Live diesel monster, CFG + FEVE

Looks interesting

http://www.justengines.unseen.org/acatalog/On_Board_Glow.html

I presume on the KISS principle one ought to ask what is the problem in having the glow plug permanently lit if there is enough battery power on board.

My local model shop says it will wipe out the glow plug but this is contradicted by many forum comments. I will soon find out.

That's very interesting and very similar to the Kavan glo system.

I said on another thread about this and I have been permanently energising the glo plug for 3 1/2 years with only one change of plug.

Of course it won't wipe out the plug because even in normal use it is being heated up by combustion.

Must be the same model shop who told me that everything I did would result in a massive ballistic explosion causing death and destruction to it's creator and all around....

So what advantages are to be gained by the extra cost and complexity of such a device and being able to disable power above certain revs ?

I think it's the other way round in that the advantage is automatically energising the plug at low revs and switching off at higher revs/temperature when there is no need to energise it.

I went in to this quite a lot with Bop Pope in the USA. What started as a fear of overheating ending up as concern for underheating especially at low engine speeds.

Glop plug engines rely on running within a specific temperature range to achieve maximum effiency. I think (don't quote) but the figures we discovered were 220°F-240°F for small car type engines. Aero engines can run hotter. Mine was running at around 200F° maximum when hot.

'During longer periods of idling, the temperature inside the combustion chamber drops relatively significantly, and the plug filament will not burn as well. The fuel mixture hitting the cooled filament adds to the problem, making it cooler still. When the throttle is opened and power is needed, the engine may splutter or even cut out as a result, because the filament hasn't the heat to ignite the fuel/air mixture properly.
The filament can often get 'drowned' at low idle revs especially with a rich mixture.'

For our purposes we do not need racing speed engines and our quest is for a low revving engine anyway.

A gloplug motor generator set can be made even crudely to produce enough electricity at tickover or certainly less than half throttle.

What are the advantages of switching off the power at the high revs end as opposed to a single cell battery permanently connected for the whole revs spectrum, high and low.

Only because it is not necessary to have the plug energised at high revs to keep it glowing as the combustion heat will or should do that.

Keeping the battery connected at high engine revs/temperature just wastes the charge and supposedly damages the glo plug which I have yet to see.

I leave my 5ah battery connected and it lasts well over an hour. So you're probably right!
What's the point of extra expense and cicuitry. Just a simple on/off switch would do.

My wiring looks like spag bol as it is.

In fact I've just had a great idea.

I had a 6 volts relay in series with the generator output supplying the speed controller which dropped out at below 6 volts (actually 5) and low revs causing traction batteries to switch in.

All one needs is to connect the glo plug feed through a set of relay contacts and when the generator revs are high the voltage output is above the relay threshold and switches off the glo plug and when the revs are low the output is not enough to hold the relay open and thus switches on the glo plug.

Where's my soldering iron....?

Nice idea Carl.

Additionally I suppose other options are to use the p92 below for a stable receiver supply and a fuse and wiring tidy:-

http://www.action-electronics.co.uk/pat.php

or these is P43/44 switches for r/c remote manual ic starting, changing from ic to battery or glow battery on/off.

http://www.action-electronics.co.uk/switches.php


David

Some uesful gadget circuits there.

Everything remotely switched would be ideal and very professional but I'm not quite sure it would be that easy in practice.

I think on the RCS controllers there is a facility for remote switching. I will have a look and experiment.

What would be really useful is a remote temperature gauge!

Today I started up my nitro motor for the first time.

It started perfectly and went downhill thereafter. After 30 seconds it stopped and then I realised that it had unscrewed itself from the sleeve connecting it to the generator. This is because I forgot to modify the coupling after finding out that the manufacturer had sent me an incorrect email about rotation direction. Still my fault because I did check with a friend who did say the manufacturer had got it wrong but in the excitement I forgot to modify the coupling.

Anyway this mishap seems to have damaged the engine and I presume it has stressed the rod connecting the crankshaft to the piston head. Consequently I am awaiting a replacement which I will try harder to protect.

Now I dont want to profit from the hard development work of others but am reticent to spend valuable time reinventing wheels that have already been turned.

Therefore if Anton, Carl or anyone else, can advise how to connect a brass sleeve/collar to the nitro engine where the thread unscrews with the propshafts proper rotation, I would be most grateful. The only thing I can come up with is loctite but that seems a bit of a lash up.

Also did you both settle on a generator fixed down solid to the engine base or did you leave it to float and just anchor against the rotation force.

Disappointing so far but a lot of fun.

David

Thinking a bit more about shaft connection and alignment between the nitro and dc shaft 2 further options seem feasible.

1 Use a nitro car transmission with a couple of plastic gears with the two shafts parallel. Presumably this would require no metal engineering or turning facilities. Probably would be cheap if one can find a retailer with stocks, maybe noisy, but would not require precision shaft alignment and probably little vibration.

2 Similar to above except using a rotating cross beam on one in line shaft end and a couple of substantial metal pins on the other in line shaft. Presumably this would require some alignment but not absolute and would have probably little vibration and easily disassembled.

Any comments appreciated, critical or otherwise.

Sorry to hear about your engine David.

I went through a number of couplings before using a solid brass sleeve from a marine model shop.

This is held on the engine and motor shafts with simple grub screws.
The engine shaft is threaded and the grub screw grips on the thread. Occassionally it comes loose but is easily retightened without any ill effects.

The electric motor is allowed to float a little on it's clamped mounting.

The best type of couplings are in my opinion the Oldham type. They are high torque/high speed and allow reasonable misalignment...but they can be very expensive.

There many ways to couple the two. A short belt drive is another way.

I have an idea for a simple manual clutch/engagement which I would like to try soon.

David.....

The way in which me DC motor is connected is using a simple steel sleeve. I use grub screws to attach the sleeve to motor and to engine. Each end was drilled to fit perfectly over each shaft...(one coming from the nitro engine and one coming from the DC motor). I filed a flat edge on the nitro motor shaft in order to give the grub screw something to grip. the motor came with a flat edge already...

I have found that using screws with a Allen key head as opposed to a Phillips screw head is better as they seem to go tighter. mine have come loose now and again but rarely do and are very easy to tighten. They only problem i have is im worried that they may come loose while the engine is running and have the possibility of flying off and hitting me in the face which i am sure would cause serous injury. I SAY i plan to put a safe guard around the sleeve in order to protect myself but doing it is another issue as i have already started work on my next loco.

If you would like...i can take so close up pictures of the coupling? let me know...

Carl did mention to me about using a "Oldham Coupling" but I have no idea what they are. Im sure they must be good as we all know he had knowledge in that field

Just a little thing for Carl..... What percentage nitro fuel are you using?

Ohh and about fixing the DC motor down....I have actually used a mouse matt cut to the shape of the motor mount as it has a foam part to it....i have actually doubled it up so ive got effectively 2 mouse matt underneath each other....make sure that you put the foam side facing up (so the motor is sitting on the foam and not the plastic laminate. I have screwed the mount down just enough to allow a but of movement but not enough to rock it and brake anything. I have only added 2 screws as well (diagonal to each other) to allow extra movement in all direction.

This an Oldham type coupling.

Huco Oldham Couplings

Anton I am using 10% (nitro methane) fuel at the moment. Although I have used 5% which seemed a bit better. This is a castor and synthetic oil mix.

My sleeve coupling sometimes comes loose but nothing happens except the engine races off at higher revs with no load.

Ahhh i see now...

I am using 16%.....im not sure of what difference it makes?? I was told this one was good for my particular engine. What is the difference?

And yes mine has never actually flown off touch wood

See this:

Nitro fuel

There are two percentages quoted in fuel.

The main one usually refers to the amont of nitromethane - the active ingredient. It seems that car engines prefer or require more than aero engines.

I'm not exactly sure either what the real difference makes especially if you use an aero engine like I am in an enclosed space.

Although I'm always looking for something that slows the engine down and still keeps running smoothly.

I have been looking at alternatives to a solid brass coupling to connect the nitro engine to a dc motor.
Oldham couplings seem to be max rated at about 3k rpm, even with minimum misalignment at low values of say around 0.2mm. I would imagine that at 5k or more these would be get very hot and/or fail. Additionally they seem expensive for an R&D exercise, so, as Carl did before me, I will not be persuing this option.
A more promising option might be to use the plastic gears that are used on model cars and these would presumably allow the two shafts (nitro and dc) to be located in parallel, allow a ratio to be applied and also remove the alignment/vibration problem.
Now I have no direct experience of r/c car gears, so if Carl, Anton or anyone else has an opinion or knowledge of these systems please post. I plan to visit the large r/c car shop in Leicester in the next week or so I could gather and post more data then.

Gears can be a problem direct on the glo plug engine. Too much power/force, it will strip gears.
You will almost certainly need a clutch arrangement.

Dave Watkins wrote about gears on his Detritus mechanical machine.

I definitely agree with Carl that just having the nitro engine direct onto gears will strip them I i once tried to do this when attaching a nitro engine direct into a model boat...well it never worked and i gave up. If you are using a car engine, then it should have come with a clutch.....I have a spare clutch bell and fitments which i took off the force 15 engine and if you think it would fit your engine, then you can have it. A nitro car uses a farley large, heavy duty gear that attaches to the clutch gear which I would recommend considering if you are not going to use a sleeve to connect engine to motor.

I was actually going to talk about having a look at Dave Watkins loco but Carl beat me to it .

These are a few of is his videos anyway

https://www.youtube.com/watch?v=w6tdS0EjJ3s

https://www.youtube.com/user/quothick#p/u/5/hZsy23rpuVQ

Wow. I now know why Carl and Anton are so keen on this live diesel concept.

Ran in the nitro engine with generator this afternoon and very exciting it was . I think today indicated

- Simple brass coupling worked fine at about 5k revs, maybe I was lucky wiith the alignment. - - Vibration levels appeared to be OK and possibly similar to Carls.
- Noise levels with an off the shelf quiet silencer were adequate and would be good if an after pipe further reduced noise levels.
- Used about 5 oz of fuel running at about 3/8ths max revs in about 11 mins

I have just arranged my knee replacements to be fit for Villebon.

Vive le diesel en direct or whatever live diesel is in French.

I'm very happy and excited too....Do you have any pictures David?
I can post them if you wish.

What brass coupling did you use and where did you get it from?

Don't try and anchor the electric motor down too much, although enough to stop it flying off and to be safe and secure but with this rigid coupling it is crucial that it has enough play in the mountings to follow the glo plug engine's (crankshaft) movements and not resist them at all.

You can anchor the glo plug engine down tight though. I did originally try fixing both on (expensive) rubber mountings which was not overly successful and everything wobbled about alarmingly like an ample buxom ex-girly I once knew.

I reckon this year is the year of the diesel on the forum and I think there could be a couple more built too before the next solstice.

Im happy for you...i remember the excitement of getting my first engine running....

Yes do make sure you do not attach the motor to to firmly..not that i have done this but i can imagine what will happen and it could be expensive and dangerous to you...

Ive used a good old mouse matt which i have placed the motor on, as the foam part allows movement. I have 2 cut out pieces on top of each other for extra flexibility and two screws holding the motor and motor mount onto the matt (diagonally), fixed in two opposite corners.

I cant wait to see your loco and please, please upload some photos the minute you have any

In France (French) if you are looking for couplings the phrase is coupleur d'axe
Having just recently found this term I have discovered many sources of cheaper couplings.....
e.g.

Conrad coupling

Thanks for the recommendations regarding floating the dc motor.

The coupling I used yesterday was the one I made last year and is shown in the photographs in the thread "Gijon Villaviciosa Covadonga" in the Garden Railways section.

I wonder if one had a long enough coupling and no gravitaional forces whether the two shafts would be self aligning. I set my dc motor alignment by clamping the whole motor assembly in the verticla plane and carefully shimming the gap between dc motor mounting and the whole motor assembly and fastening down tight. Not sure how much this would reduce the life of either the nitro and dc and also how lucky I was with the final alignment.

I am also thinking about trying one of these

http://www.budgetbeam.co.uk/

although at about £20 are expensive.

Try this- it's much cheaper. Use a short section of flexible polymer tubing as a coupling. Get the tubing in a slightly smaller diameter than the shafts. Look for a thicker wall tubing if available. Force the tubing ends over the shafts - perhaps with a touch of contact cement to hold them on.