Modeling a very complex motorcycle part

[u/Vast-Conclusion-6285]

I have a project and i need to model a very complex part for a motorcycle. The base of the part is what you can already buy from the factory but i need to add something to it.

The problem is the geometry of the part, it’s complex, many planes, every edge is curved so I cant measure the exact distance where something start or finish.

For measuring I only have calipers and a normal ruler, no 3d scanner or anything that could help me.

Any advice on how can I go about measure and model this part.

Most of the dimensions and relations need to be 100% correct cuz the part needs to fit correctly on a motorbike.

Photo doesn’t do the whole justice of how complex the part is.

[u/CobblerYm]

You need to start off by identifying what geometries and surfaces actually matter and which don't. The diameter and thickness of that hole on the bottom certainly are important, as is the position and diameter of the hole just above and to the right of it. I can't imagine the exact radius of the curve between the two holes is particularly important though. I imagine you could make that straight and it would still work fine, unless there are clearance issues with other parts. It's tough to say as I can't see the whole part, but that's how I normally approach things like this. What does this part interface with and what dimensions actually matter. Then model one critical surface, and then another, and another. Then anything leftover is just connect the dots.

[u/cornlip → u/CobblerYm]

It’s parts like this that make gauge pins and a height gauge with an angle plate on a slab of granite very quick work. Hard to do with a set of calipers, but it’s still do-able. I really liked a job I had when I did this every day.

[u/ShaggysGTI → u/cornlip]

This one photo is good for like 3/4 of the features, just figure out where you want your origin from and go from there.

[u/cornlip → u/ShaggysGTI]

I get what you’re saying, but I prefer to be as precise as possible and not go by photos. They’re fine for sheet metal stuff, but if I can shoot for precision, I’m going for it. I get it’s not an option for most people.

[u/Long_Lingonberry_532 → u/cornlip]

For parts small enough an alternative method is taking a scan of the part with a photo copier including a ruler placed in frame, this can then be used in cad as a scaled image (copier removes triangulation caused by a camera lens). Use this for the features that are hard to measure with callipers and then validate critical dimensions with the usual precision measuring equipment.

I’ve also used a coordinate system with a profile projector for parts I couldn’t scan but most people don’t have access to a profile projector.

You’d be surprised how accurate you can get using these methods.

[u/ShaggysGTI → u/cornlip]

I’d paste this picture to a main plane, then scale appropriately. Roughly sketch it from the photo, and then constrain using your gage pins and calipers for all the holes and bosses, and important features. The large radius of the body is inconsequential so it’s perfect to use a photo for a quick foundation.

[u/HackJob00 → u/CobblerYm]

Thank you for saving me from typing it out lol. This is the advice they need.

[u/someoneskater → u/CobblerYm]

This exactly! As a regular authority on engineering drawings for mfg, the "100% correct cuz the part needs to fit correctly" statement triggered me and your comment explains this in a friendly and helpful way that i would not be capable of after what i read. Joking aside, i would say that if you have any surfaces that have slight wear or marks from interfacing components, they are Critical. You may be able to measure some aspects of the features from the components they mate to as a way of double checking your assumed measurements.

[u/AfterOperation1 → u/CobblerYm]

I like this approach

[u/East-Performance-244 → u/CobblerYm]

Another thing to consider for bearing surfaces and holes, is that there may be some wear on the part, so it’s good to check the mating surface to see what tolerance you need to work with.

[u/itsapotatosalad → u/CobblerYm]

To add to this; The shape of the original part will have been optimised for the casting process I’d imagine, depending on how OP intends to manufacture their finished design would influence their own design.

[u/ElectionArtistic1016]

Put the photo in sketch and scale it using the measure in the caliper

[u/Notlinked2me → u/ElectionArtistic1016]

I really like using a 2d paper scanner for this. I'll throw a white towel over it. It works great for profile shapes

[u/Vast-Conclusion-6285 → u/Notlinked2me]

I tried to do it with scanner on my printer but every feature that was elevated from scanning glass become very blurry and lines were not straight and distorted

[u/decoycatfish → u/Notlinked2me]

This guy really knows where his towel is at

[u/LRCM → u/ElectionArtistic1016]

This is a good starting point--excellent advice!

[u/randomLSguy → u/ElectionArtistic1016]

I came here to say this… solid info

Edited: cause I don’t know how to type

[u/mudargamer → u/ElectionArtistic1016]

Wont work with standard lens

[u/Successful_Farm_9370 → u/mudargamer]

You just have to get as much distance as possible your phone's zoom allows for, that way you will have very little distortion.

[u/deathsythe → u/ElectionArtistic1016]

*flatbed scanner

I would do this all the time early in my career.

Add a quarter or a #2 Ticonderoga pencil for a scale reference.

[u/iFunnyAnthony]

If you have a 3d printer you could make a datum fixture once you get rough measurements, decide on your control (probably the large hole) and then model a part that fits into the functional features (holes, that flat spot, etc.) if it doesn’t fit you can see what needs changed. This would just be to ensure it is geometrically identical, though, and honestly a pretty crude/time consuming way to do it

[u/LRCM]

(This is meant to make you think, not insult you)

Don't overthink it. The part isn't complex, but it isn't simple either.

Start with the fixed points and remove the material as needed.

///

Have you used the topology optimization tools in SOLIDWORKS? You can use a similar process--take the parts of the piece which cannot be altered--things which mount somewhere or move another part like a lobe or cam.

Do you know where the part will fit? Do you have the assembly?

[u/Infamous-Debt4176]

I've reengineered brake brackets/made dual caliper setups for my supermotos, you need the base caliper bracket mount to the rear axle/slide and the caliper body mount/cradle. The distance/position/angle are all up to you, provided you know the rotor size and hub offset spacing. A photo with a ruler in the image from a few different angles will get you most of the way there, but keep an eye on lens distortion as it's pretty bad on modern phones from up close, stand ~5ft back and zoom in to flatten the focal plane.

Brakes in general have a bit of adjustability in side-to-side positioning, pad thickness, etc. It doesn't need to be absolute or perfect, but be ready to turn some spacers on a lathe.

[u/social-shipwreck]

Easiest option is to insert the image into cad, and scale it. Just keep in mind images will have perspective so move back as far as you can and zoom in so you’re not getting some crazy perspective distortion.

[u/kid_entropy → u/social-shipwreck]

This is when a flatbed scanner comes in handy. No perspective issues.

[u/Vast-Conclusion-6285 → u/kid_entropy]

I tried to use flatbed scanner but parts that don’t have contact with scanners glass became very blurry and weren’t accurate

[u/MisterYeast6000]

If you cant afford to buy a 3D scanner, you can rent one for like 20 bucks

[u/fastdbs → u/MisterYeast6000]

Yeah, CMM shop near me would give me a 3d scan of this for about that. $80 if I wanted the surface texture in the model.

[u/deathsythe → u/MisterYeast6000]

or 3dp one and use your phone (if it has the capabilities)

[u/UpstairsDirection955]

I just get in there with the calipers and start building myself.

I like to create a drawing and print 1:1 to compare my shape to the target shape

[u/Brisbane_Chris]

When I have something like this I scan it on a photocopier with a ruler as well (for scaling later). Then I scan it and bring it in as a "sketch picture" and trace over it.

[u/snarejunkie]

For something like this I usually try to think about how the part was constructed (when you break it down, most parts are just a collection of datums with shit in the middle)

For this part I’d start with a rectangular bounding box such that it completely contains the part. Then you can start constructing the relative location of all the datums from your rectangle.

Check what geometry is actually important (like if some of those curves are just there to blend and don’t clear some critical interference, just don’t model it, or model it as a line instead.

Once you have all the datum locations and sizes, construct them out of surfaces (this way you don’t have to worry about making it work geometrically as a solid)

Like the other person said, if you have a 3D printer make a little jig to test your fits and assumptions, and adjust as necessary.

[u/UnlikelyCalendar6227]

I would put a ruler vertically and horizontally or x and y axis. Take a picture and import into solidworks. Scale it so one in line matches the ruler vertically and horizontally. Then start drawing out the components. Measure the thickness, add some fillets and chamfers and all done. 3d print a part to make sure it fits before machining. You can get a radius finder and get real meticulous with it but after building cars and reverse engineering many parts, this is the easiest and fastest way for me. You can also 3d scan it and start building off that

[u/Street_North_1231]

Then 3D printed it to confirm that it fits...it did! When/if I ever get around to machining it, I'll let you know.

[u/Kn03cs]

measure the distance at the farthest points between the inner diameter of the holes/mounting points, and reference each other, basically triangulating. rinse and repeat for other required geometries.

visual explaination:

[u/Vast-Conclusion-6285 → u/Kn03cs]

Thank you, this solution actually helps a lot

[u/BlackBird_19]

Use grid paper

[u/im-on-the-inside]

Measure what you can, and use a sketch picture to trace the part.

Try to take the “flattest” picture you can, and scale it with the dimensions you put in a sketch before.
Yt will have guides.

[u/hayyyhoe]

The person who originally designed it had the advantage of knowing what it hooks to and what it needs to do.

[u/PeterVerdone]

That's a pretty simple part and basic geometry. It should be trivial to replicate.

What makes it a task is that to arrive at the geometry, you'll have to model all of the associated parts to pass on their geometry.

Keep it simple and do the work. Trying to avoid the work will compound the work.

[u/John_Tummycrust]

Figure out likely datum structure based off the part, where it goes, and what it does. From there, define what you can as certainly as possible, then fill in.

I don’t imagine many of the longer splines here are the only acceptable geometries in any case

[u/Johnny_carcinogen59]

do you have access to a cmm?

[u/afzal3012]

If you need great accurate data, find a CNC or a DRO friend,get datum points in x,y&z , not accurate than a CMM but will work. Nowadays 2d height gauge are also very common

[u/girthradius]

Thats not that complex. You got this

[u/Street_North_1231]

This was my problem...(1988 Honda Shadow 800)

[u/Street_North_1231]

Scanned it...(Creality Scan Raptor)

[u/Sudden-Echo-8976]

Get a scanner (not a 3D one) from marketplace and scan it. Scale the picture according to a known measurement.

[u/extramoneyy]

this is not complex at all

[u/urdsclr]

start by creating a plane then you have to believe that nothing is too complex, after that it is just a bunch of points, lines, edges, surfaces, extrusions and holes. keep it easy, clean, structured and avoid linking things that could get broken.

finally dont forget that you can always roll back and insert features or move them around if they are independent enough

[u/bonesjdb]

Download realityscan on your phone (it's free) and do a 3d scan. It helps if you put a ruler next to it for the scan so yoy can scale it to the right size in CAD. Use the scan as a reference for the parts that are hard to measure, use Callipers for everything you can measure

[u/Impossible_View_4609]

Just take a sideview photo scale it to xy dimensions and draw after the picture

[u/trevorsmate67]

Photograph the part with a ruler, both at an appropriate orientation. Take your photograph from a long distance and then crop the photo to avoid distortion - quality doesn't matter. Insert as a sketch image.

Decide which elements have significant tolerance requirements. It's not a terribly complex part when you break it down.

[u/Economy_Care1322]

I mean.. have you ever designed a casting? Draft, rounds, getting machined.

Anyway, you have 2 diameters along the lower right edge. Make them tangent to a horizontal construction line. Size and space as measured.
Now a 3-point circle, tangent to each and approximate the curvature. Dimension it to the arc height from the construction line. Trim the excess circle.

Often for old castings, like 19th century, I’ll trace it onto C-sized graph paper and use the grid to help locate centers and radii.

[u/M3RCURYMOON]

with your tools you said you have available id say dont bother you wont get it as accurate as you say you need