MicroTrac
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MicroTrac is a small scale, walk-behind version of LifeTrac. This page documents MicroTrac Prototype I.
Industry Standards
- The BCS Tiller is the main competition.
Tools
- Tiller
- Mower
- Chipper
-Laimet conical screw design. Makes nice big, uniform sized chips.
Design
Engine
The engine will be a modular removable unit consisting of engine, fuel tank, hydraulic pump, hydraulic reservoir, and frame. The frame will be the hydraulic reservoir, made out of 4x4" square tube.
Specifications
Engine should be a 12-20 hp 1 cylinder diesel engine, with air cooling. The engine will run the hydraulic pump.
We have a 17.5 HP engine.
Dimensions: 18x16x13" Shaft: 1x?"
Turns CW from above. CCW from below.
Sourcing
- 14 hp 2 cylinder engine no starter $975
- 11 hp 1 cylinder generator $899.00
- 13 hp 1 cylinder silent $1300
- 13 hp $695 GAS
- 23 hp water cooled diesel engine with radiator $1000 - $1349
- 62 hp 4 cylinder tractor $1828
- 65 hp 4 cylinder tractor $710
- 40 hp 3 cylinder $1500 - $2300
- 35 hp 3 cylinder tractor $1185
- 90 hp 4 cylinder diesel 2000 vw beetle $2000
- 11 hp 1 cylinder $400
- 13.7 hp 2 cylinder $666
- Perkins 402C 13.7hp 2 cylinder Same as above, asked for quote 3/5/09 talked to jeff
Hydraulic Pump
Specifications
- 10.1 GPM at 3600 RPM and 2500 PSI, requires 17.3 hp to drive it - best match to available engine - [2]
Sourcing
- .677 cu in, 10.1 gmp @3600 RPM, 3000 PSI max, 4000 RPM max, $180 - [3]
Coupler
Wheels
- one set of drive wheels in the middle balanced with the engine so the Microtrac can be rotated easily, with a motor on the side
- doubled up for traction
- have support wheels on the back sides so it doesn't tip easily
- drive wheels the same as lifetrac, 30" high 10" wide
Power Cube (MicroTrac engine cube) Details
- The coupler halves and spider are shown in the pictures, from McMaster Carr page 1157
Power Calculations
Pump
- From [4] - Pumping = 1 Hp = 1 GPM x 1500 Psi - (linear relationship i.e. 2 GPM @ 1500 Psi = 2 Hp)
- For the above pump, 14.2 gpm with 3000 psi indicates 28.4 hp requirement
- Hp to drive hydraulic pump = Psi x GPM / 1714
- For the above .97 cu in pump, 3000*14.2/1714 = 24 hp
- If we run at 2200 psi => 18 hp required
- For .86 cu in pump, need 3000*12.6/1714 = 22 hp
- For the same with 2500 psi, 18.3 hp
Power Available
- Assuming 85% pump efficiency, we have 17.5*.85=14.8 hp power available to the machine
Wheel Motor Calculations
- 32 cu in wheel motor: 20 gpm, 5170 in lb torque, 145 rpm
- Using 12 gpm, 5170 in lb torque, at 87 rpm - uses 7 hp of the engine
Spider Torque Rating
The Hytrel coupler spider has a 401 in lb torque rating. This is at 3600 rpm. If this pump is driving a hydraulic motor at 87 rpm (wheel motor at 12 gpm fluid flow, at its rated torque), what would be the maximum torque that the 87 rpm could have? 401*3600/87 = 16600 in lb. That is well within the 5130 in lb torque of the wheel motor. Coupler spider will hold up.
Resource Map
(could use more review)
Reviewers:
- http://www.tractorbynet.com/forums/build-yourself/140170-homemade-modular-hydraulic-engine.html
- No response as of 4.28.09
- http://forums.hydraulicspneumatics.com/eve/forums?a=tpc&s=4721063911&f=8641063911&m=74110526&r=74110526#74110526
- Useful response, including hydraulics primer, Mr. Hanson's contact as a consultant, etc.
- The response claims need for 30 hp if we want 15 gpm at 2200 psi. We have 12 gpm at 2500 psi.
- CadTrac uses 16 gpm pump and 18 hp engine, at 2000 psi for 1/2 of the flow (to wheels) and 1000 psi to rest of flow (loader)
Coupler info:
- http://www.lovejoy-inc.com/uploadedFiles/Catalogs/jw.pdf
- http://www.ohiobelting.com/pdfs/lovejoycplg.pdf
Notes
- On calculations (right picture) - formula for horsepower to drive pump (with 1714 factor) includes the efficiency of the pump (about 85%)
Parts Buildout
