Race chassis

[guyhockley]

Guy, thanks for the video link. I wonder if he looked at Hoyt McKagen's bikes/patent before he built his KTM?

http://www.eurospares.com/mckagen/hoyt001a5.jpg

http://www.eurospares.com/graphics/c...US4627632A.pdf

It is nice to see someone do something different and actually get it to the track.

Hoyt's bikes were what it reminded me of, I think Hoyt said he had a full foot of travel on his front end. Any idea what happened to his stuff after he died?
Harry Stitt has a trials version as well. What he doesn't seem to have, considering he looks about 14, is a webpage!

[guyhockley]

One has a lathe - but one does not have the dosh for a range of milling cutters...

I do do swingarm to crosstube profiling in a jig with a holesaw though. It's the only time I do - and that's simply to accurately get the legs the same length...

One of the british factories, I can't remember which one, possibly Velocette?, used to make cutters out of tube offcuts. Guess it wasn't one of those that hearth brazed straight end tubes into bloody, great chunks of cast-iron.

[Michael Moore]

You can also make different sized rollers for a belt sander so that roller OD + 2x belt thickness gives you the diameter in the tube.

I've used a boring head to single point the cut but it is slow.

I've found it helpful to offset the cut towards the end of the tube so the "points" don't taper to a feather edge, as I've had that edge get grabbed and folded into the cut by end mills. The thin bit of tube has to be clipped off anyway as it just burns up if you don't, so set the cut so that it stops just short of getting into the wall at the outside end.

[guyhockley]

http://jebustownmotorcycles.blogspot...r-all.html?m=1

Looks like a bucket engine!

[Grumph]

Looks like a bucket engine!

Looks like a Suzuki TC120. The two cables going into the rear of the box suggest it's the dual range gearbox.
He does nice work. You can always pick work done with an inline fluxer too.
Wish filling them wasn't so expensive here....

[guyhockley]

http://jebustownmotorcycles.blogspot...brace.html?m=1

http://jebustownmotorcycles.blogspot...rames.html?m=1

Couple more posts on that blog showing more of his stuff.

[guyhockley]

No comment...

[Grumph]

[QUOTE=guyhockley;1131No comment...[/QUOTE]

"Blade Runner" comes to mind.

[guyhockley]

One has a lathe - but one does not have the dosh for a range of milling cutters...

I do do swingarm to crosstube profiling in a jig with a holesaw though. It's the only time I do - and that's simply to accurately get the legs the same length...

From: http://enigma1050.co.uk/index.php/te...uild-part-two/

"Dave Pearce of Tigcraft reckons that the Stakesys Hole Saw Tube Notcher is the best two hundred quid he’s ever spent on a piece of tooling. When you join two pieces of tube, they have to meet precisely and this is where the notcher comes in.
“You can use a file and a hacksaw to achieve the same result,” says Dave, “But it takes forever and you end throwing a lot of tube away when you get it wrong.”
To use the notcher, you select a hole saw of the same diameter as the tube you want to prepare, set the angle of the tool to the work to the same as the angle of the tubes to be joined then cut the notch. The tool is powered by an electric drill. The shaft which holds the cutter rotates on needle roller bearings in a substantial aluminium alloy housing which ensures both accuracy and longevity."



They have several models.

https://www.stakesys.co.uk/tube-notchers

[Grumph]

The problem with anything using holesaws is how the saw blade is held on the arbour. I've never seen one which used the two dog drive which didn't wobble. Any wobble and the cut is 1/ bigger and 2/off center.

[Michael Moore]

Another problem with the machine tool solutions is you need to know the angle you want to cut to and be able to set it accurately.

For a production series you'll have drawings and the proper tools to use. For a one-off that you are building around an engine/steering head placed on the frame fixture you might be able to easily do a number of 90 intersections for cross tubes with the hole saw/milling cutter, but the other tube ends, especially on tubes that have been bent to be "pretty close" may be faster to fit with saw/snips/files/grinder.

Dave is right that you can end up with more scrap by hand while you are getting the hang of things. I like to start with the longer tubes so if they are stuffed I can trim them back and have another try with them as a shorter tube.

A lot of it will depend on your hand/eye coordination and the ability to visualize how the profile will look.

If you have a very long/shallow cut, say something where the tube axes are only 20 degrees apart, you can easily run out of length on the cutter/saw arbor before you get the cut finished.

A few discreet taps with a small hammer don't seem out of order when that helps save a tube from being scrapped.

[Ocean1]

The problem with anything using holesaws is how the saw blade is held on the arbour. I've never seen one which used the two dog drive which didn't wobble. Any wobble and the cut is 1/ bigger and 2/off center.

You can cut the top out of them and weld them to a solid arbor, which you can then hold absolutely rigid in a big fuckoff collet chuck in t'mill. And the fuckers still sometimes spit teeth, fold up and turn your day to shit.

So I've acquired a small collection of rotabroaches, which work splendidly. Especially as I happen to have a 5" dual angle adjustable vice. I also have split half round jaws for 3/4", 1' and 1 1/4" tube. Anything else just gets a bit of solid up inside.

But then, most of my tube work is in 316...

The very best tube notcher I've seen was made out of a spindle moulder, with a belt roller taking the place of the cutter and an infinitely adjustable toolpost/tube clamp. Perfect.

[Ocean1]

For a production series you'll have drawings and the proper tools to use.

I have a very short attention span, there's just no way I'm hand fitting tube for more than two of the same jobs, it's going out to a laser cutting service.

Which, admittedly presupposes you've modeled the job in some appropriate system...

[Grumph]

You can cut the top out of them and weld them to a solid arbor, which you can then hold absolutely rigid in a big fuckoff collet chuck in t'mill. And the fuckers still sometimes spit teeth, fold up and turn your day to shit.

Agree - and I'm around 80km from the nearest stockist with no courier service. Disc grinder still looks good to me.

[husaberg]

Agree - and I'm around 80km from the nearest stockist with no courier service. .

Just get Mainfreight to pop one on a pallet and send it to you.