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Author Topic: STD 250APS/PF build for 2010  (Read 5499 times)
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WhizzbangK.C.
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« on: April 03, 2010, 07:02:51 PM »

I started design work and building the frame a few months ago, then it got sidelined by illness and death in the family, finally recovering from all that and getting ready to start building again. I thought I should take the time to post some sort of build diary here. Maybe at least some folks will get a laugh.  cheers

To start, here's the bike as it was at the 2009 BUB meet.



And here it is in impound, ready to check displacement after bumping the class record  grin which I held from last year, to 75+, up from 54.  rolleyes



 Some may recall that I've had repeated piston failures with this engine. I think we've finally figured out what the problem is, and it's entirely self inflicted. In my zeal to get the lowest possible profile to minimize frontal area, I put the oil tank in the large down tube behind the engine. I had plenty of head on the oil to prevent aeration on the suction side, but the return was below the level of the rockers. There was not enough back pressure on the return side to force sufficient oil flow to the rockers to allow it to return through the drain holes and hit the flywheels, which in turn is splashed up into the cylinder to lube the piston. I was starving it for oil. This oversight will not be repeated, I assure you.  cheers

Next up, the 2010 build.
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« Reply #1 on: April 03, 2010, 08:38:20 PM »

The plan for 2010 is a complete frame redesign, for several reasons. The oiling problem previously mentioned is one.

Another is the fact that the old frame, being thrown together in haste 2 years ago, prevented me from mounting the carb directly to the head due to the large downtube/oil reservoir. I had to run an extended intake to the carb and this created tuning headaches, including a reversion effect that I could not get past. The long runner actually made positive pressure in a very narrow RPM range (6000-7000 RPM) but the engine would not pull well below or above that range, and I was never able to get into that range in 4th gear.

The long chain run is also eliminated in the new design. Not that it caused any problems at all, but buying that much chain gets expensive after a while.

The biggest benefit is that this design, with the engine mounted to a cradle that bolts to the top of the frame structure, does not limit engine choices. Assuming that the handling and aero work out as well as I think it will, I'll be able to step up in displacement simply by building a new engine mount cradle to fit almost any power plant I care to use. This should make it easier to run in the future by minimizing the amount of rework to run different displacements.

So, here's the basic plan in a computer generated picture, as posted on the garage wall for inspiration.



The final fairing shapes are not finalized yet, so this is just a general idea. I'm going with the principle of making as small a hole in the air as possible and leaving it as air smoothly as possible under the rules. (I was really hoping that AMA/BUB would follow SCTA's lead on rear fairing rules, maybe some day.)

The frame was designed with a CAD program that I've started learning to use, and then redesigned several times to match the reality of what I could actually bend and weld in my garage. rolleyes

I've always struggled with coping tubing for nice fits, especially when both ends of a tube need to be coped at different angles to the tube and to each other. I came up with a fixture that bolts to my rotary table to hold the tube. With the tube in the fixture on the rotary table, and a digital miter box on the tube for rotational angle, I am now able to cope tubes precisely. Combine this with the CAD program to give good numbers to work with, and I've saved a lot of time getting good fits, and money on wasted attempts.



I bought some 3/4 MDF board from Lowe's, and had them cut it in half on their big guided saw. Brought it home and glued the halves together on top of my bike lift. This made a nice flat build table that I could mount angle iron locating fixtures to, along with toggle hold down clamps that I got from Harbor Freight. (not trying to put in plugs for any vendors, just source references in case anyone is interested.)  cool



The build table allowed my to make 2 almost identical rear frame sections. I then changed out the fixtures on the table to align the sides and weld in the cross members.





Once the rear frame halves were joined I moved the assembly to my "frame jig" to make sure that the neck would be properly aligned with the rear axle slots. I didn't take any pics while that was happening, I tend to get very one track minded when I'm working on something like that.  tongue Once the neck was located and welded it went back to the table.





I then set the engine roughly in place to start setting up motor mounts. This was in late December, and is the last thing I did to it. It has been stalled since.  cry I hate trying to restart a project once momentum has been lost, so I'm hoping putting this up will motivate me to get back in gear, looking at the calendar I'm running out of time already.  shocked I still need to do some gusset work to the frame, and get the engine mounts and other tabs/brackets located, and the seat structure built. Then I'll be able to suit up and assume the riding position while someone traces my aero profile. Then I'll be able to loft the fairing shape and get started on that.

Does anyone have any pointers for making a female mold in one shot without a plug? The CAD program I'm working with will allow me to make full scale profiles from the shape at any spacing I want. I'm thinking I can take the files to a quick print shop and get them printed out full scale, and then use those prints to make an "egg crate" assembly. Fill the spaces in the egg crate with something like expanding foam and then top coat it with plaster. Paint the plaster and then wax the beejeezus out of it with mold release before lay up. Does this plan make sense or is there a better way that I'm not aware of?? I had planned to be at that stage now, but we all know that "life is what happens while we're making other plans".  tongue

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« Reply #2 on: April 03, 2010, 09:25:32 PM »

Ed, I've always been a fan of you guys and ladies, and it is nice that you have a build diary.  I learned a bit already.  Post how you build the mold and fairing.  Maybe I can toss the pop rivet gun and learn how to do things right.
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« Reply #3 on: April 03, 2010, 11:46:05 PM »

You may want to look into how the Rutan type aircraft such as the Long-EZ were built. I don't have the details, but I do know they carved a male mould, glassed it up, then removed the foam and sanded the heck out of the outside. It seemed to work well as lots were built and there are a few are still being put together.

Pete
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« Reply #4 on: April 04, 2010, 02:18:32 AM »

Ed,

Great job on your build table...effective and economical.
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WhizzbangK.C.
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« Reply #5 on: April 05, 2010, 06:41:14 PM »

Ed, I've always been a fan of you guys and ladies, and it is nice that you have a build diary.  I learned a bit already.  Post how you build the mold and fairing.  Maybe I can toss the pop rivet gun and learn how to do things right.

Well, I don't know about right, but whatever I end up doing I'll show it. Actually, I love the work you've done on your fairings. Reminds me of WWII airplanes, and I love those.

You may want to look into how the Rutan type aircraft such as the Long-EZ were built. I don't have the details, but I do know they carved a male mould, glassed it up, then removed the foam and sanded the heck out of the outside. It seemed to work well as lots were built and there are a few are still being put together. Pete

I've helped on home built aircraft before, and the problem I've seen with this type construction is getting a nice smooth exterior finish requires a lot of sanding and filling on the outside of the body work. I hate sanding fiberglass. If I can avoid having to fill and smooth I can also keep it much lighter. The inside can be rough and not make a difference. I also hate sanding foam for the plug, for that matter. What I'm hoping to come up with is a one shot female mold to minimize the parts that I may have mentioned I hate. If I can make the molds rigid enough I'd like to vacuum bag them to get them as light and strong as possible.

Ed,

Great job on your build table...effective and economical.

Thanks, economical is of utmost importance, since this whole thing is being done on a real shoe string budget, LOL.
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« Reply #6 on: April 05, 2010, 10:14:52 PM »

I'm not trying to be stubborn but you did give me an idea. It doesn't eliminate sanding the foam and you'd have to use a slow kicking resin, but maybe you could vacuum bag over a male mould. It might be the best of both worlds.

Pete
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« Reply #7 on: April 06, 2010, 07:58:43 AM »

I'm not trying to be stubborn but you did give me an idea. It doesn't eliminate sanding the foam and you'd have to use a slow kicking resin, but maybe you could vacuum bag over a male mould. It might be the best of both worlds.

Pete

The big advantage to vacuum bagging layups is that it pulls all the air and any excess resin not strictly needed for binding the fibers out of the part. The vacuum forces the layers of cloth into contact with each other, without a layer of resin between them, making a much stronger part.

When setting up to vacuum a layup, you first lay out your layers of cloth and impregnate them with resin. Slow curing and free flowing resin is a must for this. Then a perforated film is laid over the layup, followed by a layer of mat, which will absorb the excess resin. This is topped with a layer of  un-perforated film that is sealed air tight to the mold all the way around the layup. When vacuum is applied the pressure of the atmosphere pushes evenly on the layup and squeezes all the excess air and resin out of the part.

 The downside to this is that it will inevitably leave steps where layers of cloth overlap, and some ridges will be formed in compound curved areas due to the perforated film puckering. With a female mold all these flaws will be on the inside, away from most of the airflow, and will be easier to live with.

Another problem is that the mold must be absolutely rigid and air tight. Foam will allow air to penetrate from the back side and push too much resin out of the layup, weakening the structure. If you can get it air tight, foam can crush or deform from the pressure of the atmosphere when vacuum is applied. 14.5 PSI is a lot of pressure when you spread it over a large area.

I do appreciate that a male plug is easier to work with and visualize the final shape while working. It's just a couple of added steps that I'm wanting to try to bypass on this one. If it works it'll save me some time and grief, and if it doesn't I'll be running almost naked, LOL.
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« Reply #8 on: April 06, 2010, 10:54:35 AM »

I can hear Jimmy-John (STD body man) running for his passport and the first flight outta Dodge!
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« Reply #9 on: April 06, 2010, 03:48:18 PM »

Does anyone have any pointers for making a female mold in one shot without a plug? The CAD program I'm working with will allow me to make full scale profiles from the shape at any spacing I want. I'm thinking I can take the files to a quick print shop and get them printed out full scale, and then use those prints to make an "egg crate" assembly. Fill the spaces in the egg crate with something like expanding foam and then top coat it with plaster. Paint the plaster and then wax the beejeezus out of it with mold release before lay up. Does this plan make sense or is there a better way that I'm not aware of?? I had planned to be at that stage now, but we all know that "life is what happens while we're making other plans".  tongue


It sounds like you want to do a one off type construction, but reversed and pull the part off of the foam?  It's crazy enough to work, but I have never done it nor heard of anyone doing it.

I think the seam where the two halves meet will be very problematic, and end up with a lot of sanding and finish work.  Find a good solution to that issue and it will be well worth the effort I think.

Another problem is that the mold must be absolutely rigid and air tight. Foam will allow air to penetrate from the back side and push too much resin out of the layup, weakening the structure. If you can get it air tight, foam can crush or deform from the pressure of the atmosphere when vacuum is applied. 14.5 PSI is a lot of pressure when you spread it over a large area.

There are several denser foams on the market, they are not cheap, but it's all relative.  Some work quite well when soaked with heat, but not as easily with a heat gun.  Floppy like a rubber sheet when forming into shape, and harden back up when cooled down.  If you can't find what I'm talking about, I will ask around as I am blank to the name.  Aircraft Spruce and Specialty probably carries this.
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« Reply #10 on: August 04, 2010, 12:05:14 PM »

My Mother in Law had a saying, "Life is what happens while you're making other plans". That definitely applies to me this year. One thing after another has conspired against my plans to build this bike in a leisurely manner, so it's back to thrash mode I go,  smiley . Those who know me well will tell you that it's my normal M.O. I live in constant envy of guys who can get things done ahead of schedule, but in my life I suppose that's not to be.

So anyway, here's some update on what's happening with the bike.

I got a front end build for it, my original plan for a narrow Earle's type fork didn't work out as well as I thought it would, and would have been very flimsy, so I built a short girder, works very well on the limited testing I was able to do.



Got the engine mocked up in position and had to try out the riding position to make sure there would be enough clearance between the exhaust and me.



The subject of how to build a fairing quickly and neatly has been kicking around in my head for a long time. Now that I'm out of time I had to pick an option and run with it. A quick trip to the local big box home improvement store yielded some nice birch plywood in 5.2mm and 1/2 thicknesses. This will be the basis of the fairing, for better or worse. Hey, it works for boats and airplanes, so why not?

I started with a flat piece stood up right behind me in the riding position, and had a friend trace around me as I sat on it wearing my leathers and helmet. Averaged out the shape and cut 2 simple formers from the 1/2" and mounted them to the frame. Then I cut the thin stock and temporarily attached it to them.



My daughter stopped by to help, and cut some wood, provided input, and was generally very helpful all day. She was planning to come to Bub with me to be pit crew, but just got signed up for college using her GI bill, It starts the week before, so no trip to the salt for her.



Made a narrower former farther back and pulled the sides in to it to start the taper, making sure there is plenty of clearance for the engine and other stuff.



Pulled the tail ends together and clamped them. Look at that sexy shape! Unfortunately, That made it about 3 1/2 feet too long behind the rear of the tire, so some trimming was in order.



The compound contour of the top presented a slight problem to pull off. I fell back on basic boat building technique, bastardized just a bit. Cut thin strips of plywood and lay them out along the curves. I didn't get too involved with fine fitment like on would for a boat, just roughed in the shape. Glued the free ends of the slats down with bondo and layed a layer of fiberglass over them and applied resin. I used aluminum foil under the glass to prevent resin from dripping out, and laid a sheet of plastic over it to help work out the bubbles as much as possible. This gives me a single layer of glass as a cap for when I start glassing the whole thing. I'll glue the thin layer down and lay up over it. There are some dips between the slats, but nothing a thin layer of filler won't hide, LOL.





This morning I came home from work and glued the side panels to the formers. After the glue sets up on the sides I'll glue the top. Then a quick filling and sanding of the joints, and laying glass over the whole thing. After that I have to cut access doors for major components and get hinges, latches, etc installed, then paint. Should be easy. (or not)



Oh yeah, I also have to get the new piston fitted in the engine, and all the ancillary systems working, piece of pie!!

If I don't get any more updates done, it's because I'm scrambling to get this thing done, so come see us on the salt!!!



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« Reply #11 on: August 04, 2010, 12:13:03 PM »

It's rudimentary land speed vehicle building 101 -- that's what you're doing.  Don't let anyone give you crap because you're starting with wood - your work looks good and you're making do with what you've got (and can afford).

Best luck, and keep at it.
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« Reply #12 on: August 04, 2010, 12:45:57 PM »

Do you not need a rollcage to run it as a streamliner? I sure thought you did.

Or are you thiking this is going to pass tech as partial streamlined?
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« Reply #13 on: August 04, 2010, 12:48:17 PM »

It's rudimentary land speed vehicle building 101 -- that's what you're doing.  Don't let anyone give you crap because you're starting with wood - your work looks good and you're making do with what you've got (and can afford).

Best luck, and keep at it.
0.

Don't let anyone give me crap? Heck, I'm counting on it, LOL. I figure I'll be on the salt with the biggest woody there.  cheesy

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« Reply #14 on: August 04, 2010, 12:56:18 PM »

Do you not need a rollcage to run it as a streamliner? I sure thought you did.

Or are you thiking this is going to pass tech as partial streamlined?

It meets all the rules for Bub as far as the class I'm running in, APS, special construction partially streamlined. Rider fully visible from the sides and top, no streamlining behind the rear axle below the top of the rim. That's pretty much it (with a few little details here and there like fuel shutoff from the bars, etc.)

Nothing in the special construction rules about seating position, placement, etc. that I could find. If you see something that would disqualify it from running, by all means speak up and let me know.

I do know that this is going to handle more like a streamliner than a regular bike, due to the long tail and slab sides. It's an experiment I wanted to do, to see how much performance improvement I could get out of the same engine that holds the class record now. It's not as slick as I was hoping to be able to make it due to time constraints. If it works out my next move may be a much better set of body work for next year. We'll see.
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