BX project: trash that air cleaner strap!

[UncleAl]

I opened my hood the other day to do my 100 hr oil change and found a broken air cleaner strap. (I've been expecting it.) I decided to try something different. The root problem as I see it: engine vibration causes the air cleaner housing to "wobble" excessively on top of the bracket, eventually causing metal fatigue and breakage of the strap. What is needed is a better "cradle" for the housing and a better strap to hold it in the cradle. Here's what I came up with.
I added a second bracket to the original using the original nuts, bolts, and lock washers. The rest of the original strap hardware is discarded. I tried to keep the bracket as original as possible, but the welded on "wings" work well, so I compromised originality here. The revised bracket assembly now forms a shallow "V" for the housing to rest in, which is more stable than the single, flat, factory mount. This configuration also allows the bracket and housing to maintain clearance over the injector pipes and under the hood. (Overall, the air cleaner housing is in the same location as before.)

 

[UncleAl]

In this picture, you see the revised bracket in place on the engine, waiting for the housing to be attached.

 

[UncleAl]

Here's the finished product. The wings allow the use of standard hose clamps. My local auto supply shop didn't have any hose clamps bigger than #64, which is about 1 inch too short. I bought two and added 1 ½ inch clamps to acheive the needed length. Note the "head" part of the clamps are offset from the top of the housing, which maximizes hood clearance. The other heads are under the bracket, out of the way.

 

[Junkman]

It always amazes me that TBN members can resolve problems with out all the technical expertise that is behind Kubota, when Kubota can't or won't do it themselves. Great idea. Mine hasn't broken yet, so I will wait and then give your method a try. Thanks for the pictures.

 

[r0GuE]

I don't know if mine is different than the ones that are breaking... I have 125 hrs and no breakage BUT, I do experience the hose clams vibrating off because my air cleaner pretty much free floats in that huge band that goes around it. There is no definitive grip on the cleaner, the band is much bigger than the aircleaner.

 

[bluecon1]

Great idea. I'll be doing that modification to mine. It finally broke after 500 hours. I temporarily TIG welded it to get me by until a fix like yours came around. I'm sure that the number of hours before this strap breaks has a direct comparison to the amount the engine is at a lower RPM and shaking more vigorously, but what a piece of crap it is to begin with.

 

[gsxr1100]

It seems that they could also stop a lot by just adding an isolator on the base of the bracket. By looking at the bracket I think the base, where it goes in the bend or radius will be stressed and vibe cracks overtime. I do not know the material so I do not know the natural freq. of it. Notches on the part effect the fatigue limit, also if it shot peened will effect it. How about where it mates is it clean (no rust) or is the mating surface galled? These will affect the material limits in some form.

Also if I remember correctly most metals under fatigue loading have a limit of like 50% of the tensile strength. So if the material has a limit 40,000 lb/in sq it will be only 20K lb-in. Also you need to use the right equations, do you want a cycle life of 2 million, 10 million etc. Also how much time will the engine be idling for max vibe? All these affect the parts and how they are designed.

The new bracket UncleAl made looks better then Kubota’s! /forums/images/graemlins/smile.gif Unless it has a high load on the bracket for shear on the bolts, it should not brake as soon.

If I was Kubota I would widen the flange part to be as wide as the base plate. If I was to aid in UncleAl design, I would have used two smaller bolts in the plate to help reduce stress from the holes of the plate. Then welded it all around. Maybe if needed for deflection (and thus reduce stress) add a small rectangle center brace (like a cantilever beam)


Ok class is over….

 

[UncleAl]

I figured (hoped) some engineer types would weigh in. Please view my ideas as simply a starting point. Maybe together we'll perfect the project. Thanks, all, for your comments.

<font color="blue">"A pessimist sees the glass as half empty, an optimist sees it as half full. An engineer sees it as being twice as big as it needed to be in the first place!"</font> /forums/images/graemlins/smile.gif

 

[gsxr1100]

At least you are bringing this to the table; which I like that. I am not a "master or chief engineer"; at all, just a lonely mechanical engineer looking for the normal, fixing the world /forums/images/graemlins/smile.gif kidding ....just trying to make a living.

Oh, I would have to guess here, but things are not that simple to change in the manufacturing world. Aside that people hating change; things like testing, design, configuration management, tooling, operation support, purchasing etc all come in to play. So it would take sometime to get a new bracket out on the market.

 

[UncleAl]

I understand. It's probably cheaper for any manufacturer (not just Kubota) to replace inexpensive pieces that break under warranty than to fix the real problem. Once the warranty is gone, easy money! That's partly why I'm being proactive about this, even within the warranty period - I have a hard time spending money (probably over and over) for something that should have been done correctly in the first place.... /forums/images/graemlins/tongue.gif