Engine size for tiny 4-wheeled 7.5" ga loco?

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Jawn
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Engine size for tiny 4-wheeled 7.5" ga loco?

Post by Jawn » Thu Jan 01, 2015 8:18 pm

I'm kicking around the idea of a gas version of the Cannonball Super Mack. How much horsepower does such a loco need to be effective? Or more accurately, how much torque?

Pontiacguy1
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by Pontiacguy1 » Fri Jan 02, 2015 11:04 am

good question: It depends on how much it will weigh, and how much it should weigh depends on how much you want it to be able to pull.

You have to be realistic about what you want to pull with it: You're not going to use a Mack to pull a string of 7 or 8 cars with passengers up a 2 1/2% grade. So ask yourself what do you want it to be able to pull? A gondola car with two adults will weigh somewhere between 450 and 600 pounds.

Look at some of the other threads in here. Most of them are using a small 500 watt scooter motor. For a small locomotive that doesn't weigh more than a couple of hundred pounds with the batteries, that should be enough.

just re-read and saw where you were building a 'gas' version... DUH....

3 HP is more than enough on a small locomotive that will only weigh 200 to 250 pounds. I used a 3.5 HP motor on a freelance 6 wheel switcher that weighs about 400 pounds, and it has plenty of power. Are you going to use a hydrostatic transmission or mechanical??

Jawn
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by Jawn » Fri Jan 02, 2015 4:50 pm

Pontiacguy1 wrote:good question: It depends on how much it will weigh, and how much it should weigh depends on how much you want it to be able to pull.

You have to be realistic about what you want to pull with it: You're not going to use a Mack to pull a string of 7 or 8 cars with passengers up a 2 1/2% grade. So ask yourself what do you want it to be able to pull? A gondola car with two adults will weigh somewhere between 450 and 600 pounds.

Look at some of the other threads in here. Most of them are using a small 500 watt scooter motor. For a small locomotive that doesn't weigh more than a couple of hundred pounds with the batteries, that should be enough.

just re-read and saw where you were building a 'gas' version... DUH....

3 HP is more than enough on a small locomotive that will only weigh 200 to 250 pounds. I used a 3.5 HP motor on a freelance 6 wheel switcher that weighs about 400 pounds, and it has plenty of power. Are you going to use a hydrostatic transmission or mechanical??
I don't expect a "mountain division helper", but I do want to haul myself and a car or two around. No idea on grades, I don't have a home loop and I'm not officially part of any club (yet).

3hp is quite a lot. I was hoping that far less would be sufficient. Starting with a 500w scooter motor... translate that to horsepower, that's about 2/3 HP. I realize there's other factors to consider, but that's a starting point for the math. I had my eye on a 25cc or 35cc 4-stroke Honda, I have one (25cc) on my Husqvarna weedwacker and it's a stout little powerplant... starts easy, idles smoothly and quietly, seems torquey for its size, and doesn't sound like a weedwacker or a lawnmower. The 25cc version is about 3/4 HP, and IIRC the 35CC is a bit over 1 HP.

As to transmissions... which will be more efficient with limited HP?

I guess I could work backwards, starting with a certain amount of weight and a certain grade and do the math for what it takes to move that. But that still leaves unknowns such as rolling resistance, adhesion, etc.

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steamin10
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by steamin10 » Fri Jan 02, 2015 11:20 pm

The original Mack had a whacker motor in them, and it just sounded silly. Given its small size, I dont think a Briggs 3 or similar will fit, given the cooling issues. I have not seen, but there is claimed success with single and dual motored Macks on a boat battery. I think that is the way to go, as opposed to gear, and chain transmissions and mechanical Goldberg to make it go, in the small size.

Given more room like a Gasser type critter, (like I am slowly building) I have a 3 hp gas engine in the cab, slipper clutch, for that grab and go off idle, a flywheel on the motor shaft to slow and smooth the idle, (steel slug) and a simple reversing gear box from a riding mower. I use 40 chains from tractor supply, and they have a selection of weldable sprockets in small sizes to get the final drive ratio to the axles. So it is a simple matter to lathe out some flanged slugs to fit the axles and idlers/ tensioner to get things rolling with your choice of sprockets.

Al you have to figure is the max speed of the engine, rpm, down to the wheel diameter for ground speed, and select the sprockets accordingly in the drive. (12 mph max).

Focus on the rolling chassis, and suspension, and work the body out to fit. My gasser is based on a 10 Ga sheet that is 16 wide and 33 long. This is the floor that is over 6 inch channel iron side frames, and heavy 3 inch angle iron ends to form out the subframe. Holes and clearances are worked out as needed. I use loose axle boxes in the cutouts on the side frames, with over springs. Movement is only about 1/4 inch for flex, the heavy frame is for tractive weight more that anything else.

The cab sheet metal will be screwed to the base to welded angle iron mounts for easy access, the cab roof will be rubber mounted with magnet cabinet catches. Large windows I plan to cut on the mill for perfect looks and shadow frame, the windows of course providing cooling air and venting through the floor. A piece of heater core split on the bandsaw will provide the radiator look on the front, 1/4 inch wire will dress out handrails mounted on soldered over cotter keys.

An eye must be kept to engine cooling, as the carbs are volumetric, and will run leaner as they heat the engine and fuel, so exhaust routing is important, as is insulating any extension. (Muffler wrap).

Just some ideas to feed your project, and remember the kiss rule. I learned form a friend that derailments are hard on equipment, and he rebuilt his original gasser with all steel frame, as the original aluminum gasser parts broke over time. It was simple tho, and we put a ton of miles on his critter. Now that he is gone to the great Mainline, I am trying to restore my fun memories.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
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Shakeyjake36
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by Shakeyjake36 » Thu Jan 08, 2015 7:45 pm

Call Mr. Poole at Plum Cove , the little box cab is the most fun you can have without a shovel in your hand. They will pull two adult and engineer up 2% . If you can get past it not having a gas engine it's worth a look.

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SteveM
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by SteveM » Thu Jan 08, 2015 8:48 pm

With gas, you have a torque curve that starts at zero, goes up and then falls.

With an electric motor, you have torque much earlier.

That's probably why the electric can get by with less.

Steve

chooch
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by chooch » Thu Jan 08, 2015 10:48 pm

All kinds of advise except Certain examples or links of what a small Four wheel loco might pull for sure .
OK, on a Flat track a Plum Cove boxcab will pull 7 -10 empty cars, with some riders I think it was 7.
I have the Same powered chassis but a much less weight switcher body. flat track--5 cars 3 riders, wheel slip on start.
Mr. Motion--his site shows 3 videos, 7-9-10 cars, some with loads.
Above on Flat tracks with that many care I opinion might do well on a grade with Half, maybe a Little less cars
A link to Plum Cove boxcab video accelerating on a 2.1/4 grade--count the cars.
http://www.plumcovestudios.com/movies_01.html

cbrew, member here with his boxcabs--will have to say what His loco can do on flat or grades.

My point--you don`t need Big HP motors, High priced controllers, Heavyweight locos to have a good fun time train hauling a few cars and riders. Small industrial or yard switchers, a Short line boxcab and maybe a couple passenger freight cars would be the right fit--ELECTRIC-- powered for the question asked.
The Electric motors, controllers, gears or chain and sprocket drive can be easily and Simply (stress Simply) answered here.

Weight--I believe two 12 vdc batteries would about equal a 3 HP gas motor.
Just my thoughts, git-er-dun!!
chooch


http://www.plumcovestudios.com/movies_01.html

chooch
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by chooch » Thu Jan 08, 2015 11:11 pm

Count the cars on his video.
chooch

http://www.mr-motion.net/

Pontiacguy1
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by Pontiacguy1 » Fri Jan 09, 2015 10:17 am

I would avoid using any type of 2-stroke motor for powering any type of 7 1/2" gauge locomotive. I know it has been done successfully, but there are some very annoying things, and definite limitations.

Steamin 10 states that he gears his locomotives for 12 MPH max. I gear mine a bit lower... at most tracks that I go to, about 5 or 6 MPH is about all that you should be running, and is about how most traffic moves. I try to gear just a bit above that, so that you don't have to run your engine at wide open throttle to go normal track speeds, so I gear mine for about 8 to 8 1/2 MPH, top speed. That would be with the engine running at 3,600 RPM, top gear. That will also give you a little bit more lower end power, with the deeper gears, which might allow you to use a slightly smaller engine.

I would also recommend that you go electric with something so small. A 250 watt motor on each axle, geared for about 8 MPH top speed, and one controller, you should have a great running little locomotive.

Just for reference: The powertrain losses on a hydraulic or hydrostatic drivetrain will be more than a mechanical one, generally. I think that most mechanical drivetrains figure in about 10 to 12% for losses, ballpark, and most hydraulic or hydrostatic is more like 20% or slightly more.

If you really want to make it a gas-mechanical unit, here's a motor that 'might' come close to fitting in there: http://www.smallenginewarehouse.com/GXH50QXA.html

It's a bit pricey, though, and you'd have to adapt some type of clutch to it.

Jawn
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by Jawn » Fri Jan 09, 2015 10:38 am

Pontiacguy1 wrote:I would avoid using any type of 2-stroke motor for powering any type of 7 1/2" gauge locomotive. I know it has been done successfully, but there are some very annoying things, and definite limitations.
Right, not sure if you caught it but the "weedwacker motor" I mentioned is a 4-stroke.
Pontiacguy1 wrote:Steamin 10 states that he gears his locomotives for 12 MPH max. I gear mine a bit lower... at most tracks that I go to, about 5 or 6 MPH is about all that you should be running, and is about how most traffic moves. I try to gear just a bit above that, so that you don't have to run your engine at wide open throttle to go normal track speeds, so I gear mine for about 8 to 8 1/2 MPH, top speed. That would be with the engine running at 3,600 RPM, top gear. That will also give you a little bit more lower end power, with the deeper gears, which might allow you to use a slightly smaller engine.
That's about what I figured, speed-wise. Of course the smaller engine turns faster, which means even further drive reduction.
Pontiacguy1 wrote:If you really want to make it a gas-mechanical unit, here's a motor that 'might' come close to fitting in there: http://www.smallenginewarehouse.com/GXH50QXA.html

It's a bit pricey, though, and you'd have to adapt some type of clutch to it.
That's only one step up from the 35cc I was looking at, but the 25/35cc units come with a clutch apparently.

Not dead set on a gasser, but it's an idea for something different.

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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by Pontiacguy1 » Fri Jan 09, 2015 10:50 am

My thinking about this motor would be that it would be (a) compact enough to be able to fit (b) reliable enough to be worth messing with (c) wouldn't have that high-pitched, high-RPM sound that would make it sound like a chainsaw.

If you did want to go with a cheap and different drivetrain, you could always make one out of a chainsaw motor, and just make yourself another clutch drum with a sprocket on it instead of the cups for the saw chain. Some of those chainsaw motors are really powerful too. It would be a loud and white-smoke belching beast that would assault your ears and probably vibrate every bolt out of the body... but it could work. I'm not being serious about trying it, just what-iffing.

I did see a guy one time that had taken a motor off of a small motorcycle and had it adapted and geared down in a small 4 wheeled switcher... complete with transmission and all. It was a bit funny watching them stand up behind the thing and literally kick-start it to get the motor running. I don't think it had a reverse, but it ran, and ran pretty well. With all those gears, that thing would absolutely haul the mail, too! They ended up getting warned a few times about keeping their speed down, if I remember correctly. It was pretty cool, though, and definitely outside-the-box thinking. A great example of 'use what ya got available'. I'm sure that they didn't have much in the locomotive, but they had something that looked pretty decent, and that they could use and enjoy.

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cbrew
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Re: Engine size for tiny 4-wheeled 7.5" ga loco?

Post by cbrew » Fri Jan 09, 2015 11:11 am

As chooch said, I have produced a small run of box cabs loosely based off the GE box cab.
this is the business end of the drive train,.
the total of the ratio is ~4.05 to 1. its using a single 24v 500 watt motor with a top speed of 9mphs (via gps)
i designed the system for a steeper reduction if wanted. (this is basically the fasting configuration)
Drivetrain.jpg
I know of some that use a small gas engine turning a 160 amp alternator with out a regulator driving a motor like this with great results.
I will have to dig up the site that explains all the ins and outs if interested

here are you tube videos of the shake down runs
first one


and second using the new digital command system with a Soundtraxx sound unit


this drive system is the same that is going into a larger set of locomotives I am building
20141229_154706.jpg
I will be happy to answer any questions you or any one else may have
If it is not live steam. its not worth it.

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