twin engine project help

[maxatron]

thinking of running twin nitro engines .18 rear and .15 front each running the diff at each end

is there a gear ratio difference between front and rear diffs that could cause speed problems is fronts running faster than rears

[Feedtheinferno]

Guessing you are referring to firestorms? Considering your detail in that post was brilliant.....

Have you measured up where you could actually mount these engines and surely you would loose any gained power by the weight of a extra engine. Sounds like more agro than it's worth. But please if your not all talk, take some pictures and sort out a thread.

[maxatron]

Last post ???

Any how no not firestorms I've just got a bunch of 4wd front and rear ends and was planning on making a chassis from scratch my main concern is i plan on running the two engines completely separate from each other on opposite axles and wasn't sure on front and rear diff gear ratios and if there would be any problems

[Nitroholic]

Your first problem is your intention to run two totally different engines. Balancing gearing will be a requirement...and since the two motors will deliver different power at different revs, I don;t see how you will ever achieve that.

 

This will be far worse as your motors are not driving a common driveline.

 

What you will get is the more powerful .18 motor will do the work, and the .15 will just supply drag if it's not able to keep up.

 

Look at any twin engined project out there, and you will note they use matched power plants. There are good engineering reasons for this!

 

Twin motor electric trucks use 2 identical motors driven from a common speed controller.

Twin nitro trucks work best with matched motors driving a common gearbox/centre diff.

 

Otherwise....you will end up with a car that is slower, heavier and thirstier than stock.

 

Having built and run a twin motor Savage....I have some experience when it comes to the issues of dual nitro power.

[Shudson]

More to the point, there will be no synchronisation between the two engines - you won't even be able to match revs, let alone any sort of predictability of relative power output to each axle. Diff ratios are therefore a complete red herring.

 

I cannot see how the thing could be other than a total nightmare!

[maxatron]

reason behind the smaller engine running the front axle was along the lines of  more power to the rear wheels, if that's not going to work then I can easily use the same engines.

are we saying that the split power delivery idea wont work either

[jizwizard]

if you want more power to the rear wheels then that's when diff oils come into play. You can set up the power delivery the way you want it, and its cheap

[Nitroholic]

It's not a question of applying less power to front/rear through physical engine size....you have to match the revs too.

 

Different engines will rev differently for a given throttle opening. What will happen is that the one engine will drive the car, and the other will just suck fuel and act like a drag brake. Puts stress on the drivetrain too...most of the time having the front/back wheels spinning at different speeds. On loose terrain....it would work to an extent. Soon as all 4 wheels grip....they will be fighting each other.

 

There have been 1:1 vehicles with split drive, and variable power delivery to front/back wheels...but these use elaborate and complex gearbox/diff setups driven by the same engine. That ensures the power is proportional at all revs, and coupled to a flexible drive system. You won't have that. You would have 2 engines with 2 different power curves.

 

Your idea would work with matched engines driving identical gearboxes/diffs/wheels. You can only control the throttle with a single input, using y-leads to the 2 servos on throttle control...so your input will be the same. Using same systems means the outputs will be too....near enough. No 2 engines run identically...but near enough is close enough! This will give you 4WD and power from 2 engines ( though not twice the power )

 

The setup on my Savage invovles 2 motors driving a common spur gear, and it works very well. I had to use a steel spur, though, as the plastic one would strip if one engine stalled under load. The time it took for the clutch to disengage was enough to tear the teeth of the still driven spur gear. I still need to be careful that both motors are warmed up and run smoothly. Of course...development work resulted in a need to beef up every aspect of the driveline too..... but you won;t have to worry on that score, as each front/rear unit will not be taking more load than it's designed for.

 

What you will have to do is either have the motor in front of the front gearbox ( not a good idea if you can avoid it ) or reverse the diff in the front so you can mount the front gearbox back to front.

[Anthoop]

I would not even contemplate running two engines independently...one driving front, the other rear.

 

Even if you have two identical engines then they will perform differently even under perfect running conditions/settings....and these little engines are never going to run independently anywhere near what would be required.

 

The logistics of the idea are a nightmare, yes, you could make it work to some extent but it would never be worth it. Far better to hook the engines together and divide the front/rear distribution in other ways. 

[ajlovering]

There was a mini with 2 engines in 1966 called a Twini. It almost killed a couple of people so only a few were sold before being axed. If you want to run 2 engines then have them both driving the same gear and then split the power to front and rear via drive shafts. Using seperate engines for the front and rear and also different engines will not work but might be interesting to see

 

Cheers

[maxatron]

Seems my idea isn't viable on an rc nitro setup no harm in asking, as im new to the nitro engine and still have a lot to learn.
On a 1:1 note it is possible to run this setup it has been done many times before . No elaborate gearing etc basically engine g/box and front subframe welded into back. this is were I got the idea from. I fabricated and built the rollcage for a mk1 golf about 15yrs ago that had this setup in

Edited May 22, 2014 by maxatron

[Anthoop]

Seems my idea isn't viable on an rc nitro setup no harm in asking, as im new to the nitro engine and still have a lot to learn.

On a 1:1 note it is possible to run this setup it has been done many times before . No elaborate gearing etc basically engine g/box and front subframe welded into back. this is were I got the idea from. I fabricated and built the rollcage for a mk1 golf about 15yrs ago that had this setup in

No harm to ask at all...in fact it may have saved you much pain.  

 

I agree that it is possible to do it 1:1...and there are many examples (I remember the Twini (A.J.Lovering mentioned) and many Mk1 Golf and I saw a twin Ford Puma only a few years ago...but not so many (if any) examples will be running two strokes.