Rubbish to stop or go into Reverse

[blackrose]

If the boat moves forwards from a standing position without too much revving then I don't think the issue is under-propping?

Edited October 25, 2023 by blackrose

[Tony Brooks]

1 minute ago, blackrose said:

If the boat moves forwards from a standing position without too much revving then I don't think the issue is over-propping?

 

It sounds more like under-propping to me.

 

To the OP, unfortunately your table does not show the gearbox reduction ratio so we can't see what a prop calc app suggests, but higher than others revs for a given speed suggest under propping.

[nicknorman]

26 minutes ago, robtheplod said:

Thanks all. It all engages fine and i see the wash up the side etc... its definately 'different' to our other shareboat in how responsive stop/reverse is.

 

 as an aside when generally cruising i seem to need more revs than others i see - seems to be around 1700rpm for slow walking pace... could this be related?

 

Sounds like it is grossly under-propped. We have a Beta 43 and a bigger boat (59' and 32" draft, so much more displacement). Our normal cruise rpm is 1300 which gives us 3 to 3.5mph on an average midlands canal. 1700rpm would only be for water-skiing! Although on large rivers we sometimes get up to 1500 or 1600 rpm but that is quite fast. The engine will still reach 2700rpm on a big river so it is not significantly over-propped.

 

Just as an aside, it is a complex subject, as I mentioned our boat is really good at stopping, but only stopping from going forwards. If we are going backwards (and it picks up speed going backwards quite quickly) and you try to stop by engaging fwds, for a couple of seconds you can feel the thrust but then it all goes a bit soggy, thust wanes and you can see the water recirculating in a votex, ie the prop is circulating the water, not pushing out the back. (Bit like vortex ring for any helicopter pilots out there!). It is very easy to accidentally reverse into the bank etc. And no effective steering whilst going backwards in fwds gear. Only once the rearwards speed reaches zero does it suddenly all start working properly. Still, given the choice I prefer good stopping from fwds direction to good stopping from reverse!

Edited October 25, 2023 by nicknorman

[robtheplod]

10 minutes ago, Tony Brooks said:

 

It sounds more like under-propping to me.

 

To the OP, unfortunately your table does not show the gearbox reduction ratio so we can't see what a prop calc app suggests, but higher than others revs for a given speed suggest under propping.

Hi Tony, just found that its 3:1

[Tracy D'arth]

1 minute ago, robtheplod said:

Hi Tony, just found that its 3:1

That is why you rev more, generally with a Beta 43 you would have a 2:1 ratio into something like an 18" X 12" prop or bigger but your swim height is not so great.

By generator do you mean a Travelpower?

[robtheplod]

Just now, Tracy D'arth said:

That is why you rev more, generally with a Beta 43 you would have a 2:1 ratio into something like an 18" X 12" prop or bigger but your swim height is not so great.

By generator do you mean a Travelpower?

yes i believe it was a travelpower - removed before we got the boat but there is evidence it was there...

[nicknorman]

 

3 minutes ago, robtheplod said:

Hi Tony, just found that its 3:1

 

I think a gearbox change to 2:1 would be advisable.

[robtheplod]

7 minutes ago, nicknorman said:

 

 

I think a gearbox change to 2:1 would be advisable.

is that a big job?

[nicknorman]

7 minutes ago, robtheplod said:

is that a big job?

No, but quite expensive to buy a new gearbox, looks like around £1600. It might be possible to open up the gearbox and change the reduction ratio as a cheaper option, but that is beyond my pay grade! Maybe the manufacturer could advise.

(edit, when I said "gearbox change to 2:1" above, I meant removing the current gearbox and installing a new one with 2:1 ratio)

Edited October 25, 2023 by nicknorman

[robtheplod]

7 minutes ago, nicknorman said:

No, but quite expensive to buy a new gearbox, looks like around £1600. It might be possible to open up the gearbox and change the reduction ratio as a cheaper option, but that is beyond my pay grade! Maybe the manufacturer could advise.

(edit, when I said "gearbox change to 2:1" above, I meant removing the current gearbox and installing a new one with 2:1 ratio)

Suddenly i have an overwhelming urge to put up with this! 

[magnetman]

PRM Newage are apparently good on the phone. 

 

I imagine they will sell you a new box 2(ish):1.

 

If there was a travelpower perhaps the boat was designed to be providing a certain amount of 230v wattage at cruise speed. 

 

 

[Alan de Enfield]

37 minutes ago, robtheplod said:

Hi Tony, just found that its 3:1

 

 

Is she an ex hire boat ?

 

Our Reeves boat had a 3:1 gearbox and on asking why, apparantly they fitted them to all their hire boats as it meant the engines ran at higher revs, made more noise, so the hirers were less inclined to 'speed' as it would deafen them.

 

I have an 'unused since a full refurbish' PRM 150 2:1 gear box (that was part of my spares kit - along with an LPWS4 engine)

Its just sat in my shed so could be available if you wanted one.

Edited October 25, 2023 by Alan de Enfield

[magnetman]

 

I seem to think that travelpower is a system which works regardless of rpm but you get less power. 

 

Rather than needing a fixed rpm to get the voltage it needs higher rpm to get more wattage. 

 

 

[Tracy D'arth]

A travelpower should not be run at less than 1500 rpm engine speed.

 

Your 3:1 gearbox will have a second hand value, you seem to have a good offer of a 2:1 box there.

[Tonka]

7 minutes ago, Tracy D'arth said:

A travelpower should not be run at less than 1500 rpm engine speed.

 

Your 3:1 gearbox will have a second hand value, you seem to have a good offer of a 2:1 box there.

How does that work on a  Beta JD3 then?

[Arthur Marshall]

1 hour ago, blackrose said:

The OP said he can be in "full reverse" in a lock and his boat is still moving forwards. Then a couple of people chimed in saying all boats do that... Really? In full reverse? That's not normal surely?

Mine does. Possibly the curse of a short boat, but in single locks on the T&M, if I get caught in the surge when filling a lock, full revs with a Lister won't stop me smashing into the gate. Which is why I always tie it up in locks when singlehanding, and why I've broken two ropes while doing so, when some helpful person has opened a paddle too fast!

I do try to avoid such clonks as, for some reason, they usually put the fridge out of action.

[Tracy D'arth]

10 minutes ago, Tonka said:

How does that work on a  Beta JD3 then?

Pulley ratios?  Part of the reason for the speed on a Beta 38 or 43 is to avoid the damaging torsional stress on the front of the crank which can cause failure. The BD3 crank is considerably more robust.

[Wanderer Vagabond]

1 hour ago, magnetman said:

It depends how fast the forward movement is. 

 

Some boats will stop quicker than others.

 

The best thing is to go into locks slowly and not need reverse to stop but use a rope.

Have to say, that is what I tend to do. I approach the lock on tick-over and once the bow is into the lock mouth, knock the drive into neutral and drift into the lock stepping onto the lockside when I can and bringing the boat to a slow halt with the centre line on one turn around a lockside bollard. You obviously need to make sure that you wrap the rope around the bollard the right way so that it doesn't 'lock' and bring the boat to a sudden stop (probably where the other poster has seen bollards pulled out).  I went for this technique after going into Ryders Green Locks on the Walsall Canal once and after going into the lock under power, put it in reverse to stop and got a whole load of crap wrapped around the prop and found myself unable to stop, the boat then hit the bottom gates a whole load harder than I would ever wish to.

 

Just as a separate, unconnected observation, people have been describing 'overcoming inertia' regarding stopping boats by putting them in reverse, surely it is momentum that they need to overcome?

[Higgs]

Crap in locks is almost guaranteed to be getting worse from now on, as the leaves are falling. It's sometimes hard to get any forward power to get out of a lock. It's not always easy to shake off vegetation by going in reverse. In forward or reverse, there's likely going to be a ball of crap around the prop shaft. 

 

 

Edited October 25, 2023 by Higgs

[robtheplod]

1 hour ago, Alan de Enfield said:

 

 

Is she an ex hire boat ?

 

Our Reeves boat had a 3:1 gearbox and on asking why, apparantly they fitted them to all their hire boats as it meant the engines ran at higher revs, made more noise, so the hirers were less inclined to 'speed' as it would deafen them.

 

I have an 'unused since a full refurbish' PRM 150 2:1 gear box (that was part of my spares kit - along with an LPWS4 engine)

Its just sat in my shed so could be available if you wanted one.

Thats so kind of you Alan, she was a ex shareboat so probably same?

I'd not know what to do with the gearbox but thanks for the offer....

[Mike Todd]

It could be down to the hull design. There is considerable variation. Strangely, no-one seems to mention its significance much in canalboat chatter but in the context of 'proper' ships it is a fundamental and much studied subject. So much that not only are towing tank tests often require before a new ship is accepted but also confirmed in sea trials. It is (or was back in the 70's when I was last involved very much a black art, whatever the 'experts' might say!

[nicknorman]

1 hour ago, Tracy D'arth said:

A travelpower should not be run at less than 1500 rpm engine speed.

 

Your 3:1 gearbox will have a second hand value, you seem to have a good offer of a 2:1 box there.

It can be run at anything from idle upwards, depending on how much power you are taking from it. If you want full power, then yes 1500rpm but otherwise something in between depending on the power drain. At a pinch ours will put out 1kw or so at idle without complaining but we do try to keep the revs around 1300 if it is operating the tumble drier (2kw).

Pretty sure Beta specify to not charge at below 1300rpm but of course that is being simplistic as it depends on whether you are chucking in 175A to flat batteries or 5A to nearly fully charged ones

15 minutes ago, robtheplod said:

Thats so kind of you Alan, she was a ex shareboat so probably same?

I'd not know what to do with the gearbox but thanks for the offer....

 

Well you could get someone to swap out the gearboxes, it's not a big job. Or even do it yourself if you have spanners!

[Tony Brooks]

I suppose the alternative to another gearbox is a different prop. With a limit on diameter, it would mean more pitch or even a four bladed prop, but that probably would be less efficient. It should, however, give a better reverse and a slower cruising RPM.

[Bee]

Looking at your photo you have not got any room to get a bigger dia. prop and it looks as though your prop is about the right size anyway (not very scientific I know) If you had a 2:1 ratio gearbox that would make a big difference, you would get about 20 - 30% more rpm at the prop for the same engine speed. (no I haven't worked that out, it just feels about right)

[robtheplod]

6 hours ago, nicknorman said:

IWell you could get someone to swap out the gearboxes, it's not a big job. Or even do it yourself if you have spanners!

is it an unbolt/bolt on change?  i'm fairly handy but need to know my limitations!