Steel idler = new Internal ratio?

[Cardnim]

Hi all,

Having problems gearing my car correctly for low heat, and high speed.

Can anyone tell me how to calculate the internal drive ratio of the Cat SX2?
I need the NEW values which take into account the new steel idler upgrade as the internal gearing has now changed.

(Im running 33/22 now)

Thanks all!
Andrew.

[Cardnim]

Just to add a bit more info to above request...

It seems there is a HUGE difference in what people say you "have" to run with the Cat SX2 gearing. This is making it really frustrating to diagnose and solve my running problems and Im getting a bit fed up with it to be honest

Here's just one example..
Both quotes are taken from the one issue of RADIO CONTROL RACER MAG - December 2010 (the issue with the Cat SX2 review)

page 69 - Steel Upgrade in the "Inside Lines" section:
"The standard setup is 33T and 22T, which will be different than standard so bear that in mind..."

page 98 - interview with SImon Moss about the new Steel Upgrade:
"...and providing you run a total combination of 56T (ie 33T and 23T) you can do what you like on the cars gearing."

!!!?!?!?!?
So, in one magazine I am told two different things, and that it will be supplied with the wrong gearing!?

Am I being thick (again) or is this a mystic art which I am not allowed to know

[bigred5765]

we havent change gear ratio (pinion size wise) because we run steel idlers,

[Cardnim]

Cheers Carl, I didnt know that info was in the SX3 manual.
It certainly clears up one question, which is: "do I run a 56T or 55T combination".
Looks like Simon was right, its 56T all the way.

Which means the flipping steel upgrade set that Schumacher supply comes with the wrong gearing!!??

Im still confused though...
I was recommended by others (see my thread in Electrics section) that Speed Passion v3 motors need geared higher. So I was recommended (by more than one person) to run this gearing on my 6.5t motor:
24-25/78-80

So I just bought a new 78 spur - but:
a) - it isnt even on the SX3 manual's list
b) - assuming I change my internal pinion to a 23T so my IDR is 2.58 then running a 24/78 would give me an FDR of 8.39 - which is outside Speed Passion's recommended gearing for the 6.5T motor Im running!!!????

Argh...my brain hurts.

[bigred5765]

matty always runs a 80 spur gear
speed passion motors seem to work better offroad slightly over geard, ratios stated are onroad i think,
with a 5.5 matty runs 80 x 20 23 track dependant
6.5 80 x 22 25 again dependant on track
aim to get the cars screaming at 3/4 the length of the longest stright

[Cardnim]

Carl - thats brilliant mate - really really appreciate that.
Helps clear up alot of the crap that I havent been able to get my head around.

Frigging annoyed that Schumacher supply the steel upgrade set with the wrong gearing, and also that I've just bought a spur gear that I no longer want.

Oh well, at least I know now.

Thanks again!

[bigred5765]

76 will work fine in the cougar thats were we run ares, what do you mean buy wrong gearin?

[Cardnim]

When the Steel Idler Upgrade Set was released by Schumacher it came with 33/22 steel pinions. This is what I bought.

But Simon Moss, the SX3 manual, and yourself (and others) have all shown that actually, you need to run any combination of 56T - ie. I need to change my 22T to a 23T (which leaves my with yet another gear that I aint going to use and another £5 lighter in my wallet)

Small money I know, but it all adds up, and recently it feels like Ive been buying lots of things on bad advice/research.

EDIT -> this aint the Cougar, its the Cat SX2 I drive.

EDIT -> this is the set I bought and it came with 33/22:
http://www.racing-cars.com/pp/Old_Ca...SX2/U3794.html

[Cockerill]

There is nothing wrong with running the 33/22 combo you have. It will slightly change the IR of the car, but probably not noticeably.

The 56T total was very important when running the plastic/alloy gears, however with two steel gears, you can get away with running 33/22 as the gears will not break.

The IR with 23/33 is 2.58
The IR with 22/33 is 2.70

This equates to about 0.5 on an overall ratio, which roughly means going up 1 pinion.

The 78 Spur doesn't appear in the manual because it's not a Schumacher product, I believe RW Racing make it.

For a SP V3.0 6.5 I would run an overall ratio of ~8.50

You can get this using your current internal gears (22/33) and your 78 spur by using a 25T (8.42) or 24T (8.77).

[Cardnim]

Aaaaarrrrrgh, yet more info! *brain explodes*
Just when I thought Id got to the bottom of it.

OK, cheers Tom - thats good to know.

However, I feel like Im back to square one with my motor issues, as I had hoped that the difference in the internal ratio would explain my heat problems with the motor now.
(they only seemed to appear once I upgraded to the steel idler shafts and gears)

I'll order a few different spurs and pinions and fool around to see if I can find something that works.

Thanks again Carl and Tom for all the help.
Im new to all this and have found it very confusing, so its really helpful to have experienced guys like yourselves to talk to over with.

Im off to throw my Cat out the window..... (joke!)

[Cardnim]

Cheers for clearing up the 78t question too Tom - you're right , its from Neil at RW.

[Cardnim]

P.S. Tom - just so I can do this for myself in the future, how are you calculating the IR?
Thanks!

[Cruise]

With the pinions you need to use a 55t sum as 56 will run noisy and without any play.
That is the reason of the confusion.
Original gears=56T sum
Convertion with pinions=55t sum

I run accidentally with 56 sum and it worked but not as it should.

Cruise

[Cardnim]

Vielen Dank Cruise!
Im glad that I dont need to change anything in the internal ratio, so I will keep it at 55T as you suggest.

mit freundlichen Grüßen!
Andrew.

[Cockerill]

Internal Ratio for the Cat is (Diff Pulley (36) / Drive Pulley (20)) * (Big Side Gear / Little Side Gear).

[Cardnim]

lol.
Since earlier Ive been sitting with the calculator out, trying to work backwards from the figures you gave. Knew the 20t pulleys had to be in it somewhere - but Id forgotten about the diff - oops.

Thanks Tom!