Build a strock-250 type travel telescope for 255 to 325mm ... · PS Se construire un télescope de voyage type strock de 250 à 325mm. Build a strock-250 type travel telescope for

PS Se construire un télescope de voyage type strock de 250 à 325mm

Build a strock-250 type travel telescope for 255 to

325mm mirror diameter

Pierre STROCK - Plans - october 2014

Le strock-250 dans le Sahara en 2006

page 1 / 19 Pierre Strock 2014/10/31


Plans modification for mirror up to 325 mm diameter For telescope makers who do not have optics with exactly the same caracteristics than the original strock-250 design (diameter and thickness), we propose here to adapt the plans. These adaptations have often been requested in view of the variability of the optical fabrications and also because many amateurs want larger mirrors.

On plans, we left the original model dimensions (with 254 mm diameter mirror). But we have incremented some dimensions using the following differences:

D Diameter difference of the primary mirror compared the original measures 254 mm

E Thickness difference of the primary mirror compared the original measures 29 mm on the side

d Diameter difference of the secondary mirror compared the original measures 50mm

e Thickness difference of the secondary mirror compared the original measures 10 mm

x Offset difference of the secondary mirror (the original offset is 2.5 mm)

To simplify certain notations, we wrote: H the sum E + d + 1,4.e which are the total thickness offset due to optics différences.

To get the good cutting dimensions, it is necessary to calculate all modifications on the plans the variables above. Exemple : With a primary mirror D=279mm and Th= 25mm associated with secondary mirror D=55mm and Th=13mm,

différences have the following values : D = +25, E = –4, d = +5, e = +3 et H = +5 mm

We will find a outside box with the these dimensions : lenght = 420+D , width= 360+D and heigth = 159+H, so 445 x 385 x 164mm.

Limitations : In opposite the original plans from 2003, developped by Magnitude78 association, we didn't build all combinaison of optics size. We didn't check all dimensions for all plans with all possible values D E d e & H, it is not possible.

• Especially, we can't guess the good weight balance the structure.

• Especially, the dimensions of the cut corner on the primary box could be not well defined

• Especially, we didn't imagine to go further than 325mm with the primary mirror

We kept the focal point at the same length ouside the secondary ring. So quite short focuser is necessary.

Plans are not defined for 2 inches focuser, this focuser creates many problems and involves to change many things to be able to close the telescope in its box.

Once dimensions dones, drawings are not at the right scale anymore, then it is not possible to calculate values with mesures.

Exemple : For primary mirror with D =325mm and Th= 35mm and secondary mirror with D= 66mm and Th=14mm, the closed box will be 495 x 435 x 187mm. It is a quite big box which is difficult to travel with, that's why we chose to stop at 325mm, to keep the genes of the original concepts of the strock-250.

Wood Laser cutting Already tried with the french society Damengo and other Fablab.



It is necessary to manage the part position to respect the maximum size of the cutting machine usually 80x60cm. We find very often plywood thickness in 5 or 10 mm.



Drawings Files are in free format like SVG.

If we change the plywood thickness from 8mm to 10 mm on the biggest thickness, we have to also change the thickness offset in the drawings.

2 mm longer inside the box to add on the heigth on the lid side. 2 mm higher on the side of the primary box 4 mm longer (L & l) on the top and on the bottom of the box. 4 mm longer (L) on the longest side of the box.

Page du site Internet de DAMENGO ( http:// damengo . com )

Nota Bene : things to do and possible improve left : We advise to modify the secondary mirror plate hanging and draw it at real scale before to start aluminium cutting. It is also possible to do this part and spyder with 3D printing. In the following drawings, you will find the design and dimensions for secondary mirror D=50mm and Th=10mm

Print the following drawings in A3 paper sheets at scale 1.

On the 4 top corner of the primary box : use 8mm carbone tubes / corner drilling just at the tube diameter without play.

For M shape wedge in the secondary box, put the thickness of this part 1mm lower than the tube.

There are 2x2mm of play around the primary box to avoid the friction on the rocker and all assembly hazards. It is possible to reduice this gap at 2x1mm to keep shorter the case width. There will be always a free space in the lid to tidy the bearings

Be careful on the mirror cell geometry, radius of the contact between mirror an triangles have to adapt. We will prefer to keep 34% and 78% of mirror radius for thin mirror (25 mm). It is really important for larger blank...



List and detail of component for original model: strock-250

Qty Component and material Size or surface Name and comments Case

1 PLYWOOD 5 360 x 420 Low rocker (case bottom) side in 5 mm 1 PLYWOOD 8 360 x 420 Lid top (telescope base) in 8 mm 2 PLYWOOD 8 146 x 420 Longer side of the case 2 PLYWOOD 8 146 x 344 shorter side of the case 1 Glass canvas 200 g/m² ~1 m² To reinforce the surface 8 Corner reinforcer for the cases With screw or needle for fixation

Case accessories 1 Rough Formica ring d~300 D 360 Or rough plastic sticker (used to make shower glass darker) 4 Teflon pad (PTFE) ~25x8x5 Altitude: don't use furniture pad too soft 3 Teflon pad (PTFE) ~25x~10x5 Azimut: furniture pad could be available 14 Wood screw 3x10 For pad fixations 4 Thread inserts M5 Bearing fixations 2 Thread inserts M4 azimuth vertical axis 1 CHC screws 4x20 azimuth vertical axis 1 knob for CHC screws M4 Knob on the screw for azimuth vertical axis 1 handle and screws Option / old luggage handle can be used 4 Latch clamp with spring The hook part are used like telescope base feet 16 Screws + nuts M3x10 Put the nuts inside the case thickness

Bearing 1 PLYWOOD 10 410 x 410 Bearing in 10 mm 2 Alu Plate 2x10x1000 Prepare the arch shape before epoxy gluing 4 Thread inserts M5 Transform the screw which can't be lost (remove some threads) 4 CHC screws 5x20 Case fixation (or knob screw) 4 knob for CHC screws M5 Strong tightening needed

Spring for balance 1 Thread inserts M4

d1 D9 L60

Balancing spring fixation 2 Screw M4x25 Spring fixation (large flat head) 4 Nuts M4 Do an offset with several nuts 1 Steel pulling spring Stretch with a string length to reach ~2 kg force 1 String L 200 Connection btw spring and -hook

1 Wood spacer for the spring 20x15x10 Keep space btw string and screw head 1 Steel hook d2 x 100 To hook the string on the rocker (brass paper clip)

Caisse du primaire 1 PLYWOOD 8 293 x 330 Mirror cell in the primary box bottom 2 PLYWOOD 5 142 x 340 Longer side 2 PLYWOOD 5 142 x 330 Shorter side 1 PLYWOOD 5 55+ x 330+ Cut corner (adaptable dimension)

Box accessories 1 PLYWOOD 15 (two layers) 150 x 200 Low fixation of the carbon tubes (epoxyde gluing ) 4 Thread inserts M5 Bearing fixation on the primary box 1 Fan fan 5 volts low profile (< 8 mm) +screws 1 Fan power supply support for 4 batteries 1,5V AAA + switch + cables + screws

Mirror cell lever 2 Square shape pipe Alu 8x8 L 210 Lever (if square pipe not available use full square alu 8 mm) 2 Square shape pipe Alu 6x6 L 180 Inside lever Reinforcer 2 Steel axis diameter 2mm d2 x 40 Lever axis des leviers (neddle, paper clip , brass) 1 L Shape Alu profile 15x15x1,5 L~140 Collimation screws support 2 Wood screw 3x10 L shape profile fixation for collimation (file l'excédent) 2 CHC screws 4x30 Collimation screws 2 nut M4 Collimation nut (Dessus limé bombé) 6 round L4 brass Necessary for smooth settings



Qty Component and material Size or surface Name and comments 2 Steel compression string d0,5 D6 L25 keep the collimation lever always at the right place 1 Allen wrench for CHC4 Tool for the collimation setting (need to cut in 2 parts) 2 rod diam 3,5 à 4 L~300 Collimation rod (pvc, carbone, fibre, ...) for front setting 2 Tube diam int 3,5 L 20 To clinch the Allen wrench on the rod extremity 2 Handle knob diam ~10 Toothpaste tube lid or similar 2 Eye screw Eye screw or brass bracket (framing material) 2 Elastic band or O-ring diam 15-20 Keep the collimation rod vertically

Mirror cell triangles 3 Plate Alu ép. 2 (ou 2,5) 110x55 9 points mirror cell triangles ( stiffer with 2,5mm) 2 Steel ball diam 5 Lever support (bearing available in bicycle shop or in the drawer rails). 1 Steel ball diam 6 à 7 Support point on wood (bearing available in bicycle shop).

9 Ballhead nail 1,3x13 in brass Mirror side contact and to stop triangles rotation 9 Tube diam 2-3 in brass L 8 mm Nails guidance in the bottom

Primary mirror box 1 Mirror primary Ép. 28-30 Blank diam 250-254 mm / Focal 1200-1250 mm 4 PLYWOOD 15mm (2 couches) ~40 x ~20 Side support mirror primary 4 Wood screws 4x30 Stiff fixation btw side support and bottom 4 Screw M5 (ou M6) Nylon Spacer btw side support and mirror 1 Mirror lid : pie plate Internal diameter 275-280 mm / Heigth 20-30 mm 4 Taquet PVC ou Alu 40x15 x 1,5 à 2 Mirror superior wedge (plastic below if Alu) 8 Wood screw 3x15 Vis à ras du taquet/ Tête fraisée à 90° 4 PLYWOOD 15 (deux couches) ~40 x ~25 Lid lock 4 PLYWOOD 15 ou chute de bois ~40 x ~5 Lid and lid lock Support / heigth adjustement 4 Thread insert M4 4 CHC screw 4x30 Screws for Lid and lid lock 4 Knob for CHC4 Handle Knob for lock lid

Secondary box 2 PLYWOOD 5 316 x 316 Octogonal diaphragm 4 PLYWOOD 5 90 x 145+ Long sides (cut a little longer) 4 PLYWOOD 5 90 x 131+ Short sides (cut a little longer) 1 PLYWOOD 5 ~50 x ~200 Tightening part / M shape piece 4 Spacer for assembly 55mm thickness Temporary parts for octogon assembly

2dary box accessories 4 CHC screws 4x16

L40 h29 p7

Rods Tightening (or screw + knob) 4 Knob for CHC4 Strong Tightening needed 4 Round L4 large Tightening flange on the wood 4 L shape profile 30x10x1,5 Alu Tightening jaws 4 Thread Insert M4 For the thread on the jaws (epoxy gluing )

spider 1 Elliptical mirror Th. 10 50 mm small diameter 1 Mirror protection D int > 50 h 80 Plastic bottle lid 1 Plate th=.1,5mm 50 x 70 Electrical circuit in epoxy/glass fiber (default aluminum material) 2 Double side tape 50x~70 For insulation and survival blanket fixation 1 Thin plastic film 50x~70 Thermal insolation of the plate on the sky side for alu plate 1 Survival blanket 50x~70 Thermal insolation of the plate on the sky side 8 L shape profile 15x15x1,5 Alu Many length To make all spider parts 2 Screw + nut M3-10 Spider parts assembly (CHC possible) 3 Screw M3x30 in brass Secondary mirror collimation screws – knob head screws 1 Élastic band or O-ring diam 20 Ajust the friction for collimation screws 1 Tube diam 4-3 in brass L~5 Collimation screw lock in heigth or with a nut 2 Tube diam 4-3 in brass L~15 Guidance for the 2 collimation screws 1 Steel traction spring d0,8 D5 L20 Link btw spider and mirror (strength => steel diam d0,8 à d1,0) 1 Rod diam 2 mm in brass Spring jumper 2 Brass sleeve diam int ~2 To freeze the jumper height



Qty Component and material Size or surface Name and comments 2 Carbon flat profil 12x1mm (or Alu) 316 mm and 146 mm Spider branches

3 Screw + nut M3-10 For branches fixations on L shape profil (CHC possible) 3 L shape profil 15x15x1,5 Alu Length. < 55 mm. For spider fixation on the secondary ring 6 Screw + nut M3-10 L shape profil fixation on the 2d ring (file excess material)

Filters slider 2 U shape profil 4x4 PVC L~160 Slider for filter support (U scale modeling shop) 1 Plate Alu or PVC 210x53x2 at 3 mm Filters support 1 Steel spring Spring from old pliers 1 Screw + nut M4x20 + round Spring fixation by its axis on octogon of the secondary ring

Focuser 1 focuser 31,75

90x80x2,5

Favourite design : KineOptics HC1 4 Srew + nut M3-20 + round Fixation porte-oculaire 1 Polycarbonate Option PO fixation reinforcer (we can put label below)

Structure 16 Carbone tube ext.6 mm/int.4mm 50 cm From kite or arrow (diam 8mm will be stiffer for heavy mirror) 8 Steel threaded rod M4 For Carbon tubes coupling 8 Alu sleeve M4 diam 6 Coupling of the 2 carbon tubes parts 1 Thin fabric ~600x~150 Storage cover 520 x 70 on flat 16 Alu reinforce diam int 6 Tube int 6x20 Carbon Reinforce at the connections 8 Low stop Tube int 6x20 Tube stoper on the low parts to glue after sttings (4) Stop in PLYWOOD 10 Triangle 40x40 Tubes stop to glue and nail after length settings 1 Screen 440x340 Black Plastic material (paper folder or Polyphane)

NB : Thread inserts can be named Pronged tee nut or T-nut.

Le strock-250 au bord du cratère météoritique de Monturaqui dans l’Atacama en août 2013



Un des deux schémas de conception du télescope



Le débit de bois



Découpe des flancs et profil de la valise fermée

Détails de forme, de découpe et de montage des patins

page 10 /

Pierre Strock 2014/10/31


Découpe des haches (vue du coté des têtes des vis moletées)

Implantation du dessous du rocker et du dessus du socle



Le ressort d’équilibrage en position de travail et de rangement

Découpe du baffle minimum



Découpe du fond de la caisse du primaire et plan du barillet

Nota Bene : Il faut tracer le dessin sur le bois avant découpe pour positionner les éléments qui ne sont pas cotés.



Découpe des flancs de la caisse du primaire



Schéma du pan coupé théorique et d’un pan coupé adapté

Découpe des fixations basses des tiges

Loquet du capot - cale latérale et taquet vertical du miroir



Schéma du barillet à réglage par le dessus

Détails du calage du miroir et du rangement en poupées russes



Plan de découpe et d'accastillage de la cage du secondaire



Montage de la cage du secondaire et détail du passe-filtres



Vue en perspective du dos de l’araignée à trois branches

Le porte-oculaire hélicoïdale



Plan de l’araignée à trois branches du strock-250


Documents

Build a strock-250 type travel telescope for 255 to 325mm ... · PS Se construire un télescope de voyage type strock de 250 à 325mm. Build a strock-250 type travel telescope for