Ok - A question that's driving me nuts ...

[JED]

... & it's directly relevant to my dark scheme. Still bench-building here, & I'd like to know this one before I go further - & the search has me ready to set my thinning hair on fire.

The K1100 has a reduction gear-set in the intermediate case behind the engine. Does anybody know what that ratio is?

Given the 789.08 revs per mile for a 160/60ZR18 tire, at 60 mph w/ 2.82 final drive & 1.61:1 5th gear ...

789.08 x 2.82 = 2225.2

2225.2 x 1.61 = 3582.6

But K-Bike engines turn faster than that at 60 mph in 5th gear, correct? Having thrashed high & low all over the net for the last few evenings, I've seen many posts with very mushy values, have yet to find a credible speeds in gears chart, & no suggestion of a ratio or even a tooth count for that reduction gear.

I haven't yet been able to ride the bike, but just using 5,000 rpm @ 60 mph as an example - if that were the case - the reduction would have to be around 1.4:1 - which explains the much-appreciated broad-range torque of the K1100s that actually chart a bit of a peak. A modest 80 lb ft at the crank becomes a far healthier 112 lb ft at the transmission input shaft.

So, any help with that ratio? ... or just some accurate speeds in gears? My bike has a 2.82:1 final drive & a 160/60ZR18 rear tire, but if you post what you have we can adjust. Given the data, the rest is just third grade arithmetic.

Thanks Much

[Scott_]

http://www.largiader.com/articles/gearing/
See if this helps any..

[JED]

I found that earlier & noted the URL. Now that I'm home I'll have to fire up a PC & check it with that - Java's a no-go with the iPhone. With what I'm seeing on the phone, it isn't even clear what it does.

Thanks Much

[JED]

Well ...

Just read Steve Engelbrecht's Leading The Way With A Special K article, & got an anecdotal 152 mph @ redline, or 8,900. Assuming a stock tire on a factory test bike, that works back to 9,069 rpm through the transmission, or well within the eyeball precision of a guy that's hauling ass on anything at 150+ mph.

Surely the "reduction" isn't 1.019:1 ...

I'm also recalling a posted chassis dyno run yielding 70 lb ft @ 5,500. You could expect any random dyno tech to factor in tire diameter & the rear gear, but a buried reduction gear that nobody seems to know about?

That's a stretch. That was a very tired engine, or 1:1 from the tranny's input to the crank.

Is it possible that it's just a 1:1 countershaft to shift the output?

[Scott_]

I'm thinking that 1:1 would not be out of line.
The intermediate housing basically allows for: 1, changes the rotation from the crank to the output shaft, and 2, makes for the starter and alternator drive connections.

IIRC my 'LT runs approx 3500 rpm @ 55 in 5th with stock tire and FD ratio.

[JED]

Thanks for the rpm @ speed input - it's helpful.

I'm looking at a RealOEM page titled K589 (K1, K100RS) K100RS (0523, 0533) Starter 1-Way clutch/reduct gear shaft. That's verbatim - I can't explain the apparent redundancy in the page title, & I'd just punch in the URL for you but it truncated along the bottom of the page.

I got interrupted while looking into this & at this point I'll pass on unlocking my office for a surf session that'll surely go on longer than intended - but - what I have shows the engine side of the intermediate case with an aux shaft & a counter shaft with a big hole where the clutch should be. What I don't have is a good & complete detail of that gear train, but the starter drives the counter shaft, the alternator is driven by that shaft, & pictures of the rear of the engine show what has to be a splined aux shaft in a big, sealed bearing. That's on the transmission input shaft center, or centered on the clutch clearance. I have another RealOEM page showing the crank, & it has a big honking gear on the end of it. That big gear plus a countershaft plus another aux shaft means that there's another gear on the transmission input, & that it rotates with the engine.

All of which makes one wonder why they call this page the clutch/reduct gear shaft page when 1) we've confirmed no reduction, & 2) it shows no friggin shaft through a great gaping hole where the clutch lives.

This is at least slightly annoying.

The purpose of that assembly is to move the rotational thrust of the engine from the starboard side to a closer-to-center position. If not for that countershaft arrangement, a good portion of the engine would be hanging out of the port side of the bike. Having made that choice to lay a fairly conventional I4 down on it's side, the necessary countershaft arrangement offered convenient positioning for the starter & a gear driven alternator.

The question that remains is the ratio of the gear train - it's looking like no reduction but we haven't confirmed it one way or another. I would love to find a detail of that assembly & I'll do some more looking, but at this point I'm thinking I'll be tearing mine down & drawing it myself.

Ultimately - for my own project - that intermediate case will be very different, & the information I need is on the bike.

Thanks For The Input

[Scott_]

Well, I suppose that technically the shaft in that parts page you reference, is a "reduction shaft" for the starter and alternator drives.



Here's a K75, yea it's only 3 cyl so it will have the balancing weights on the shaft that the 4cyl won't but the intermediate gearing would still be the same.

[JED]

So where'n hell did that come from? Wherever, it's a beautiful thing!

Thank You!

[Scott_]

Surely the "reduction" isn't 1.019:1 ...

I rode with my GPS today to/from work for a better MPH reading, anyway....

I ran some numbers tonight.... I came up with a similar calculation.

5th gear at 1.61:1, final drive on my LT is(33/12) 2.75:1 my 150/70/15(new, less than 150miles) has an estimated circumference of 79.38in and 798.18 rotations per mile.
per (https://www.tacomaworld.com/tirecalc?tires=150-70r17-140-80r17)

55mph at approx 3500rpm
60mph at approx 3750rpm
70mph at approx 4500rpm

running the calculations forward and backwards I also came up with an average reduction(or maybe I should say discrepancy) of 1.08:1
Could this error be in the accuracy of the tach?

It would be interesting what you find in your tear-down and inspection.

[JED]

Thanks for the interest. I'm guessing the biggest factor in that slight error is revs per mile on the tire. Does the quoted number come from 5280 / by the static circumference in feet? Probably, I doubt it's a 3rd wheel derived test with warmed up tires.

Little imprecisions stack up - like using 2.82 for the RS final drive instead of 2.818. That's 2 1/2 rpm @ 60 mph, or less than a tenth of a percent that doesn't even qualify as a rounding error, but that's exactly the kind of thing that stacks up to a percent or two throughout an assembly.

In a lab environment +/- 3% is often considered acceptable, & that's not just ball parking it - that's in the batter's box with home plate right there in front of you - but you're still not on the plate. As a young engineering tech / lab support machinist, I started to get my head wrapped around that when it became clear that the calibration guy responsible for maintaining our data acquisition equipment was more than happy with +/- 1% on things like digital tachs & dynos & load cells. That's when my mold-making tenths mics & indicators & the like went home for safe keeping - & what we were testing were gear boxes.

I'm starting to pull the details together, I have the K75/100 manual that the above assembly came from, a K1100 manual, etc ... & developing even more of an appreciation for these machines as a result. They are exquisitely innovative & well-engineered machines. Not to dis the K75, but I'm seeing the K1100RS as the e30 of the 1 liter & above class.

So far as I can tell, a stock RS should do 16.8 mph for each 1000 rpm in 5th gear - & there is no reduction on the driven gear in the intermediate case, it's 1:1.

[rbm]

Have you seen this speed calculator?

[JED]

I hadn't, & thanks for posting it, but seriously - while gear math can get pretty intense, calculating ratios is literally 3rd grade arithmetic. A scientific calculator is gross overkill, a slide rule is faster, & you need only the correct values to quickly & easily figure ratios & speeds in gears for yourself.

More to the point, speed reducing an output increases torque - that 4:11 gear in my granny's Camaro served a purpose. In the K11s, 1st gear puts about 990 lb ft to the axle, in 2nd it's 651 lb ft, in 3rd it's 505 lb ft, in 4th it's 413, & in 5th you still get 354 lb ft out of an engine that peaks at 78. A 10% increase in torque at the crank is a multiple of that value to the pavement.

When my garage buddies & I were kids, we often over looked this as were intensifying otherwise underwhelming cars with commuter-grade drivelines. We'd tweak & tweak until something seemingly minor like the torque advantage from a set of long tube headers started breaking things, but that extra 20 lb ft or so in 1st gear could easily be another 300 lb ft on the axles.

I think it's helpful to understand that.

[JED]

... & I now have the dead tree edition of Clymer's K-Series manual.

Gotta love Amazon ...

 :riding: