yakfish

My Feedback: (27)

I am wanting to do some bench testing on some of my car engines. The best way I can figure to put the same amount of "load" on each engine is by using a prop from a plane and then take RPM readings off of the prop. but I am not sure how to attatch a prop to a car engine that has an SG shaft. I could use a threaded clutch bell and drill the hole in the prop out enough to get it to fit over the threads but I am not sure how i would get the engine started from there since all my engines are bump start only. can this be done somehow? Does anyone have any ideas for me?

Also, any one know of a tach that reads higher than 32,000 RPM? Some of my engines will crank out over 40,000 RPM and the mini hand held tacks I have found only read up to 32,000 RPM

How do I get this


on this?

Mr Cox

Sure, it can be done, all you need is a prop-driver and a different carb.

yakfish

My Feedback: (27)

Oh yeah I forgot about the carb. I will definently be in the way. and I really should use the stock carbs for testing since using a differnt carb (assuming I could even find one that would be out of the way enough) will affect performance. maybe I can run some kind of a pulley or gear system off of the crank to a seperate shaft that the prop will be on?

HWM77

Hi yakfish
                 if the engine has the std 7mmØ shaft the cheapest way is to buy a super tigre 27 prop drive and collet.Make up a std venturi about 9mm for a 21.DO NOT use any thing but a carbon fibre prop,i use a Sherlock 7x4 prop for test use,my sts 21 turns 30k plus.

1QwkSport2.5r

I've wanted to do this same thing for a long time to break in my car engines, I think it is probably the best way to break in any engine, but especially ABC engines. The crankshafts on my .20 smallblock car engines only 5mm, and its probably too short to boot. My big block engines (.26 and .28) are probably long enough, but the crank isnt completely threaded so putting a prop nut/spinner on it is out of the question. I think a different crankshaft may be in order to make this work, at least for me anyway..

The prop driver is one thing, that probably would help clear the carb... But getting/keeping the prop tight to the crank is gonna be the tough part, as I see it.

Edit: Here's the crank from the Super Tigre .27 Airboat engine.

Here's the crank from my SH .28, and Traxxas 3.3
SH

TRX 3.3


If I could fit a prop to one of these without having to change crankshafts, I'd break all of my engines in on a test stand instead of in the car.

earlwb

You need to either find a prop driver/thrust washer and collet to fit the crankshaft, or make one up on a lathe.
Then you may need to make a special prop nut and washer to fit the threaded part on the crankshaft. it depends on how thick the propeller is. Usually you make a spinner nut with a long shank on it to fit the threads and then you ream out the prop to fit the shank on the spinner nut.
The prop driver washer may allow enough clearance to work with the car carb, but you may have to flip the carb around and angle it. Otherwise you have to use a different carb.

You can see how it was done on this Toki or Fuji .05 engine. They made a more thick thrust washer to clear the carb and then the spinner nut was made longer with a threaded shank on it to extend the prop out farther. You need to ream out the prop more for this method.

ThumbSkull

My Feedback: (57)

APC and other manufacturers limit their props for safety reasons to 190,000/diameter. They can explode at RPM's over that.
That means an 8" prop is limited in capability to under 24,000.

The extra airflow from the prop over the large car heatsink means the engine will never reach operating temperature so your break-in won't be proper.

1QwkSport2.5r

Man I wish I had a lathe even more now than ever....


I have cylinder heads I can modify (cut most of the fins off) to use as a break-in head OR if I get an oddball, I'd just cover part of the head with foil or ziptie a piece of tube sock to the head. This is what we normally do to break-in a car engine in the car in colder weather.

I would think a custom prop would be the ticket to handling the higher rpm of a car engine.

I personally dont think car engines ever break-in to run at their peak the way they are outlined by the engine OEM to be broke in. As I understand it, ABC, AAC, and ABN engines should be run at or slightly faster than the RPM they're expected to run at during normal use during break-in, though slightly rich. Running 1" smaller dia. prop and setting carb rich enough to run at that rpm is how Jett recommends breaking their engines in. I ran my TT .46 in this way and its still getting better every run and its at about 1.25-1.5 gallons now.

acdii

What Thumbskull said was my first thought too. Your engine would run cold, and not work properly. Years ago I had a Heli engine that I used in a plane, I could never get it to run right in the plane, but ran great in the heli. 

ThumbSkull

My Feedback: (57)

The cylinder is one of the main components that needs breaking in.

Nitrovein

Could Novarossi: 29062 be the answer? I haven't tried it, but it looks like it´s intended for this.
http://www.novarossi.it/eng/products/accessories/

ThumbSkull

My Feedback: (57)

This is a bad idea as well. When I was a kid, I ran one of my dad's engines with a flywheel I made on the lathe.
It would really spin up with no load and eventually broke the crank and shot parts out of the case and the engine was ruined.

1QwkSport2.5r

I know the cylinder is one of the main components that needs breaking in. I've ran glow engines in cars for 14 years and airplane engines (on airboats) for going on 3 years now. If the engine uses a head button, swapping on a different heatsink wont effect the break-in of the piston/liner. Even if a different head button is used, that isnt going to have a dramatic effect on the break-in of the piston/liner unless the engine doesnt get to operating temp.


The flywheel would have to be rather heavy (and probably large) to use alone, and if putting a sprocket on it to drive a separate propshaft and drive by belt or chain would need some careful and precise engineering of which I dont have the tools to do. Running a flywheel alone would be ideal, but it would need to be heavy - probably 2-3lbs or more to provide enough load to not grenade the conrod. Think Dynamometer here... The conrod is usually the first to go when doing a shaft run; which is essentially what one would be doing running an underweighted flywheel like what would be used in a car or truck.

I suppose a "car" jig using the standard car clutch and flywheel, and fashioning a spur gear setup to drive some sort of "load" would work. This is far more complicated than I would want to get into but it could be made to work.

1QwkSport2.5r

That'd work if it came with different sleeve nuts to fit different crankshaft sizes/threads.

acdii

Thats what I had in mind. If you clutch the engine, it should be able to be disengaged when throttled down so the flywheel doesnt overtake the engine. Worked on my heli.

OTOH if you were to use pulleys to go something like 2-1 and offset the prop so it isnt blowing directly on the engine, you could do something like that too. Spin the prop at 20k with the motor at 40K. Just make sure you use a good prop that can handle that speed. You can probably take a piece of angle iron, put some slots tor the mounts so you can adjust the belt tension, and bolt that to a sturdy bench as a test stand.

ThumbSkull

My Feedback: (57)

I wouldn't want to be any where near 2-3 lbs spinning at 20-30k. That's a LOT of stored energy just waiting to find a weak point.
A flywheel alone will not limit the RPM's at all. A dyno is more than just a flywheel, there is a torque applied load.

Warnings made. Let the process of natural selection begin.

1QwkSport2.5r

I know there is more than just a flywheel in a Dynamometer. I have seen a few R/C Car engine dyno's in action, and they use a flywheel that I estimate at 1-2lbs and its geared down so it isnt spinning as fast as the engine is.

Nonetheless, there is a way to do it safely.. Its just a matter of getting creative.

airraptor

My Feedback: (66)

You need to break in the engine how you are going to run it during normal use.

You dont break in a F-1 engine in a airplane then trow it in your F-1 car and go race lemans.

break it in mounted in the car like it was intended. If you break it in with a constant load then throw it in a car with a changing load all the time then you are adding a different load and heat set in the engine and it wont last as long. Running with a constant load with a propeller or anything else you will be running the engine with more oil and more fuel to run for a few minutes and WOT. In a car you are running less oil and a leaner mixture to get that accel that is needed in a car. Because a car engine is only WOT for 10-15 seconds or less it builds a different heat set in the piston and sleeve. So they will have different wear patterens in the engine if ran differently.

I know everyone likes to tinker and all. Its you engine do how you like but i dont think you will get the results your looking for.

yakfish

My Feedback: (27)

Thanks for all the replys. I am going to order that run-in test set from novarossi and see what I can do with it. I may also try to rig something up using the standard flywheel,clutch and clutch bell setup to a spur gear on a lock center differential and attatching a prop to a driveshaft somehow. I have abunch if soare parts from an 8ight 2.0 buggy that I am pretty sure will work. If I go that route I won't have to wory about the prop getting anywhere near the carb, and the prop won't be directing airflow over the engine so i will be able to get it up to proper operating temps.

Also I'm not nessassrily doing tis for break-in. I am wanting to test different engines to see the rpm potential of each engine and by running diffeent props I will be able to determine how much power different engines have relative to each other.

Thanks

ThumbSkull

My Feedback: (57)

BTW, for racing, the engine with the most power is not usually the winner.
The one with the best chassis setup and driving skill usually is.
That's where I'd spend the R&D time.

acdii

With proper gearing, you can run a flywheel safely, Step it down do it isn't going like a BOOH.  An 8:1 ratio puts the flywheel at no more than 5K at top speed.  That and since you wont really want to run it WOT, it would be lower than 5K. It also doesn't need to be very heavy either, it just needs to be balanced.  When you think about it a prop isnt very heavy, but the shape of the blade is your resistance, so the flywheel can be something like a ducted fan. Hmm now that would make a good setup. You can use compressed air blown into the discharge to simulate load under varying throttle settings too. 

asmund

Get yourself one of these and save yourself alot of troubble: http://www.rc-mushroom.com/product_i...-stand-p-18775

Here`s another one: http://www.horizonhobby.com/products...stand-RDL15000

acdii

I guess engrish is a 3rd language on that first site.  LOL

airraptor

My Feedback: (66)

You will still not gain anything buy running props on the engines then compairing them to each other. Some have different porting, carb sizes and so on. one with high timing but low transfers may turn a prop the best but suck on the top end and vise versa.

The work has already been done for you. just look at see what the local car guys are running in their fast cars and then get that engine.

Also if you are going to run a prop then you will need add more oil to regular car fuel which is in the 10-14% range for revabilty. props are more of a steady stae running which regular car oil will not be enough.

but again your stuff have fun and good luck.

acdii

That explains why the LHS doesnt have 18% lube fuel, they cator to the car guys. Kind of funny though, they dont have an outdoor track, and indoor is electric only.