Precision Clock Drives
Drive Montage 1 Drive Montage 2 Drive Montage 3 Drive Montage 4
Optic-Craft Machining has developed a completely new clock-drive that meets the exacting needs of today's astronomical community. The operational characteristics are unique and are not available from other drive manufacturers.

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Features and Specifications

Drives produce one revolution in 1436.3 minutes +- 3 ARC second per sidereal day.
Gear Specification
Both 6" & 9" drives have 32 pitch main worm gear, with companion worm. All gears are precision ground and lapped. R.M.S. lead variation does not exceed .00007". AGMA level international standard 15.
Worm gear is made from high tensile strength aluminum & worm is made of stainless steel. Secondary worm/worm gear is made of bronze and stainless steel.
All Worm gears are anodized a light gold color. There is no extra charge for this service and is included within the cost of each clock drive gear assembly. Many manufacturers charge extra for this service.
Gear Mesh Load
The worm mounting plate assembly is tension loaded to the 6" & 9" gears. This flotation action eliminates all gear backlash & maintains 100% tooth to tooth engagement. This is a patented mechanical system.
Protective Coatings
Use white gear grease for long term protection on gear teeth.
Both 6" & 9" drives deliver 2060 in oz. torque at worm. Slip clutch will manually produce 50 ft. lbs. Minimum gear train torque at polar shaft 2200 ft. lbs.
Worm Housing
Housing is plate mounted. Pre-load of secondary bronze motor change gears are established at time of manufacture. Main worm bearing blocks are pre-lubricated and are machined to within .0003 ". Worm shaft lateral end play is canceled by two worm shaft thrust bearings and two thrust washer clamps and two roller bearings.
Slip Clutch
Clutch surface area is 70% of gear. Clutch faces are lined with pressure pads. The material provides an excellent gripping surface. Also, a .250" thick keyed aluminum thrust plate locks gear in place.
Motor Speed Control
Because of the precision of our drive assemblies, a motor speed control is not needed. If customer prefers one, we recommend the "Accutrack" Model 2361 which varies AC line fi-equency. 12 V. D.C. input 110-115 V. A.C. output or the "Accutrack" Model 3117 which varies the A.C. line frequency and has both 12 V. D.C. and 110 V. A.C. input. Output 110 V.A.C. They are available from Orion Telescope Center. Also, for those wanting to construct their own A.C. line frequency controls the following is available from Willmann-Bell Inc.
For GO-TO applications, we suggest the AWR system. Please visit their GO-TO web site for more information.
The Back-Plate
Worm motor assembly is screwed onto the housing surrounding the polar shaft, on the telescope mounting. Three threaded 1/4-20 screw holes are provided either vertically or horizontally placed, based on the customer's need. Back plate assembly. clearance hole cannot come into con- tact with polar shaft. State clearance hole diameter required when order is placed within 1/16" increments.
Slip Clutch
Clutch is engaged by turning threaded pressure plate clockwise by gripping one or more of the three knobs provided. This will provide approximately 80 foot lbs. of torque. If further torque is required, screw down each knob clockwise which allows an additional 50 to 60 foot lbs. of clutch pressure.


Subject to Change
Always contact us
for quote
CastorRA65 lbs.5.6"4.0"0.254.0:1643590.625"$695.00
PolluxDec.65 lbs.5.6"4.0"0.254.0:1643590.625"$695.00
ArcturusRA80 lbs.6.6"4.0"0.147.1:1322021.000"$794.00
AltairDec.80 lbs.6.6"4.0"0.147.1:1322021.000"$794.00
PolarisRA95 lbs.9.0"4.0"0.205.0:1322851.000"$997.00
DenebDec.95 lbs.9.0"4.0"0.205.0:1322851.000"$997.00
SiriusRA180 lbs.12.0"5.0"0.273.8:1323831.000"$1398.00
MizarDec.180 lbs.12.0"5.0"0.273.8:1323831.000"$1398.00
SpicaRA250 lbs.13.5"6.0"0.224.5:1243222.375"$2980.00
AlgolDec.250 lbs.13.5"6.0"0.224.5:1243222.375"$2980.00
AntaresRA320 lbs.16.0"6.0"0.273.8:1243832.375"$3785.00
CapellaDec.320 lbs.16.0"6.0"0.273.8:1243832.375"$3785.00
AldebaranRA500 lbs.20.0"7.0"0.342.9:1244902.375"$5990.00
RigelDec.500 lbs.20.0"7.0"0.342.9:1244902.375"$5990.00
VegaRA800 lbs.24.4"8.0"0.412.5:1245862.375"$7480.00
BetelgeuseDec.800 lbs.24.4"8.0"0.412.5:1245862.375"$7480.00
ProcyonRA1100 lbs.28.0"10.0"0.472.1:1246722.375"$9100.00
SarinDec.1100 lbs.28.0"10.0"0.472.1:1246722.375"$9100.00
MiraRA1400 lbs.32.0"12.0"0.531.9:1247682.375"$14980.00
AlorDec.1400 lbs.32.0"12.0"0.531.9:1247682.375"$14980.00
  • D.P. - Diametrical Pitch
  • Worm gear rate - The speed of the rotation of the worm in RPM to yield one turn of the main gear once each sideral day or once every 1436.3 minutes
  • Sec. gear ratio - Input turns vs. output turns of the additional gears that match the worm rate to the input shaft which is designed for 1 RPM standard. The numbers above are approximate. (other rates are available)
  • RPM - Revolutions per minute

Before purchase always verify specifications with Contact Optic-Craft

* - OPTIC-CRAFT MACHINING larger precision designed clock drives incorporate the following features as standard equipment:

  1. Bore shaft sizes up to 8" I.D. at no extra cost
  2. All worms made from 303 stainless steel.
  3. All worms mounted in precision sealed taper / roller bearing housing eliminating both radial and axial movement while affording a smooth turn- ing action. This bearing block design is used on 16". 20" and 24" drives.
  4. 600 in oz. HURST AC synchronous motor provided on all models over 9 inches in diameter.
  5. No assembly required. Drives incorporate unitized construction design attaching to your mounting simply within minutes.

The nearest comparable California manufacture of clock drives charges an additional amount for these standard OPTIC-CRAFT features and this does not include unitized one piece construction.

** - On 20" and 24" drives customers specialized housing and mounting plates will be considered as part of purchase price that may deviate from OPTIC-CRAFT support plate design.

Ordering Information

All drives are assembled with HURST synchronous hysteresis reversible motors 110 volt 60 cycle. 220 V 50 cycle can be obtained by using a step down transformer.

Provide The Following Dimensions When Placing An Order:

Need 3" polar shaft length to accommodate thickness of clock-drive assembly.

  1. Maximum bore size available on clutch is 3.5" from 3.5" to 5" add $45.00 to order for special machining. This applies to 6" & 9" drives only.
  2. Delivery - 5 to 8 weeks from receipt of order.
  3. Warranty - 5 years parts & labor.
  4. Shipping - C.O.D. United Parcel Service shipping charges only U.S.A. & Canada. C.O.D. Air Mail only foreign orders.

Myths about Gear Specifications

There are some myths that have been communicated by advertisers over the years that include statements like, patented production techniques that make a drive train accurate or that aperture size & gear diameter should be the same. The facts are all drive manufacturers must conform to recognized machining & machine tool national standards that have been the guideline for instrument manufacturers for more than 50 years. If a gear is made to a A.G.M.A. standard or class 15 then that class defines its accuracy. It is one of the few systems that the manufacturing community recognizes. Aerospace gearing is class 14. Optic-Craft gears are class 15. Our 6.6" gear is just as accurate as our 20.0" gear. As protection to you as a consumer, ask the manufacturer what class of gear they produce in order to test their advertising claims.