead.

Colin

Edited By Colin Bishop, Website Editor on 10/07/2012 09:01:47

[ashley needhamParticipant @ashleyneedham69188]

Michael. I would adjust the shaft withe the motor shaft coupling loose,and then do up the coupling on the motor shaft afterwards..this will ensure that no thrust is transferred to the motor (assuminmg its the normal grubby screw type)

Ashley

[Michael BordParticipant @michaelbord10152]

Thanks, Colin and Ashley.

Very good advice, establishes that the motor bearings shouldn't take any end thrust which is what I needed to know, and I was right to add washer. . I'll set up prop shaft accordingly until shaft is free. Ashley, I've filed a flat on the prop shaft where the coupling grub screw goes to give a better connection without overtightening screw so should be easy enough to adjust coupling.

2nd trial on lake next Tues…

Thanks for that,

Michael

[Michael BordParticipant @michaelbord10152]

Hi Colin and Ashley,

Had second trial run at pond today, boat sailed very well, absolutely no water got in via shaft, prop shaft also turns freely after your setting up advice. So I'm pleased with results. Just got to start adding fittings to make it more realistic now…

Did drain the 3.4 ampere/hour lead acid battery after 35 mins though (545 motor driving 35mm 3 blade Graupner plastic prop) so maybe motor isn't quite as low drain as I'd thought. Still project very satisfying so far.

Thanks for your help,

Michael

[ashley needhamParticipant @ashleyneedham69188]

Michael.

Need to stick an ammeter on the motor leads to see how much current it is pulling. The only way to see what is "low drain" and what isnt, and get the best combination of prop/motor/battery etc.

See another post, I had a 555 motor on 12v turning an X50 prop and powering a 39 inch boat very well, and the measured current drain was about 2 1/2 amps !! thats what you call low drain. Motor not even getting warm.fantastic.

Ashley

[Michael BordParticipant @michaelbord10152]

Thanks for that, Ashley.

I'll have a go with my meter. Shaft freed up a lot now, turns very easily so should use fewer amps with luck. Good point about motor getting hot, didn't seem too bad last session. Still, experimenting all part of the fun. Another report soon, I hope.

Michael

[Michael BordParticipant @michaelbord10152]

Ok. Couldn't find ammeter in loft. Know it's there somewhere in boxes of electrical bits. Work got in the way. Then realised that my multi meter had connection and setting to measure up to 10 amps. So I connected the meter in circuit with the 6v battery directly to the motor (ie cutting out esc etc.).

Putting the boat (without superstructure) in the bath and connecting battery pulled 6.8 amps. This is full power and I expect that the current drain would be a little less when the boat is actually running. I haven't needed anything like full power when the boat was operating. As the model is based on a pilot boat, it doesn't need to travel too fast but still needs the capability of enough speed to give a reasonable scale wash to look the part. It doesn't need to be a "fast electric" type of boat.

6.8 amps would give a bit less than 30 mins on a 3.4 ampere hour battery (to the point when the performance noticably drops off and it's time to get to the bank!) so this ties in with my experience of the 2 runs so far (which did use less throttle to try boat handling out).

An article in an old Model Boats (sept 95) on a fast patrol boat with a similar length hull (my boat is 28" ) a 545 motor but bigger 37mm prop claimed 15 minutes run from a 6v 1.4 amp/hr battery at a steady cruise so perhaps 35 mins from 3.4 a/hr with various full speed bursts isn't too bad. (Got another 6 mins in bath when I got it home as well before batt finally drained).

The trick may well be to get a spare battery.

Should have some time for another test run this week,

Michael

[ashley needhamParticipant @ashleyneedham69188]

Michael. A couple of things here.. draining gfel batteries not a good idea as they tend not to recover fully from a complete discharge. About 2/3 capacity i think is the sort of recomended figure. so a 3.4 Ahr gel battery isnt quite 3.4Ahrs… I use them until i notice a drop in performance, meaning that it is starting to get flat and you should stop. Getting a bog standard 7.2V NiMh pack, a 3700 mAhr or something WOULD give you a full 3.7Ahr at reasonable cost. Or simply buy two batteries as suggested.

My experience is also that NiMh batteries give up more current and so you would probably see a performance increase with no further changes.

Always worth trying different props. On a semi-fast boat you cant beat (often) a good old fashioned plastic two blade "S" pitch prop…NOT an X pitch. You may even be able to go down to a 30mm example and release more revs, decreasing current consumption AND increasing performance!!

Theres no doubt a nice brass prop looks the part on most boats, but they dont always deliver the best performance.

Ashley

[Michael BordParticipant @michaelbord10152]

Thanks for that, Ashley. I'll stop boat when performance noticably drops off next time. Had intended to get NiMh battery pack to try as well (may well be needed for future models). Also I'll try your tip about experimenting with smaller (and 2 bladed) prop. Great fun!

Cheers,

Michael

[Michael BordParticipant @michaelbord10152]

Third outing today. No-one else on lake, just cruised about on light (1/4 – 1/2) throttle, boat going about fast walking pace. Ran for 53 mins on one charge, still power in battery but performance when throttle opened more was dropping off. Propshaft/motor spins very freely so guess it's run in more now. No water up shaft so set up fine. Run for getting on for 2 hours in total over 3 sailings. Motor got a bit warm but not over hot.

Next time I should have alternative props to try. Thanks for all the advice,

Michael

[JaryoreParticipant @jaryore]

Hi I don’t think anyone has asked this but if so I am sorry. I am building my first boat & I am stuck on the driveshaft setup on my boat…well that & the setup of my rudder…the main thing I am having trouble with is I don’t know where to start i know that i need a copper/brass tube to incase the shaft but that’s as far as I go I know I need something other than the shaft in the tube to keep after from going into the boat its self. I don’t know what that is or where to get it. And sadly all the hobby stores in my area are clueless about what I am asking about. This is my first boat & I want to do it right & not have to swim after it once I use it. Any help that can be given in pointing me in the right direction would be welcome. Oh it’s a single prop 1/32 scale PT 109 if that helps any.

[Colin BishopModerator @colinbishop34627]

People don't usually make their prop shafts and tubes, they buy them. There is a huge selection available, rudders too. Have a browse through the websites of some of the bigger model retailers such as Cornwall Model Boats or Westbourne Models. You are bound to find what you need there.

Colin

[John W EParticipant @johnwe]

Hi Jaryore

 

Your posting looks as though you may be new to the hobby of model boats and building them? If so, may i suggest that a good web search of all the model boat forms – one in particular would be Mayhem Model Boat Forum as there are1 or 2 builds on there for the PT 109 boat as well. In the master class section there are 1 or 2 builds for the beginner with lots of pics to go along with thebuilds

**LINK**

 

aye

john

 

Edited By bluebird on 25/07/2012 13:04:36

Edited By bluebird on 25/07/2012 13:05:00

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