A new project - Nichimo Spirit FF - The first of a kind

[silvertriple]

I still had a bit of time before my eyes are telling me it's time to go to sleep, so I started another component...


Started the bottom of the radio box.... That's getting even more fun than with one single component as I only need to add the measures which are missing... I'm surprised how much it looks easy!

[silvertriple]

I have now my second component. The RX box bottom part is defined...

[silvertriple]

I got my third component finished. I can close the radio box now...


In terms of broken parts, for which I have no other escape than printing a new part, there is.

- Chassis bottom half
- Bumper
- radio box top
- roll cage left
- roll cage right
- Front bottom arm left
- Front bottom arm right

That makes 2/7 of it
However, since It is easier to get attachement points from a given existing design, I think my next step is the gearbox right and left half.

[Dadio]

Are you going to do an external model of the gearbox for reference or a correct working gearbox case ?

[silvertriple]

Well, I don't have a clue yet...

Today's lesson was that it is easier to see the symmetry axis of a gearbox when you have the gears visible inside...

I started to model the left half of the gearbox... Almost used the full panel of my Confusion360 skills within a single sketch to pull just this first step...

As soon as got the solid done with an extrusion and a a revolve on 180°, I did use section analysis to review the chassis and where it fits all together...
There is a few things that let me think that the design is right (the gearbox symmetry axle is right at the level where the chassis halves are splitted)... I just have to offset one surface about one millimeter but it's because I offset 1 mm in the other way earlier...



I believe I'm on the right path... Even if I sometimes ask myself in what I'm getting engaged

Functional gearbox or not is a good question. Knowing the whole thing seems to be done in ABS, and with mod 0.8, there is fair chances that Nylon PA12 SLS/MJF printed parts could do it. And I believe that soon we will able to print in Polycarbonate with SLS process with a higher deflection temperature point than Nylon, so it is really tempting to design the gearbox functional so we can print it later... But I believe it will take time (there is a few things I do not have the skills yet)...

[silvertriple]

@Dadio , your comment about measurements being hard is running in my head since a few days...
I think I have an idea in mind to facilitate this... Need to refine it, but I think I will need to print some stls soon for that

[Dadio]

The problem in measurement is when say two holes are on a different height and the walls are angled for injection molding so finding the distance centre to centre is hard , you need an odd length leg caliper .
Or often there is no direct path to get a measurement between two points .

This has been a really helpful and cheap tool I'd recommend to anyone doing reverse engineering , modelled by our dog Frey .

Getting angles right is eye bending at times as well, it all sounds so easy , I mean they teach you to measure by the time your 8yo , but 8 year olds tend to be able to see better

[silvertriple]

Well, measuring holes distance when the holes are at the same height is dumb easy... And when it's not at the same height, or that there is something which doesn't allow to get the caliper set right, that's were it complexe and any method may imply parallax issues...

I've ordered few 2.5mm diameter rods. They are the right size to enter in 3mm screw holes. Key assumption is that there is always a way to access holes perpendicular, as you need to put a screw in.

And I've designed a tool which I plan to insert 2.5mm rods and set them perpendicular to the tool.


The idea is to push the rods in the hole, and measuring the distance between the rods with the caliper. The measure will need to be offset with the the sum of the half diameter of the rods. Note that you can use different sliders with different rods diameter to adapt to the situation you want to measure...

I will print this tonight.

And for angles, at the time, I'm applying @optimaforever 's method : human do simple angles (assuming by 15° steps seems to be a good approach)...

[optimaforever]

I use smartphone app (Photo Protractor) to measure angles; it uses the phone's camera and then you can draw on the picture and measure angles. It's very precise. Of course, as @silvertriple said, I always tend to find simple numbers.

[silvertriple]

The work on the gear box continue...

At this stage, I have three sketches for the gearbox. One for the profile, and the target is to use it as well for the right gearbox.


It's not even complete as I added other things inside the sketch later on...

I have another one for the motor plate profile, and one for the internals of the gearbox (basically whatever would be applied inside the gearbox after having shelled it.
Then there will be 3 additional sketches for the remaining stuff (arms attachements top and bottom,and for gearbox closing fixation).

Here is what I have in CAD for the left half of the gearbox - the right part is not exactly symmetric due to the motor.


And the gearbox irl. I think I got the shell more or less ok.


And on the whole view...



The most complex things are done already, but I will need to wait the tool to be printed to check my measurements...
https://www.thingiverse.com/thing:5260398

[silvertriple]

This morning I was not feeling well, so I dropped a message to my boss I'll get a day off and moved all my today's meeting before getting back to sleep...

And around 11 this morning, I woke up, and decided to restart the work on the left half gearbox...

First work out the supports of the suspension arms....


Then t was time to be able to close the gearbox with some ears


A small check is needed here...


I had to review the width of the chassis shell in this area to get it correct both on the rear side and the left side, as there was no room for the screw...


I made more sketches than I thought but they should be reusable for the other half of the gearbox... I have a small modification to do on two of the ears on the motor side but that will be done quite quickly, otherwise there would be no way to put a screw in there...

The more I worked on this gearbox, I think I may not have started by the easiest car to model

[silvertriple]

I had nothing else to do so I continued working on...

Started to work on the second half of the gearbox... A component symmetry, first.


Then filling the holes, drilling new holes and extend the gearbox mount on the right side... It seems the fit is right on the chassis... Nothing really complex as the hard work was already made for the left gearbox half...
Now, the main difficulty is to determine the motor position, and where I should put the extension to get it right...

I confirmed first that the gearbox fixation points on the motor plate were symmetrical. Easy compared to what I've done until now....
next was to find the motor center... and position it. and then determine the diameter of the circle to use... and guess what : it seems spot on with the gear box fixation...


Next was just to deal with a few extrusions, and boom, done...




Not sure what I do next. I decided to delay the chassis test print when I had to modify minor details... I will probably wait I have the Bumper model to get there...

[Dadio]

I'd have had a test print of the chassis done by now , I have no patience at all this was certainly not the easiest car to start with When you print the gearbox use a filament that does not shrink , I tried ABS for the dogfighter gearbox and the gears would not mesh due to shrinkage but it was fine in PLA or CF Nylon .

[silvertriple]

Yesterday, I made a lot of progress...

I started during the lunch break by doing some reverse engineering of two parts closing the gearbox on the motor side...


Once you have it done, it looks definitely easier to understand - I guess I will have less difficulty next time I'll model a motor plate or a gearbox, and probably I should have started by this before the gearbox...
I finalized the components at the end of my day of work...


Then it was time to start the suspension arms... I started by the front bottom ones...





On the top one, I changed slightly the way I worked, based on the learnings of the bottom one... It went very much faster...



Then I had to take care of the rear ones... I spend a lot more time on it as it is done differently, and second the measures are a bit difficult...



I got all the arms now... That was quicker than what I thought initially...



Few things I found which helps to work faster and with more insurances on the results :

• drawing a line on a sketch not exactly on the line you want to apply it makes it easier to set the colinear property

• defining circle by their tangent lines positions makes it quicker that defining the center position as it corresponds most of the time to what you measure

• sometimes its worth to apply a constraint: it will tell you if it is already considered

• applying a fillet on a sketch means loosing the definition point of the lines, you have to reset the colinear property after having done the fillet

Next step will require me to understand the metal sheet mode of Confusion 360... I guess it is another learning curve (again another hint that I did not start by a car easy to model in first place )

[silvertriple]

I started this morning by two parts that are mounted on top and on the bottom of the gearbox, one to fix the front sway bar, and the second one to fix the skid plate, That was very easy part to do... And another set of complex things begin : part of what I had to do relies on the fact the bumper is properly seated on the skid plate, and the skidplate itself sits on a metal plate, bended and joining the motor plate and the radiator, annd going along the gearbox...

Few videos on youtube and some chat with my mentor later, I was able to pull some edges using metalsheet mode of Fusion 360...
Once done, I did the sketches on the faces of the metal plate requiring holes as per the measurements I done with the caliper and it's joyful to see a hole in the plate discovering a hole where the screw goes in...


It seemed to me that the chassis measurements may be more accurate than what I think. I therefore launched a print. I still have a doubt on the gearbox mounting points, but this will hep to clear out the doubts.


I then started to work out the battery holders (asymmetric, just like a Hotshot), and some parts which would allow mean to pull some edges of metal sheet again with the shock towers...


Once this was done, I used inspect to check if the battery pack would find home... 133.5 mm ouuups!!!


Small correction later (added .25 mm on each battery holder sides) it's now where it should 134 mm!


I also tested my measuring tool and it may still require a bit of adjustment but it's already a good start...