PEERPSI

Does anyone know of a shop or individual that has a dyno for RC engines?

chief3452

I have only seen 2 so far, John Finch built one for a RCBM pipe testing article and I've seen a purpose built dyno for sale... I seem to remember it was stupid expensive, I can't remember exactly, but it was thousands of $$$, no joke. Mr. Finch's was rather ingenious, utilizing a ducted fan, drawer slides, and a digital fish scale. You are better off just buying a cheap GPS, in my humble opinion. Hope this helps,

Scott

MrMikeG

M&D engines
CC racing
There are plenty of others too.

noahdear

My Feedback: (2)

I saw one last week all hooked up to a laptop. The guy said it cost him $10k. I was impressed !

Dockman

A tachometer, GPS, and a notebook will work pretty good???

nothinbetr2do

try getting ahold of these guys, i know they do hpi baja motors. maybe they will do a boat http://www.lunatikengineering.com/

PEERPSI

I have a GPS and tach. Problem is it`s really time consuming and the water changes as does the wind when you`re out on the lake. Today for instance I was doing fine then the wind picked. Next thing you know it does a roll on me. It actually landed right side up still running I was so surprised for a moment I didn`t realize how close I was to shore. Thankfully I set my throttle up to kill the engine!

What I want to do is tune it on a dyno so that the carb settings and pipe are at their optimum.

I priced out to dyno`s one was $5K and the other $10K. You`d have to sell a lot of dyno time to pay for that. I have some ideas on how to build one using an automotive alternator.

In fact if you`ve every used a Lifecycle or Liferower at the gym that`s how they work. Using voltage and current measurements on a know resistance I can determine horsepower. Should be simple to build just make a fitting for the front of the alternator that accepts a square flex shaft.

gasnut

Bruce Lykins @ [link]http://www.gizmomotors.com/[/link] does great engine work too :-)

martno1fan

The only place to tune a motor and setup a boat is on the water not a dyno.Unless you know what your doing id say its pointless.In any case we see such wild claims as regards hp and dyno claims id say many of them are wrong.
Mart

PEERPSI

I've done a lot of dyno tuning for cars and to me it's what to do before you head out.

When I go down to the lake I turn a few laps bring it in check the tach and GPS, do a few more bring it in again and so on and so on. Tiresome way to do it. A load is a load. On a dyno I can move the pipe up and down the header quickly with out having to fit my hands in and around eveything. I can also set the carb up quicker. Last time out by the time I got in and out a few times the water had changed.

I think I'm going to have a go at building a dyno using an alternator and a 3 phase AC motor for a load.

MrMikeG

I thought about the alternator route as well, I would belt drive it, not direct or you could have a lot of broken parts to repair all the time. steer clear of the "water brake dyno's" they don't give a good representation of the boat on the water.

PEERPSI

I was thinking I'd put a square drive collet on the alternator. I'd then use a flex cable to easily and quickly connect the engine. Originally I was thinking of pulling the 3 phase full wave bridge rectifier and running an AC motor load. However, in order to do that I'd need to use a pulley system with about a 3/1 ratio to keep the frequency down to a maximum of 120 hz. Instead what I might want to do is use a DC motor and keep the rectifier. I figure due to efficiency losses the maximum you'd need to load would be 6500 watts for a 10 HP engine, this is assuming 85 % effeciency. I could use a known motor to drive the alternator and calculate the efficency loss as well.

LawHound

Why not build A resistor Load Bank instead of the motor for the load you could use Switches or Relays to cut more or less Resistance in the load and Monitor the Alternator output with Meters Amps, Volts, and Power (might be Expensive for power meter) would also do double Duty in Winter to help heat the workshop Doug.

PEERPSI

I thought about using a battery load tester or dryer element. I have plenty of motors around so that's easier and no issues with the heat. It's also easier to fine tune the load by adjusting the field voltage.

MrMikeG

Once you got it set up you could use another electric motor to calculate the HP through the volts and amps it draws to get to a specified RPM.

PEERPSI

Thats my intention. Run a motor at it's peak current with a know hp and measure what I'm able to get on the other side. That will give me an efficiency number. With that I can calculate roughly what the hp of an engine is.

Of course the point isn't to be able to find out hp but put a load on an engine on a stand out of the boat so that I can see what changes carb settings and pipe movements will make.

noahdear

My Feedback: (2)

[link=http://www.trik-dyno.com/prod01.htm]this is the one I saw[/link]

MrMikeG

The "trik dyno" is a water brake dyno

nvs motorsports

If you know a fitter and turner get him to machine up a power disc
F1 power boat racers use them on real boats to load motor up with out worrying about thrust it work on the tesla effect

Its bit like a fly wheel but goes in the water the drag on the surface of disc causes friction hence set a load on the motor
you may need to experimenting to get right diameter for the right drag
you just fit where the prop would go

PEERPSI

Both Trik and Land and Sea make dyno's suitable for RC engines. They are about $5000 and $10000 respectively. Too much money unless you wanted to go into business tuning eninges. I thought about it but I live to far off the beaten path to make it work.

I beleive the friction disc Tesla effect you refer to is an eddy current load. That's pretty much what I'd be doing with the alternator at a lower cost. If you've ever been on a Lifecycle or similar exercise bike that's exactly what they use for the load. Change the field voltage to simulate hills etc..

I could easily turn up an inertia load on a lathe but how do I measure the output? With the alternator I can use current and voltage to calculate wattage. Divide that by 746 and you have horsepower. Use the hp number and the engine rpm to calculate torque.

The reason this is an easier route for me is these are the sort of things I do at work.

nvs motorsports

You cant measure horsepower with the way i suggested but you can set tune up at the location where you race
Horsepower is irrelevant in motors you are better off looking for a nice torque curve and drivabilty
With the class 1 boat we a restricted to 930 hp per motor so we chase torque it makes a massive difference on the race course

brodjack

Why not just fit a 16-8 aero prop and use a tach to measure rpm.
A stock 260 spins about 8500 rpm.
Brod..

MrMikeG

Because our "Mod" motors are turning 17,000 in a boat, how do you think tuning the carb at 8,500 is going to help at 17K?
There is a big risk of an airplane prop flying apart at the revs and power we see in a boat engine.

brodjack

Just using a stock motor and a prop for an example.
he could say try a 12-6 prop for more revs,
I tried a few nitro props on my Zen7,it didnt rip to bits,scary but i,ve run brushless motors far quicker...[8D]
Brod..

PEERPSI

Using an airplane propeller at those speeds would not allow you to set the pipe up right.

I'm not interested in top HP either just an easier way to load the engine so that I can tune the carb and set the pipe distance. I went through two tanks at the lake today trying to do that but with a new pipe and trying to figure out the right strut height I just don't seem to have enough time to get anywhere.

I make a setting try a few top speed runs and then do a lap or two at a slower speed to cool down before stopping. Time consuming. On a stand with a adjustable load I can load it down set the carb and pipe while I have a constant cooling source flowing. No cool down laps required.

Last night I gave the method of connecting the load much thought. I think in the end the best plan will be installing a geezer pully and using a belt drive system. After some thought and research the flex cable drive would only work with a one way bearing. Otherwise if the load speed becomes higher then the engine the flex cable will unwind and fail. The one way bearing would solve that but make building it more costly and difficult. Using pulleys I can change the ratio to have the alternator produce 60 to 120 hz so a three phase motor can be the load. That eliminates the diodes and one more failure point.

So system would be geezer pulley on the engine, alternator load (Delco 100 amp), 3 phase AC motor and dc power supply for field voltage. Of course a stand would need to be made to mount the engine and alternator.