Last year we had a lot of problems with our dowel pins flying out of our transmissions. I was thinking of maybe tack welding them…Can any one see anything wrong with this idea, Other then the fact that we will not be able to take them apart??
Bfirst
You have to be a little more specific as to which dowel pins you are talking about. If you are using pins through a gear and shaft to hold it together (assuming a solid pin and not a spring pin) you can use a center punch to spread the metal at both end of the pin. Again you will not get the assembly apart without damage. Another trick that is harder to do is to cut a slot for an “E” ring around the outside of the gear and use the ring to hold the pin in place.
We had a similar problem in 2001 and ended up wrapping a velcro strip around the gear to keep them in, this temporary solution served us thru the rest of the regional and nationals, and never had a problem out of them agin.
If you use a drop of locktite, the pin will not come out. You will still be able to drive it out with a punch if you need to service the gearbox.
Be sure to use solid dowel pins, and not roll-pins, or spirol pins. These are not nearly as strong. We sheared several last year.
I like the “locktite” idea. Im thinking of just using solid dowel pins and then a drop of locktite.
Loctite is the best invention ever (maybe even better than Duct Tape).
Loctite is VERY pricey tho, and when you’re buying it (and I think you should, it works wonders) make sure you get the right “modle” of it - There are various kinds of Loctite for different uses (some for plastics, some for metal, etc).
Another, cheaper, solution our team also did last year, is just put a tie-wrap around the pin that is coming out. Just make sure it is as tight as you can get it, and then cut off the excess (so it doesn’t get in the way of things).
Keep in mind, Loctite is FOREVER, so don’t use it on things that you will have to take apart.
so then we should just go with the Loctite, and forgot about tack welding them?
*Originally posted by BBFIRSTCHICK *
**so then we should just go with the Loctite, and forgot about tack welding them? **
Personally, I would just go for the Loctite.
The welding is probably a bigger pain than it’s worth for the pin.
A little caveat is appropriate here…
Loctite does come in various forms, some for permanent locking of threaded devices, some for eventual disassembly. However, none of the products are immediate setting except those containing cyanoacrylate. They require at least 24 hours or more to set up. A heat gun carefully applied can speed things up a bit. They also tend to migrate, i.e. from the pin to the shaft to the gear to the bearing, so apply with caution. I use Locktite 222MS for small fasteners that I need to get apart later. Also, a mechanical guy on our team has pointed out that a pin inserted off center to the shaft has a better chance of not shearing. That is to say, drill the hole so that it does not pass through the center of the shaft, but slightly to one side. I think he called this a “Dutch Pin”.
I would say just use the center punch idea. Peen the edges in about 4 spots. The dowel won’t come out and the nice thing is you don’t have to worry about how to get it out you just file the peens off and the dowel will come out. Then you can just repeen the hole. Another alternative is to use something called a taper pin. It’s a dowel pin with a taper. You have to get a special reamer to use one but they hold great. Sometimes to well. Tapers are a great friction holding device. You can also use loctite just use the right kind. Sometimes it helps if you grind a little flat on the pin just in case your hole is to close to the size of the pin. You need so much clearance for loctite to work right. I can’t remember what it is but if you don’t have it all the locktite gets squished out. Another trick it to make your hole smaller. You take a ball bearing and place it over the hole and hit it with a hamer it with mushroom the hole over on all the sides uniformly so the dowel will still be centered.
Loctite 609 or 680 is a cylindrical adhesive. Why not use that to hold it in place? My book says you can use it to hold gears in place so why not use it for a little pin. Of course you could overdose it and use all of the ideas so the pin will stay in there no matter what.
You need so much clearance for loctite to work right.
According to my book, the gaps should not exceed .005inch for the 609 and .015 inch for 680.