Bulldozer Geardown
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Design Proposals
Day 1 - Dorkmo
- Folder of first draft Sketchup Files - [1]
Design Review
Further Conceptual Design
Geardown Iteration Day 2 by Dorkmo
Review of Day 2 by MJ
It turns out that the sprocket sizes make the geardown particularly large. So I am looking at Page 82 of Martin Sprocket Catalogue and see that the smallest 100 pitch sprocket is 8 teeth, Diameter of 3.8". Shaft is smaller than our 1-7/8" size, so the only way we can use it is if we weld on our own hub.
Initial Conceptual Design
Design Conditions of Satisfaction
- Uses exising Quick Connect Wheel rotor - its shaft output.
- Geardown module is CNC cut from 1/2" steel sheet
- Notches are made such that the structure can be assembled only one way
- Mechanism for quick disassembly is included
- Mechanism for tensioning the chain drive is included
- Enclosure allows easy replacement of parts
- Quick attachment of wheel onto the output shaft of geardown module is possible
- Wheel is secured via a keyway
- Input shaft is 1-7/8" thick, output shaft is 3" thick
- Standard cold rolled shaft is used
- Mechanism for retaining axial thrust is included
- Geometry must line up for the connection to Quick Attach Wheel
- Guards protect any exposed chains/sprockets for safety
- Method of coupling to existing Quick Connect Wheel must be used - via chain drive - while considering geometry of frame a drive components
- Quick Connect Wheel and Geardown units must be sufficiently stable to maintain chain tension. Tightening mechanism must lock in place.
- Reference must be provided to verify existence of off-shelf parts
- 100 Pitch Chain must be used.
- Concept must show approximate dimensions (+/- 2") of the geardown structure
- Geardown unit must be no more than 250 lbs in weight
LifeTrac Existing Design
- LifeTrac - LifeTrac_III frame documentation
- Quick Connect Wheels - shows dimensions
Parts
Sprockets
Notes: practical limit for 100 pitch ~ 36 teeth - or 15" OD - [2]
80#
- 1-7/8" bore 20T - [7]
- 1-7/8" bore 14T - [8]
- 1-7/8" bore 13T 2.3285" O.R. - [9]
- 2" bore 13T - [10]
- 2" bore 22T 3.79" O.R. - [11]
100#
- 2" bore dia, 11T, 2.504" O.R. - [12]
- 26 tooth - OD 11" - $10 - Surpluscenter - [13]
- 2517 2. tapered bushing [14]
- 2.938" bore dia, 16T - $123 - [15]
- 2.938" bore dia, 25T, 5.3225" O.R. - [16]
- 2" bore dia, 25T - [17]
- 36T 3020 taper bushing [18]
- 3020 3. bushing [19]
tapered sets
1-7/8" shaft to 13T 100# sprocket
- keyed 1-7/8" to 2012 size tapered bushing
- 2012 tapered bore, 13T, 2.9105" O.R.
Sourcing Problems
- 100# chain sprokets hard to find
- 80# chain sprokets with bore dia above 2" hard to find
- minimum teeth on 100# sprocket for 3" shaft with 3020 tapered bushing = 28
- max shaft size for a bored to size 100# sprocket = 2.938