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Old 11-14-2013, 03:18 PM   #31
Keith
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Quote:
...So it was time to really abuse the Sherline.

What is the mill/lathe/whatever?

I tried browsing their site, but it is a jumble of links and text. It looks like a sweet little tool!
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Old 11-15-2013, 12:31 AM   #32
Luke OP
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Originally Posted by Keith View Post
What is the mill/lathe/whatever?

I tried browsing their site, but it is a jumble of links and text. It looks like a sweet little tool!

It's a model 2000 mill. I took out the ram and the Z ways and mounted the headstock directly to the bed using a spacer block that they sell. There's an addidtional block (the big chunk of raw aluminum in the picture) to raise the headstock up enough to fit the cylinder head.

Here's what it looks like from the factory:



I've got mixed feelings about the Sherline mill. I've gotten a lot of use out of it, and it is pretty small. Try finding another 10" lathe that weighs less than 60#. The downside is that there is a lot of flex and slop in it. So cutting is really slow, and it takes a lot of practice to figure out what kind of cuts it can do and what it can't. I am noticing that it does better as a lathe than as a mill. The 2000 is probably the least rigid of their mill setups
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Old 11-15-2013, 10:08 AM   #33
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Thanks for the details.
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Old 11-25-2013, 12:23 AM   #34
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No news is good news.

New handlebars added, along with a new clutch perch that has a much smoother pull. Other than that, just ride it. I have a bit over 100 miles on it since the rebuild, and the motor is doing well. There will be some more fussing with the bike once the weather turns bad. But until then, it's time to ride.


I don't know what it's called but I like it. The water gets frozen out of the ground and lifts the sticks and pebbles up in the air




Most of the puddles were thin enough that the bike punched through the ice. Not this one.




The Pacific is off in the distance. Pretty nice to see it at this time of year.
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Old 12-09-2013, 06:50 PM   #35
Roostboy101
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Awesome! I tried and failed to build basically the exact same thing. Mine ran and was rideable but I couldn't get the pipe right and didn't want to put a lot of money in it... I was using a 98 ktm 200 frame (plated) with the blaster engine. Early 80s yz tank... I'm glad to see someone did one and succeeded! It's the bike they shoulda built! air cooled, inverted forks, etc etc...

Have fun with er
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Old 12-10-2013, 12:26 AM   #36
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Originally Posted by Roostboy101 View Post
Awesome! I tried and failed to build basically the exact same thing. Mine ran and was rideable but I couldn't get the pipe right and didn't want to put a lot of money in it... I was using a 98 ktm 200 frame (plated) with the blaster engine. Early 80s yz tank... I'm glad to see someone did one and succeeded! It's the bike they shoulda built! air cooled, inverted forks, etc etc...

Have fun with er
Thanks!


Good on you for trying. Do you have any pictures of the build?


There are a lot of different 'they shoulda builts' out there. This one just bumped my Husky TE 250 from the fleet. It's definitely got less power, is probably a bit slower but is just more fun to ride.
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Old 12-20-2013, 09:28 AM   #37
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Teaser Photo

Just one photo of Luke's latest upgrade, he has many more pics and a good story to go with this...



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Old 12-20-2013, 11:58 AM   #38
Lutz
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Oooh! Shiny!
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Old 12-21-2013, 12:12 PM   #39
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Oooh! Shiny!

Yup, stainless is purdy.





So it's time for a new pipe. The first pipe on the bike was an FMF fatty designed for the blaster and modified to fit in the YZ frame. It's pretty good but I'm looking for a flatter torque curve, and a little more clearance at the side of the frame. The FMF is a little peaky (although nothing compared to the original 125 motor) and sticks out pretty far to each side of the bike.

I was inspired by this thread: http://advrider.com/forums/showthread.php?t=655547
I bought the software, plugged in all the numbers and it spat out a design. I was hoping to build the entire chamber out of premade cones and bends, but I couldn't find the right parts. So I settled on a compromise. The header and stinger of the chamber would be pre-bent tubing and the middle chamber would be hydroformed sheet.

The design of the exhaust suited this, as there is a long header section of nearly constant diameter, and then a complicated curved section with several tapers of cones. Even if the cones and bends were available, they would be very expensive and difficult to fit.


There are a few youtube videos showing how to hydroform using a pressure washer, I don't have a pressure washer and a suitable one would be pretty big. So I bought a hydraulic ram pump instead. I don't know what mine is rated for (craigslist special) but they'll typically do 6-10k psi. The burst pressure of a pipe similar to my expansion chamber is 2700 psi, so that is plenty.


The software gives the chamber design as a set of lengths and diameters. I took these and plotted them along a curve in order to get the bend that I wanted. Then printed out the outline and traced it twice on to some sheet metal. I welded the two peices together and added hydraulic fittings to each end. The pre-inflation setup looked like this:



The pump normally uses hydraulic oil, but that would be to messy. It turns out that windshield washer fluid works fine. Water might work if it were warmer out. The whole operation was moved inside after it was confirmed that a leak wasn't too messy.



The pump was modified so that it could be refilled without tipping it sideways.

I made one big mistake with the first pipe. It was mild steel and I forgot to clean off the mill scale before welding. The welds had lots of pores in them which turned to leaks as soon as the weld was stretched. I switched to stainless filler rod to patch it up and that helped a lot, but the welds were still really ugly.


The routine was to weld, refill the pipe, pump it up a little until it leaked, then drain it and weld and repeat. A pretty slow process. Having a second port on the other end sped things up considerably. After a while, the weld held long enough to get a considerable bit of pressure, and the chamber split.



This is why fluid is used instead of gas. My argon welding tank has enough pressure to form the pipe, but it wouldn't have been nearly as gentle when it split.


The results were really encouraging. The template and the first formed pipe:



The template was cut wider than the pipe (by pi/2) so that the diameter would be correct when it inflated. The other tricky bit was the curve. The curve got tighter as the pipe inflated. I guessed at how the bend would change based on the length inner and outer seams of the pipe and it turned out almost exactly right. I wanted 180 degrees exactly, and got really close. The biggest problem was the inside of the curve. The metal didn't inflate all the way and so it lost some volume there. I seemed like that was going to be the hardest part of the pipe to inflate, so instead of re-welding and trying again I gave up and made another.

Version 2 was made from the same template but from 18ga stainless sheet instead of 16ga mild steel. The thinner gauge is harder to weld, but being stainless more than makes up for it. The thinner gauge should also be much easier to form in that inside part of the curve.


Results? Excellent:




It still has a few dents in it, but it'll only take a few rides before they're dwarfed by new ones. The curve isn't quite 180, but it's close enough to fit on the bike.


So away we go. The first few sections are pre-bent tubing, and it turns out that in order to fit there's no stinger at all on the expansion chamber. Fortunately the muffler has a pipe that's long enough.






The process (if you can call it that) is to duct tape everything together in place, working from the front and back to the middle. Re-taping as necessary in order to get everything to line up. Then start replacing the tape with tack welds, again working from the ends to the middle.

The pictures are how it sits now, all the joints are tack welded. The kickstarter doesn't quite clear the new pipe, so it will need to be reworked. It's all so close it's itching.
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Old 12-21-2013, 01:37 PM   #40
TwinDuro
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Oh man, that's so cool, and what a beautiful result! As far as "trick" parts go, it's hard to beat a hand built, hydro-formed, stainless steel expansion chamber! The shop looks great as well!
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Old 12-21-2013, 02:51 PM   #41
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Oh man, that's so cool, and what a beautiful result! As far as "trick" parts go, it's hard to beat a hand built, hydro-formed, stainless steel expansion chamber! The shop looks great as well!
Thanks. The shop is great. Rick is making huge improvements. The lights I added are rather nice too, if I may say.




If you want to see the bike in action, look over here:
http://omraoffroad.com/forum/viewtopic.php?f=4&t=14360

Four of us from the OMRA forum went out last Saturday and rode some trails. It is definitely small bike country, there were 3 200 2 strokes and one 250 4 stroke
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Old 12-21-2013, 07:41 PM   #42
dirt hokie
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hydro forming, cool. now to build my valveless pulse jet
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Old 12-21-2013, 08:54 PM   #43
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hydro forming, cool. now to build my valveless pulse jet




It's probably for the best that I already sold the quad chassis.
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Old 12-22-2013, 06:21 PM   #44
dirt hokie
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Lockwood Hiller , have fun and wear ear plugs
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Old 01-03-2014, 10:22 PM   #45
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I finally finished up the new pipe today.

I added a gas line for back shielding the stainless steel. This is to stop the back side of the welds from oxidizing.


It runs off the same flowmeter as the torch. That seems to work ok, but if I do a lot of this I'll probably get a dual flowmeter setup.


I did most of the tack welding earlier, but I added some extra tacks to make it stable and then finished the seams. Some seams had good fit and were easy.




Others, not so much:




The green hose going to the tail of the expansion chamber is the back shielding gas. It fills the chamber and




Old and new:











The new pipe is longer than the old one, and the tapers are more gradual. This was supposed to move the peak power down to a lower rpm and make more consistent torque across the rpm range. My first impression riding it around the driveway is that it does do that.

I'm going out for a proper trail ride tomorrow, hopefully I won't dent it up too badly.
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