MAl l BRAY

3.6m telescope MAINTENANCE MANUAL NUMBER 2

@

MAIN GEARS

Edition jan. 1977 J. Roozeveld van der Yen

3.6m telescope MAINTENANCE MANUAL NUMBER 2

@

MAIN' GEARS

Edition jan. 1977 J. Roozeveld van der Ven

CONTENT

page

1. Principle 1

2. Description of parts 2

3. Maintenance 9

4. Manual driving of the gearboxes. 10

5. Demounting procedure of the declination gearbox 11

6. Demounting procedure of polar axis gearbox 13

7. Mounting procedure of the declination and

polar axis gearbox

8. Replacement of the nitril rubber seal between

gearbox and gearwheel cover at the

declination axis

9 • Replacement of the nitril rubber seal between

gearbox and gearwheel cover at the

polar axis

10. Demounting of the motor assembly

15

17

19

20

- 1 -

1. PRINCIPLE

The complete main gears are shown on drawings T 10-100

and T 11-100. Both telescope axes are driven by Inland

torque motors and a 3 step reduction gearbox. Most of

the parts and subparts of these ge~rs are identical at

both telescope axes. The gear backlash is eliminated by

the braking action of one of the drive motors. The motors

are built together to one unit with a tachometer and an

electromagnetical friction brake. This brake automatically

engages by spring force when the motor current is cut off.

To the gear boxes are mounted an incremental encoder,

a Heidenhain backup position encoder and a Siemens absolute

encoder. Each main gear consists of two main parts, the

big gearwheel with cover, and the gear box. To obtain the

correct position between the main parts, a system of guiding

rollers has been applied. Between the parts is a flexible

rubber seal to prevent oil leakage.

A moment arm, provided with 2 ball heads connects the

gearbox to the telescope structure. Gearwheels and bearings

are oil lubricated. At the polar axis the lubrication unit

is part of the gearbox. At the declination axis, this unit

is located inside the V-beam to obtain a correct oil return

in all telescope positions. The load on the guiding rollers

is reduced by a compensation mechanism. At the polar axis·

it is a simple spring system and at the declination axis

a counterweight-lever system with vibration damper.

The gears are protected for too low oil pressure by the

manometer, that is provided by electrical contacts giving

a signal that cuts off the motor current.

- 2 -

2. DESCRIPTION OF PARTS

2.1 11otor assembly T 10-101

Identical for both telescope axes, the motor assembly

consists of Inland motor model T12008,'Inland tachometer

model TG-5723 and a Pintch Bamag electromagnetic

II Zweiflachen-Federdruck II brake" type EFB 5 Ost, that

automatically comes in when the current is cut off.

These parts are fitted on a heavy shaft that is

supported on a pre loaded set of conical bearings and a

needle bearing with reduced clearance. The brake is

fitted on an extended shaft that is screwed to the main

shaft. Its end is provided with a hexagon for manual

drive. The shaft is oil tight sealed to the gearbox.

Between motor and gearbox is a cell rubber dust seal.

The first drive pignon is part of the motor shaft

between motor and tachometer, a mumetal shielding

plate is fitted. Motor and tacho are located inside

an aluminium casting.

2.2 Geartrain T 10-102

It is identical for both telescope axes, besides

the bore of the big gearwheel.

The big gearwheel is welded from mild steel sheets

and is stress relieved. The rim of alloy steel

34 Cr Ni M 06 is welded to the inner part by a special

process. The complete gearwheel forms a rigid part

which is reenforced by radial ribs. The rim at its sides

is provided with flanges, that serve as track for the

guide rollers and incremental encoder roller. Gearteeth

and side flanges are ground to a very high precision.

- 3 -

Fixation of the gearwheel to the telescope structure is

done by screws. The other gearwheels are hardened and

ground to a high degree of precision. Pignons and gearwheels

are respectively made from 14 Ni Cr 14 and 10 Ni Cr M 07.

The gearteeth are protected for overload by a spring

loaded friction coupling located inside the first gearwheel.

The shafts are supported by pre loaded conical bearings and

at the other side by cylindrical bearings. Bearings and

gearteeth are pressure oil lubricated. The gearwheel

housing is welded from mild steel and stress relieved.

The calculated life time for gearteeth and bearings is

infinite.

Main data of the gearwheels

No. of Norm. Press. Helix module Width teeth ang. ang. rom

Big gearwheel 720 4,68 17°30' 12° 125

Pignon 40 4,68 17°30' 12° 125

Intermediate gearwheel 169 2,44 17°30' 15° 50

Pignon 25 2,44 17°30' 15° 50

First gearwheel 88 2,21 17°30' 15° 45

Pignon on 17°30' 15° motor shaft 43 2,21 45

2.3 Guide roller units T 10-103

(4 for each gearbox, all identical)

In each unit are located 3 rollers. One of these serves

for axial guiding and rolls over the side track of the

gearwheel rim. Adjusting and preloading is done with

spacers. The other rollers are fitted on spindles provided

- 4 -

with excenters. The rollers at the gearteeth side are adjusted

at the MAAG factory to obtain the correct gear teeth clearance.

The position of these excenters always should remain the

same. The nuts for that reason are locked by pins. The oppo­

site rollers are also fitted on excenter spindles, which

serve for preloading. The preload moment on the spindles

is 3 mkp. All spindles are iocked by special locking screws

located at the side.

2.4 Moment arms T 10-104 and T 11-104

(Basically the same for both telescope ax~s)

The moment arms transmit the teeth force to the telescope

structure. The supports on the telescope structure are

different, as well as the length of the "floating" parts.

The ball heads however are identical. Each ball head is

preloaded by a belleville spring washer unit. These units

give a preload of about 2500 kg in each of the ball heads

to eliminate backlash in the ball units. A small moment arm

is located between gearwheel cover and gearbox.

2.5 Gearbox upperparts T 10-105 and TIl-lOS

(Identical for both gearboxes)

These parts are welded from mild steel sheets and are

stress relieved. At the flange side there is a provision to

fit a flexible rubber seal. Four guide roller units are

located in each part, and connected and located by screws

resp. adjusting pins. To prevent oil loss, each unit is

closed by a steel cover. At one of the short sides, there

is a provision to fix the moment arms. At the center the

incremental encoder is located.

- 5 -

2.6 Gear cover T 10-106 and T 11-106

(These parts are mainly equal)

The cover is bolted together from two pieces. Both are

welded from thin steel sheets. At the center there are two

steel rings. These rings serve as bearings for the gear cover.

The bearing surfaces are provided with a bronze layer.

No teeth forces are loading this part. There are only forces

on the bearings coming from the weight and from friction.

The bearing rings are provided at its· inner side with an

oil catch. It is possible to demount the covers from the

telescope without demounting bigger telescope parts. Friction

forces from the bearings are led to the gearbox upper part

by a small moment arm.

The oil returns at both gearcoversare different. At the

declination axis the gearcover is provided with an oil return

that serves in case the telescope is nearing the 6 hour

position.

2.7 Gearbox bottom parts T 10-107 and T 11-107

(Besides a small detail these parts are equal for both axes)

At the declination axis there is an oil return at the side.

At the polar axis the oil flows directly to the oil tank that

is located underneath this part.

Both parts, upper- and bottom, together form the gearbox

that rolls over the main gearwheel by the guide rollers.

The Heidenhain encoder and Siemens encoder are located

near the flange connection of both gearbox parts.

- 6 -

2.B Incremental encoder Itek Wayne-George RI lB/55(C)-QPZ T 10-10B

(At both axes this part is identical)

The encoder is provided with an extended shaft, on which

end a very precise friction roller is mounted. The encoder

is mounted in a box that is open at one side, and can

rotate about one axis. This axis is rigidly fitted in a

frame that is screwed to the gearbox upper part. Between

roller shaft, box and frame a seal is fitted to prevent

oil leakage. Concentric to the rotation axis of the box

an intermediate frame is mounted that supports the pressure

roller that presses the friction roller to the surface of

the big gearwheel. The pressure force can be adjusted by

to .compression springs.

2.9 Lubrication system of declination axis T 10-109 and T 10-116

The oil tank, with motor pump, overflow, filter, etc.

are mounted inside the V-beam in such a way that the oil

return flows back by gravity forces in all position of the

telescope.

Because the lowest position of the oil return in gearbox

and gearcover shifts gradually over from the lower part of

the gearbox to the gearcover, two return flows are necessary.

To bbtain a better result, also these two oil returns are

split, each in a V type tube configuration.

All tubes meet near the root of the forkprong and a common

tube leads the oil to the oil tank. Several flexible units

are fitted in this tube system to prevent overstressing.

From the oil pressure unit, oil is pumped via an oil

distribution system to the gearbox and lubricates gearwheels

and bearings.

- 7 -

Parts of the lubrication system are:

1) 1 luboil pump 5) oil distributor

2) 1 pressure regulator 6) oil tank

3) 1 ArIon filter 7) level indicator

4) 1 pressure indicator 8) drain.

with el. contact

The oil pump (of the gearwheel type, make MAAG) is driven

by a Landert motor. The normal pressure is 1,5 kp/cm2 .

This pressure is regulated by a pressure regulator, which

is adjusted to the correct pressure. The oil pressure can

be seen on the pressure indicator, make Haenny, type 220V/IA,

and is provided with electrical contacts that cut off the 2 motor current when the pressure drops below 1,2 kp/cm .

The oil filter, make ArIon GA60, has a capacity to filter

an oil quantity of 60 l/min at 10 microns. The actual pump

capacity is 6 l/min, so there is a big oversize of the

filter. The filter is provided with clogging indicator.

The oil tank is provided with a level indicator.

2.10 Lubrication system of polar axis T 11-109

The lubrication system of the polar axis is in principle

the same as that at the declination axis. Its layout however

is much simpler, because the gearbox stays always in the

same position. The oil tank including pressure unit for that

reason could be mounted rigidly underneath the gearbox.

2.11 Transverse component reaction member;' T 11-110

This device compensates the side force on the gearbox,

that results from the component of the gravity forces parallel

to the polar axis.

- 8 -

This force can be adjusted to 200 kp by a nut and

screw spindle, that compresses a set of 38 Belleville

spring washers. The deflection is 13 rnrn for a force of

200 kp.

2.12 Heidenhain backup position encoder TIl-Ill

Encoder type Rod 1/45.7 with 72000 inc./rev. is driven

over a backlash free coupling from one of the pignons

acting on the big gearwheel and making a ratio 18:1 to it.

The same unit is fitted on the declination gearbox.

2.13 Counterweight declination axis T 10-112

This device has a similar function as T 11-110. Because

of the rotation of the gearbox in different positions, it

is necessary to apply a counterweight lever system.

It mainly consists of a square tube rigidly fixed

to the fork prong, that supports the counterweight. The

gearbox is fixed to it by a shaft provided by two ball

joints.

2.14 Position indicator Siemens V23463-KOlOl-Dl13 T 11-112

These units are equal at both axes and coupled to one

of the pignon shafts acting on the main gearwheel.

2.15 Arnortisseur T 10-113

This part is necessary to damp the vibrations in the

counterweight device T 10-112.

- 9 -

3. MAINTENANCE

3.1 Lubrication oil system to be checked

a) oil pressure 1,5 kp/cm 2

b) pollution filter (indicated on

filter)

c) oil quantity in pump

(visible on glass)

3.2 Plain bearings of gearcover

To be greased at 12 locations with

about 10 CC grease at each location.

3.3 Moment arms

1 x prl:) week

1 x pro week

1 x pro week

1 x pro ; year

Some dripps of oil on the ball joints: 1 x pro; year

3.4 Counterweight declination axis and arnortisseur

Some dripps of oil on ball joints: 1 x pro ; year

3.5 Oil change

Shell Tellus 133 ' 1 x pro year

(In combination with hydraulic plant)

- 10 -

4. MANUAL DRIVING OF THE GEARBOXES

When the motor current is cut off and it is for some

reason necessary to drive the gearboxes, this can be done

with a lever that fits to the hexagon on the extended motor

shaft. Before this, both friction brakes have to be disengaged

by the three MS screws at each brake. (It has to be made sure,

that the telescope is well balanced or protected for running

away, because the gearboxes are not self locking). For

manual drive it is normally not necessary to engage the luboil

pumps. After the manual drive the MS screws directly need

to be turned to the left sufficiently to be sure that the

brake can work correctly again.

- 11 -

5. DEMOUNTING PROCEDURE OF DECLINATION GEARBOX

- Put the telescope into the 12 hour position with tube

vertical and cut off the hydraulic oil of the declination

bearings.

- Disconnect the oil tubes, counterweight, cabling, etc.

- Close the open ends of oil tubes.

- Put both brakes into no brake position by right hand

rotations of the 3 MS screws (fig. 1).

- Take over the weight of the gearbox from the moment

arm by manuable hoist (fig. 2).

- Demount the 2x4 M24 bolts of the moment arms. Take care

that all parts, spring units and spacers will be fitted in

the same position afterwards.

- Move the gearbox to the top side by crane and manuable

hoist (fig. 2 + fig. 3).

- Engage both brakes by left hand turns of the 3 MS screws

- Prevent any rotation between gearbox and gearwheel cover

by tightening both M12 screws at the corners.

- Demount the small moment arm between gearbox and gearwheel

cover.

- Demount the rubber seal between gearbox and gearcover.

- 12 -

- Demount the incremental encoder, after diminishing the

force on the friction roller by relieving both compression

springs. Both adjusting screws always should remain in the

same position.

- Take off the covers of the guide rollers.

- Turn of each roller unit the excenter spindle which

is nearest to the declination axis (in total 4) by left hand

rotation. (fig. 4)

Before this, the four M8 locking screws have to be

slackened as well as ~he four M30 nuts.

Remark: the four other nuts M30 are locked by pins ------and never should be unlocked.

- Lift the gearbox very smoothly, over a very small distance,

just enough to take over the load from the guide rollers. (fig. 5)

It is advisable, for getting this small lift, to use a manuable

hoist of 2 tons hanging on the dome crane. The gearbox should be

lifted as indicated. Four cables are fixed to the upper lifting

ears of the gearbox and at the other sides to the hook of the

manuable hoist. The second manuable hoist with a capacity of

0,5 ton is fixed to the drive motors and horked on the 2 tons

manuable hoist. With this arrangement smooth lifting and adjusting

is possible.

- Demount the four guiding roller units from the gearbox.

- Lift the gearbox from the big gearwheel and put it on two

supports. Take care that the fragile frame for the connection

of the rubber strips do not touch the supports. Positioning

on the supports should be done by means of two steel bars

through the four lower lifting ears. Each bar is supported

at its end by two wooden blocks of sufficient thickness to keep

the frame free from the supports. (fig. 6)

- 13 -

- Close the gearwheel cover by its steel protection against

dust and mechanical damage.

6. DEMOUNTING PROCEDURE OF POLAR AXIS GEARBOX (see also declo axis)

- Demount parts of the existing floor structure near the

gearbox and make an auxiliary floor.

- Disconnect moment arm, transverse component reaction

member, cabling, etc.

- Put the.brakes into no brake position by right hand

rotation of the three M5 screws.

- Move the gearbox to the top side by crane and manuable

hoist.

- Engage both brakes by left hand turns of the three M5 screws.

- Prevent any rotation between gearbox and gearwheel cover

by tightening both M12 screws at the corners.

- Demount the small moment arm between gearbox and

gearwheel cover.

- Demount rubber seal between gearbox and gearcover.

- Demount incremental encoder after diminishing the force

on the friction roller by relieving both compression springs.

- Take off the covers of the guide rollers.

- 14 -

- Lift the gearbox very smoothly over a very small distance,

just enough to take over the load from the guide rollers.

It is' advisable for getting this small lift to use a manuable

hoist of two tons hanging on the dome side crane. The gearbox

should be lifted as indicated. Four cables are fixed to the

upper lifting ears of the gearbox and at the other sides to

the hook of the manuable hoist. The second manuable hoist

with a capacity of 0,5 ton is fixed to the drive motors and

hooked on the 2 tons manuable hoist. During lifting the gearbox

should stay at the same angle to enable demounting of the

guide rollers without any force.

- Demount the four guide roller units.

- Lift the gearbox from the big gearwheel and put it on

two supports. Take care that the fragile frame for the connec­

tion of the rubber strips do not touch the supports. Positioning

on the supports should be done by means of two steel bars

through the four lower lifting ears. Each bar is supported

at its ends by two wooden blocks of sufficient thickness to

keep the frame free from the supports.

- Close the gearwheel cover by its steel protection against

dust and mechanical damage.

- 15 -

7. MOUNTING PROCEDURE OF THE DECLINATION- AND POLAR AXIS GEARBOX

This should be done in the opposite sequence as described

in the demounting procedure (see also the figures). Care has

to be given to the following:

- Positioning of the gearbox, before placing it on 'the

big gearwheel, should be done very carefull and at the

correct angle. This means the flanges of gearbox and

gearwheel cover should be parallel and the two pignons

should meet the big gearwheel correctly. To do this,

the gearbox should be lowered with small steps within one

millimeter, at the same time observing the approach of the

gears. Stop lowering just before (±O,5mm) the gearteeth are

totally engaged in each other.

- Fit the guiding roller units (each one has its own

number) to the gearbox, fit the dowels and tighten the

six fixation screws.

- Lower the gearbox until the full weight comes on the

four rollers which are located on the still locked spindles.

- Preload the opposite roller spindle (in total: four)

with a torque of 3,5 kpm at its inner hexagon.

- Lock the spindle with its M30 nut (prevent rotation

of the spindle by holding it on the 'inner hexagon).

- Lock the spindle (second lock) with the M8 screw.

- Fit the rubber seal after once more checking the

parallelity of the flanges of gearbox and gearwheel cover.

For the rubber seal fitting a special procedure is worked

out in detail on page 17.

- 16 -

- Fit the small moment arm.

- Turn the gearbox in the correct position with help of

the crane and manuable hoist.

- Fit the moment arm with spring units (fig. 7). All parts

should be fitted in the same position as before.

The spring units cannot be fitted in the correct position

without help of four M8 screws. The spring units (after

greasing the ball surfaces with molykote grease) have to be

fitted to the central piece and provisionally kept in position

by the four M8 screws. During tightening the M24 screws,

it has to be checked that the spring units are in the correct

position, that means the spherical surfaces should fit

into the cones.

After tightening the M24 screws the M8 screws have to be

taken out.

- Before fitting the incremental encoder, the guide roller

units and covers and other parts that have to be fitted

oil tight, their surfaces should be cleaned from fluid packing

rests and provided with fresh fluid packing (f.i. Hylomar).

The force in each of the encoder roller compression springs

should be about 10 kp.

- 17 -

8. REPLACEMENT OF THE NITRIL RUBBER SEAL BETWEEN GEARBOX

AND GEARWHEEL COVER AT THE DECLINATION AXIS

(Before starting this should be read completely)

Dimensions: 27 x 4 rnrn, length ± 5,5 m

Deliverer: Angst & Pfister

Type of rubber: Nitril rubber.

The rubber seal can be cut from a standard rubber sheet.

This quality is highly oil resistant; and is of the same

quality as that of standard 'Sirnrnerring' type oil seals.

The life time of this seal is many years and cannot be

predicted. .

Replacement of the seal is possible on the telescope,

in the 12 hour position, with the tube vertical or somewhat

inclined to the north. Some cabling and oil tubes should be

demounted before starting.

Fixation of the rubber seal is done by steel strips, that

press the rubber to gearbox and gearwheel cover. For this,

M4 screws are used. The steel strips are marked and should be

replaced in the same position.

The holes in the rubber seal for the M4 screws have to be

drilled with special made hollow steel drills, as described

hereafter.

It is important to know that the most critical part of

the seal is at the lower short side of the gearbox. At the

other short side, no oil ever will corne. For that reason,

both free ends should meet at that side.

- 18 -

For hole drilling and fitting of the ~ubber seal, the

following sequence of operations should be made:

Fit the rubber seal provisionally on its location with

both free ends meeting at the upper short side.

- Put both bended steel strips in the correct position at the

lower short side, that is at the oil return side. These strips

serve as guider for hole drilling.

Only the four holes in the centre of the short side of each

strip will be drilled. When this is done correctly, these holes

correspond exactly with the threaded holes. Both strips have

to be fitted each with four M4 screws, that should be tightened

to give a compression in the rubber, equal to that, when finally

fitted. This is necessary to get the neighbouring holes in the

circular part drilled on their correct locations. Each nearest

hole can be drilled in the same way and a M4 screwed in before

drilling the next hole. The end holes serve as reference for

the holes at the long sides. The more efficient way to drill

those is to demount the rubber seal and to drill the holes on

a wooden table with the steel strip as a guider and the last

drilled hole as reference. After drilling the holes in the

short lower side and both longer sides, definite fitting

can be started.

To get a good oil tightness, the rubber and steel strips

should be degreased carefully also inside the screw holes.

Same has to be done at the contact surfaces of gearbox and

gearwheel cover. Attention has to be given to oil that drips

from inside the gearbox. Direct after cleaning, fluid packing

shoul~ be put on all surfaces that have a seal function.

To prevent drying out, this has to be done over smaller lengths,

to start at the short bottom side (oil return side).

- 19 -

Fitting of the bended strips has to be done in the same

way as during hole drilling to continue lateron with the

long sides. Drilling and fitting of the holes at the other

short side can be done in the same way as at the other side

starting in the center of the straight part and going to

both ends. The rubber ends have to be cut to the correct

length, that they come close together. It is not necessary

to put fluid packing in this region, because no oil will come

at that spot. The rubber seal should be fitted without tension.

Tension results in oval holes that may result in oil leakage.

The M4 screws,if they should be replaced,should be taken

exactly in the same length.

9. REPLACEMENT OF THE NITRIL RUBBER SEAL BETWEEN GEARBOX AND

GEARWHEEL COVER AT THE POLAR AXIS

(See also procedure declination axis)

The rubber seal is identical to that of the declination

axis. Both ends should meet at the longer upper side and

preferable excentric, near the short bended strips. The

critical side is the lower long side with the lower parts

of the short sides. On the top side no oil will be inside the

gearbox.

The sequence of hole drilling and fitting is different from

the declination axis, and should be started at the lower long

side. This can be done on a wooden table with help of the

proper steel strips.

After this, the seal has to be fitted provisionally to the

gearbox and gearwheel cover, the side holes should be drilled

with help of the bended strips, in the same way as at the

declination axis, starting with the 2x4 holes at the center

- 20 -

fitting 2x4 M4 screws firmly, etc.

After this, the holes at the upper side can be drilled

(after demounting the seal on a wooden table using the

last holes as a reference).

Final fixation has to be done after carefull cleaning,

same as at the declination axis, and screws fitting in the

same sequence as before.

10. DEMOUNTING OF THE MOTOR ASSEMBLY T 10-101

This can be done in 4 steps: brake, tachometer, motor and

shaft.

Brake

Demount 6 screws M6 at the fixation flange (after disconnec­

ting the cabling). The brake than can be moved easily from

the shaft. The brake shaft can be demounted by 6 screws

MB x 25 (and eventually by slackening the 6 radial screws

MB x 30).

Tachometer

Demounting of the tRchometer has to be done in a special

sequence in order not to destroy the magnetism of the stator.

Lock the statorring (by small force) provisionally h~~screw lB.

Demount carefully brush ring 21 and insolator ring 20.

Demount the fixation screws for the stator ring 19.

Fit the keeper ring at the place of the insolator ring 20.

Demount the locking nut from the motor shaft.

Pull off carefully cover 09. At the same time stator with

keeper ring and rotor with commutator will be pushed off.

Stator with keeper ring can be taken out from 09, after

slackening screw lB. The keeper ring has to stay at the

- 21 -

stator until during the next complete fitting the rotor

is located and remains inside the stator.

Motor

Demounting of the motor has to be done in a special sequence

in order not to destroy the magnetism of the stator.

Press the auxiliary poles (carefully) to the rotor by the

fixation screws.

Slacken the 6 fixation screws M8 between rotor and shaft.

Fit the shipping clamp between stator" housing and rotor.

Slacken the 8 fixation screws M12 between stator~housing

and gearbox.

Motor shaft

During demounting and mounting care has to be taken

not to damage the oil seal and other parts by rough handling.

The weight of the shaft is about 35 kg. The shaft can be

taken out after demounting 6 screws M8 x 40 and 4 screws

M8 x 30 near the conical bearing.

Due to its inclined position (at the polar axis), the

shaft can slide out with a force of about 20 kg. This

should be avoided. Demounting only can be done, when care

is taken, that neither the gearteeth nor any other part

will hit the oil seal. This can be done by carefull demoun"ting

by hand, with help of a tube with diameter of 58 rom, that

fits into the hollow shaft.

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