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Learning how to build Lotus Seven replicas...together!
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 Post subject: Re: sprite into locost
PostPosted: January 29, 2015, 5:17 pm 
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Joined: January 31, 2008, 5:34 pm
Posts: 746
Location: SW Wes Consin
Lonnie
I have a wheel which I bought in my bike part days and now I wish it were bigger although Mark Gerisch (a man of average height) says that big wheels are good for big panels which require TWO people. So move to Wes consin and we'll start a maker space.

My first day back in the shop after the flu followed by roaring ear infection and I have come up with my buck fix todo list:

fix the baby butts at the buck’s centerline stations
fair everything in better
cut in the side trim tubing and detail
refoam the tail light
add some cross supports to the bottom of the buck frame
add some fittings to the buck frame so I can disassemble it into two parts
build a collapsable (for storage) layout table (4x4)
paint the table and the frame
if I have time finish the lower side panels
figure out the flip-up bonnet

So right off the bat I am in REAL trouble the baby butts are at the centerline of the buck and exist, to some degree, at every station. This seems to be an error in lofting. It comes from using an almost flat curve as the curve moves out from the centerline at each station. The baby butts are only 1/8" to 3/16" so the stations aren't far off. But it makes a big difference trying to raise a panel that spans the centerline. The panels look right but don't match the buck at the centerline. I bet Signor Anderloni never made this mistake. :cry:

The fix ???


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 Post subject: Re: sprite into locost
PostPosted: January 30, 2015, 4:00 pm 
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Joined: October 24, 2008, 2:13 pm
Posts: 4160
Location: Carlsbad, California, USA
Is there a photo of what you call the "baby butts" in your build log? I'm not sure what you mean by that term.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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 Post subject: Re: sprite into locost
PostPosted: January 31, 2015, 4:27 pm 
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Joined: January 31, 2008, 5:34 pm
Posts: 746
Location: SW Wes Consin
Baby butts are an fit up problem in metal shaping when two parts of a body, like the hood and it's mounting surface, don't have matching tangent surfaces. Like a baby's butt. This is generally caused by excess crown being put in one of the panels. In my case it was caused by the surfaces on either side of the centerline being too flat. Because of this the panels that lap across the centerline would have to be uncrowned. I guess raising a panel with a flat in the center might be possible but I don't think it would look right. The photo shows my fairing sweep clamped to one of my stations and shows the gap between it and the buck that results from the buck being almost flat in this area. As is often the case with complex surfaces it gives the illusion of being a baby butt.

I hope this makes some sense.


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 Post subject: Re: sprite into locost
PostPosted: January 31, 2015, 5:41 pm 
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Joined: October 24, 2008, 2:13 pm
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Location: Carlsbad, California, USA
I still can't visualize the correlation to a baby's butt, but (no pun intended) here's my take on it.

Your curvature, side to side is too flat, like here:
Attachment:
File comment: My perceived flat curves
Locost-1.jpg
Locost-1.jpg [ 27.53 KiB | Viewed 3246 times ]


How about getting some of that inexpensive, shape-able foam (comes in red, blue) from Home depot. Ripping some strips of it to suit, gluing it on to your flat areas, and shaping it with Stanley Surform tools?
Attachment:
File comment: Blue foam, glued, shaped and faired.
Locost-2.jpg
Locost-2.jpg [ 30.63 KiB | Viewed 3246 times ]

Attachment:
File comment: Stanley Surform tools.
Locost-3.jpg
Locost-3.jpg [ 57.07 KiB | Viewed 3246 times ]


Use your fairing strip to get it right?

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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 Post subject: Re: sprite into locost
PostPosted: January 31, 2015, 6:05 pm 
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Joined: January 31, 2008, 5:34 pm
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Location: SW Wes Consin
You are correct as to the problem.

Your solution is possible but I can band saw some pieces in plywood and do pretty much the same thing. Ply being preferable as bucks get a lot of abuse. Either way it will be a lot of stations and a lot of work :(


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 Post subject: Re: sprite into locost
PostPosted: January 31, 2015, 6:19 pm 
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Location: Carlsbad, California, USA
What did you use to layout your body shape (the curves you want the skin to take)? How did you then translate the characteristics of the curves to dimensions and shapes on the plywood used to make your buck?

I'm really curious as to the process you used from start to finish. I'm assuming some software was used in it somewhere. Or, did you do it all by hand?

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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 Post subject: Re: sprite into locost
PostPosted: January 31, 2015, 7:54 pm 
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Location: York,Pa
I like to know how you made your buck as well. I read your build log awhile back and I don't remember seeing it in detail. I have a Ron Covel video that explains it pretty well but he copies an existing body to make the buck. He made templates off the old body and transferred them to the buck. I was making my mock up to get a shape that I like but also something to take templates from.

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 Post subject: Re: sprite into locost
PostPosted: February 1, 2015, 1:58 am 
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Location: SW Wes Consin
Yea that Ron always taking the easy way.

Picture this I live in the sticks in Wes consin. I have seen one 166MM in the flesh but I have collected about a thousand photos. I wanted that shape for my locost but I had to scale it to fit my Sprite parts. During my design for money life I did a lot of cad work in 3d but I have been out of it for quite a while (17 years) and know how time consuming it can be. So I decided to use my 2d cad with it's infinitely large drawing board. Like Signor Anderloni with his full scale drawing board. 3d seemed too much work.
First I made front, back, top and side outline views using the photos as guide.
Next I sliced the top and side views at regular intervals, with more slices in high shape areas.
Then I used what ship builders refer to as lofting to draw the contours in the end views.
I plotted the contours onto paper and then cut them out in beaver board.
Finally I cut them out of 1/4" plywood and glued them to my ply covered buck frame.
All in all a pretty simple old school technique. If you would like a more detailed explanation I post under crocksnrockets on the MM site.
The baby butts in my case are actually an optical illusion. Like when a flat panel looks concave.
Oh, I built a number of small scale models to.


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 Post subject: Re: sprite into locost
PostPosted: February 1, 2015, 12:59 pm 
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Location: Carlsbad, California, USA
OK, I understand now. I was thinking your CAD program (I assumed it was done in software) just didn't have the right kind of curves available and let you down. It's too late now, but there are some less expensive tools available now that could have helped you out and made it easier to loft, even if you did the final lofting by hand.

One of these tools is MOI (Moment Of Inspiration) which is $295 and a much simpler program that Rhino 3D, but written by the same guy. You can check it out here ==> http://moi3d.com/ You could have caught those curvature issues very early on.

Well, it's crying over spilt milk now. I sure hope you keep going though.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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 Post subject: Re: sprite into locost
PostPosted: February 1, 2015, 1:36 pm 
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Joined: August 19, 2014, 5:17 pm
Posts: 685
Location: England
vroom wrote:
This is my stump cut to height after waiting 4 days to get my chain saw repaired. The stump is wet oak so a hand chiseling was slow going. So now I'm waiting for one of those 4 1/2" grinder discs with chain saw teeth. (A combination of the two most dangerous tools in the shop.) :shock:
This thing is HEAVY I can barely lift the chunk I cut off.


I was at an ARB show recently and there was a guy with one of these air chisels, made very short work of his carvings.
Its a shame there is a pond between us because we have plenty of timber off cuts going begging.

https://www.youtube.com/watch?v=FsoY6MLbhoM

Bob

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 Post subject: Re: sprite into locost
PostPosted: February 2, 2015, 1:28 pm 
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vroom wrote:
If you would like a more detailed explanation I post under crocksnrockets on the MM site.


Found your build log, I registered and I'm just waiting to be activated so I can see the pictures.

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1930s Style Sports Car viewtopic.php?f=36&t=16888


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 Post subject: Re: sprite into locost
PostPosted: February 2, 2015, 2:35 pm 
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Joined: January 31, 2008, 5:34 pm
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Location: SW Wes Consin
Lonnie
Thanks for the tip on MOI interesting but I am really trying not to be distracted from actual metal shaping. Maybe for my next build.
87k
Warning there lies monsters!


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 Post subject: Re: sprite into locost
PostPosted: February 2, 2015, 6:02 pm 
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Joined: October 24, 2008, 2:13 pm
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Location: Carlsbad, California, USA
Yes, I fully understand. It's not really helpful to you at the moment since you're 90% there now.

Conversely, I'm not in metalshaping mode at the moment. Rather, I'm in design and fab mode on the chassis, so I can get a basic roller, ASAP. I've tried to stop thinking about all else, but that still involves a lot like suspension design, steering, fuel system, various mounts, braking system, etc. Metalshaping is more exciting to think about though.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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 Post subject: Re: sprite into locost
PostPosted: February 4, 2015, 6:13 pm 
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Location: SW Wes Consin
Got the butts fixed by extensive use of the sander and some little glue blocks for the worst stations.
Managed to tear up an edge on the cockpit surround trying to put in a groove that would also hold the support tube. I filled in the FU and now I'll use a round over bit instead :BH:


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 Post subject: Re: sprite into locost
PostPosted: February 5, 2015, 6:21 am 
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Another idea for rib adjustment.

Cut out 4 inches of rib, add a guide fence behind rib about 7 inches wide, adjust cut out rib contour, clamp to fence and drill then screw. Add front guide/doubler to adjust longitudinal position of top of rib and for support. Standard drywall screws would be fine.


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