Sunday, August 14, 2011

Week TechVideo, 2011 #32 - Yet another transmission

Crowkillers presents us a new transmission concept for his next car in 2012 (which car will it be?...).

The transmission shifts in the same pattern as the real 5 speed models of the Ford Mustang and Subaru WRX with the Reverse Gear on the Right Side below the 5th Gear. However the Reverse Ratio is similar to First Gear which is how it should be...

The first part of the video has the Power functions motor hooked up to the Output of the transmission so you can see the engine speed changing (which would normally be "constant", besides the engine throttle) and the second part shows the Power Functions motor hooked up to the Input so that you can see the speed of the rear wheels changing, which is the proper way that the transmission would be displayed, but not as easily visible when changing Gears...

Ratios are as Follows:

  • 1st Gear 2.08:1 (Close to Reverse as it should be)
  • 2nd Gear 1.60:1
  • 3rd Gear 1.25:1
  • 4th Gear 1:1
  • 5th Gear .75:1
  • Reverse 2.25:1 (Close to First as it should be)

If you want to compare, "Standard" Gearbox Ratios like in 8448 and 8466, are:
  • Reverse 2.5:1
  • First 1.66:1
  • Second 1.5:1
  • Third 1:1
  • Fourth 0.9:1
  • Fifth 0.6:1

This new design looks perfect so maybe it's time for a change from the standard...
The tranny works smoothly and everything is lined up underneath so nothing is off 1/2 a stud throwing the whole thing off from connecting to the rear wheels unevenly...

With the transmission plate only 6 studs wide, this will easily fit into a 1:10 scale car with the same exact distance between the seats as Paul's previous models including the last Supercar Deluxe he did.

For additional photos, take a look at Crowkillers BS folder.


Dave said...

Since I doubt Crowkillers would make a model of a Subaru, it must be for a Mustang Boss 302 or something similar.

Erik Leppen said...

I've rebuilt the gearbox from the pictures and it works pretty nicely. I only copied the gears, I completely redesigned the frame, see below as to why.

I like how all axles fit in whole studs, which means easy assembly into a frame with transverse beams, rather than having to use axle joiners as was needed for 8448's design.

Although there are a few disadvantages. First, I'm not fond of the double 8t combination. Second, the combination of two 24 tooth gears means one requires a pretty wide chassis to fit it all in (13 studs).

But the coolest of all is that it enables for a nice improvement which I'm not sure was intentional. At least I found it a nice coincidence. If you look at the central axle, it has a 24t and a 16t and nothing else. If you move either part by a half-stud, those two gears are three studs apart. This means they can be replaced by a differential! This in turn means the gearbox can be used in combination with four wheel drive with center differential, with no changes to the gears!

Maybe I should try to build a supercar around this thing, I'm confident that Crowkillers wouldn't mind.

Erik said...

Finally something different! This is a really great design and yet it looks so simple. It is also very tight at being only 7 studs wide at the shifter axle. Nice video demonstration too. The best part is that nothing is offset like in the 8448 transmission and the ratios are a little more realistic. I see what Erik Leppen means by the 24t gears taking up space, but it looks like Paul has them hidden under where I guess the dash would be. I can see this being incorporated into many builders MOCs in the future.

Ricardo Oliveira said...

I didn't analyse it thoroughly, but I'm wondering why are those yellow half bushes needed, wondering if it wasn't possible to reduce one stud in the length of the gearbox (besides the fact that the lever would have to be shift half a stud to fit the clutches).

crowkillers said...

You could knock off a whole stud but eventually somewhere and somehow you are going to have to center the Changeover Catch(Centering had always been an issue with models that I had built in the past) and it is much much easier to do that and keep everything solid by using 1/2 bushings to do the work centering...

If I built this as a separate component, then I might try something different, but I built it already into the chassis and wanted to use the upper liftarms not only for the transmission change-over, but also as part of the chassis support, so I needed those to stay centered with the rest of the car...

@Erik Leppen

Yes, I did in fact start this out with a center differential in that exact spot for that exact reason, but dues to centering issues, I removed it and just went with the regular 24 tooth gear. I too am not a fan of back to back 8 tooth gears(Another Gear that needs revamped) as they have a tendency to move about the axle, but surprisingly, this worked amzingly well and is the sole purpose of how I pulled this off with minimal gears...

Sure it could have been done differently(Believe me I tried about 1,000 wacky combinations with many more gears added)but in the end, this was the most efficient way as far as part count went.

As for the 24 tooth gears back to back. Sure, they may take up a little room, but this is a small 1:10 scale car and I am going to have no trouble at all as far as space goes...

I am not sure how small of a car this could be incorporated into, but obviously as the car gets smaller, not only will the width with the gears be an issue, but so will the actual width of the transmission shifting width...

My primary goal was to try and build something different that worked well and could possibly inspire some other new ideas...

Ricardo Oliveira said...

Oh, and I forgot to mention the obvious: great work! When we are already expecting great results, we easily forget to congratulate them. ;)

Overall, IMO, "simplicity" is preferred to size/complexity. No big deal with the bushes. :-)

Erik said...

"I like how all axles fit in whole studs, which means easy assembly into a frame with transverse beams, rather than having to use axle joiners as was needed for 8448's design."

Erik what exactly do you mean? I wanted to start building this, but if there is a better way, then I wouldn't mind hearing your thoughts.

Erik Leppen said...

Sorry, English is not my native language so I might not have expressed things the way I meant. But don't worry, I haven't really made a "better" way of connecting things than the original.

Anyhow, when you wanted to build 8448's gearbox in a studless design, the problem was that one of the axles was offset by a half-stud (because of the 24t-16t combination). In the studded system this was no problem as you could simply use a technic brick 1 x 2 with two holes. However in the studless system the axles had to be supported with axle joiners, like this:

Crowkillers's design has no half-offset axles. This means you can just use beams to support the axles (like crowkillers has done already). This allows for a stronger frame.

My only change was that if you move the section with the driving rings a half-stud forwards, then the 16t and 24t at the bottom will align in such a way that you can replace them by a differential. But you only need that if you want four wheel drive with center differential. The disadvantage is that the gear shfit plate is moved a half stud too, which makes it harder to connect (I used the same method as 8070 to connect the gear shift plate).

Stephen Walters said...

I have built a 5+R gearbox that is only 7 studs wide and 12 long, with the half stud offset at the changeover catch and no 24T gears. It uses 17 gears which, I believe, is superior to the design shown above. How big was 8448's gearbox?

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