Crazy Gear Inch calculations

Watched a video of a guy with:

Schlump mountain drive up front, 11 gear cassette in back, PLUS an IGH with 3 gears.

In the end his GI range was like 9.2 - 156. Insane!


  • edited October 2016
      Gah, links! Where the hammer?? image

    ¬ ITL
  • This is data from SA Triker's 9 minute video on calculating gear inch. Watch it!

    His wife's bike has the same except for the schlumpf, and in its place there's a 3 gear sprocket set. A total of _54_ gears! They can climb trees with those trikes.

    @jamesr, have you seen any of his videos?
  •   Links man, give us links... ! Ctrl+C & Ctrl+V are our friends. :)]

    ¬ ITL
  • I'm watching youtube via FireTV and doing this on a cell phone
  • edited October 2016
    I think what I'm going to do is to just install a Patterson up front. So, smaller Patterson is smaller than the TT stock front sprocket (28t vs 32 I think) and the larger of the Patterson is . . . Larger. So With that and the stock 8 spd SA IGH, I should get a little lower low and higher high.

    I'll wait until I have numbers for the IGH lowest and highest (and count the rear teeth) so I can figure out the actual GI numbers.

    Front/Rear * IGH low ratio * 20" tires = low GI
    Same but IGH high = high GI

    I'm hoping for maybe 12 GI low, but we'll see where the math leads.
  • edited October 2016
       <- used to understand gear inches once...

      Seems the Schlumpf Mountain Drive was the only way to go lower than 1.0 - yet for the expense for a lower-end trike that doesn't make sense ... unless one's resources is exuberant. Be cheaper to do with an external derailleur, 3 chain rings up front, a decent cassette, and go with 24" wheels. And that put the rider up another 2 inches.

    ¬ ITL
  • edited October 2016
      The small bike trail along the Payette River is relatively short. The dirt trail that is seen on Google Maps has been barricaded off due to the area being unsafe. The trail has been washed from underneath the river and also dangerous due to the transient populous that resides in those "wooded" areas.

      WRT I'm quite aware of, and is a nice 4% to 6% grade from New Meadows on down to 18 miles above Council. Then it's a mixture of flatlands and such. Will be a bit muddy since we've had nothing but rain for 2 weeks.
      Problem with riding down the WRT trail is finding someone willing to take you up to New Meadows. That's how I ended up breaking my shoulder as I wanted a nice leisurely ride back, but the only guy (Colonial Motel) willing to take anyone up wanted $250 per person, minimum of $500 to make the run.
      So went to Brundage thinking the easiest MTB trail would of been similar. Was about 35 miles north of Council, on $25 of fuel the entire trip. Unfortunately what I wanted is not what I got, although tried to make the best of it. LOL

      Am thinking of driving to Weiser, which is about 30 minutes down the highway, and offloading the Rover and riding up the trail. But have to wait for the moisture to drain as it could be muddy in the area. The trails are paved in town, but not sure how far out, then it's mostly hard pack, some gravel, dirt. Not ridden from Weiser on up so don't know the trail between there and Council.
      There is a yearly two-day ride most the trail with an over-night camp at a hot springs. Not been to a hot springs yet. This year's 2 day October ride was held really early in the year.

      Is a proposed dam in Weiser that's been the talk of the town, and a good section of the WRT trail would get submerged. And the damn would be another mud hole anyhow. There is a lot of opposition on the dam.
      Was a member of "Friends of the Weiser River Trail" and have plans on renewing again.

      As for a route between Payette to Weiser, there is no set cyclist trail. So the only way is along side a two lane highway with stupid drivers. Very unsafe for a lone cyclist.

    ¬ ITL
  •   The one local ride I'd like to take is from Fruitland into Ontario, OR. The biggest issues are the turn-off into Walmart at the base of the Snake River Bridge, the intersection at Panda Express, the turn-offs to the freeway, and the Underpass at the railroad. Those sections are quite dangerous. Rest of Oregon is friendlier.

      The local LBS is to the left of the railroad underpass, and a small strip of shops along the way.  :)

      Going back is perty much all that except the gas station by TVCC... best to go around it. And crossing the Snake River bridge is a bear! That's the one that kills your legs going up. Even in granny gear on the Rockhopper I was left panting at the top. Made it a few times, not many. It's not like I go out of my way to take that grade, though it is a nice ride. The Rockhopper did 27 MPH coming down that bridge with no help from me pedaling. But... that turn-off going into Walmart is bad news. Most people will let you ride past there, giving you the right of way on the marked bicycle lane. it's the other 30% of the population that will over take, cut in front of you, and put on their brakes to make the turn. All bad news for the cyclist that can't do 25 MPH ~ or brake suddenly.

    ¬ ITL
  • edited October 2016
    Damn, @Elrique64, you stole all my thunder! I'd used TT and Patterson site specs to come up with this:

    Spec GI, 25 - 80. Front, 32 teeth, rear, 25. A little math leads to 0.97 hub low, 3.125 high (sort of matches the SA specs that say 1.0 to 325%)
    (32/25)*0.97*20 = 26, (32/25)*3.125*20 = 80

    Adding a Patterson:
    28/25*0.97*20 = 21.7
    45/25*3.125*20 = 112.5

    So adding a patterson will reduce the low end from 25 GI to 22 GI, and increase the high end from 80 GI to 113 GI.

    So, I'd get the equivalent of just a little bit more hill climb, and a lot more top speed.

    Honestly, I don't think a 3 GI reduction in the low end is enough for the FOG hill climbing. The 33 GI jump on the high end is nice, but I want lower.

    Schlumpg Mountain Drive sounds great, but it really only adds lower. Their High Speed and Speed adds higher. So I'm stumped on the easiest way to get both lower and higher, without going to the extreme of adding a 3-ring at the front with a derailer and chain tensioner. I have none of that, just nice clean chain of set length.


  • edited October 2016
    $100?  The MTB alone is $600.

    I'm willing to put a 3-sprocket set on the front (during the winter non-riding period), with something like 22T, 32, 45 and try to find a derailer and tension system . . . but the lack of a strong front post like UT used to make is making me very . . . leery of going ahead with it.
  • OK, so we're back to the Patterson but I change the drive sprocket on it to a smaller sprocket and that will, in effect, bring the lowest GI down below 20, is that what you're saying @jamesr?
  • Would this work for the 3 ring front set?

    Shimano Altus M311 22x32x42t 7/8spd 170mm Square Cranks
  • My front crankset was about $32. A derailleur hanger is ~$5 while the derailleur itself is ~$30. More chain is ~$13, putting the overall cost at ~$80. ($94 if you need to buy a crank puller.)

    So $100 is a pretty good ballpark for adding a triple to a Rover while keeping the rear hub.

    - PaulNM

  • @jamesr and @PaulNM, I know I'm being obtuse here - we've done the math and the Patterson wouldn't really go low enough in GI as-is. Are you saying I could put a smaller sprocket as the driver to the Patterson (with the 165mm cranks Patterson offers) and drive the Patterson to sub-20's?  I don't need 15 or even 10 GI, just 20 or a little less, I think.

    @PaulNM, can you provide exact names to that equipment? Plus, what the heck did you use as the derailleur hanger? Rover has no front post . . . - Got pics for us?

    @jamesr if the M311 is "good enough", can you provide the Lasco and Sugino model names (or even links) that you feel are better choices? (P.S. I asked you about it because it talks about "standard taper" and such, which I wasn't sure was right for the Rover - I don't want to modify the frame components if possible)

    I'm going to do this. I'm going to make this Rover into what _I_ want it to be - a hill climber that can reliably hit 16 - 18MPH on the flats at a cadence of 60 - 70 rpm. 

    If you guys can put up with me as I do it, I would greatly appreciate it.
  • Hmmm, I can buy the 22T chain ring alone for $4.07 from Amazon - that'd be an inexpensive way to test the 22T ability to lower my low end . . . but that assumes that the default crankset that came with the Rover can have the ring alone replaced. I just don't know enough about the equipment that's on it yet . . .
  • To be clear, the derailleur hanger I was referring to is for the rear. Same for the derailleur, which is meant to act as a tensioner. I currently have no front derailleur as I have no front post. I do have a plan to fashion one with a friend, for now I just grab the chain tube and use that to switch front cogs. 

    I was mostly responding to Elrique64's post that elaborated on jamesr's idea to just go with a "regular" front crankset replacement.

    I have pics of my setup on the photos thread.

    - PaulNM
  • Thanks for the clarification @PaulNM.

    Now that I think about it, my own son-in-law (he married my eldest daughter) is a welder. If I can get my hands on the specs/drawings for the one Utah Trike used to make for the Rover, I'm sure I can browbeat/ask him to make me one or two front posts . . .
  • Does ANYONE have a link to a pic, or even PDF and specs, for the Rover front post Utah Trike used to make?
  • Next on the list is a chain tensioner. 

    My Amazon shopping cart currently has:

    1. Shimano Altus M311 22/32/42 7/8 spd 170mm crank set for $31.74
    2. Shimano FD-2403 3x8-Speed Front Derailleur for $19.60

    Looking at a Chain Gobbler, but the damn thing is $80 at TerraCycle!!!
  • Amazon calls it " Origin8 Torqlite UL Chain Guide" but it appears to be the same thing.  Does this seem right?

    If so, I'll add it to my Amazon list                             
  • Hmmm, what about this thing?

    Seems to me that I just need to compensate for the chain length difference between 22T and 42T, so something simple like this might do it?
  • @Elrique64, my son-in-law is a welder, and I've found the tube diameter (1 1/8"), so as soon as I can figure out the angle, I can browbeat him into making me one or two of them . . .  or 3 or 4 if you guys want one too.
  • All these $$$$ add up fast . . . .
  • ewwwwww . . . . Money Pit!
  • I think I've been stupid. worrying about adding chain tensioners, etc.

    I've got a garage and shed full of old bikes with rear derailers - which include tensioners of course!

    So I just mount one in a static position under the igh 25t gear, add the 22/32/42 crankshaft from Amazon, and add some chain (13"?).

    Simple. Except for the front derailleur, of course.
  • edited November 2016
      Railroad spike on a 1x4 might work till you get something more tangible? Least with a railroad spike you'd be original. :)

    ¬ ITL
  • @jamesr, no comment about using an old df derailleur/tensioner under the igh 25t drive sprocket as a tensioner?
  • Ahh, so while an old rear derailleur will work, it isn't optimal. Makes sense.

    Plus, with the Origin8 rig, I can keep it a bit more streamlined, eh? :-)
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