Originally Posted by boltrc

Yes, top (tensile) and bottom (compression) is taking the stress. ie. doing the hard work whereas the centre does very little.

Not sure I understand the rest of the question.

Interesting. Does that mean you're gonna use some sort of coating or perhaps a thin layer of another material to give it additional toughness?

Rod Santos has done some sensational images for our upcoming Kraken release. We are very happy with how they have turned out, thanks Rod!

The first image is available as a T shirt for purchase here

Our community's very own artist, check out the rest of his work here.

100% of the proceeds from this Kraken merch go to Rod's store, please support his great work. For international buyers, please note there are various local shipping options near you.

Originally Posted by boltrc

Rod Santos has done some sensational images for our upcoming Kraken release. We are very happy with how they have turned out, thanks Rod!

The first image is available as a T shirt for purchase here

Our community's very own artist, check out the rest of his work here.

100% of the proceeds from this Kraken merch go to Rod's store, please support his great work. For international buyers, please note there are various local shipping options near you.

Solid work . Love it!

@peteG - yep, you have got it nailed.

@Levendis - The feathering is just one way to spread the stress. Whether it is the best way with the requisite compromise, given the application?

The arm is in fact more than 33% stronger! I will post the matching 4mm arm image tomorrow.

In regards to the chassis plates. This is quite a complex beast beyond the scope here. Have a look at the modelling we did here around a year ago. In our experience, the main issue is not the plates themselves but rather the deformation of the chassis caused by poor support between them.

@LearningQX - sorry, I really don't mean to be tease....

arg! ok coming along for the ride , i need to see this!

A couple of frame designs have explored the sandwhich material concept but it certainly hasn't been used to its full potential yet

Can't wait to se this Krieger killer!

Will you keep your blog up to date with this new frame? That's how I discovered your bolt250.

Originally Posted by boltrc

@peteG - yep, you have got it nailed.

@Levendis - The feathering is just one way to spread the stress. Whether it is the best way with the requisite compromise, given the application?

The arm is in fact more than 33% stronger! I will post the matching 4mm arm image tomorrow.

In regards to the chassis plates. This is quite a complex beast beyond the scope here. Have a look at the modelling we did here around a year ago. In our experience, the main issue is not the plates themselves but rather the deformation of the chassis caused by poor support between them.

@LearningQX - sorry, I really don't mean to be tease....

Mark, have you considered honeycomb structure between the plates? Is a common light weight solution.

@powis and @vis101 - yes, I agree and continue to consider this in detail. The main challenge occupying my mind are the lateral forces. This is both in a general broad impact (eg. ground) or hitting a sharper object (eg. goal post). I don't have an answer on this but it does concern me particular when you look at my last post where the stress is applied to the edges. These honeycombs have no structural edges when purchased as straight laminate. If vacuum molded, that is a different story, but cost, complexity, I am not ready for that.....

In summary, IMO sandwich construction has a major role to play but it is more complicated than just a sandwich. Besides, in our case, adopting a traditional sandwich material would likely only save another 5-10 grams......

@Robomaniac - not at this stage. we are using this thread to document our notes. I may copy them over in a few weeks.

As a final note, the chassis of a H frame is in fact a sandwich. In the case of the BOLT250, the insertion of the arms, washers and front bumper are in fact the 'honeycomb'. Somewhat crude and heavy with all that hardware but very effective. The BOLT250 H frame is extremely strong for this very reason.

Originally Posted by boltrc

@powis and @vis101 - yes, I agree and continue to consider this in detail. The main challenge occupying my mind are the lateral forces. This is both in a general broad impact (eg. ground) or hitting a sharper object (eg. goal post). I don't have an answer on this but it does concern me particular when you look at my last post where the stress is applied to the edges. These honeycombs have no structural edges when purchased as straight laminate. If vacuum molded, that is a different story, but cost, complexity, I am not ready for that.....

In summary, IMO sandwich construction has a major role to play but it is more complicated than just a sandwich. Besides, in our case, adopting a traditional sandwich material would likely only save another 5-10 grams......

@Robomaniac - not at this stage. we are using this thread to document our notes. I may copy them over in a few weeks.

As a final note, the chassis of a H frame is in fact a sandwich. In the case of the BOLT250, the insertion of the arms, washers and front bumper are in fact the 'honeycomb'. Somewhat crude and heavy with all that hardware but very effective. The BOLT250 H frame is extremely strong for this very reason.

I was thinking about a seperate honeycomb insert that goes between the bottom and mid plate. Agree that doesn't help with lateral impacts. You need a spring along the outer edge to deal with a point impact on the lateral direction.

This image compares 3mm and 4mm arms. The force has also been increased to 30N (previously 20N) in order to accentuate the differences.



As you can see the 4mm arm is a lot stronger than the 3mm arm, much more than the 33% increase in thickness. You can also see that the stress remains on the edges for both models.

As previously demonstrated, the strength is primarily coming from the edges/surface with the only difference in the arms being the thickness (separation).

A key take away is that we have underutilized the potential tensile strength of the CF in the 3mm model. The 3mm is deforming and giving way at loads much lower than the potential tensile strength of CF.

If we were to have a greater separation between the top and bottom layers, the result is that the arms are a bucket load stronger.

Note: These arms are different model to the earlier posts showing similar feathered arms. A small change in the feathering delivered a material improvement.

Originally Posted by boltrc

This image compares 3mm and 4mm arms. The newtons have also been increased to 30N (previously 20N) in order to accentuate the differences.



As you can see the 4mm arm is a lot stronger than the 3mm arm, much more than the 33% increase in thickness. You can also see that the stress remains on the edges for both models.

As previously demonstrated, the strength is primarily coming from the edges/surface with the only difference in the arms being the thickness (separation).

A key take away is that we have underutilized the potential tensile strength of the CF in the 3mm model. The 3mm is deforming and giving way at loads much lower than the potential tensile strength of CF.

If we were to have a greater separation between the top and bottom layers, the result is that the arms are a bucket load stronger.

Note: that these arms are different model to the earlier post showing feathered arms. A small change in the feathering delivered a material improvement.

i dont know what any of that means

all i heard was bit more CF = much stronger arms

hope that was the message lol

Fascinating stuff, Mr. Boltrc.

But just so you know, I'm buying your new quad only because of that T-shirt (which I do hope comes with the quad?!)

Originally Posted by Joseph3LK

i dont know what any of that means

all i heard was bit more CF = much stronger arms

hope that was the message lol

Actually, the incremental CF is not directly adding a huge amount of strength. Additional strength (and stiffness) is also been added due to the greater separation of the top and bottom layers. Hence we get a more than 33% increase in strength.

Originally Posted by Levendis

Fascinating stuff, Mr. Boltrc.

But just so you know, I'm buying your new quad only because of that T-shirt (which I do hope comes with the quad?!)

Thank you. Unfortunately not, the t-shirts are supplied separately by the artist, Rod Santos. Please note that our frames generally sell at a fraction of the many brand name frames.

I'm very excited about this new frame, I'm just about due to replace my old one that I bought through Bolt ages ago, and am on the lookout for what's next.

With the arms for this frame though, what is the purpose of the curved or "Feathered", as you call them, edges to the arms? You can see through your FEA sim that assuming a point load at the tip, the stresses are concentrated mid way through the span. An optimal plan form for a beam loaded as such has straight edges tapering from root to tip. Stress in the beam goes down with the cube of the thickness (height) of a beam loaded like this, so no surprise that the stresses are significantly lower when going from 3mm to 4mm CF.

Further, what are you trying to assess with FEA of the design. It makes nice pretty pictures and all but surely the stress in a simple arm like this can be calculated on the back of an envelope, or are you planning on using FEA for other more complex parts of the machine?