2024-10-06 Mechanical SRR Notes

 

Dynamics:

  • ASME-Y drawings standards

  • Jamie has metrology tools in the

  • Caution against just using one person as your check. In industry you can release something, then you can do three signature (your immediate superior, then the lead, then the chief engineer or mechanical lead)

    • Give piece of mind to everyone involved

    • Look up Industry standards for reviewing things

    • Checker

  • +/- 5 pounds is the start of a good plan or goal

    • If this is a goal, there needs to be a weight tolerance on a by-part basis

    • Start with your smaller goals and then come to a larger goal that makes sense

    • How would you determine how much weight you need allowable on a part

  • 5 thou profile tolerance is pretty standard

    • Take the dimension of the part increase by 5 thou and find the weight

 

Suspension:

  • My questions:

  • The reason the pushrod broke is because we slammed the wheel into the uhaul for gone to engineering

  • The reason the rod ends were loading in bending is because the design was bad and we were using rod ends in an improper application, the reason they actually bent is that we didn't pressurize the shock before driving to competition

  • What is "the relevant systems" mean wrt CG

  • I caution you to use decimals in places that are supposed to be a rough estimate. Are you really sure of your estimate within 5 significant figures of precision

 

 Other ppl's questions:

  • For CG bias - need to use CAD to validate that 60-40 is a reasonable CG bias front to rear

  • Do you plan to consider the actual speed you will be going at in determining lateral load transfer and stuff

  • 1g of acceleration not force

  • Is your 1g a total car of lateral acceleration?

  • What does it mean to consider weldability

    • In the past we used aluminum welding, so we want to consider

    • Its fine to say you don't want to spend time and resources learning how to design for welding aluminum

    • Challenge us to deep dive a better reason why we don't want to aluminum weld

      • He said the aluminum welds themselves

      • The materials lab upstairs can redo heat treating

  • Waterjetting

    • Try to come up with cool shit and come up with cool processes for making it

  • Factor of safety >2.5 - How do you decide what part gets what factor of safety

    • We don't know how to decide

    • Recommend: make a list of what you base your factors of safety around and then wholistically go through each part and assign

    • Where did we get this number from: 2.5 seems really high, used a FOS of 3

  • Considering fatigue

    • Need to figure out how understand it and design for it

    • You say considering the endurance limit, you're never gonna hit the max number of cycles for material

    • You clearly haven’t gone too deep into it

    • How would you go about finding cycles for suspension

      • Road noise isn't going to affect that much

      • The big loads: accelerations, heavy decels, bumps

      • How much starting and stopping and turning and things that would actually show up in an amplitude graph

    • If we are designing for a factor of safety of 2.5, that mean you expect some random peak load at some random time, then you already built in a ridiculous amount of margin for fatigue

  • A simplified way to characterize cycles is with shock pots

  • Pissed at UT for never explaining:

  • The shocks we use: do they have a certain spring rate? We are trying

  • Do you know what you're actually gonna use your telemetry data for

 

Steering

My questions:

  • The reason the cardan effect was neglected was

  • What do you mean by mechanically complex for the upper steering architecture

  • Why do we want to use Ackermann

  • Why a hall effect sensor and not just a potentiometer at the pinion

 

Their questions:

  • Are we planning to make changes to reduce bump steer

  • Backlash in the gears might not be as big of a concern in the gearbox as we think. There are ways to design around it.

  • Look at the track on google earth and look at the geometry. Also look at DoT turn guidelines to see what radius we might see

  • Look at how deflection and manufacturing issues might affect steering geometry sensitivity

  • Rack position telemetry might also be cool to get wheel angle telemetry to see how our model compares to real life

  • How are you looking at tunability. Recommend doing that. Tune your car for the specific road or track you are going on that day

  • Steering effort: go into what our plan is based on last year to reduce steering effort

    • How are you going to decrease the steering effort while also making steering faster

    • These goals oppose each other, how do we measure how much effort is acceptable

  • Designing around most common corners

 

 

Unprung

  • 20 thou seems excessive for non critical features

  • It isn't that much harder to get within 5 thou than 20 thou

  • The brake disk was extremely hevay last year. They are basically harley davison disks that are waaaaay heavier than they need to be.

  • You said you "want to do" each of the design considerations, we can't do all of them

  • What is the benefit of deep groove ball bearings over taper roller bearings

  • The main issue with the caliper mount being machined on the upright was size of stock

  • You don't actually know how many miles you need to drive

  • Do you have an idea of how you are going to size your calipers

    • No

  • How do you know our calipers are excessive

 

 

 

Body
 

  • For frame tabs an mounting, how are you going to go about the spaceclaim process, and have system be able to communicate where they want their tabs to be while also maintaining oversight wrt to weldability and conforming to VR3 standards

  • Make a tab sketch

  • Increase in second moment of the area

  • What is the purpose of experimenting with composites

 

Other questions:

  • You should not need to use FEA. If you can't do a substantial amount of analysis with hand-calcs, you cannot really trust your FEA

  • 20 hours of welding practice sounds good on paper, but where does 20 hours come from on a per team member basis.

    • How do you determine an "effective weld" from the number of hours

    • What metric will you use to measure if a member is ready to weld the frame

    • Timelines often get rushed.

  • Something Jonathan did when welding the combustion frame was have people who were interested and had no experience just go crazy on the frame and he would fix it

  • Don't make this too significant a barrier of entry to learning to weld. Don't want to discourage people

  • Why make tubes diameter larger and walls thinner?

    • Is it for bending? A space frame should have minimal bending

    • The types of load cases we sim for on our regs induce bending to test your joints

 

Frame:

  • Terminology: ultimate yield is not a word

  • How are you going to ensure that you and your members gain a foundational understanding of solid mechanics such that they can properly utilize FEA, and have confidence in its results

  • Frame jig - you don't really address

  • What is "redundant" cross tubing? If it is redundant why is it there

    • Something you need to consider that you didn't list on there: how are you actually going to test it. You keep bringing up this topic in an abstract sense but I've seen no actual testing plan or specific details of any kind. We already had the discussion that we are not going to put substantial resources into this project because why are we trying to have composites on the frame when we clearly don't understand well enough how to design a regular space frame, which is unambiguously easier

  • Composite simulations - do you really think it is realistic to know how to sim composites when we barely understand regular structural FEA?

 

  • Setting metrics: you are going to get to the point where you need to make compromises. Thinking about this early on will save you a lot of pain

  • Do you have an estimate of longitudinal CG?

  • On the timeline: have roll cage design or position finalized

    • With aeroshell, their timeline is going to be really long. End of october if they want their molds in on time

    • The biggest driving thing isn't overall dimension, it is the roll cage

    • Need to give aeroshell the bounding box

  • What drove 30% weight reduction

    • Winning solar car weight is 120 lbs.

    • Be careful with your metric. Using written reference is fine, but think about what you are willing to compromise. Frame isn't the number on priority for weight reduction.

    • Stop being so vague

  • How are the jigs made

  • Egress

    • What changes do y'all imagine to make egress easier

    • What does this actually look like

    • A lot of teams had an open roll cage design

      • Our was caged in from all directions

      • This makes packaging of the aeroshell easier

      • Think about bars they can hold onto, and footholds

  • For VR3 timelines, you need to play way more in advance, at least on paper

    • Do be careful about relying on a single manufacturer

      • Keep CR in the background looking at other options

      • Minimum lead time is 3 weeks

  • Ansys: what is stopping you from using beam elements to iterate?

    • Nothing

  • FEA was taking 8 hours long. This is ridiculous amount of time. You should be able to iterate with beam elements in seconds. There is no requirement for you to simulate the entire frame as solid elements. You can use beam elements

  • Great we are trying to validate to hand calcs first

  • Didn't mention anything about tube material, only tube geometry

    • Last year used 4130 chromoly steel

    • Learn about weldability

  • Timeline

    • Has this timeline been discussed with the other teams

    • Your frame welding timeline is in direct conflict with other teams

  • You keep saying bounding boxes and packaging, how are you going to actually track it

    • Highly recommend you turn construction lines into solid bodies

 

Ergo

  • What is the point of carbon fiber on the seat? Expanding foam is good and fine, the fsae team did it, but why not do regular upholstery

 

  • Wouldn't go with carbon fiber for ergo stuff. Seems like overkill. Could get favorable weight reduction by using some waterjetted aluminum piece or something

    • CF panels are strong in tension but this case its not the same. You're trying to bend it. Do you really want a composite panel?

    • Seen great success with 1/8" waterjetted metal

    • If you want to use a composite panel, why CF? Would be easier to use fiberglass. Rigidity without weight

    • Fiberglass is cheap and easy to manufacture

  • Carbon fiber steering wheel

    • Not really seeing high loads- maybe 3D print something

    • They said not to do that, especially because of the quick disconnect

    • Discern what is a structural component and what isn't

    • Forged carbon fiber will take longer than you think it will

    • Pedalbox is going to be a timesink

  • Ergo jig

    • Great direction to go in

    • However, can't get reliable information based on height

      • Short torso, longer torso, etc

    • Better way to approach: set some standards, measure from top of head to hip-bone, etc

    • FSAE has a rule for encompassing drivers, solar doesn't

  • Egress

    • Have you thought about how you will model egress?

      • Moreseo happening in the ergo jig?

      • Haven't planned a set method of testing egress

    • It is hard. Esther never figured it out. Try and find something that isn't just "I think somebody could jump out of that"

  • If this is intended to race ASC, ergo needs to think about race strategy, check boxes

  • Measuring people front

    • Be more granular with how you measure

  • In your jig, have something where people sit down

  • You can have the steel backing help the roll cage structurally

  • Sensing braking

    • Be careful with measuring the angle of the pedal. Don't pick something that is separated too far from the actual action of the brake calipers closing. Keep it more closely linked, ie fluid pressure, force, etc

  • Controls actually has all the sensors. Taking over the brake line sensor, since they will need for electrical braking etc.

  • How measure braking force for drivers

    • Calculate how much force we get through the pushrod of the master cylinder from pedal ratio

    • They figure out how much pressure this goes into the brake lines

  • No, like how much force the driver is actually applying to the brake pedal

    • Figure out how hard a driver can step

    • The takeaway: think of a way you can get to that metric and multiply for adrenaline

  • If you didn't have plans in measuring how strong your drivers are when braking, how do you size your components

  • Expanding foam is kind of hard. Need to consider. If you add too much padding it is useless

  • What is the value of the driver model

    • This is purely for packaging

    • How does your dynamics team feel about CG with your driver

  • Plan for ballast

 

 

Emech

  • Again, CFD is impossible without an understanding of the thermodynamic and heat transfer principles behind it

  • Do you have any specific plans wrt characterizing the thermal conditions of the battery? If you want to do hand-calcs of thermal FEA, you need inputs. If our cells have poor documentation that is a problem, if we don't know how much heat they are generating in varying conditions that is a problem. It is good and fine to say we are going to figure it out, but the how is the important part. It is your responsibility to learn

 

  • How are you going toe valuate the viability of the heat pipe and cold plate prototypes

 

  • You mention a lot of testing for the composite panels. You need to make a structured plan for how you are actually going to conduct this testing, the logistics of where and when, the variables you will be changing, how many tests, and how you will document the results. Testing without organization is a waste of time

 

 

  • Average RMS current draw

    • Dependent of the weight of the vehicle, haven’t fully tested

    • 8 amp nominal low voltage system

    • 30 amp nominal on motor

    • 40 amp pull nominal

    • Don't know what the cruising current draw is for the motor

      • What about charging

        • Able to chart at 6 amps during MPPTs

        • Assume maybe an amp extra?

    • 5 amps per cells, do you even need that much cooling?

  • Average ambient outdoor temperature

    • 32 degrees Celsius

 

  • Kevin: pick one thing you want to have that safety factor on. If you have a bunch of safety factors stacking up

    • If you want to set the cell temp at 45 C, have maximum operating envelope on every part along the way so you don't derate your pack

  • If these cells are so poorly documented that they harm our engineering process, maybe we need to find better cells

    • Dr Subramanian's lab - mech e professor with a lab electric used to characterize their battery

  • Are we testing water ingress

    • Yes, without the cells in there

  • Other teams have seen 5g as development level for bump loading, will it kill the design if you bump that mechanical to 5g

  • Have we considered a new electrical architecture for the battery? Having current collecting board

  • Really only think we need 3 point bend test and shear test, and then can extrapolate everything else in a spreadsheet - Kevin

  • You have a PCB for every battery module? That is a lot

    • When we are rushing to manufacture the wires can break off easily

    • The fuses are on the BPS side. If you have live wires that are not intrinsically fused, put the fused on that board. Also put it on the BPS

 

Enclosures:

  • There is a 1D vibe table at ferguson at pickle

  • The majority of failures are stuff that are poorly soldered and poorly crimped. Do quality control

  • Only get automotive rated connectors. If you get JST connectors, bullet connectors, they pop off. You need positively locking connectors

 

Wire harnessing:

  • When did we actually see signal interference at comp?

  • I'm kind of confused what the problem with the E stop is? Why do we need to look at other solutions?

  • You should create a standardized inspection scheme for verifying that connections are done correctly, won't snap off etc. You want piece of mind, and even experienced people make mistakes. You want redundancy.

  • Why don't we just buy more crimpers. Like literally rn

 

Other:

  • Panel mount connectors

    • Electrical standardizing can and 12v to use panel mounts

      • Are there plans to look into that

      • We started trying this last year, but we never really implemented it

  • Kevin: Recommend that the board in the enclosure not mount to the panel mounted connector. Generally for 2 to 4 pin connectors it is hard to find panel mounted connectors.

    • Want to spend more time learning about what we can use, see what's available to us

  • Are you shielding high voltage wires?

    • No they weren't. This is what caused the Emi problem

    • Shielding is gonna happen this year

  • How fast is the CAN running at

    • 1.5 kbps

    • No, the frequency of the CAN

      • Each system will have its own internal CAN line

        • YIKES - Kevin

      • That is a lot of wires. Is that four can lines all separate

      • Doesn't make sense to have 4 different CAN lines. Should have enough bandwidth to process all of the systems

      • It's not implemented yet.

        • We need more discussion. Reduce the number of CAN lines

    • Figure out how fast and how frequently you are pulling sensors, what is your critical communication, and then see if you can squash all of that into one CAN line because it will really simplify your architecture

      • Were able to fit telemetry and controls into 1 CAN line

  • In terms of waterproofing in the context of panel mounts, are we waterproofing the whole enclosure or the board?

    • The enclosure

    • In terms of the connector, we will have one board per enclosure

  • Cable sizing

    • Are you going to run a lot of different sizes of wires

      • We have more than we needed last year

        • We were using the 50 year old pickle wires

        • Going to invest in new wires

        • If we are buying industry grade connectors might use 2 gauge for the wires

          • If your RMS is 30 amps you can run the 12 gauge wires

    • Low voltage, 22 gauge to 16 gauge

      • Want to reduce the variance in cable sizes and standardize it

  • Do we have twisted pair CAN wires

    • We make them on our own, EPLAN helps with length

    • Kevin says we should buy them and they have shielded

  • If you want to make your CAN line faster, shield bold sides of the wire, make it shorter, reduce number of wires

 

Cooling

  • How did you determine that 8 fans were needed

  • How are you going to validate these hand calcs?

  • How are you going to learn about and teach members about heat transfer

  • What testing are you going to do to characterize the thermal conditions of the battery

 

  • Are you just measuring the temperate of the cells? That doesn't tell us the heat generation if we don't know the thermal capacitance of the cells?

    • What if a thermistor is on a cold spot of a hot spot

      • They epoxy it to the center of the cell

  • In general 60C is a good target for the center of the cell

  • You need to set the RMS current number at the golden number that you look at

    • It is what you try to design around

    • It drives heat generation for everything in the whole loop

    • It is what causes the heat generation. If you cant quantify it you need to choose a number and if a car goes above it you have to rerate

  • Thermal mass of the cells would also be good

  • Design our cooling system slightly above the power budget and then having tachometer and anemometer at the end of the cooling pipe.

    • You will get leakage through you lid

    • Tachometer: built in to the fan and measures the speed of the fan to extrapolate flow rate

    • Anemometer: goes at the end of the coolant loop to measure how fast air is leaving

      • You can estimate drop

      • You should run your fan duty cycle based on how much at the end of the loop

        • At the battery exhaust

  • The biggest thing that affects your cooling design is the THERMAL GRADIENT BETWEEN CELLS

    • The cells first will be cooled more than the ones in the end

    • Tend or parallelize your airflow paths so your cold air touches the most number of cells in the shortest path, so you have the best thermal gradient

 

Aeroshell:

  • Why does surface finish matter if we will be vinyl wrapping it

  • What types of reference points do you want to have on the mold

  • How are you going to develop your knowledge of fluid mechanics

 

  • Is there a numerical reason for going to 4 ply. It is flimsy with 6 ply? How do you know you did the 6 Ply

    • Why was the six ply flimy. Maybe the error is with your manufacturing and not with 6 ply

    • If you have a lot of resin in between your ply you are cutting a lot of strength

    • How do you plan to validate that?

      • We are doing testing. Advait will talk about composites stuff

    • He would go with 1 or 2

      • Not 1. Concerned with pin holes, don't want to do bondo work

    • I would make the structure that holds it strong

  • Esther Ply

    • Understand wanting to reduce the pky. Even one layer reduces 5 hours of time

    • Discern who is focusing on the track race and who is focusing on ASC

    • The shell is not structural but it still does have to withstand these environmental conditions

    • The sheet amount of time that goes into such a thick layup, the resin is already blushing by the end

  • References in the mold

    • Wheel cutouts can have bosses/indents for the cutouts

    • What references were you thinking about

      • Just having a boss

      • Even just having an accurate center line, would be useful in terms of measurement

    • What does your reference physically look like on the mold

    • Say you have the bottom shell mold that is female, and you have a little bump out of the bump on either side and pull a string across

    • Drill the mold, put a locating dowel pin in, then do the surface prep to seal it, then you have dowel pins/locating and you'll increase your bearing reinforcement, and you have actual locating holes

      • Worry about setting a locating feature and it being on the actual part

        • Want to make sure that you can hand it to inexperienced people

    • Nothing on the mold surface, it is on the boundaries?

      • For the example of the wheel cutouts,

  • You don't want references on your mold surface

  • If you see these reference points changing, you could have laser cut plywood that follows the curve

  • If you want more information on that style: talk to electric

  • Why 3 minutes for tilting?

    • Want to think more about. Came up with it a few days ago and said it was a good idea. Need to solidify it more, but seemed like a reasonable number

    • A good target but not really important

 

Aerodynamics:

  • How are you going to develop your knowledge of fluid mechanics

  • A shell made up of the best performing sections from 3 different shells may not make the best shell. How do you even characterize if a "section" performs well

  • I'm not sure we really fully understand the cons of an external suspension. Why did they move away from it on texsun? We should investigate

 

  • How are you going to make sure that the ansys sims are valid

  • What is the defined engineering fundamental when it comes to aerodynamics?

    • For combustion and electric need to worry about downforce, angle of tilt of airfoils

    • For us, it is really just the equation for CD

    • How the roughness of the surface impacts the reynolds number

    • What we see is still a good usage of engineering fundamentals - Wesley

  • Ansys fluent gets really bad when you start to go transient. Your ability to visualize fluid flow is good, but it becomes a multidimensional thing

  • Sharp corners bad

  • Avoid 3D printing in a wind tunnel. The surface will affect the results a lot

  • Your job is not finding the most optimized shell design that can exist

    • You will be limited by frame and dynamics

    • How to make sure sims are accurate: you won't know, just pick the best design

  • Excel sheet is a good way to keep track of things

    • Statistical analysis: how do you figure out which combination of things will be the best. There are so many combinations; You will notice trends in the data from Ansys, some of them will be conflicting

    • Try to think of how you can keep track of that

  • Unfortunately the best way is just to run everything

  • There's a reason why F1 still has a wind tunnel. If sims were perfect they would just use those. Doing physical validation is important. You could get a good surface quality 3D print if you go to SLA or SLS, and start doing more surface prep, you can get a close surface prep

    • We have machines that can measure surface roughness, you can calculate how much your different roughness affected your quality

    • The biggest way this aeroshell will impact is drag, but WEIGHT.

    • Energy is your acceleration, the more mass you can drop the more efficient. See aero push dynamics, battery, frame on not having a car that is so big and so long.

      • He looks inside the car and there is a lot of empty space

  • Esther's comment on the size

    • The array, want to have discussions with them. Designing for 4 m^2 isn't the best

    • Need to have a plan in mind

      • Start with the frame, see how many cells you can fit inside the frame. Start with the most compact frame you can, and see how many cells fit in that footprint

      • From there increment out, instead of starting at 4 m^2

    • Push back against array. Array will want more cells, and Aeroshell needs to push back with reason

    • Most critical part for shell to care about is the roll cage. Slope and height of the roll cage

  • Design approach is great. Can look at other cars

    • This depends on us having our top shell and bottom shell fixed. Who controls this?

      • Are there going to be versions of this as well or will you split them after

      • If one team is working on the nose and also the top shell, this will be another factor

      • Might be Aidan does the top and the bottom and everyone works with it

    • His pitch: nose separate, canopy separate, tail separate

      • BUT: these all rely on tangency with the profile of the top and bottom shell

      • Esther did the whole profile at once, and then split it across the top and the bottom

        • Maintain tangency

        • The downside: only one person works on it

  • Once the frame and dynamics are set, you can start doing the body work

    • Packaging is our hardest battle

    • Esther says have ribbing to support the topshell outside the bottom shell

  • Aero and Solar's next action item is to have a big discussion regarding the roll cage. It will affect everything

    • In her experience, the biggest headache has been fitting the roll cage

    • It kept changing every day

    • Occupant cell affects the angle of your windshield and the location and height of your canopy

    • Say you have a set length. You know where it is steeper you know where it tapers off

    • You also want the canopy to be aerodynamics. It is all because of the roll cage

    • With the discussion

      • Frame wants it to be structural

      • Aero wants it to be aerodynamics and manufacturable

      • There is a lot of wiggle room, more than you think there will be

    • Packaging is king

  • Are we doing bulkheads?

    • IDK

Composites:

  • What constitutes "finishing" wrt the composite frame aka sandwich panel testing

  •  

  • For windshield, you could get a fiberglasss surface, heat it, and droop the polycarb over it

    • The issue with thermoforming polycarb is that it sucks up every bit of texture that is there

    • The thermoforming tool is 19000 dollars because any degree of granularity creates fogginess on polycarb

    • Try to design the canopy in a way you don't need thermoforming

    • Once you cut the canopy all the stiffness comes from the polycarb

  • Don't use carbon fiber for the canopy

    • Just use fiberglass for the canopy

    • Or you could do what

    • Map out where fiberglass goes on the mold.

      • Consider making the area larger

    • Just do the layer of kevlar and the layer of fiberglass. The stiffness will come from the polycarb. Don't need to worry about reinforcing with CF. It is strong through continuous strands.

    • Or make it all kevlar

Wesley

  • Carbon control arms

    • Trying to make it all yourself out of prepreg

    • That is a very challenging thing

    • There are issues with doing it with the melt out core

    • Making your control arms air foils, the performance gain you will see from that is super super minute

    • Making a carbon control arm interior that is stiff, and then putting an aerodynamic shell on the outside would be easier

    • Just buy carbon rods off rock west and then do an outside carbon shell

  • Worried about sealing the split mold

    • If it's not a perfect match and you don't have good compression, you will have a bad seal

    • You will have leakage, you won't get vacuum

  • Interested in the canopy, and what determined our metrics for the plys. The ply count seems arbitrary

    • It's regs :shrug:

  • The issue we had with the PVA was that we would spray the PVA, and you'd do it on Saturday, they workday would end and everyone would leave. Then you'd go that week and do it in April (when it was rainy) and PVA dissolves in humidity.

    • When you spray for PVA< spray at 7AM, then layup that mold. If you wait too long you will have rpbolems

  • Last years they did apply the same day as layup and still had the same issue

    • You have to let the PVA fully cure and then spray on another layer

    • Or spray a bunch of thick layers and then do it once

  • Demold R&D is interesting. If you're having molding problems, acetone and hammers

  • Composite frame and testing

    • Seems great, seems like it would be fine

    • However, aluminum core density is what makes or breaks your bending strength. If it is too low of a density you will just crush your core, if it is too high, should have just made an aluminum monocoque

    • Do remember you need adhesive sheets, don't just hope and pray it will bond. You need some kind of post bond or added adhesive

    • You would be making the skins independently. Secondary bonding

    • ASTM standards - > good luck. Their composite standards are OK.

      • There is no set way to get a panel's strength

      • You are better off doing the standard composite theory test to determine your individual moduli in tensile compressive mode and a shear mode to correlate back to the simulation

      • Panel strength doesn't matter: there are so many orientations the panel and carbon can came

      • You want to test the material not the panel

      • The properties of prepreg changes over time

    • You can test wet layup material properties. Its not an easily repeatable process wrt to density which is your biggest player

    • Your panel might be better or might be worse later

    • The testing is mainly to see if we need filler etc. Figure out what we need to use

  • Molding for bottom shell and top shell: gel coat

    • It is ok.

    • For bottom shell, gel coat does maintain its thickness, but bad for vertical walls

      • The high vertical wall you'd have a lot of buildup on the bottom

      • Imagine you are pouring molasses down the side

  • Testing demolding

    • Hot wire cutting suffers with the 2d part of it

    • Our molds are not 2 dimensional

    • The biggest worry is that our molds are not 2 dimensional

    • A bowl is way harder to demold. We are an elongated bowl

    • Look at milling pucks of foam into bowl shapes

      • Could even scrape it out with your hands into a bowl

  • Pushrods

    • Pretty easy

    • Adhesive testing in pushrod, matters how your dynamics is set

    • If your dynamics is well thought off, and your rebound strength doesn't go into a tensile strength

      • You don't technically need a bond

    • Buckling testing can be important. FEmap will do your work for you

    • A 6x safety factor will still be 8x lighter than the steel equivalent

    • This is not as big of a concern

  • Resin Infusion

    • The time it takes for the resin to flow vs the tacking and curing time will be a problem

    • For this big of a part, how do you get a good seal and succeed at a drop test

    • Need a 6000 dollar pump. If you want to do this you need to own the pump

  • Battery layup

    • Might look at fiberglass instead of kevlar

    • IDK how much impact resistance you need

  • Cooling on cells

    • Cutting holes in the top shell would make it extremely flexible

    • Youd probably need to increase weight back up

    • Try seeing at intercooling through your core

    • Save weight, save time, save hole saws

  • Steering wheel

    • Don't let ergo do the composite steering wheel

    • You will spend a lot of time going back and forth with them

 

Clayton

  • Doing big layup over summer?

    • Why are you trying to get your plug manufacture in may

    • If you let it sit at pickle over the summer something bad will happen

    • Actually we just need it by start of school year

  • Resin infusion

    • You have to be very sure

    • You will have at least 6 resin entry points on something this big, with a perfectly sealed vacuum bag, and many pots of resin being mixed at the same time

    • Resin infusions this big you'll have a team of 6 professional layup people working on it

 

Esther

  • Having a mold by May: keep it

    • Deadlines will always get pushed back

    • Keep your timelines early

  • So easy to push stuff back than to quicken it up

  • Keep your timelines early

 

Eesha

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