G3 Forum

Diesels, Electrics & All Things "Modern Image" => Locomotives (diesel & electric) => Internal Combustion Power for Model Locos. => Topic started by: John Candy on Feb 18 2013 20:20

Title: Diesel Electric?
Post by: John Candy on Feb 18 2013 20:20

ADMIN NOTE : This thread is a continuation of http://lakes-pages.com/gauge3.co.uk/G3Forum/index.php?topic=125.msg5286#msg5286



Quote:

Starting and cooling are not big problems

Unquote:

Errmmm I beg to differ.... I did the maths (and actually they did turn out to quite nasty). The amount of cooling required for a small G1 model can be coped with a simple fan and provided the model is not supposed to run for more than about 10-15 minutes -then an 8cm @240 Litres per minute fan can (just) keep a finned 3.5cc aero engine within bounds, (i.e. below 60C). The amount of waste heat that my engine has to dissipate is 300 Watts. This is a rate of flow of 1.2 Litres per minute with a drop of 15C across the radiator.

I don't think that anybody, (without green skin), could flick over the 7.5cc engine that I use. The starter motor is 7cm diameter and 17cm long with Car Battery croc clips....

As to sound -that is a physical and mathematical no-go area. It is impossible to produce a note of the depth required to emulate a true exhaust system tone within the confines of the G3 loading gauge. I have no problems with sound cards and the like -but I accept what is possible.

My locos have chassis made of 3mm thick metal and are very heavy compared to a G1 model(!)

regards

ralph
Title: Re: Diesel Electric?
Post by: Peaky 556 on Feb 18 2013 22:29
Put like that Ralph, 300W is a large amount of heat to dissipate.  I'd like to see your calcs for this if poss?  Are you assuming about 65% comes out as heat, 35% mechanical power? 
I could estimate we don't need more than about 30-35W mechanical power at the wheels for a loco in G3, but I have no experience.  It's estimated like this:
Assuming a pretty poor efficiency of 50% for the final drive electrical to mechanical conversion at the bogies, gives electrical power consumption of ~65 W to drive our train at scale speed with a rake of coaches.  This is 5A drawn by a 12V electric set up.  Does that sound reasonable to the battery-electric guys?
Taking this one step further and assuming our D/E has a fairly inefficient generator and driveline/gearbox of about 40% efficiency, we need about 75-90W of mechanical power from the engine. 
This could give about double this as waste heat output, ie 150 - 180W needs to be dissipated by a fan blowing cold air over the fins, or one of Ralph's liquid cooled radiators.  This seems more likely to be achievable without the engine cooking.
However for a much less efficient transmission......such as could might be achievable in a diesel-mechanical, then engine power requirements and waste heat are going to rise badly!
Any thoughts?
Regards,
Tim
Title: Re: Diesel Electric?
Post by: Moonraker on Feb 18 2013 22:57
There is a lot of information on live diesels on the continental garden railway forum at http://www.cgtrains.com. The guy who runs it, Carl Hibbs, has built four live diesels so far and has a lot of knowledge to pass on.

Regards
Peter
Title: Re: Diesel Electric?
Post by: cabbage on Feb 19 2013 07:56
Having unearthed the notebook and deciphered the LSD doped spiders death convulsions that seems to be my natural handwriting style…

Engine: ASP 0.46m

Fuel: Methanol 70% Nitro Methane 5% Oil 25% SG=1.1

LHC Methanol:  726kJ Mole

Air/ Fuel Ratio: 7 to 1 Air to Methanol =  4.9 to 1 (call it 5:1) Air to Fuel

Idle 2,000RPWM Peak 4,500RPM Use 4,000RPM

Energy = (4,000 x 7.5 / 5) x (0.7 x 726) / 60  = 6,000 x 508.2 / 60 = 50,820

Assume 9% Thermal = 0.09 x 50,820 =  4,573.8

Usable power 25% = 1143.45 Watts (manu specs say 1.2kW!!!)

spent through exhaust 50% = 571.7W
spent as cooling 25% = 285.8W
tractive power 25% = 285.8W

Torque convertor ratio 4.2 : 1 therefore tractive power to gearbox = 68Watts

Tim, most of my electric locos use 12 Volts at 5 Amperes, (the NER EE-1 uses 20A -but then it has 6 Motors). If you like I can do the calculations for you based on the dynamo design that I used for the Heiilmann Steam Electric loco.

regards

ralph
Title: Re: Diesel Electric?
Post by: 454 on Feb 19 2013 10:16
OK I was a sceptic but now I am convinced.
Just been checking out some you tubes.

http://www.youtube.com/watch?v=gSwha_Ug7sk

Try this one

Come on Tim Peaky squeeze that little lot into a class 45 or a 40.  :)

Cheers
Dave
454

Title: Re: Diesel Electric?
Post by: Moonraker on Feb 19 2013 10:22
Rather than just re-inventing what many others have done, with mediocre results, how about taking a new direction? Last weekend, a friend demonstrated a Maier Mechanic gas engine which he purchased on Ebay. It uses butane gas fuel, runs at 200-1500rpm and makes a much more appropriate sound than a model aircraft engine. Could it be the basis for a live diesel loco? Google "Maier Mechanic " for details.

Regards
Peter
Title: Re: Diesel Electric?
Post by: cabbage on Feb 19 2013 11:15
I have to admit that they are incredibly pretty.... But as a source of power I don't think they are robust enough. There are no details as to the torque curve or power output of the devices. If it was to be used for a torque source for a dynamo then Rho the Voltage Generation Loss factor (here I am guessing) would have to be something colossal like 9 or 10!!!

The rating of the a dynamo is the number of lines of flux cut per second X diameter of rotor X 1/Rho

Rho you look up on the tables but it is a function of the thickness of the wire and the number of winding on the rotor. A 3 phase alternator could be made by rewiring a 3 phase brushless outside runner aero engine with a 3 phase bridge,  a "dustbin" of a capacitor and a HUGELY over rated Voltage regulator to provide a 12 Volt source.

regards

ralph
Title: Re: Diesel Electric?
Post by: andrewfoster on Feb 19 2013 15:29

spent through exhaust 50% = 571.7W
spent as cooling 25% = 285.8W
tractive power 25% = 285.8W

Torque convertor ratio 4.2 : 1 therefore tractive power to gearbox = 68Watts

Tim, most of my electric locos use 12 Volts at 5 Amperes, (the NER EE-1 uses 20A -but then it has 6 Motors). If you like I can do the calculations for you based on the dynamo design that I used for the Heiilmann Steam Electric loco.

regards

ralph
Ralph - you've lost me in the calculations. Is there a typo in the units? The power (torque x speed) delivered by a torque convertor is reduced only by its efficiency, not the torque ratio, so it looks as though the figure should be rather higher than that. Apologies if I am misreading you!

Andrew
Title: Re: Diesel Electric?
Post by: cabbage on Feb 19 2013 16:50
Quite right! Last line should read

Torque convertor rotation reduction 4.2 : 1

output RPM 952.3 @ 0.6Nm = 58Watts

I think I can get a higher rating but the problem is with pumping the fluid in and out of the torque convertor chamber -it is made of layers of 6mm thick polycarb....

regards

ralph
Title: Re: Diesel Electric?
Post by: Peaky 556 on Feb 19 2013 23:15
Peter - thanks for the CGTrains link, am awaiting approval to get on the site.  The gas engine has a Victorian beauty, but is probably just a display piece that will not produce useful power.  Look at the weight and size too!  There is a lot more power density in an aeromodellers glo-engine, but it only achieves it by running much faster.  My approach is to run such an engine more slowly to get the right pitch and only demand about 20% of its peak power (which may be plenty)!

Dave - I'm trying, really!  But I need to match powers and speeds and atune my ear to distant memories of Sulzers, before ordering gears or cutting metal!  It might happen, with the encouragement of this forum!  :) ::)

Ralph - thanks very much for going to that trouble.  Not quite what I was expecting - a 1st principles approach.  There must be a fuel flowrate term in there somewhere, but difficult to pick out factors and units.  No matter, I am heartened that we are talking similar orders of magnitude of waste heat to dissipate.  Are you saying that the 300W of your 7.5cc engine is a losing battle and it cooks up after 10 mins or can you keep it steady-state?  Will I have a big problem with a PC fan or two trying to blow away 180W of heat do you think?

Regards, Tim
Title: Re: Diesel Electric?
Post by: cabbage on Feb 20 2013 07:13
Tim -Sorry!!!  ::) Being a Chemist I tend to think of things in MOLES....

1 Mole of methanol is 32Grammes. Call it an Ounce of Fuel!!!

The fuel tank is a 6oz one and it keeps the loco in grumble for at least 20 minutes -the longest operational run has been in the 40 minutes mark. The constant coolant temperature from my AMD XP1700 CPU cooler and 43 Litres per minute 80mm fan is 36C with a nominal air temperature of 20C the volume of the coolant is 0.6 litres. I chose the XP on the grounds that it had a nice thick base that I could drill and tap into! The radiator element is a 1mm thick sheet of ABS cut into a folded pathway and epoxied to the base. This is then covered with a gasket and a plate of 6mm polycarb which is tapped and has the brass "hose fittings"... The Lucas style windscreen washer pump flows the coolant (50/50 water and fernox) at a rate of 1.2 litres per minute.

regards

ralph
Title: Re: Diesel Electric?
Post by: Peaky 556 on Feb 20 2013 13:04
Tim -Sorry!!!  ::) Being a Chemist I tend to think of things in MOLES....

The constant coolant temperature from my AMD XP1700 CPU cooler and 43 Litres per minute 80mm fan is 36C with a nominal air temperature of 20C the volume of the coolant is 0.6 litres. I  The Lucas style windscreen washer pump flows the coolant (50/50 water and fernox) at a rate of 1.2 litres per minute.
Ralph -
1. I won't hold that against you!
2. Looking only at the water side of your heat balance I calculate 595W is being added to the water. 
I am encouraged that you can take away this much heat.  My coolant fan is rated at 31.5 CFM (892 litres/m) and to carry away my estimated 180W only raises the bulk air temp by 10 deg C.  Check your air flow rate, it seems far too small. 
All very manageable I'm thinking.  Very good....
Tim
Title: Re: Diesel Electric?
Post by: cabbage on Feb 20 2013 15:28
Yes you are right! It should read 43 Cu ft per minute(!)

regards

ralph
Title: Re: Diesel Electric?
Post by: andrewfoster on Feb 20 2013 19:23
Quite right! Last line should read

Torque convertor rotation reduction 4.2 : 1

output RPM 952.3 @ 0.6Nm = 58Watts

I think I can get a higher rating but the problem is with pumping the fluid in and out of the torque convertor chamber -it is made of layers of 6mm thick polycarb....

regards

ralph
I'm still not quite with you, but it may just be my reading of it.  With 286W going into the torque convertor and 68W emerging, then its efficiency is about 24% - probably quite good for a very small unit, though now you also have to dissipate the lost 218W.  But your torque ratio appears to be the inverse number (4.2:1) if I am reading this correctly, which seems more than coincidence. Presumably that's a steady state when running, as the ratio will vary with speed and load?

Andrew

PS Remember the complaint of the sick D800 Warship? "I can't torque - I've lost my Voith!"
Title: Re: Diesel Electric?
Post by: Peaky 556 on Feb 20 2013 20:05
Ralph - back to cooling, I had assumed your coolant temperature varied between 20C after cooling and 36C after heating.  A bit presumptious that your radiator is so efficient!  If the cold leg was say 28C then the heat dissipated is more like the 300W of your calcs. 
I'm also impressed by a 43 CFM fan at 80mm diameter - I want to get one!
Regards, Tim
Title: Re: Diesel Electric?
Post by: cabbage on Feb 20 2013 21:43
Tim. OK how would you like to try one at 67Cu Ft min ?

http://www.ebay.co.uk/itm/New-Case-Fan-12V-DC-50CFM-PC-CPU-Computer-Cooling-Sleeve-Bearing-3-Pin-80mm-25mm-/170889333366?pt=UK_Computing_Case_Fans&hash=item27c9cc4a76 (http://www.ebay.co.uk/itm/New-Case-Fan-12V-DC-50CFM-PC-CPU-Computer-Cooling-Sleeve-Bearing-3-Pin-80mm-25mm-/170889333366?pt=UK_Computing_Case_Fans&hash=item27c9cc4a76)

This is the XP1700 heatsink (And cheaper too!)

http://www.ebay.co.uk/itm/AMD-XP-Aluminium-CPU-Cooler-Cooling-Heatsink-Fan-702430-/370529692567?pt=UK_Computing_Case_Fans&hash=item56454a6b97 (http://www.ebay.co.uk/itm/AMD-XP-Aluminium-CPU-Cooler-Cooling-Heatsink-Fan-702430-/370529692567?pt=UK_Computing_Case_Fans&hash=item56454a6b97)

Andrew. Yes the system is under steady state (ie with the bar and weight fitted to the output shaft on top of a work mate). The figure you have of 4.2:1 is the shaft rotation reduction and yes there is a separate cooling system for the water that is the working fluid using P2  CPU cooler. The original used Diesel fuel! How the torque varies under load I have no way of measuring as "Kitchen Sink Engineering" lacks the equipment. So all I can tell you is that at 4,000 RPM into the T/C I get 0.6Nm out of it. This feeds the gearbox which has a ratio of 90:1

Has anyone anymore questions before I go to bed???

regards

ralph
Title: Re: Diesel Electric?
Post by: Peaky 556 on Feb 20 2013 22:07
Thanks for tip Ralph, I've ordered one at that price!  It's slow boat from China tho, so will report when it arrives in March!
Rgds, Tim
Title: Re: Diesel Electric?
Post by: andrewfoster on Feb 21 2013 03:31
. ..... "Kitchen Sink Engineering" lacks the equipment. So all I can tell you is that at 4,000 RPM into the T/C I get 0.6Nm out of it. This feeds the gearbox which has a ratio of 90:1

Has anyone anymore questions before I go to bed???

regards

ralph
OK - we're talking the same language, then! I also have impeccable kitchen sink engineering credentials, as well as a little of the other kind - just ask my long suffering wife.  It's a fascinating kind of project you've got going.

Andrew
Title: Re: Diesel Electric?
Post by: Peaky 556 on Mar 06 2013 12:28
Tim. OK how would you like to try one at 67Cu Ft min ?

http://www.ebay.co.uk/itm/New-Case-Fan-12V-DC-50CFM-PC-CPU-Computer-Cooling-Sleeve-Bearing-3-Pin-80mm-25mm-/170889333366?pt=UK_Computing_Case_Fans&hash=item27c9cc4a76 (http://www.ebay.co.uk/itm/New-Case-Fan-12V-DC-50CFM-PC-CPU-Computer-Cooling-Sleeve-Bearing-3-Pin-80mm-25mm-/170889333366?pt=UK_Computing_Case_Fans&hash=item27c9cc4a76)

This is the XP1700 heatsink (And cheaper too!)


My (claimed) 67 CFM cooling fan has arrived from China.  [It came by airmail, so how do they market this for £1.20 inc postage and make any profit?]  Short of testing in just a very subjective 'draft in the face' comparison with other fans I have, any ideas from anyone on how to demonstrate some comarative advantage?
Cheers, Tim
Title: Re: Diesel Electric?
Post by: cabbage on Mar 06 2013 15:12
Well the method used by my son for his fans does seem applicable here... A 10cm square of cornflakes packet hinged at the top with parcel tape on a coat hanger wire "football goal post frame". The distance needed to blow the square an inch off vertical is the measure used by him.

regards

ralph
Title: Re: Diesel Electric?
Post by: Peaky 556 on Mar 07 2013 08:07
Well the Cabbage Mk2 air flow meter I constructed last night (see pic, modified with ballpoint pen as weight) shows that the new super-cheapo 67 CFM fan blows no harder than the 31 CFM fan I already have!  In fact there might be subtly less performance, and the package is bigger too at 25 mm thick cf. 15 mm.  Oh well, you get what you pay for...
Regards, Tim
Title: Re: Diesel Electric?
Post by: John Candy on Mar 07 2013 08:25
Do you think some of the airflow may be lost "radially" and not reaching the "gauge".

How about blowing it through a tube?

Centre of a fax machine paper roll/kitchen towel roll, etc.

Toilet roll centre may be too short.

John.
Title: Re: Diesel Electric?
Post by: John Candy on Mar 07 2013 08:41
Another suggestion (came to me while brushing my teeth)!

Why not mount the fan in a length of plastic waste pipe/drain pipe, then cut squares of card sufficiently large to cover the end.

Get some small weights (lead shot would be a good source) then glue differing weights to each card, then see how much "lift" each fan can generate in "vacuum cleaner" mode.

Perhaps not the ultimate test but could give a better (calibrated) result then the "flap" method.

John.
Title: Re: Diesel Electric?
Post by: 454 on Mar 07 2013 15:54
1) Make a duct.
2) Mount the fan.
3) In the duct make a hole for a tube to be normal to the flow.
4) make a tube like a hockey stick to sit in the flow, pointing into and inline with the flow.
5) Connect the "tappings"up to a bent glass tube filled with water.

Make a pair one for upstream of the fan and one for downstream of the fan if you are that keen.

The tapping in the wall normal to the flow measures the static pressure.
The tapping in the hockey stick tube pointing into the flow is the total pressure.

The differential separation distance of the water levels in the "water manometer" tube will be a guide to the flow.

6) You now have the basis for a mass flow meter. However, you will also need a thermometer
to measure the absolute temperature.

7) Find the barometric pressure of the day. The colder the air the greater the mass flow.

Total pressure minus static pressure is called "dynamic head".

 Do a bit of a calculation & hey presto result mass flow.

Thats how it was done in the aeronautical industry, when I was a lad.

Don't ask me any embarrasing questions as I am now retired!

Cheers
Dave
454



Title: Re: Diesel Electric?
Post by: Peaky 556 on Mar 25 2013 20:36
Hmmm....
I think I have a pitot tube liberated from the scrap heap!  Definitely not a bent bit of glass tube though.  I'll have a think if I really want to quantify the airflow, but in reality I just want to know which fan blows more...   I may next build the 'Candy-pipe' flow meter instead!
Regards, Tim