Cecil's ride - 2017 Raleigh Kodiak 1 full suspension 27.5 plus bike with 750w TSDZ2 mid drive and rear rack dog carrier

[amberwolf]

Mostly thru breaking things and having to fix them in a way that won't next time.

I've been fixing badly-designed racks for a really really long time, and started building my own when I got sick of that, cuz there's not that much out there made to *actually* carry 30-50lb loads.

(they might be able to hold up a 50lb load just sitting there, but not with the bumps and potholes causing inertial "increase" of mass via acceleration, or the "wag" of pedalling/etc. causing cyclic stress on all the joints of the support structure, etc.)

[John and Cecil]

Yes, you have me thinking now too. I will probably add the drawer sliders to the front because I think that those 8mm alum struts will be the next to break, and I will start working on a new design from scratch that has a better support structure and a carrier for Cecil that is not so heavy. I appreciate you sharing your wisdom!

[John and Cecil]

Well I hopefully made the final revision to Cecil's carrier (aside from painting the new parts and adding a tail light and maybe a convertible sun shade. I removed the 8mm aluminum upper rack struts and replaced them with a pair of steel drawer sliders that I cut and drilled to fit. I think the steel will hold up better as steel will flex and bend rather than snapping like aluminum. It seems very sturdy and hopefully we can put a lot of miles on it until such time as I can design and build a lighter carrier (with better side to side triangular support as Amberwolf suggested).

[wturber]

I think you should add an extra set of struts that go from your forward mounts directly down to your lower attachment point near your axle. That will create a fully triangulated structure that will be very rigid and largely devoid of bending loads. Right now, that short strut is putting a substantial bending load on the upper portion of your rear strut. Take a look at the red arrow. Now imagine a large vertical load. Now imagine that your bolts are all just finger tight like they were hinges. Your front strut is going to want to pivot at bot of its attachment points.The same would be true of your rear struts except that you have those two small middle struts that attach to the rear struts. So as the whole assembly starts to pivot, a large bending load is applied to the attachment point of those rears struts. That makes the structure less rigid and that is the weak point of your structure.

If you add a long strut from the front mount to the lower attachment point (yellow line), all of the structural members will be in either compression or tension as far as vertical loads are concerned. Even if the bolts are just finger tight, the structure would be pretty rigid. The small middle struts would no longer be needed and could be removed. If you want to save weight, you might consider using 1/2" aluminum tubing rather than steel shelfing rails. That's what I'm using.

[John and Cecil]

If you add a long strut from the front mount to the lower attachment point (yellow line), all of the structural members will be in either compression or tension as far as vertical loads are concerned. Even if the bolts are just finger tight, the structure would be pretty rigid. The small middle struts would no longer be needed and could be removed. If you want to save weight, you might consider using 1/2" aluminum tubing rather than steel shelfing rails. That's what I'm using.

Thank you, I will give your suggestion some thought. I was hoping to build an entirely new setup but that may be a while. I have pretty much given up on saving weight, it is an exercise in futility at the moment.

I have a couple extra steel drawer sliders that I used for the upper and lower struts. I cannot mount them on top of each other though as you have suggested, well maybe with some sort of spacers. Perhaps I can mount a middle strut that bolts directly to the front strut (about 2-3" from where you suggest) and have it extend down to the bottom of the lower strut (again about 2" from where you suggest)? I would leave that small aluminum cross brace on as well, that is only part left over from the original rack.

Something like this maybe?

rack.JPG (173.67 KiB) Viewed 194 times

[wturber]

I'd mount them on the inside of the aluminum L bracket and the other side of your lower bracket so that the flat faces of each new strut is facing the flat face of the existing struts.

If there isn't room on the lower bracket, then mount it about an inch above the existing bolt. Get it close, but not so close that you don't have a good enough amount of material left between the two holes.

BTW, this will make the setup pretty rigid. It's possible that Cecil's current ride is being cushioned by the current setup's lack or rigidity. So make sure he has enough cushion. Maybe also consider lower tire pressure.

[John and Cecil]

Actually it is pretty rigid now. I have those bolts tight and the drawer sliders are coated with enamel or something and they really grip well. I carried 40lbs of groceries home the other day without any problem, and I can push down on it with 50-60lbs of force and it does not budge at all. It is pretty strong side to side too, much stronger than it was with the aluminum rack underneath. I think the aluminum was the problem, the steel holds up much better since it will flex a bit. Cecil has lost 2 lbs over the past couple months too. If he can lose another 1-2 lbs it will be a huge help, plus I moved the tools, pump, etc up front. But the summer is coming and that means we will be carrying 5lbs of ice water back there too. If I can replace his wooden box with a plastic crate I can probably shave 5lbs off his carrier, but the wood box will withstand a fairly substantial impact.

The tire pressure needs to be quite high, otherwise it is brutal to keep it moving with the 3" tires. He has a nice camping mat under him though and he doesn't seem to have any comfort issues. I really need a mirror so I can see his face when we ride though, that is the only way I can see if the bumps bother him. I will probably get him another cushion eventually too, but we only ride about 2-6 miles at a time now. I know he would like an opening in the rear so his tail could hang out however there are too many asshats in the world and I am afraid someone will yank it from a car window or something.

Thank you for the advice, it is much appreciated. I will have to see how much clearance I have inside the aluminum brackets to the tires.

[amberwolf]

Something like this maybe?

rack.JPG

The closer the connection points are to each other, the better the triangulation and the less stress on every part.

It should be possible to flip the new diagonal slides over and file or cut (hacksaw) or grind away just enough of the "L" rail on each side of the main flat area at the mounting end point to allow it to fit under the existing rails and up against the dropout/frame.

Without the L portion all the way to the end it won't be as stiff at that end but since it's just triangulation tying two points together, it makes less difference than it would to the other (vertical and "horizontal") struts.

If it could be welded along the mating edges it'd be better, but bolting the flat part is good enough for this.




Regarding the mirror, if you have a celphone, you could temporarily mount it to the back fo the seat and leave it recording video while you ride, then watch it later to see how he behaves thru all of it. Since the phone is on hte seat and he's on the suspension, you 'll be able to see when you hit bumps cuz he'll move up in the vid, and when you hit holes he'll move down.

[John and Cecil]

Thank you. I will see what I can do but my capacity to fabricate is severely limited at the moment. I have already sold 90% of my tools and most of my parts collection is gone. I don't even have any wrenches or sockets anymore. I only have a small set of crappy homeowner tools to be able to make some house repairs if needed until it is sold. I probably sold 1000 lbs of tools.

I don't have a cell phone either, but I do plan on getting a crappy burner phone when we leave California. We will need a new phone when we get to Europe anyway. I don't think he is uncomfortable though, he lets me know when he does not like something. He actually nudges me in the back with his nose when we go to slow The bike suspension does not do very much anyway, especially the way I have it pumped up as stiff as I can get it. He has 85,000 miles already in his box from the motorcycles!