GianFrancesco

hops!
sorry: addensed mix = thickened mix

abufletcher

No problem. I understood just fine: "a dense(r) mix..."

abufletcher

Here's a key fact for the Benz dummy: The scale distance from the engine center line to the flat top of the cylinder is 95mm. So I need to superimpose that height over the kit plans and see how much stands above the engine mount beams (and ply flanges).

Or 30mm from the engine center line to the bottom of the cylinder flange.

abufletcher

I've put together a photo overlay that looks right. But, OF COURSE, the photo upload isn't working. I'm beginning to think this is a time-based problem.

Mein Duff

Congrats Don for hanging in there and getting these done...yes, some of ths scale stuff ain't easy, it's tedious, and it does take the right frame of mind to "get er done"...This will all be of even greater use in the future...the lessons learned will be invaluable down the line.. Looking forward to seeing your engine come together.

abufletcher

The red overlay shows the scale position for the Benz and would involve cutting off about 5mm from the base of the cylinders. The blue shows a "fudged" position with the cylinders (uncut) on top of the engine bearer (separated by a 1/16" ply flange).

geezeraviation

My Feedback: (3)

Hard to split hairs over 5mm, does not cutting them off simplify the entire engine installation or does it just mean you dont have to cut the cyls off? In other words what are you getting for what you're giving up.
Doc

abufletcher

I'm tempted just to let those 5mm slide. It would be so much simpler if I didn't have to cut off the bottom (which I know is flat and level because of how the master was constructed).

But Flying Fox's great work on his crankcase inspired me to "fake it" with the illusion of looking down on the whole thing. I can use some shading to create the impression of depth. So I started looking at the top view to use as a template and base for the dummy. Unfortunately, the drawings I'm using (from the DF) are both degraded and partially suspect. For example, the side view doesn't like up perfectly with the top view and I had already determined that the cylinder details weren't quite right. Also the sides of the crankcase (for example the bolt holes) aren't exactly aligned. So I decided to use my old trick of copying half and mirroring it to create a symmetrical drawing.

And in doing that I noticed something VERY interesting! The cylinders are NOT centered on the engine center line! As a non-engineer that seems very bizarre to me. Is that normal? Or is this an error in the drawing?

abufletcher

Note that on the benz IV drawings the cylinders are dead center.

GianFrancesco

For me it is an error of the drawing; the offset of the cylinders, my opinion, would be a nonsense for balancing of the forces toward the crankshaft

geezeraviation

My Feedback: (3)

I know of an American 6cyl engine that while I believe the cyls are centered on the crankshaft, the piston pins (wrist pins-grudgeon pins) are not centered in the piston. The object being I believe to provide additional torque due to the angularity imposed on the connecting rod even at top dead center. May bear no relation to what you have found and Gian may be correct and its an error in the drawing.
Doc

Mein Duff

I also don't see the need to cut off the 5mm from the cylinders..hardly noticable in the end effect, unless it causes problems with getting your exhaust system to line up to a relevant position?
I think the missaligned top view was just a hasty drawing blooper on somebody's part...doesn't make any sense to be offset.

TFF

http://thevintageaviator.co.nz/proje...engine-gallery

abufletcher

Hmmm...almost makes me want to start work on a second set of Mercedes cylinders...[&:]

abufletcher

If it's an error in the original drawing, it's an error that's repeated in both the top and rear views! It seems like such a ridiculous error to make...twice.

Flying Fox

Don, your mold making process has been a fascinating tutorial for us all. I have no experience whatsoever with this method but from what you have shown us step by step it looks like it has great potential.

In spite of a few teething problems with the resin cast the cylinders look really great! The next time you try it you will know what to watch out for.

I understand you have to spend a lot of time perfecting the first master cylinder for the mold but then isn’t the bulk of the work done for the remaining castings – I’m thinking if you made each cylinder individually from wooden disks by hand you would still have to do all the major sanding, shaping, and finishing, six times over. With casting, most of this grunt work seems to be finished up front. Either way with resin casting or disk buildup method you still have the final touchup and finishing so this aspect cancels out with either method. Which method do you think is easier to do? Also you must consider replicating the six cylinders exactly. With the wooden disk method it is quite tedious and time consuming to get each cylinder just right.

I’m not sure but it would seem that putting in your time and due diligence on the first cylinder knowing that the six castings will turn out very nicely equates well with making each cylinder by hand out of wood and then sanding, shaping, filling, etc. I know you prefer wood over resin but now that you’ve had time to reflect, what do you think about this?

As for the resin cylinders, what king of adhesive will you use to glue the cylinders together? Would something like Gorilla glue (a glue anything to anything) work? Is the resin hard like fiberglass or soft like rubber? Does it sand easily or is it quite strong and difficult to sand and shape once cured? Sorry for all the questions but I am about to work up six cylinders for my Benz Bz IVu engine which is very similar to yours. I have built up construction approach that I will post when I get to it but your excellent work on casting the cylinders has me considering this option.

Cheers,
Brian

Flying Fox

Don,

Be very careful with these simplified drafted "sketches" of the various engines... as you are discovering they often contain many, many errors. In drafting plans for my Benz Bz4u enging I noticed so many errors in the engine 3 views that I could not rely on them at all. I had to find better engine plans and rely on photos as well. In fact I basically abandoned them once a more detailed engine plan was found. It took many hours to sort out. For example, in drafting up the overhead view for my Benz Bz4 engine I noticed the main camshaft was centered in the front but offset to the right or left (can't remember which way) at the rear of the engine. At first I thought maybe it was built in right thrust but it was more than one degree. This did not make any sense because it is a straight shaft that drivers the propellor. Research revealed that the actual engine itself was offset a degree or so for thrust by the way it was mounted on the engine bearers in the airframe. Like yours, the offset was substantial, and it was/is an error in the sketches.

Check your photos and other documentation, and the the Vintage Aviator website provided by TFF. I think you will find that these drafted "sketches" as I like to call them are just that - they are fairly accurate sketches but can not be considered totally reliable for measurements, etc. Try to have confirmation from secondary sources, photos, engine manuals, etc. I might have a manual on your engine in PDF form. If so I will post it to you.
Good luck.

Cheers,
the Fox

Mein Duff

Now that cylinder offset is really bizzare...we better call in the experts on this one, this defintely needs to be clarified or I won't be able to sleep !![:@][&:]

abufletcher

I suppose the process itself, once you have all the materials, is fairly simple. And of course, getting those materials in the US will be a lot easier and cheaper than getting them here in Japan. The problems I had with the silicone not curing were largely my own fault. On the first half of the mold I didn't use enough of the catalyst (no information given on the bottles even in Japanese) and the temperature was too cold. On the second half I used a LOT more catalyst, stirred it for over two minutes, and put it in a heated room. And by the next day it had set but was still a bit tacky and by the day after that it was ready. So If I had done it right the first time, it would have taken 4 days to get a mold ready. I suppose that's not unreasonable.

True. But I won't be trying again on this model. I've already spent well over $100 on casting supplies (and that doesn't count the $100 I spend traveling to the hobby shop in Osaka). I suppose I could have ordered in online somewhere and waited a month or so for it to arrive.

Doing six cylinders by hand would undoubtedly be "more work." However, given my situation, I'm quite certain I could have done that work in half the time it ended up taking to do the casting THIS TIME. Next time, it would be more efficient so next time the casting would probably be faster. It did take me a couple of days to produce the master. But once I had everything figured out, I think I could have made each of the other cylinders fairly quickly. And a lot of the work was cutting and shaping all the disks by hand. Had I started with a set of pre-cut disks it would have cut the time in half. Of course then I would have had to wait a month or more to get laser cut parts. So in the end, even hand-cutting them was "faster."

There's also the "aesthetics of cost." It just chaps my ass to think that I spent over $100 on this so far! That's not what WWI modeling is supposed to be about. That's not a "clean" modeling solution in my book.

The resin will be easier to make look like metal so I guess that's an advantage. But then the master turned out pretty well. Also the cylinders were painted black so they don't need to look like "turned metal" as on, for example, a LeRhone engine.

Hmm...I was going to ask you the same thing! I suppose I will use regular epoxy to glue the engine parts together. Since it sits right on top of the engine, it needs to be sturdy.

I will never ever again use Gorilla glue. That is the messiest, nastiest stuff in all creation.

The stuff I used is exactly like plastic model parts. It seems to cut and sand exactly like plastic model parts.

abufletcher

Please, please, please!!!

abufletcher

Yeah, I realized almost immediately that the drawings didn't match and of the photos, do I did some "photometry" in photoshop to come up with the rough drawing I used for my cylinder master. It's is substantially different from the "sketch."

abufletcher

Looking at this photo, I think I can pretty well throw out "the sketch" as a useful basis for anything. In this photo, the cylinders look centered to me. And the shape of the "base" is different.

Brian, if you have any more info on the Benz Bz III, I'd love to see it. If not, I guess I'll just draw up my own sketch for the base.

geezeraviation

My Feedback: (3)

I think its possible they were offset but have no proof, I just dont think it's impossible may be a wiser way to state it. Things were done for a reason and it would be interesting to know more about it, if indeed there is an offset.
Doc

abufletcher

The only thing I can think is that offsetting the cylinders MAY have laterally balanced the engine. It appears that offset cylinders are a possibility (if I'm readying this correctly):

http://www.patentstorm.us/patents/60...scription.html

TFF

The only time I have seen offset cylinders is when the camshaft is in the block next to toe crankshaft, but it would be offset the other way I would think. One thing to remember is that technology was changing fast and in just 10 years the engines improved so much that those designs were just forgotten. If it was wrong no one cared. There is another reason to offset the cylinders which just came to mind; it can help with wear on the cylinder walls. Cars do it by offsetting the piston pin to the connecting rod; moving the whole thing over would do the same thing. The expense is a slight loss in power and actually the other way would give a slight increase but would wear faster, some race car engines do this.