Need trim router advice

[SPINNAKER]

So I am going to finally start building my 7th Sojourn and need help. You can try and steer me to another design if you have valid reasons. But the 7th will make what I want it to, and what I really want is to learn the process.

How can I express this PC? I don't like chincy stuff so I plan on using drill rod for rails right from the start and servo motors and better software etc. are not highly constrained financially right from the start. I want it to be better than a stock machine as I will be making competition grade RC sailplane tails.

I need help with everything but right now I want to validate my design choice before I start and select the best trim router for it. Not likely that I will be running it with a Dremmal tool. Maybe a Rotozip. As a Carpenter I know that the Porter Cable trim router is not square. The Bosch is square, at least for carpentry purposes. Maybe it does not matter, as it will be fixed in a little 3 sided cage.

What I do know is that I have been checking the play in the bearing of these small routers/Dremals and Rotozips by hand for the past two years every time I go into a tool store and can't reach a decision as to what one to get. Just becouse there is no slop before it has a couple hours of run time on it does not mean it will be tight after 5 hours. They all have slop, seems like too much. Maybe I am too picky, as there might be bending and vibrating in other things beyond control in a machine of this type.

[I]I know that accuracy starts at the tip of the cutter and what I am getting at is that you guys have hopefully reached concensous as to what is the best moter to drive that cutter for a machine of this size[I]

Seems like they all have too much slop, please help!

Thanks!!

[ger21]

Originally Posted by SPINNAKER You can try and steer me to another design if you have valid reasons.

Is the fact that as soon as it's done you'll want something better a valid reason?

Changing from gas pipe to drill rod won't make any difference at all. You'll still get flexing. Anyone here who's built a machine with unsupported rails will tell you that they flex. You won't gain any accuracy, you'll just spend more money. And you'll be building a better machine when you're done anyway, so why spend the extra money.

And servos on a machine like that will be a waste of money. Steppers will give identical performance and accuracy for probably 1/4th the price of servos.

If you want a better machine than the stock design, go with a better design. 5 years ago John's designs were about all that was available. But if you spend some time reading through the threads here, you'll see that no one here is building them. I honestly haven't seen anyone on this forum build one of John's designs for several years. There are better, free plans available here and elsewhere. Not knocking John's plans, or designs. He's done a tremendous amount for Hobby CNC. But I think his primary goal is to build a machine cheap, and easily. Not necessarily heavy duty or high precision.

As for the spindle, you might want to look at a Bosch Colt. A little bit bigger than a laminate trimmer, but smaller than a standard router. And variable speed, too.

[SPINNAKER]

Thanks for the help Gerry, can you suggest a design? Can be bigger than the 7th but not too much, and I would like to stay away from welding, but could get it done.

Yeah variable speed would be a very good feature. I will check out that Bosch this afternoon.

Thanks.

[ger21]

I didn't realize that the 7th was such a small machine, at only 9x14 cutting area. I really don't know of any other plans for anything that small. I was going to recommend the Joe2006 design. There's a forum here. http://www.cnczone.com/forums/joes_cnc_model_2006/

But it's a much bigger machine than you wanted. At such a small size, the 7th might be your best option. But again, don't spring for the drill rod and servos. But I'd give it plenty of power and some good acme screws.