Why won't these plastic inserts fit into the flex wheel

I can’t seem to fit these plastic inserts into the 1.625 flex-wheels, would it be better to use these or insert shaft collars into the flex-wheel and use spacers on both sides to keep it in. I even tried to use a hammer and they wouldn’t go in.
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It takes a lot of force to get these to go into the black flex wheels. If you’re method with shaft collars works well, is easy to use, doesn’t fall out, and is centered, I’d go for it. Personally I used a vice to get these in.

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So overall it’s better to insert a shaft collar into these, as overall they are easier to put it, and provide a more centered flex-wheel, than compared to inserts, which are much harder to put in, and bend and stretch the 1.625 flex wheels causing a less centered flex-wheel.

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Note how I said “If”.
I don’t know if using a shaft collar is better because I personally haven’t tried it.
If after trying it yourself it works good, then use it, if not find a new way and try that.
It’s all part of the engineering process.

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we use lockbars and they do the job, just need 2 half inch standoffs to put in between them

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If you have a vice, align it and squish it. If you align the insert and the flex wheel right the insert has no choice but to go in place.

I have not used the black/harder wheels… but I’d look at putting them in boiling water (NOT boiling the wheels themselves… HUGE difference) to soften them.

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People don’t usually use 1.625 flex wheels, I could only imagine it for the intake, and even then a better option is the 2-inch flex wheels. Our team was able to put on these plastic inserts with 3 people, but it was an extremely grueling process, we found that doing this, actually bent and warped the flex wheel, which resulted when we installed it for our intake, the flex-wheel being off-center. I think it’s a much better idea to use shaft collars, and then hold it in with spacers, it’s much more centered and aligned. If you plan on using 1.625 inches flex-wheel for your intake, I’d suggest removing them and putting 2-inch flex-wheels on.

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What we did was put on the back of a chair to bend it and push one side in and then turn it 90 degrees and push the other side in.

??? the hole is the same size. what are you talking about

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They don’t fit because the wheels actually have a 3/8" hex opening and the adapters are for 1/2" hex openings. So Vex just tells you to cram it in and deform your wheel. It is what it is.

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For ours, we use metal 12-tooth gears in the middle hole.

With less rigid wheels, I’ve noticed that you can spin them on the adaptor with some force, and the reason they are over sized is to prevent this. It is known as an “interference” fit.

With a 2 inch, even though the holes are the same size (I might be wrong here I haven’t tried it) I would think the wheel would deform better and it would be easier to insert.

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Yes, with the less rigid wheels, it is easier to cram the 1/2" adapter into the 3/8" hole.

Here is how you get them in.

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