Aug 15, 2011 - All molds were received – now it is possible to make different thickness’s springs: 1.5, 2.0, 2.5, 3.0 mm. Also was proved – amount of carbon fiber / threads inside the mold 1.5mm – 4 layers of carbon fiber , 3 layers and just threads (no fabric) gives a different linear elasticity (easy to measure – on a electronic scale – amount of a weight require to connect sides of a spiral). Also was discovered a mistake (may be not) – if to place the assembled mold into a vacuum chamber, then excessive air pockets inside mold squeeze out epoxy from the mold. From one point it is not looking good – a cross section of a spring is not regular – but spring become lighter 25%, epoxy stays just on carbon fiber, and coefficient elasticity is bigger. For future use – placing in a vacuum chamber has to be done before closing the mold (for nice looking springs), or in assembly (for saving weight and increase elasticity). Also was found a way to speed up process (up to 5 times) and make spring more controllable. The carbon fiber has to be in a braid (or a plait) – different technique can be used to control amount of fiber and physical dimensions (5 x 1.5 x 500 mm). Also was proved an easy way to control temperature for epoxy’s curing – the induction stove from Wal-Mart + connecting sequentially to a thermo element variable (10-100kOm) resistor and the temperature inside the chamber wrapped by aluminum foil will stays with 1 centigrade range.

 

June 31, 2011 – Tweaking of a mold was done. Download to www.shapeways.com and ordered.

view eDrawings : Top mold (Will install plug-in):

and view bottom mold (Will install plug-in):

download top mold, bottom mold

or pictures:

June 30, 2011 – Parts for a rover springs arrived. Plastic is not strong enough to assemble into wheel. This is okay as I wanted to see how it molds – final goal is to make same part(s) from carbon fibre). Nice idea to use 3D printing but for a spring fabrication it is not good. Needs to make 3D mold directly – without step. Nothing available to withstand thermal curing of epoxy. Another solution is to use aluminum – the same 3D printing but with aluminum powder – should work at 175C – more than enough for composites. Spring model needs to rebuild to make 2 mold parts.

This page will be updated step by step to reflect current changes on recent drawing in attempts to resolve problems appeared in design.

Blender files (http://www.blender.org/download/get-blender/) design (.blend+.STL) available here:  teamPlamB_vehicle.zip

View in SolidWorks eDrawings here. (Will install plug-in).

SolidWorks assembly and parts here.

 

 

Wheels. Each wheel has 16 springs made from ether steel or carbon fiber. For steel’s it is easy to cut parts from specific thickness steel’s sheet and a coefficient for a Hooke’s formula can be easily calculated, confirmed and controlled. More complicated process is for a carbon fiber – all controllable parameters are: amount of layers (one, two, or three layers of a carbon fabric), different types of fabrics, and amount of epoxy (solo depends on a mold). The mold manufacturing can be complicated. It was chosen simple approach - first made 3D model and manufacture it at http://www.ponoko.com/showroom/TeamPlanB. Ponoko Personal Factory can produce parts from a plastic which is not suitable for real springs, but plastic model can be used in mold’s manufacturing. Then depend on a results (carbon fiber’s molding or steel springs cutting) can be made the decision: what is better. Arbitration are usual - the weight of a wheel, and performance at different temperature.

Absence of a gear will definitely reduce weight, and springs flexibility can accumulate energy to get momentum enough to travel over obstacles and craters. Coefficient in Hooke’s formula and precision delivery of a momentum by stepper motors can pump energy (using resonance frequency) into a spring system and a precision release (of that energy) will give jump’s type of movement for a vehicle. This is similar to a case (if somebody remember from past) when a car was stuck with one wheel at road’s hole, small oscillation (as back and forward push) can release car from road trap. From another hand (to save a time) plastic parts can be used in vehicle software development, some flexibility plastic already has and braking plastic part can be indication of a proper resonance frequency achieved. Wona stated that this type of wheel is totally useless without controllable software.

Problems to solve:

1. How to make a mold for carbon fiber? Probable answer on that question – to order mold from Ponoko Personal Factory from a different type of ceramic/plastic.

2. How to control stiffness/elasticity for carbon fiber’s springs? Probable answer – to make 3 different (1, 2, or 3 layers of carbon springs) and use combination of different springs.

3. How to calculate resonance frequency of a wheel in assembly? Probable answer – software has to be adaptable to different parameters/performance of springs.

4. Does it require carbon fiber clothe wrap to make bigger surface contact? Answer for this question is actually: Yes.

 

 

 Frame design. Two aluminum tubes with two aluminum plates, holding tubes in parallel each other. Four stepper motors – two for wheels and two for antenna and camera stands. Motors for a camera stand and antenna was to be with gears with 1.x 3.5 ratio. Gears made from ceramic grinding tools. On a frame mounted an aluminum mirror allowing HD camera’s observation in holding position.

On tubes mounted flexible solar panels with angles 45 degree to the center line, solar panels both sides orientation. Aluminum frame and plates will be warped for enforcement with one or two layers for a carbon fiber. This will create “composite’ structure – soft aluminum inside and carbon fiber outside. For mockup all parts except aluminum tubes ordered over Ponoko Personal Factory.

Problems to solve:

1. Needs to find flexible solar panels with good performance in temperature range and under of UV and high charged particle’s conditions. Current power capabilities are around 6-8 W total, and in real life it will be around 2.5-3 W. Which is not acceptable at all.

2. Orientation for aluminum mirror.

3. What a minimum distance from solar panel to antenna’s stand rotation axe? (To avoid interference with communication).

4. Protection for a two wheel’s stepper motors. Originally wheel’s springs will give protection at impact, but looks like it will require some carbon’s bees’-comb-like structure for additional protection.

5. Manufacture molds for top layer of carbon fibber (for tubes and plate) with bees’-comb-like pattern.

6. Protection for a gear needs to be decided.

7. Holder for solar panels does not look good.

 

 

Antenna stand. Helical antenna for a 2.4 GHz communication made from fiberglass. Conductor for antenna glued inside the cylinder body of antenna.

Reflector made from cuprum layer on top of carbon fiber layer. On the same stand connected hermetically sealed box for main HD camera (requirements for competition), capacitors, and main onboard computer. HD camera has a window allow observation from a low point at vehicle movement.

In holding position box with camera located near aluminum mirror, this will give additional angle of observation. Box has solar panes glued to its sides. Solar panels are different type than mounted on a frame.

Problems to solve:

1. Center of mass of antenna stand needs to be “adjustable”.

2. Which direction to shift center of mass (related of a rotation axe) to the antenna side or to the main sealed box?

3. How to clean lunar dust from exterior surface of the antenna?

4. Power wire’s elasticity should be accounted at antenna stand movements.

 

 

Camera stand. Made from carbon fiber. On top of stand 4 cameras mounted with pinholes. Two sealed boxes for capacitors. All parts for mockup ordered from Ponoko Personal Factory.

Problems to solve:

1. Center of mass needs to be “adjustable”.

2. Does it require two or (for bigger space) one sealed box?

3. Power wire elasticity has to be accounted as for antenna stand.

 

 

Air bag system. For now was consider “composite” design with 3 layers – polyurethane internal shell to cover vehicle, inflatable foam, and thin film bag. Shell cut in sections and each section glued to deflated airbag with deflated foam inside the bag. Two similar “big” air bags covers top and bottom of vehicle, and two “smaller” on a sides. In deflated position bags formed two “rolls”, with polyurethane side out. To protect polyurethane from UV exposure cut sides can be covered with thin flexible solar panels, which can give additional power at orbit flight. After landing the solar panels (if survived and recovered) can give source for additional power. Inflation of bags has to be in sequence – top and bottom bags will be inflated first then side bags after. Inflating of bags will unroll internal polyurethane shell and covers top and bottom of the vehicle, then side shell covers and hold all polyurethane’s shell together. Time for inflating foam inside bags needs to be considered. Impact will eventually tear sections from bags and released vehicle on the Moon. For now it is just an idea – no experiments was done yet, except attempt to make internal shell (video available here soon).

Problem to solve:

1. Time for inflating foam has to be calculated.

2. Performance of polyurethane at vacuum has to be checked.

3. Deterioration of polyurethane under UV and temperature needs to consider.

4. Foam – where to get such?

5. Bags has to be deflated with good vacuum pump, otherwise needs to do drainage at orbit (at vacuum).

6. System for inflating totally not designed yet.

 

Assembly.

 

Problem to solve for all assembly:

1. Center of mass in plane perpendicular to a frame has to be projected to wheel’s axes.

2. Air bag mount is not finalized et.

3. 4 solid state engines mounts is not finalized yet. It has to be connected somehow to frame of the vehicle.

4. Small thrust engine mount is not finalized yet. The same problem – mount must be on vehicle frame.

5. Release mechanism of each solid state / small thrust engines - no idea how to do this. Pyrotechnic fastener definitely is out of questions.

 

 

Apr 24, 2011. In a vehicle development was discussed an  idea to use carbon fiber instead of springs (steel springs can eliminate vehicle’s gears). Made from carbon fiber spring needs to be longer and spiral shape. Question how to make a mold for that shape. Was tried bent aluminum sheet to make desirable shape. 6 hours was spend in experiments with no results. Mold for a wheel’s mount does not bent properly. Total 64 springs needs to be manufactured for two wheels, one or two can be, but it can be a challenge to make 64 exact molds.

Mar 20,2011. Spring tension wheel was build for a testing.

Mar 19, 2011. Concern about molybdenum lubricant on stepper motors. Momentum 0.35Nm will be in this case smaller. Needs (at least for wheels) to use something to increase momentum. Previous decision not to use gears make it difficult. Was considered to use some alternative way. If wheels-motor system will be controlled by microprocessor it is possible to use springs and controllable oscillation movements to accumulate energy in springs with releasing it (energy). Oscillation frequency in this case can be controlled by springs parameters.

Mar 18, 2011. thermal test -78C. All test passed as expected. It is good. Counting that previously all materials was passed thermal test +125C just give confidence in all approach. Soldering with tin also passed test, but needs to repeat that test for 10 thermal circles +125 -78 to make sure that for onboard electronics possible just simply to place manufacturing order. Test was filmed. In low temperature better performance was stepper motor without lubricant at all. Molybdenum lubrication was working but it was feasible that it has more traction.

Mar 17, 2011, was spent in preparation for thermal tests -78C. All materials was sorted, stepper motors was disassembled. Two stepper motor’s bearing was cleaned from lubricant, one was left as it is (this will confirm failure of a test). From two cleaned stepper motors in one was applied molybdenum lubricant. Main onboard computer was checked - no electrolytic capacitors was on board, microprocessors, insulation material, aluminum tapes, carbon fibre components was selected, antenna itself, wires, soldering components with tin soldering and etc.

Mar 14, 2011. Sketches for 2 wheels design and two type of movements was made. Next step to create drawing. Considered making composite structures. Parts for carbon fibre production will be done in two steps – first manufacturing at Ponoco plastic component, then testing, then using same component to make forming using modeling ceramic. Aluminum parts will be manufactured as it was done previously.

Mar 1, 2011. 16 month left to a dead line. Was made an attempt to re-design a vehicle. It will be third re-design from beginning of a project, first was flip-flop movement with 5 segments, 8 stepper motors and 2 segments/antennas used as helping legs. First design was abandoned because of a high weight (8kg) and sophisticated gears which does not reduce mass also.

Was considered different methods of movement http://www.romela.org/main/Robotics_and_Mechanisms_Laboratory. All was looking good and promising, but requires complicated mechanical parts movable against each other in vacuum, survivability of drop also will be a question.

Mechanical engineers suggest some throw-anchor-on-a-rope schema. Arguments are - if fishing line made of monofilament or fluoropolymer .36mm dia. (http://en.wikipedia.org/wiki/Fishing_line) can catch 10kg salmon then 6kg vehicle will be ok, unsolved questions will be- what does to hook-on on the moon, and - how does to throw the line (line actually can be attached to a ejected part of a craft – 501m line guarantees distance, but need to demonstrate travel ability in a desired direction - 2 or 3 lines needs to use).

 Some discussion was made about magnetic gears http://www.magnomatics.com/technology/magnetic-gears.aspx and http://www.mgt.com.au/ .

Complications with steel's gears in vacuum can be solved using MoS2 lubricant: http://en.wikipedia.org/wiki/Molybdenum_disulfide

If a re-design will be made needs to consider also weight reduction.

Feb 27, 2011. Calculation for a drop test was made to avoid complicated computer simulation. Errors for break engine shut-off will be 1% (ideally 25 kg of a solid state fuel can be dozed with 0.001kg precision, and engine can be calibrated by test firing after 1 month expose in vacuum chamber). This gives error (brake engine needs to slow down from around 2000m/s) a final speed 20m/s with an equivalent of a drop from 130m at a Lunar gravity. That 130m gives 12s for air bags inflation, with (same as error in solid state engine) landing speed 20m/s. The kinetic energy (for a vehicle mass 6kg) equal to 1271 kg*m^2/s^2. In Earth gravity this is equivalent of a drop the same mass (6kg) from 22m, or from 9 floor of a building (needs to check – does a strata agreement prohibited to throw space craft from a windows with safety precautions? And does the fine will be in reasonable limits?). To test air-bags will be possible to use the bigger mass dropped to a fixed platform. With a mass 100kg to get the same kinetic energy (1271) will be enough to achieve speed 5m/s, and 5m/s in Earth gravity equivalent of drop from 1.5 m. Swing can be used.

Feb 26, 2011. The simple drop test highlights that the ceramic gear did not survive. Critical part is aluminum holder for silicon carbide gear (ceramics was actually ok, aluminum shaft was bended). Ether needs to reinforce, or to protect gear’s part. Also was loose an aluminum connector to a motor’s steel shaft, and loose for the same reason a ceramic gear’s shaft. All assembly also looks like would not survive any significant drop test. As a result, after talking to engineers, current design of a vehicle definitely will not fly the Moon, but probably will be ended in the nearest garbage can. It is pity – weight for a 3 wheel design was in a limit of 6 kg.

Feb 17,2011, mount #1, mount#2, mount#3, mount#4, adapter#1, adapter#2 was made. An assembly video is here. After a meeting with experienced mechanical engineers was raised a question – may be a steel gear will be fine – even in a deep vacuum distance and sessions requirements does not sounds so tough, this will be allow to forget ceramic gears. May be. Engineers promised to look at a performance of a steel alloys and come with some materials.

Feb 16, 2011, Best results on 646 – see the picture , 510 kind of fragile, 672 is easy to solidify. 646 and 510 are water based and placing in a vacuum chamber is working fine for bobbles removal. Surface with 510 was rough, 646 creates nice fine perfect surface. Chemical additives in 589 and 672 creates a problem - in the vacuum chamber bobbles was not gone and a surface of a casting ceramic did not fill a model’s mold. Mix was a bad idea. It does not produce anything useful.

Feb 12, 2011. An attempt was made to design ceramic gear from available source of ceramic’s tools. First candidate are grinding sets. It has a round shape, it has roughs surface, and it is made from strong ceramics (manufacturer usually does not specify chemical formula). Design is here. Gear will be open - dust will help keep traction between rotating parts. Bearings will be simple – ceramic available from a catalogs. To keep tension between gears spring will be applied. Spring will bend aluminum mount and will bend to accommodate gear’s wear.

Gear  consist of 8 major parts: Mount#1, Mount#2, Mount#3, Mount#4, Gear#1, Gear#2, Adapter#1, Adapter#2

Feb 11, 2011. Results for castable ceramics 672, 510, 646 and its 50/50 mixture will be available later (on Feb 14-15) – it takes 24 hours to dry the ceramics and temperature cure steps. Another problem – 0.2mm precision limitation will require tailoring a final model to snooze imperfections. The last (and major) problem where to order ceramics like silicon nitride, silicone carbide, or zirconium dioxide even as cast for gear was manufactured.

Feb 10, 2011. Results for 646 vary. Cast produced from silicon was the best cast. Using a wax is complicated at the moment of separating model from a solidified wax. Silicon gives a nice snooze surface but it is difficult to extract model from a cast (it sticks to plastic unpredictable despite applying oil/liquid soap to a model). Ceramic can be cured in 200F for 3-6 hours in regular oven.

 

Feb 9, 2011, Vehicle design. Three wheels powered by stepper motors gives the vehicle the ability to travel and to steer in desired direction. However, positioning an antenna to the Earth direction will require something more than a stepper motor’s steps with 1.8 degree precisions. Obvious way to do this is to use some ceramic gearbox (one at least). An attempt was made to understand how to build such a gearbox. Was investigated way to manufacture cast for planet and sun gear in Epicyclic gear type (http://en.wikipedia.org/wiki/Epicyclic_gearing). Such gear’s type was chosen to make it as small as possible and as a result to achieve light weight. For a cast manufacturing it is handy to use a 3D printers (http://www.makerbot.com/, http://www.botmill.com/, http://www.pp3dp.com/, or a more easy way - to make 3D model design in .stl format, upload it to personal factory like http://www.ponoko.com/, and build plastic cast with precision 0.2 mm (the same technique can be used to create a cast for any carbon fiber elements of a probe/vehicle). Castable ceramic like 672, 510, 646, 589 can be used.

                                           Vehicle design:

 

                                      And vehicle picture:

reference:

 planb.sldasm

B18.2.4.1M - Hex nut, Style 1, M3 x 0.5 --D-N.SLDPRT

B18.22M - Plain washer, 3 mm, regular.sldprt

B18.6.7M - M3 x 0.5 x 25 Type I Cross Recessed PHMS --25N.SLDPRT

 B18.6.7M - M3 x 0.5 x 35 Type I Cross Recessed PHMS --35N.SLDPRT

bearing_0006.SLDPRT

fr_0001.SLDPRT

fr_0002.SLDPRT

fr_0003.SLDPRT

fr_0004.SLDPRT

fr_0006.SLDPRT

fr_0007.SLDPRT

fr_0008.SLDPRT

fr_0009.SLDPRT

fr_0010.SLDPRT

fr_0011.SLDPRT

fr_0012.SLDPRT

fr_0014.SLDPRT

fr_0015.SLDPRT

fr_0016.SLDPRT

SW3dPS-037.SLDPRT

Vehicle’s design required to withstand impact equivalent of a free fall from 125m on Earth with airbag protection. This will give easy guidance for an air-bag/vehicle ground test. Airbags deflates after landing.

Vehicle consist of a flat frame with 3 wheels, double sized two solar panels, horizon/azimuth orientation helical 2.4GHz antenna, sealed boxes/frame with computer equipment. Vehicle is capable of travel despite which side of frame is up. Making length longer than width will give capability to flip on side/edge of terrain, such move can be useful to switch vehicle's sides and as a result to switch solar panel with deteriorated performance.

All 3 wheels before landing will be in “transportation” position to make vehicle “flat”. After landing wheels will be moved to “working” position by springs – this will give flexibility for each wheel as a result third wheel can be dynamically oriented to support steering of vehicles. Radius of each wheels 125mm, antenna length 650mm, total length 1050mm. Movement of antenna and its equipment / contr-weight box can give additional steering / movement / digging capabilities.

Vehicle require 5 stepper motors to move and to orient antenna. All motors are regular stepper motors, changing bearing to ceramic may be required depend on performance at vacuum/temperature chamber's testing. Wiring on motors will require to withstand temperature range from -100C to +115C. Desired direction and distance will be sent to probe from ground control. On vehicle movement acceleration and azimuth from sensors and motors performance will be accumulated together with solar panel efficiency and on-board computer that will make decisions to achieve desired point of travel.

Upon arrival or upon time-out vehicle will orient antenna for communication session with earth ground control. For 500m travel 50-75 sessions will be required. At session point/time telemetry will be transferred first, then low resolution pictures from camera. Then decision to transfer high resolution video/picture will be made. Transferring HD images will give time to make a decision of next movement of probe. All travel should be performed during 168 hours (7 days) upon landing. This will gives 2 hour time between sessions with a travel time 20-25 minutes per session.