Gearbox Ratio?

[BDR]

G'day all.

What is the internal gear ratio of the LCC?

Want to know what other tranny can be run instead

[Olle P]

40:[pinion teeth]

[BDR]

Thanks mate.

I was hoping just for the gearbox though, with out the pinion spur

The B44 buggie has a tranny ratio of 2.6 so it is easy to work out the rest, i was hoping the LOsi would be the same

[jgrim]

Originally Posted by BDR

G'day all.

What is the internal gear ratio of the LCC?

Want to know what other tranny can be run instead

The LCC trans ratio is 0.87 to 1.

Update to the above. After reading Hardline's posts and discussion with WAM, I agree that the trans ratio is about 1.33 to 1. Jerry

[Olle P]

The 40 tooth cog on the output shaft is the spur. (And it can't be substituted!)
There is no other ratio to be concerned with since the prior cog wheels just transfer the movement without any change in speed.

[Hardline]

Originally Posted by Olle P

The 40 tooth cog on the output shaft is the spur. (And it can't be substituted!)
There is no other ratio to be concerned with since the prior cog wheels just transfer the movement without any change in speed.

You've said that before Olle and you're still wrong. Most people consider the gear in contact with the pinion to be the spur gear. You want to call that an idler and call the next gear (it's 30, not 40) the spur. Okay, let's call it that -- it's reasonable. Call the black plastic gear just an idler. Put a mark on the 30 tooth "spur" gear (on the tranny input shaft) and also on the output shaft and turn by hand. They do not turn 1 to 1. The transmission input shaft spins faster than the output shaft, so there is in fact gear reduction going on.

[BDR]

Sweet thanks, that is a pretty piss poor reduction

[Hardline]

Originally Posted by BDR

Sweet thanks, that is a pretty piss poor reduction

Well that's true, but the reason for it is the Losi's have considerable gear reduction in the axles. So it kinda works out. Personally I prefer lower gearing than that so run the LNC transmission which has much lower gearing. Around 2.3:1 maybe. Creeps great, but wheelspeed is nothing to write home about.

The two trannys have identical bolt patterns etc and are interchangeable. You can make an LNC tranny just building up with parts for about $25.

[jgrim]

Just for clarification, the LCC trans is actually an overdrive ratio. If you turn the input shaft (the idler gear) one full turn, the output shaft turns approximately 1 1/8 turn. Also note that we normally call the gear in contact with the pinion the spur gear. In this case, it is called the idler gear, consistent with the terminology in the LCC manual. Jerry

[Hardline]

Originally Posted by jgrim

Just for clarification, the LCC trans is actually an overdrive ratio. If you turn the input shaft (the idler gear) one full turn, the output shaft turns approximately 1 1/8 turn. Also note that we normally call the gear in contact with the pinion the spur gear. In this case, it is called the idler gear, consistent with the terminology in the LCC manual. Jerry

Negative on that Jerry, but you made me look. I ought to just leave the damn cover off this tranny. The input shaft is not the idler -- that shaft does not rotate. The input shaft has the metal gear with the locknut on it that goes into the tranny. If you turn that 1-turn, the output shaft turns approx 3/4 turn.

I agree with Olle that in this case the large plastic gear is not a participant in the gear ratio. It merely translates motion from the pinion to the metal gear on the input shaft, one tooth at a time to each side. If you were to change it's tooth count, it would have no effect on anything. So ignore it, slip it off and put it in your pocket. The input shaft into the tranny rotates faster than the output shaft from the tranny. That's not overdrive....that's gear reduction.

[jgrim]

Originally Posted by Hardline

Negative on that Jerry, but you made me look. I ought to just leave the damn cover off this tranny. The input shaft is not the idler -- that shaft does not rotate. The input shaft has the metal gear with the locknut on it that goes into the tranny. If you turn that 1-turn, the output shaft turns approx 3/4 turn.

I agree with Olle that in this case the large plastic gear is not a participant in the gear ratio. It merely translates motion from the pinion to the metal gear on the input shaft, one tooth at a time to each side. If you were to change it's tooth count, it would have no effect on anything. So ignore it, slip it off and put it in your pocket. The input shaft into the tranny rotates faster than the output shaft from the tranny. That's not overdrive....that's gear reduction.

I understand what you are saying, but I was considering that the idler gear is part of the transmission. Rotate the idler gear 1 turn and the output rotates about 1 1/8 turn. Jerry

[Hardline]

Yeah, but you don't want to call the idler part of the transmission at least for ratio purposes. If you substituted a 1000 tooth idler gear, nothing would change. Except your version of the reduction ratio. It makes no sense to base your ratio on a gear that doesn't matter what it's tooth-count is. Kinda by definition "idlers" don't count.

[WAM]

You guys are both right. But I'm going to edit my explanation. It all comes down to definitions. There are three shafts, motor shaft, tranny input shaft and tranny output shaft. Most people would agree the transmission reduction ratio is the input shaft speed divided by output shaft speed. In this case that is about 1.3:1. The difference between the motor shaft and input shaft is generally contolled by pinion/spur, but in this case there's also an idler gear so three gears are involved. The idler has no effect on vehicle speed so essentially the pinion/spur ratio is between the pinion and #3 gear.

Olle's "40:pinion teeth" may be mathematically correct but is not the transmission ratio. His answer would be the product of "pinion-spur" x transmission ratio. Like I said, nobody's wrong, we're just all talking in circles. (heh)

[Tydl]

I had come across this post recently, does it apply? I know the numbers will be lower with hd gears.

Originally Posted by Mad Dawg

I dug the owners manuals out for both the LNC and the LCC....so maybe this will help you out.

LNC Gear Ratio****** LCC Gear Ratio
12t - 104.19:1 ******12t - 83.25:1
13t - 96.18:1 *******13t - 77.1:1
14t - 89.31:1 *******14t - 71.5:1
15t - 83.55:1 *******15t - 66.5:1
16t - 78.14:1 *******16t - 62.5:1
17t - 73.55:1 *******17t - 59.1:1
18t - 69.46:1 *******18t - 55.75:1
19t - 85.80:1 *******19t - 52.5:1
20t - 62.51:1 *******20t - 50.1:1
21t - 59.54:1 *******21t - 47.5:1
22t - 56.83:1 *******22t - 45.5:1
23t - 54.36:1 *******23t - 43.25:1
24t - 52.09:1 *******24t - 41.4:1
25t - 50.01:1 *******25t - 40.1:1

I'm curious, couldn't we use a direct drive tranny; pinion to spur on output shaft? Maybe something like the proto bwd made...

[Olle P]

The only reasonable way to count (IMO) is "teeth out" to "teeth in".
The (40T) "spur" in contact with the pinion doesn't alter the teeth/second speed one bit.
Next we have the 30T slipper wheel, which transfer movement to another 30T wheel on the same axle. Again 1:1.
Finally we have the 40T wheel on the output shaft, and it is on this wheel the "teeth/second" speed provided by the pinion acts unaltered!

It's only when you have wheels of different size mounted on the same axle (and thus turning at the same angular velocity) that there is a change in gearing inside the gearbox.

[Hardline]

Originally Posted by Tydl

I'm curious, couldn't we use a direct drive tranny; pinion to spur on output shaft? Maybe something like the proto bwd made...

Sure, if you don't care about losing the dig. But since so much reduction is in the axle, the spur on an LCC will tend to be a lot smaller which means it's axle (the output shaft) won't clear the motor. You'd need to play with physically larger pinions and spurs to move the shaft far enough over, or include an idler like Losi did. Also remember big spurs are a packaging pain. Look at all the nonsense the AX10 guys go thru to make the spur fit a compact chassis.

You might as well just fit the LNC tranny and gear it to your preference with the pinion.

And Olle, give it up. The tranny input shaft and output shaft are rotating at different speeds. There is obviously reduction in the gearbox. I guess not obvious to you.

[Tydl]

Originally Posted by WAM

Olle's "40:pinion teeth" may be mathematically correct but is not the transmission ratio. His answer would be the product of "pinion-spur" x transmission ratio.

so, what is the Lcc tranny ratio? Is this the correct formula to get the output ratio?

Originally Posted by Hardline

Sure, if you don't care about losing the dig. But since so much reduction is in the axle, the spur on an LCC will tend to be a lot smaller which means it's axle (the output shaft) won't clear the motor. You'd need to play with physically larger pinions and spurs to move the shaft far enough over, or include an idler like Losi did. Also remember big spurs are a packaging pain. Look at all the nonsense the AX10 guys go thru to make the spur fit a compact chassis.

You might as well just fit the LNC tranny and gear it to your preference with the pinion.

I'm building a sporty, so no dig. But I like the wheelspeed my lcc has. Its my understanding that the lnc is over 2x slower than the lcc tranny, that doesn't work for me. Any clue what size spur bwd used in his tranny?

[jgrim]

Originally Posted by Tydl

so, what is the Lcc tranny ratio? Is this the correct formula to get the output ratio?

After reading Hardlines posts and after discussion with WAM, I think 1.33 to 1 is the correct LCC trans ratio. Jerry

[WAM]

But more importantly it doesn't really matter much. Gearing on any specific car is going to be a tough compromise between acceptable low speed behavior and wheelspeed. You may prefer one over the other, but experimentation with pinions is going to be required to get you where you want to be. We comp our sportys weekly and all of us have gravitated towards pretty low gearing to get the creep behavior we need. None of us are totally happy with wheelspeed. But that's the balance that works best here.

[Olle P]

Originally Posted by Tydl

I'm curious, couldn't we use a direct drive tranny; pinion to spur on output shaft?

It's possible, but much simpler to just skip the driveshaft altogether!
If you scan this subforum for MOA you'll find a heap of threads where the "spur" is a 32-pitch pinion mounted directly on the worm pinion. The motor (one per axle) is mounted right above it.