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Petrol engine build

THEPJC

Joined: 1-01-70

Topics: 2

Replies: 1

Posted: Fri 2nd Aug 2013, 7:26am
Petrol engine build

Hi,
I was wondering if anyone knew how to connect a push mower engine to either a chain drive system to drive an axel on a loco or to an electric motor which powers the axel. The engine in question is a 3.5Hp Briggs and Stratton pull start from an old push mower.

Hopefully this will be he beginnings of a ride in loco to eventually be run at a club.
 

Replies To This Post

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Fri 2nd Aug 2013, 7:36am

Hi THEPJC !?!?!

I have built a couple of petrol electrics and would be happy to give some support on this if that is the transmission choice you make.
Probably best to e-mail me directly on ivanandchaela.hewlett@bluebottle.com and we can talk directly.

Cheers and Good Luck, Ivan.
 

georgecoles

Joined: 4-08-09

Topics: 19

Replies: 90

Posted: Fri 2nd Aug 2013, 7:41am

Ivan

Is there any chance that you could carry on your conversation openly on this forum. I for one, and from conversations I have had, many others, would be interested to learn from your experience.

Thanks,
George
 

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Fri 2nd Aug 2013, 8:41am

Hi George

Thanks for the comment - Happy to do so if there is interest.
I will also put together something else for the society mag. at some point too.
Basically my comments would be that from many years playing with electrical transmissions they can actually be a very easy way to proceed, particularly given the much better availability of parts these days.
Of course mechanical transmission is possible the key issue to be overcome is that unlike a steam engine a petrol engine is always running and hence this rotational speed has to be matched to the necessary line speed (and load) of the locomotive and train. The biggest difference is at starting the train when the wheels are stationary and have to be accelerated by the rotating engine shaft. Some form of clutch is necessary to convert the rotating drive speed to the gradually increasing wheel rpm. This is usually achieved by friction plates wasting considerable energy as heat. This method is in use on a lot of very nice models though and often the original centrifugal clutch may be used with suitable gear reduction to the wheels - voila !!

However, personally I like the elegance of electrical transmission and the fact that it more efficiently matches the torque from the engine shaft to the wheels across the whole speed range. (There are still thermal losses though, hence the warming of the generator and motors).
There are several approaches, but probably most applicable for a 3.5hp engine is simply to drive a car alternator, biggest you can get - 80/100 Amps would be ideal. There is a rule that says (approx) 750Watts = 1HP therefore a 12 volt 80 Amp alternator can develop around 1 to 1.5 HP, realistically more than enough to handle the true output of your engine, at least intermittently.
I have simply taken the regulator cover plate off the back of the alternator and accessed the regulator, this usually has three connections to the alternator itself, Chassis (ground), output voltage terminal (battery monitor) and output to the control winding (armature) in the alternator. Simply disconnect all three, maybe plug in or you may have to cut some wires or copper strips and then take out the regulator. The only connection you will need is the one to the armature - connect a wire to this. I usually use the cores from 7 core trailer cable available from most car shops or similar for a quid or so a metre and with seven different colour wires per length suitably rated for most non-traction wiring. In this case when I use the term Traction Wiring I mean just those wires linking to the motors - this wire to the alternator is just a control signal. Lead the wire out through the back of the alternator, this will need some form of control applied to it, maybe an old rheostat or more likely a simple pulse width modulated controller - I will dig out a reference to these in the News and advise later.
Typically I connect the alternator to the engine at a pretty much 1:1 ratio - and it works, but just wait for others to shout that it is sooo wrong ;-)
The alternator output can then be fed to motors of your choice, or even another alternator used as a motor - I've not actually tried this, but it is a real possibility if alternators are more readily (cheaply) available to you ?
I hope this has whet your appetite, any questions please just ask.

Cheers, Ivan.
 

georgecoles

Joined: 4-08-09

Topics: 19

Replies: 90

Posted: Fri 2nd Aug 2013, 10:26am

Thanks Ivan

Exactly what I wanted to read, and what I am doing, as I am building a couple of petrol/electrics using direct drive. One of them will be a former battery/electric rejigged to be more prototypical! I know others who are also planning to use that route, but don't know where to start.

Regards,
George

 

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Fri 2nd Aug 2013, 10:32am

Hi George
Glad to be of help. I have been experimenting now for 25 years, but am still learning.
There are a couple of articles in past NEWS that might be worth a look - No. 36 Spring 1986 and No. 135 Winter 2010.

The first of these describes a simple, cheap and very effective controller and the second describes my F7 which uses this controller.

Are you planning to be at the AGM ? I would be happy to catcch up for a chat then, or perhaps at the Bedford get together ?

Cheers, Ivan.
 

georgecoles

Joined: 4-08-09

Topics: 19

Replies: 90

Posted: Fri 2nd Aug 2013, 10:50am

Ivan

Thanks for the references.

We won't be going to the AGM. All being well, we shall be at Bedford. Hopefully with something running 8-)

George
 

billhaywood

Joined: 22-05-03

Topics: 17

Replies: 30

Posted: Fri 2nd Aug 2013, 10:54am

I have a couple of lawn mowers redundant and often wondered on doing the same thing. Start thinking then thing become grey with electrics and transmissions etc.
This could be a good project for the magazine with perhaps detailed sketch drawings and where to obtain components too.
 

ivanhewlett

Joined: 1-01-85

Topics: 8

Replies: 53

Posted: Fri 2nd Aug 2013, 11:49am

Hi Bill

Interesting point - I find I struggle making exhaust pipes and fabrication in general, for me the wiring is the easy bit, horses for courses, but I agree that it could be a good basis for an article. I'll start pulling something together.

Cheers, Ivan.
 

MartynRedfearn

Joined: 1-01-94

Topics: 16

Replies: 107

Posted: Fri 2nd Aug 2013, 5:20pm

There is a very good article at http://www.smex.net.au/Reference/AlternatorTraction02.php

I am just in the process of building a loco using petrol engine, alternator with speed controlled by altering input voltage and electric motor for drive and it works very reasonably priced
 

THEPJC

Joined: 1-01-70

Topics: 2

Replies: 1

Posted: Fri 2nd Aug 2013, 6:22pm

Thanks for all the help it is musch appreciated.

Any progress will be posted up here so others can put it to good use.
 

georgecoles

Joined: 4-08-09

Topics: 19

Replies: 90

Posted: Fri 2nd Aug 2013, 7:03pm

Interesting article. Also appeared in the Hobby Engineer Magazine, issues 2 and 3. I don't know the dates of the issues.

George C
 

colinedmondson

Joined: 9-08-09

Topics: 3

Replies: 82

Posted: Sat 3rd Aug 2013, 9:59pm

I have just converted my loco DON to petrol electric following Dave Webb's article on the smex website. I am very happy with the results so far, a bit of experimenting still to do but it seems as strong as it was with a mechanical transmission.
Colin Edmondson
 

Xz

Joined: 1-01-92

Topics: 17

Replies: 244

Posted: Sun 4th Aug 2013, 8:02am

Ivan, I'm sure the new editor, whoever that may be, would welcome an article (or short series) on such a subject. We have far too few 'techy' type articles available, please do try.
 

georgecoles

Joined: 4-08-09

Topics: 19

Replies: 90

Posted: Mon 14th Oct 2013, 12:13pm

12 hours and nothing bought in or cut, except a few lengths of low voltage wire, and it works. Ridiculously simple and a minimum of 'engineering.' Mind you, something other than a test-rig might need a bit of engineering, but everything you see in the picture comes under the 'might-be-useful-one-day-so-don't-throw-it-away' heading. That includes the discarded battery which has two cells not working and only charges up to about 7.5 volts.
Succesful run on the Northampton SME 2800ft track.
Now to start on a 'real'loco.
George C
12 hours and nothing bought in or cut, except a few lengths of low voltage wire, and it works. Ridiculously simple and a minimum of 'engineering.' Mind you, something other than a test-rig might need a bit of engineering, but everything you see in the picture comes under the 'might-be-useful-one-day-so-don't-throw-it-away' heading. That includes the discarded battery which has two cells not working and only charges up to about 7.5 volts.
Succesful run on the Northampton SME 2800ft track.
Now to start on a 'real'loco.
George C
 

Pete the Pilot

Joined: 1-01-70

Topics: 0

Replies: 2

Posted: Mon 5th May 2014, 1:08pm

As one of those 'Johnny Come Lately' types who arrive late to these things (just joined ) I would appreciate anyone updating me on this topic. Have there been articles since on this topic please.
 
 
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