Custom Luggage Rack and Back Rest Design

[slo-ride]

I'm working on my winter project. I've taken it upon myself to design my own passenger back rest and a luggage rack. Yes, I know that there are many good designs already out there for purchase but I'm a design engineer so I like to give it a go when I can. So, take a look at the images and let me know what y'all think.

Clicky B)

 

[Harald]

Nice looking rack! The only suggestion I have is to make the backrest adjustable fore and aft. I ended up having to design a custom mount plate for the factory trunk so that I can move it back a couple inches. Otherwise my wife sat too close to me.

 

[Murph]

I never thought I'd say this to a guy but .... nice rack! I might be in fantasy-land here but, if your goal is to market this to a variety of riders, I think a good selling point would be a height adjustable backrest because different people need support in different areas.

 

[scubatech]

Your rack is really a good looking unit,very professional design. I think you could sell it pretty easily if you wanted to.The two previous posters ideas make a lot of sense as well.

Ken.

 

[Joe2Lmaker]

slo-ride,

What CAD software are you using?

 

[slo-ride]

Nice looking rack! The only suggestion I have is to make the backrest adjustable fore and aft. I ended up having to design a custom mount plate for the factory trunk so that I can move it back a couple inches. Otherwise my wife sat too close to me.

Hmmm. Fore and aft. I'd not thought of that. I'll see what I can come up with. Thanks for the suggestion and feedback.

 

[slo-ride]

I never thought I'd say this to a guy but .... nice rack! I might be in fantasy-land here but, if your goal is to market this to a variety of riders, I think a good selling point would be a height adjustable backrest because different people need support in different areas.

Thanks! I'm glad you like my rack.

Yes, the height of the cushion is adjustable by way of 2" oval slots. I can just loosen the bolts then move the height of the back rest up or down. I did this because my kids ride with me and they are all different heights.

slo-ride,What CAD software are you using?

Autodesk Inventor 2009. I've used Pro/E Wildfire as well but Inventor is my favorite by a long way.

 

[slo-ride]

Your rack is really a good looking unit,very professional design. I think you could sell it pretty easily if you wanted to.The two previous posters ideas make a lot of sense as well.
Ken.

Well, I guess I could sell it. I'd not put too much thought into that. I guess if there was enough interest I could do it.

 

[garauld]

Hi - what material are you planning to use? Keep in mind, PMA has a similar design and has had problems with cracking due to excessive cantilevered loading - I think the sharp corners acted as stress risers. Also, if you are planning to use AL, the BR vertical plate might be a bit wimpy. PMA added a brace to their design.

 

[Checkswrecks]

Hi - what material are you planning to use? Keep in mind, PMA has a similar design and has had problems with cracking due to excessive cantilevered loading - I think the sharp corners acted as stress risers. Also, if you are planning to use AL, the BR vertical plate might be a bit wimpy. PMA added a brace to their design.

It looks great and will be pretty, but I also have to give a +1 to what Garauld wrote. There's a lot of load and it's far aft of the mounting bolts, especially with the arm of the vertical rise. If you grab the aft end of the stock rack and press up & down, watch closely & you'll be surprised how much give it has. I'm sure that flexibility is why Givi scrapped the whole stock rack and went to the welded steel tube design they use to distribute the load.

Because that aft-most mounting bolt is to a cantilevered finger of the sub-frame, can you do a stress analysis on that aft mounting point and the sub-frame with Inventor? I think it'd be enlightening for everybody, since there are a number of flat plates, CooCases, etc, and nobody really has a good idea of what "too much" is.

 

[slo-ride]

Hi - what material are you planning to use? Keep in mind, PMA has a similar design and has had problems with cracking due to excessive cantilevered loading - I think the sharp corners acted as stress risers. Also, if you are planning to use AL, the BR vertical plate might be a bit wimpy. PMA added a brace to their design.

Who is PMA? I'd like to look at what they did especially if they had issues.

The back rest is going to be 1/8" or 3/16" Cold Rolled Steel depending on cost/availability of material/forming issues. I could add a stiffning brace if necessary.

The rack itself is 1/4" Aluminum 6061.

 

[slo-ride]

Hi - what material are you planning to use? Keep in mind, PMA has a similar design and has had problems with cracking due to excessive cantilevered loading - I think the sharp corners acted as stress risers. Also, if you are planning to use AL, the BR vertical plate might be a bit wimpy. PMA added a brace to their design.

It looks great and will be pretty, but I also have to give a +1 to what Garauld wrote. There's a lot of load and it's far aft of the mounting bolts, especially with the arm of the vertical rise. If you grab the aft end of the stock rack and press up & down, watch closely & you'll be surprised how much give it has. I'm sure that flexibility is why Givi scrapped the whole stock rack and went to the welded steel tube design they use to distribute the load.

Because that aft-most mounting bolt is to a cantilevered finger of the sub-frame, can you do a stress analysis on that aft mounting point and the sub-frame with Inventor? I think it'd be enlightening for everybody, since there are a number of flat plates, CooCases, etc, and nobody really has a good idea of what "too much" is.

Good point on the stress analysis. I used to have that capability within Inventor but my company let the license expire so I do not have it anymore. I had not considered the cantilevered and cyclic loading of the rack which, I'm sure, is worth considering. Where did I put my "Mechanics of Materials" engineering book?

I'll have a look at the OEM rack tonight. Thank you for the input!

 

[road runner]

Hi - what material are you planning to use? Keep in mind, PMA has a similar design and has had problems with cracking due to excessive cantilevered loading - I think the sharp corners acted as stress risers. Also, if you are planning to use AL, the BR vertical plate might be a bit wimpy. PMA added a brace to their design.

Who is PMA? I'd like to look at what they did especially if they had issues.

The back rest is going to be 1/8" or 3/16" Cold Rolled Steel depending on cost/availability of material/forming issues. I could add a stiffning brace if necessary.

The rack itself is 1/4" Aluminum 6061.

Slo-ride,

I think garauld ment PCA (Premier Cycle Accessories) here's a link.

I have one of PCA backrest/rack combo's and it's been working fine for me. The early ones he made had aluminum upright for backrest, those were cracking. Now they are steel (like mine) and not cracking, as far as I know. I think he may be making the rack different now also , but I'm not sure.

 

[Opelgt]

We have Inventor 08 (possibly 09) with the ansysis FEA solver plug in. It is a little limited compared to the full anysis version. If you want I can check with the inventor user (not me) to see if he cn spare some time to analyze it. Loading will be the issue however, we would need to discuss where the loads are to be placed and what the magnitudes for them would be. :glasses:

i am not going to be able to get his time to model the subframe so if you have time to put it in that would help as well.

If you feel like trying let me know.

[email protected]

 

[Brodie]

I'm no ingineer, I don't got no access to dem fancy schmancy hi tech puter stress anaylisis stuff, I'm just a lowly machenst.

This is what I came up with when I saw how much my rack hung over its last point of attachment...

You may want to add some sort of clamp back there to keep the up and down oscillations from fatiguing the aluminum where the 2 bolts attach it to the bike. I made mine out of left over delrin round stock in the shop. Let the Yamaha platform help support the load.

Brodie

 

[slo-ride]

I'm no ingineer, I don't got no access to dem fancy schmancy hi tech puter stress anaylisis stuff, I'm just a lowly machenst.
This is what I came up with when I saw how much my rack hung over its last point of attachment...

You may want to add some sort of clamp back there to keep the up and down oscillations from fatiguing the aluminum where the 2 bolts attach it to the bike. I made mine out of left over delrin round stock in the shop. Let the Yamaha platform help support the load.

Brodie

Nicely done. I will have an opportunity to look at the bike's rack and my design this weekend. Thank you for the photo.

 

[slo-ride]

We have Inventor 08 (possibly 09) with the ansysis FEA solver plug in. It is a little limited compared to the full anysis version. If you want I can check with the inventor user (not me) to see if he cn spare some time to analyze it. Loading will be the issue however, we would need to discuss where the loads are to be placed and what the magnitudes for them would be. :glasses:
i am not going to be able to get his time to model the subframe so if you have time to put it in that would help as well.

If you feel like trying let me know.

[email protected]

The Ansys plug in only does individual parts and not full assemblies so seeing reaction forces on the bike's frame is not possible. However, constraining the rack around the bolt holes would produce equal and opposite reactions to those on the bike's frame which could then be entered into a second analysis.

Thank you for the offer but I'm going to try a few things first. I may take you up on the offer later if I run into trouble.

 

[Opelgt]

The Inventor user seemed excited about analyzing the model, but really did not seem to excited about going down to the parking garage and measuring my bike, plus he had concerns about knowing the material properties and thickness of tubing. Yes he was aware of the part/assembly limitations...it drives us both nuts sometimes if we could only convinve management on buying the full version...including the CFD!

However, if you need something checked just let me know.

We have Inventor 08 (possibly 09) with the ansysis FEA solver plug in. It is a little limited compared to the full anysis version. If you want I can check with the inventor user (not me) to see if he cn spare some time to analyze it. Loading will be the issue however, we would need to discuss where the loads are to be placed and what the magnitudes for them would be. :glasses:
i am not going to be able to get his time to model the subframe so if you have time to put it in that would help as well.

If you feel like trying let me know.

[email protected]

The Ansys plug in only does individual parts and not full assemblies so seeing reaction forces on the bike's frame is not possible. However, constraining the rack around the bolt holes would produce equal and opposite reactions to those on the bike's frame which could then be entered into a second analysis.

Thank you for the offer but I'm going to try a few things first. I may take you up on the offer later if I run into trouble.