Bearings: Igus Vs Triangle Mfg

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Will Aldridge

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Maybe this will be old news to some of you but since I hadn't heard of Igus plastic bearings before a cozy builder in my local EAA chapter showed me his project I thought I'd give a short report on the differences between the Igus pillow block bearings and the Triangle Mfg pillow block bearings that i was going to use in my project before I found out about Igus.

Maybe i was just wasn't very observant but i couldn't find where to order from Igus on their site so i googled distributors and was pleasantly surprised to find that Wal-Mart sells them online and they even beat out Amazon on the price by a considerable margin. For 2 of the 1" and 1 of the 5/8" and shipping from Wal-Mart was about $25 vs $40 for Amazon.

I first heard about triangle bearings from my Thatcher CX4 plans that call for a couple 5/8 bearings for the elevator control tube. So when i was designing my plane i just found the part from triangle that i needed and drew it in, and ordered them as well. Now that I've ordered the equivalent parts from Igus i can do a side by side comparison.

20180330_202935.jpg

The larger bearings are 1" diameter and the smaller are 5/8".

First general impressions are that the Igus bearings are higher quality.

20180330_204818.jpg

20180330_204834.jpg

As you can see there's a significant weight advantage for the 1" Igus bearing. Since I'm using 2 in my build that's about 1/3 of a lb weight savings. Size wise the Igus is about .5 inches wider but only about 2/3's as tall. The mounting holes are a larger diameter so the larger bolts will negate some of the weight savings. One other advantage of the Igus is hopefully less tendency to develope stress fractures than the stamped sheet metal of the triangle housings.

20180330_210524.jpg

20180330_210602.jpg

So the Igus bearing looses out slightly in weight to the Triangle bearing and the housing is larger in every dimension, but where it really shines is in smoothness of operation.

20180330_211246.jpg

As you can see in the pic the ball in the triangle bearing is retained by 4 crimps in the metal housing which mean it doesn't change angles very smoothly as opposed to the Igus bearing which is retained around 360 degrees by the housing. You may have noticed that the ball in the 1" bearing was white plastic and red in the 5/8 bearing. The white plastic is much tighter tolerances than the red which for my purposes works just fine as the larger bearing only has to deal with rotation and the small bearing will have the elevator pushrod sliding through it and changing the angle slightly as it does (<2 degrees).

Initially I was very skeptical about using plastic bearings in my plane but the cozy builder who introduced me to Igus is no slouch. He's an engineer and his workmanship on his build is first rate. In addition these bearings are designed for high stress high vibration environments so I'll give them a shot.
 
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pictsidhe

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Igus are huge in Europe. I think they are Irish. I've used a few of their bearings. I suspect that I ordered them from Farnell, which is Newark in the US, who don't seem to carry Igus. they have a lot of different bearing types. They have some useful online tools
For dealing with vibration and oscillatory loads (vibrating control surfaces) they are likely hard to beat. They don't have the high speed capabilities of metal bearings, but at low speeds they are great, unlike metal bearings. Also cheap and light. So, probably no good as crank bearings, but great for control surfaces.
I'm sure autoreply will chime in with a 10000 word precis of their pros and cons. ;)
 

wsimpso1

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It looks like the Triangle bearings have larger angular movement available is that true? Also, any idea what the ball materials are and the stated working loads or max loads are for each?

Why do you think the Triangle bearings are likely to crack but the Igus are not? Crack growth is entirely a matter of loads being too big for exactly what materials and design you have in the parts. Not too big, no cracks... Which goes back to the question about materials and rated or working loads stated for the parts.

On this forum, we have so many really sharp folks, we educate a lot of folks, and generally maintain pretty high standards, so I expect a certain amount of competence, using the right words, etc. Wrong words get my attention. Use the wrong words, it is tough for the reader to know what you really mean. So we will hit one of my pet peeves about wrong words and making things:

Tolerance is the allowable variation in a dimension. Tight tolerances mean tiny variation centered on the intended dimension. We need sample size (quite a few parts) and precision tools and knowledge of intended dimensions to know much about tolerances on a dimension...

We can get an idea on how much clearances we have by simply wiggling one part in the other. Clearances are just that - by how much does one part clear another? Easily measured in individual parts too.

Why make the distinction? Someone who builds things needs to know if they are building stuff close enough to intended sizes for it to work. That is what tolerances are about - how close am I to intent, and how close do I need to be to get correct function out of the parts? We also need to know how tightly or loosely things need to fit together. That is clearances. And even if we have big tolerances on parts, if we need precise clearances we can make sets of parts have those precise clearances. Staking, lapping, sanding, grinding, filing, fill and fairing, etc can all be used to give what ever level of clearance is needed even when tolerances are huge.

So, if we think one part has little slop between parts and moves smoothly while another has more slop and feels rough, that is VERY useful information, please tell us that. Say "tolerances" with a sample size of two and no measured dimensions, and your educated readers know you mean something else, but have to guess at what you mean...

Billski
 

Will Aldridge

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It looks like the Triangle bearings have larger angular movement available is that true? Also, any idea what the ball materials are and the stated working loads or max loads are for each?
For the 5/8 bearing,I think they're pretty close to each other, for the 1 " bearing the Igus might have greater movement as my triangle bearing has a grease fitting that limits it's range of movement.

The 1" triangle bearing has a bronze bearing surface inside what I'm guessing is a steel sheet metal stamped ball.
The 5/8 bearing surface is nylon, triangle also offers iron in addition to bronze as a bearing surface.

Why do you think the Triangle bearings are likely to crack but the Igus are not? Crack growth is entirely a matter of loads being too big for exactly what materials and design you have in the parts. Not too big, no cracks... Which goes back to the question about materials and rated or working loads stated for the parts.
Simply a matter of stress risers in the stamped sheet metal housing. Zoom in on the pic of the crimps retaining the bearing and you'll see very clearly where such cracks could originate.

On this forum, we have so many really sharp folks, we educate a lot of folks, and generally maintain pretty high standards, so I expect a certain amount of competence, using the right words, etc. Wrong words get my attention. Use the wrong words, it is tough for the reader to know what you really mean. So we will hit one of my pet peeves about wrong words and making things:

Tolerance is the allowable variation in a dimension. Tight tolerances mean tiny variation centered on the intended dimension. We need sample size (quite a few parts) and precision tools and knowledge of intended dimensions to know much about tolerances on a dimension...

We can get an idea on how much clearances we have by simply wiggling one part in the other. Clearances are just that - by how much does one part clear another? Easily measured in individual parts too.

Why make the distinction? Someone who builds things needs to know if they are building stuff close enough to intended sizes for it to work. That is what tolerances are about - how close am I to intent, and how close do I need to be to get correct function out of the parts? We also need to know how tightly or loosely things need to fit together. That is clearances. And even if we have big tolerances on parts, if we need precise clearances we can make sets of parts have those precise clearances. Staking, lapping, sanding, grinding, filing, fill and fairing, etc can all be used to give what ever level of clearance is needed even when tolerances are huge.

So, if we think one part has little slop between parts and moves smoothly while another has more slop and feels rough, that is VERY useful information, please tell us that. Say "tolerances" with a sample size of two and no measured dimensions, and your educated readers know you mean something else, but have to guess at what you mean...

Billski
Multiple reasons for not being clear and concise enough, the main one being the only internet i have is my phone and editing a long post on such a small screen with the keypad the phone offers is tedious in the extreme. I also freely admit to not being in the top 50% of the brain trust, at least on this site. As you point out there are a lot of smart cookies here, and I don't consider myself one of them, just persistent. I just try to learn what i can and if i come across something that i think is not generally known I'll share.

As for tolerances and my meanings, they were mostly related to how the ball fits in the respective housings. Also a certain amount of hearsay in the comment about red vs white. The aforementioned cozy builder told me the white bearings were the ones with tighter tolerances so i just spewed what i remembered from 6 months ago. The red plastic balls had a very slight but noticeable amount of slop between the ball and housing and the white plastic ball was very stiff but smooth moving. On the triangle 5/8 bearing the crimps are sharp enough to dig into the nylon and leave scratches in it. The 1" triangle bearing is retained by sandwiching the ball between 2 stamped pieces of sheet metal that are clamped together by the mounting bolts and thus had no angular movement once the bolts are torqued down.

And finally as is always the case the onus is on the individual to do their own research and decide if a solution is right for them. Here then are links to the respective websites:

TriangleOshkosh (my apologies if anyone went looking for Triangle mfg and found a medical manufacturing company instead)

Igus

You should be able to find the technical info you want presented much better and more accurately than I can achieve.
 

Dana

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I use Igus bearings a lot in the machines I design for my day job, I like them a lot. Like any bearing, you have to check the usage against the manufacturer's recommendations.
 

wsimpso1

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The Igus 1" self aligning bearing has a max rated load of 585 pounds, but I could not find anything on max PV. Triangle does not list any max loads or rated loads or any other way of figuring out if a particular bearing will be OK in a particular application. Definitely not like using a ball or roller bearing catalog. I suspect they would rather have you talk to their sales guys.

Billski
 
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