Hi there again. As there was quite a lot of interest in the above
project when I first posted a few questions in 2008. I thought I would
write an update.

I had to do a search to find my previous posts in Nov. 2008. It has
been so long since I last posted. The work only resumed when the
weather go too bad to do things outside, about October I think. My
generator set was in the idea stage then and it went through various
unsuccessful stages from which I had to retract and a lot of it, with
photos, is on my website : http://www.maribelecosystems.com/OldEngines.html

Since the last entry on the website I have got the thing running quite
well and the end design is that the engine has a larger pulley on the
shaft with 3 belts to give the correct alternator speed at about 1000
rpm. I was talking to someone who seems to know his Perkins P3s and
he said it probably was from a tractor which could be set on a hand
trottle to run at 1000 and at this speed it would probably still
develop between 20 and 30 HP. It is very happy at this speed and
considerably quieter, than it was when running at 1500. It is now
bolted with 1/4 inch rubber sheet packing directly to the bed and is
very firm, but not absolutely rigid. This is how it seems most
comfortable. I have also got the beginnings of an exhaust pipe and a
silencer will be welded in between the two mounts for the flexible
pipe as it is, above the alternator.

The main problem now is that on trying to start it, the weight of the
alternator rotor is an awful lot, especially geared up a bit and -
even worse for the starter, is the extremely low temperature in my
workshop, lately, which thickens the engine oil to the consistency of
treacle!

I fitted a glow plug from another engine into the block drain plug and
I warm the whole block now, using an 8 amp battery charger

I am still thinking about this and have now rigged up a system like a
clutch so that I can start the engine, - de-coupled from the
alternator. It consists of 3 belts quite a bit bigger and an idler
that can be screwed in to push the backs of the belts in to tighten
them as soon as the engine starts. I have not tried this yet, but I
don't see why it shouldn't work. I have an old Condor mower that uses
a belt tension idler to act as a clutch. That's where the idea came
from.

The engine - at the moment has a closed cooling circuit which only
hold about a gallon, with no radiator, as it will be a CHP system, so
it only runs for about 10 mins before it starts to overheat. However I
did get the alternator up to speed and had a bulb between one phase
and neutral. Without any excitation at all it was about half bright.
I connected 2 bulbs in a series circuit with the shed single phase and
got the speed correct and then tried connecting a low dc voltage to
the excitation winding. Although I would have expected it to require
what was marked on the plate of the excitation generator, i.e. about
16 volts at 1.8 amps. It went right up to full voltage with only 6v
from a dual voltage battery charger. After I had put a proper 3 phase
socket on the side of it and wired that and a 13a single phase one, I
connected the output to my Denbigh mill and sure enough it ran
perfectly OK, - albeit backwards!

The question is, will this be enough? I can easily measure this
voltage and then feed an appropriate amount of real DC from a sort of
zener stabiliser, or will it have to be a "proper" AVR ? I reckon the
actual speed will be quite stable as it is set by the diaphragm
operated fuel injection pump and I did not notice any variation when
switching the mill on and off. The lathe might be another matter
though, - ideally I would like to run it on the 7 1/2 hp setting to
get the full capstan speed of about 1000 rpm. Up to now I could only
run on the 3Hp position - top speed 500 rpm. Went I get it starting
easily and with more cooling I shall connect the Herbert to it. That
may take the wind out of it's sails!

Next time, I am going to put in the cooling system a heat exchanger
with a central heating pump controlled by the water temp pumping
water from a big 40 gall drum, through it. This will allow me to run
for much longer.

The chassis is off the ground on timbers, now as when I was pushing it
into the workshop both the castors got stuck and all bent, I was on
the tractor so I couldn't see what was happening. I really need some
heavy duty ones under the Alternator end, as it is really heavy. I
may even have to fabricate some disks wheels out of steel plate as
they will only be used on concrete. Castors would be better but have
you seen the price of them? That end of the frame is easily a ton.

Thanks for any comments, regards George.

Fab website! One to go in the bookmarks. I love it when a real
enthusiast turns up on this forum with a whole project history.

On Sat, 27 Feb 2010 13:10:06 -0800 (PST), George wrote:

I am still thinking about this and have now rigged up a system like a
clutch so that I can start the engine, - de-coupled from the
alternator. It consists of 3 belts quite a bit bigger and an idler
that can be screwed in to push the backs of the belts in to tighten
them as soon as the engine starts. I have not tried this yet, but I
don't see why it shouldn't work. I have an old Condor mower that uses
a belt tension idler to act as a clutch. That's where the idea came
from.

I've seen very similar on a two-seater helicopter, with the tensioning
pulleys being driven in and out by an electric motor.

I'm not sure that tensioning via the back of the belts is good though - I
just feel that reverse flexing v-belts isn't a good idea and that it'd be
better to tension from the inside, out.

SteveW

On 27 Feb, 23:35, Steve Walker wrote:
On Sat, 27 Feb 2010 13:10:06 -0800 (PST), George wrote:
I am still thinking about this and have now rigged up a system like a
clutch so that I can start the engine, - de-coupled from the
alternator. *It consists of 3 belts quite a bit bigger and an idler
that can be screwed in to push the backs of the belts in to tighten
them as soon as the engine starts. *I have not tried this yet, but I
don't see why it shouldn't work. *I have an old Condor mower that uses
a belt tension idler to act as a clutch. That's where the idea came
from.

I've seen very similar on a two-seater helicopter, with the tensioning
pulleys being driven in and out by an electric motor.

I'm not sure that tensioning via the back of the belts is good though - I
just feel that reverse flexing v-belts isn't a good idea and that it'd be
better to tension from the inside, out.

SteveW

Thanks Dom, I'm glad you like it!
Thanks too Steve, with that very thought at the back of my mind, I
have made the post that supports the tensioner with the view that
should the "push" not have enough travel I can "pull" the belt
instead. I have a small three sheaf pulley that will only need some
bearing mounted inside and Bob's your uncle.

Regards George.

In message , Steve Walker
writes
On Sat, 27 Feb 2010 13:10:06 -0800 (PST), George wrote:

I am still thinking about this and have now rigged up a system like a
clutch so that I can start the engine, - de-coupled from the
alternator. It consists of 3 belts quite a bit bigger and an idler
that can be screwed in to push the backs of the belts in to tighten
them as soon as the engine starts. I have not tried this yet, but I
don't see why it shouldn't work. I have an old Condor mower that uses
a belt tension idler to act as a clutch. That's where the idea came
from.

I've seen very similar on a two-seater helicopter, with the tensioning
pulleys being driven in and out by an electric motor.

I'm not sure that tensioning via the back of the belts is good though - I
just feel that reverse flexing v-belts isn't a good idea and that it'd be
better to tension from the inside, out.

No. Look at any combine harvester. Engaging the threshing drive has been
done this way for years. Usually poly-V belting though. Plenty of scrap
combine harvesters around Norfolk. ISTR some Claas breakers at
Haverhill. However, you will introduce serious side loading to the
engine and generator main bearings.

Long way back now but the *tractor* engine would have been fitted with a
clutch capable of transmitting the rated horse power.

Magnetic clutches exist but isn't all of the energy required to spin up
going to arrive at the interface as heat?

regards

--
Tim Lamb

Steve Walker wrote:

I've seen very similar on a two-seater helicopter, with the tensioning
pulleys being driven in and out by an electric motor.

I wouldn't want to fly in that.

On Sun, 28 Feb 2010 12:41:19 +0000, Steve Firth wrote:

Steve Walker wrote:

I've seen very similar on a two-seater helicopter, with the tensioning
pulleys being driven in and out by an electric motor.

I wouldn't want to fly in that.

They use multiple belts (eight or more IIRC), providing redundancy and the
clutch effect is necessary for both startup and to allow autorotation if
the engine were to fail.

SteveW

Steve Walker wrote:

On Sun, 28 Feb 2010 12:41:19 +0000, Steve Firth wrote:

Steve Walker wrote:

I've seen very similar on a two-seater helicopter, with the tensioning
pulleys being driven in and out by an electric motor.

I wouldn't want to fly in that.

They use multiple belts (eight or more IIRC), providing redundancy and the
clutch effect is necessary for both startup and to allow autorotation if
the engine were to fail.

Is this the R22? I really, really wouldn't want to fly in one of those.

On Sun, 28 Feb 2010 14:27:18 +0000, Steve Firth wrote:

Steve Walker wrote:

On Sun, 28 Feb 2010 12:41:19 +0000, Steve Firth wrote:

Steve Walker wrote:

I've seen very similar on a two-seater helicopter, with the tensioning
pulleys being driven in and out by an electric motor.

I wouldn't want to fly in that.

They use multiple belts (eight or more IIRC), providing redundancy and the
clutch effect is necessary for both startup and to allow autorotation if
the engine were to fail.

Is this the R22? I really, really wouldn't want to fly in one of those.

No, I think it was the Schweizer H269. Having seen the promotional video
for the R22 and seeing how the controls vibrated so badly and the cheap and
cheerful flip-over cyclic control, I was pleasantly suprised by the H269,
which was quite smooth.

SteveW

On 28 Feb, 14:27, (Steve Firth) wrote:
Steve Walker wrote:
On Sun, 28 Feb 2010 12:41:19 +0000, Steve Firth wrote:

Steve Walker wrote:

I've seen very similar on a two-seater helicopter, with the tensioning
pulleys being driven in and out by an electric motor.

I wouldn't want to fly in that.

They use multiple belts (eight or more IIRC), providing redundancy and the
clutch effect is necessary for both startup and to allow autorotation if
the engine were to fail.

Is this the R22? I really, really wouldn't want to fly in one of those.

Before deciding to try this method of getting the engine to start
before applying the load, I tried with one belt of varying length and
using one with just enough length to start the engine easily, I then
allowed the engine to get up to speed and as it did, the loose belt, -
a standard car fan belt of A section, dug into the pulley slots and
squealed for several minutes before the alternator finally reach
running speed. I measured the rpm of the alternator and it was only
very slightly below 1500. rpm.

When I stopped it, the alternator ran on with the belt slipping for
ages before it too stopped. The belt was hardly warm so I think with
an even looser belt, - or rather with the 3 belts even looser, this
method should work ok. I shall have a knob pushing the idler against
the backs ot the 3 belts that I can take up as soon as the engine is
running OK. If it does not seem satisfactory, for any reason, plan B
is to pull the belt outwards with an adjustable tensioner with a 3
sheaf pulley, which only needs 2 bearings pushed in with a bolt
pulling the belt outwards, which has a longer possibility of
adjustment that may be necessary. Now what about that excitation?

Regards George.