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Author Topic: Strimmer engines?  (Read 6412 times)

BlazingPenguin

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Strimmer engines?
« on: December 01, 2006, 11:54:16 AM »

Having been given a rather large deep V hull (4ft) its sort of 'Perkasa' in appearance I made some enquiries as to how much an engine would cost and almost died at the estimates!!!!!
My brother then turned up a McCulloch strimmer engine complete with flexi shaft, works perfectly and we were wondering if it was viable to fit this into a hull for non competative use?
Should it prove a non-goer....it will be appearing on Ebay sooner than I thought  >:(

Cheers for any and all help offered!
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Peter

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Re: Strimmer engines?
« Reply #1 on: December 02, 2006, 09:59:30 AM »

Strimmer engines work fine in model boats, particularly so if they have a built in clutch.

Peter
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BlazingPenguin

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Re: Strimmer engines?
« Reply #2 on: December 04, 2006, 02:53:24 PM »

Cheers Peter...
Now dows anyone have any ideas on how to go about it?
I imagine some sort of mount will have to be made for the ending itself, I can see the square fitting where it fits onto the driving part if engine, but how would you stop it falling out of the bottom of the boat?
Any websites etc I should be looking at????
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OneBladeMissing

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Re: Strimmer engines?
« Reply #3 on: December 04, 2006, 03:28:36 PM »

Are you thinking of using the flexi-shaft with the strimmer as a propshaft? Why not use a solid shaft and make/buy a suitable coupling. I got a coupling from Prestwich Models and secured it to the output shaft of the engine with a suitable threaded stud. I don't get this stuff about using the clutch which is fitted on the strimmer. What's wrong with direct drive?
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BlazingPenguin

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Re: Strimmer engines?
« Reply #4 on: December 04, 2006, 04:41:46 PM »

On first inspection....the flexi-shaft has a squared end that marries with a square 'socket' at the engine end, the other end is held in place by the bit that holds the strimmer line so no problems for strimming, but if i remove that assaembly in the hope of fitting some sort of prop...how do I stop the the shaft...flexi or otherwise from just falling out????

If I use the existing flexi thing...no dramas, but if I opt for a solid shaft there doesnt seem any way to hold it in place. had it been some sort of 'spigot' sticking out my problems might have been solved as I could have turned something up on the lathe to fix either flexi or solid in place at the head?

Next prob?:
If I opt for a solid shaft, would I need some sort of roller bearings or would phosfor bronze bushes do?

As far as the clutch goes, I only see it as some way of running the engine at lower revs until safely in the water, although I imagine that even then she would be turning at a fair old rate?
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boatmadman

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Re: Strimmer engines?
« Reply #5 on: December 04, 2006, 05:37:46 PM »

Hi,
As far as the shaft/bearing issue goes, with a solid shaft you will need bearings for sure. The problem with roller bearings is the need for lubrication. You must have some sort of 100% effective seal to stop oil escaping into the water - pollution etc - and seized bearings.

However, my gut feeling, for what it is worth, is that well machined close tolerance pb bushes will do the trick. I use these a lot, but not with ic engines. I dont lubricate with oil, I rely on water for lubrication and cooling. It works for me. I havent had a failure yet!

Ian
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OneBladeMissing

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Re: Strimmer engines?
« Reply #6 on: December 05, 2006, 09:43:22 PM »

The square "socket" on the engine, into which the square end of the flexi-shaft fits, is (I assume) on the output end of the clutch assembly. If you remove the clutch assembly you should find that the output end of the crankshaft has a threaded hole in its centre. A threaded stud can be screwed into this hole, onto which a suitable coupling can be screwed.
An IC engine should ideally be on rubber mounts for noise suppresion, thus a rubber-bloc type coupling should be used. As there will be some movement of the engine on the rubber mounts, a propshaft assembly with a ballrace on the engine end of the shaft is really necessary.
I have a 24cc engine from a "Talon" (Chinese) strimmer. I've been told that it's the same engine as a McCulloch. The threaded hole in the crankshaft is 5mm, to which I've attached a Prestwich Models coupling. The proptube/shaft assembly (home made) has a bearing housing on the inboard end with a ballrace fitted to suit the 1/4" shaft. Shaft and tube are lubricated with ordinary bearing grease.
I have fitted aluminium plates at each end of the engine with four 15mm x15mm rubber blocks at each end. Outer aluminium plates are fixed onto the blocks, then these outer plates bolt onto aluminium tabs glassed into the hull.
I don't have any pics of the engine installation to show you, I wish I had, and I don't have a digital camera. A picture would explain the installation clearly.
I don't have any experience of running such an engine in a boat with the clutch still attached. I think it would be more trouble than it's worth. Modified CMB.91s churning out 7.5bhp are run on direct drive with no problems, and strimmer engines are nowt near that output.   
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BlazingPenguin

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Re: Strimmer engines?
« Reply #7 on: December 06, 2006, 01:00:27 PM »

I  can see that large tub of Swarfega is going to have to be purchased!

As well as the the help of a relatively mechanicaly minded friend....but if theres a threaded poiint to be found, Im sure i can connect a relevant part there. The procedure for turning the location for the bearing will be fun no doubt too!  :o

Thanks 'Blade'....any help along those lines is much appreciated, anything I can do in return you only have to ask.
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martno1fan

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Re: Strimmer engines?
« Reply #8 on: December 07, 2006, 10:40:36 PM »

STOP dont remove the clutch mate keep the square end all you need to buy is one stub shaft a skeg for the stub to go into then a collet which you silver solder or loctite onto the flex cable between the skeg and the hull the ferrule then fastens to a stub shaft that runs through the skeg via two grub screws.the prop attatches via a dog and a nut goes over it to hold it on.this way the cable stays in the slot as it cant come out the ferrule holds it in place.the advantage of the flex enables you to adjust the cable and line up the engine easier ,it doesnt have to be dead straight a solid shaft needs to be dead straight you CANNOT USE A UNIVERSAL JOINT ON A PETROL ENGINE.contact dave marles with your needs and he will advise you and sell you everything you need he knows all about gas boats hes 5 times world champ.heres his website hes a great guy to deal with.he will get everyting you need if he doesnt have it in stock.http://http://www.prestwich.ndirect.co.uk/surfacedrive.htm
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martno1fan

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Re: Strimmer engines?
« Reply #9 on: December 07, 2006, 11:28:08 PM »

by the way the clutch will allow you to start the engine and the prop will not turn untill you hit the throttle,you will need to either run the engine air cooled(open hatch) or water cool it, if you go to the site i pm.d you you will find all you need to know on how to do it and or buy a water cooled jacket to fit over the engine.gas engines get very hot so if you intend running it under a hatch it needs water cooling .any pics of the hull? is it a mtb boat or a vee hull?big diff between the two a v is a planing hull for high speed the mtb is a displacement hull .if its a v you can go surface drive which is faster if its a mtb you need submerged drive.either way stick with the square flex and the ferrule system.some gas boat racers use loctite to hold the ferrule on the cable it needs to be loctite retainier or you can silver solder it on.you must use silver solder not plumbers lead type solder it wont hold.no universal joint will ever hold under the torque of a gas engine!! so if you do go solid shaft everything needs to be lined up spot on ,not so if you go flex drive.much easier to do also.by the way the yanks never use solid shafts and laugh at us for attempting it i know from experience lol.they also hold all the world records for gas boats and most race boats and sports boats use flex cables apart from a cpl of classes over here and europe.a stub shaft should run you around 8 quid a ferrule fiver and a skeg 10 to 15 quid.props are a bit expensive so see what people  suggests and look on this site for the same one they are half price of uk shops.they too sell ferrules a bit cheaper.get your info and shop arround is my advice its suprising how much you can save lol.http://http://stores.ebay.co.uk/rcworldwide-com prestwich have a prop list that gives each props use ie what cc engine for a submered drive gas engine.if it turns out its a v you need a surface drive to get real speed .there are also cheap mods that can be done to a weedy motor ie bigger carb tuned pipe etc ,if it is a deep v that is.mine is and its getting a 28 cc strimmer engine with a few mods done to it,ports polished new carb and a pipe should see it do over 35 hopefully.with a stock engine id say 20 to 25 is possible.
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OneBladeMissing

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Re: Strimmer engines?
« Reply #10 on: December 08, 2006, 12:38:12 AM »

FSR-V35 petrol boats use solid shafts, and they use engines more powerful than any strimmer engine.
"the clutch will allow you to start the engine and the prop will not turn until you hit the throttle" , so what's the problem if you use direct drive and the prop turns when the engine is running?
As for aligning the engine with the shaft, it's very easy to do.

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martno1fan

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Re: Strimmer engines?
« Reply #11 on: December 08, 2006, 11:13:26 AM »

lets be honest here the flex cable is the easiest way to set up a boat.as i stated if you use a solid shaft everything needs to be absolutely inline.with a flex cable you can have quite a bend in the set up and it will still run well you can also get the engine lower in the boat as you dont need to worry about having the engine at an angle it can just sit parallel to the hull as low as possible which is also a big pluss.he has the cable he has the clutch id stick with it,he needs the clutch if he wants to idle the boat and its much easier than direct drive especially if you intend doing it alone or with kids near.you can put the boat in the water before you start it for one which is a good  idea.also the flex doesnt need bushes only grease in the tube to keep it running smooth.the skeg or strut depending on it beed submerged drive or surface will have bushes for the stub shaft .fsrv do use solid shafts i agree but thats not because its the best way to run a boat its a class!! surface drive boats are way faster as we all know.by all means go with a solid shaft if you choose to but make sure its lined up well,for a quick and easy option and been able to keep the clutch use what you have and add a skeg and a stub shaft .then choose the prop dog and prop you need for whatever cc the engine is.we still dont know if its a v or a mtb yet? if its a v your options are easier as you wont need water cooling for one ,if you run an open hatch boat.
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glennb2006

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Re: Strimmer engines?
« Reply #12 on: December 11, 2006, 12:01:46 PM »

I'd bin the clutch.  ;)

That way you can get a good fix (Through the threaded hole) onto the crankshaft and get a suitable coupling to fit the engine, whether that be for a flex cable collet or a rubber (or one of the many other types), coupling suitable for solid shafts.

By the way reference propellor choice, chances are this motor is going to be quite low revving and "lazy" so you are going to need a big prop. Do you know what the engine manufacturer is? (Zenoah by any chance?)

Glenn

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martno1fan

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Re: Strimmer engines?
« Reply #13 on: December 11, 2006, 12:38:20 PM »

the square flex cable will fit perfect in the square hole so wheres the problem? guys race them using this type all over the world with no problems.as long as he has the collet between the shaft and the flex  and the strut.it cannot come out .i agree with the prop though low revs high torque can handle large props i was qouted a x 482 by mr marles for a weedy but on the whole a prather 275 is a good all round prop for surface drive and if he mods the engine it will also give good performane on the higher reving engine.the us guys use the 275 as a good all round prop.this said we still dont know if its a v or a mtb hull so prop selection is gonna be hard till we know what the boat is.a decent coupling will cost him 20 so if it were me id stick with the flex cable and clutch and buy a strut and ferrule etc.
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glennb2006

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Re: Strimmer engines?
« Reply #14 on: December 12, 2006, 02:03:45 AM »

From reading post three from Blazing Penguin (Good name by the way) it appears that the square drive on the clutch he has does not have a collet, so the problem is that there may be nowt there to hold the flex cable in place. We will never know until he replies next time.

He is probably in the shed with the glass fibre and engine mounts...

Happy days.  :D

Glenn
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martno1fan

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Re: Strimmer engines?
« Reply #15 on: December 12, 2006, 10:19:37 AM »

From reading post three from Blazing Penguin (Good name by the way) it appears that the square drive on the clutch he has does not have a collet, so the problem is that there may be nowt there to hold the flex cable in place. We will never know until he replies next time.

He is probably in the shed with the glass fibre and engine mounts...

Happy days.  :D

Glenn
he doesnt need a collet he needs a ferrule at the other end where the flex joins the solid stub shaft the ferrule is between the strut and the transome and that is what stops the shaft coming out of the square hole on the clutch.some guys even buy square collets so they can use the square cable.it seems you guys arent understanding this?he does not need a collet he needs a ferrule at the other end lol.the ferrule is soldered to the flex and joins to the stub via two grub screws.some even use loctite retainer to hold the ferrule on the flex and it works well by all accounts.the pic i showed is of a square collet but there is nothing that holds the cable in at that end at all it just slips in but as ive said the ferrule stops it coming out as it runs up against the strut
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glennb2006

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Re: Strimmer engines?
« Reply #16 on: December 13, 2006, 09:52:41 PM »

I think Blazing Penguin has given up on boating!! ;D

Glenn
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martno1fan

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Re: Strimmer engines?
« Reply #17 on: December 14, 2006, 07:06:24 PM »

I think Blazing Penguin has given up on boating!! ;D

Glenn
i think your right lol oh well  ::).
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BlazingPenguin

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Re: Strimmer engines?
« Reply #18 on: December 31, 2006, 06:09:48 PM »

Given up?...no chance!

Well not on my tugs anyway...my IC career however may well be over!

Having been told a tale of a local boating pond/IC engine and a baby in a pram Im going to give it a miss I think.
1 49" GRP hull and strimmer engine (working) for swap for some nicad type packs???
(will take pics if required)
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glennb2006

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Re: Strimmer engines?
« Reply #19 on: December 31, 2006, 07:10:04 PM »

That sounds dodgy, that is what fail safes are there to prevent mind...

Glenn
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OneBladeMissing

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Re: Strimmer engines?
« Reply #20 on: January 01, 2007, 03:33:33 PM »

Should babies in prams really be operating IC engined boats?
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Colin Bishop

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Re: Strimmer engines?
« Reply #21 on: January 01, 2007, 03:41:39 PM »

Quote
Should babies in prams really be operating IC engined boats?

Have you never seen - PRAMBO?   :D
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martno1fan

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Re: Strimmer engines?
« Reply #22 on: January 03, 2007, 05:33:07 PM »

resister plugs thats what some guys forget!! if you dont use a resister plug you will lose signal and thats when the accidents can happen.
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OneBladeMissing

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Re: Strimmer engines?
« Reply #23 on: January 04, 2007, 12:51:16 PM »

What's a resister plug?
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glennb2006

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Re: Strimmer engines?
« Reply #24 on: January 04, 2007, 05:24:52 PM »

It refers to the spark plug cap, when used it reduces the RF interference that can sometimes upset radios. Bit like the old suppression problems you used to get when you fitted a car radio to your car that did not have one as standard - back in the day. Also had vinyl roofs, what were they all about?

Glenn
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