1957 175 Sport frame construction

[Rick]

I'm trying to collect some info on my favorite Ducati, with hopes of building a replica. It's the 1957 175 Sport, good pictures are here:
http://www.philaphoto.com/imageLibrary/ ... album=1158
I've read, but can't remember where, that the front downtube has a rib welded onto the tube as a reinforcement, but, when I look at the photos I don't see it as a welded on rib, but as as weldment made from 2 formed pieces of sheet metal, with the weld bead running along the joint, front and back. There doesn't appear to be a weld bead between the tube and the rib, and I can't see that any other weld beads were ground smooth, so it looks to me to be made like my cad file. I've never seen the real thing, so I'd like to know if anyone who has seen a 1957 Sport can tell me how the frame is constructed.
Here's a photo of the downtube:

1957 downtube.jpg

And here's how it looks to me to have been built:

downtube.jpg

I hope someone can either confirm my thoughts or tell me I'm all wet, so I can start drawing the frame.
Rick

[joe46ho]

Rick, Its funny that I just saw this post because I spent most of the weekend at Domiracer, scrounging for parts, and one other guy that frequents that place is Jerry Dean. He is the only one I Know that has actually hand built any frames. He lives here in cincinnati, and owns some of the rarest ducatis in the world. Hes not a member of this site though, and I dont have his email. For all I know these pics on phils site might be of his bike, maybe not, but I have noticed phil a. doesnt always have the owners name in there and i have seen a ton of pics of jerry's marianna all over the web, with either no credit give to him, or the wrong owner listed. This would definitely, absolutely be the best guy to ask, only problem is hes kind of hard to get a hold of, if i remember I will ask him in the next couple weekends if possible, I also need some help from him regarding my 66' scr restoration. I did just type in his name on phil's site and his 200 motocross is pictured on there as well... he has a lot of nice ducati's (gross understatement) Someone else on here might know him better than me, and be able to help you out quicker though, maybe they will chime in...

Joe

[Rick]

Thanks Joe- if you get a chance to see his stuff and he has one of these 'ribbed' frames, I'd like to know how you think the front downtube was fabricated. I have built and modified several frames, but not since my spine exploded- a narrow case frame is pretty light, so shouldn't be a problem, plus, I can loot parts from a vandalized frame I have. A narrowcase frame is about the easiest frame to fab that I can think of, 2 tubes running into the steering tube, so they can be welded to the steering tube and the whole subassembly is fairly easy to mount on a mill to bore the bearing pockets- best done when all of the welding distortion is over.
The closed top loop would be tricky to bend- it's 1 piece-

seat hoop illustration.jpg

But, I can probably take one from a junk frame- I've read that the 175 frame loop is narrower than a 250, but don't know for sure. I've never seen the frames with the swingarm bushings in the backbone, so that's another problem, but there's no deadline, so I'll find info where I can.
Rick

[PhilA]

Hi Rick,

That 175 Sport is owned by a collector in San Francisco, not Jerry. It is a bit hard to tell exactly how the down tube is constructed - there only appear to be weld marks on the front "flange". I can send you close up detail crops if that would be of use. Also note that the '57 had a bolt-on rear frame loop as can clearly be seen here:

http://www.philaphoto.com/imageLibrary/ ... 1158&pos=4

cheers,

Phil

[joe46ho]

I have scoured through all my pics, I have thousands from various sources. Not that many of the 175 sport though, but It looks to me that the front tube is surely constructed as you have depicted in the cad file. I think whoever said it was merely a rib welded on, was either mis informed, or just trying to simplify things, instead of explaining why it was built that way. Plus if ducati had welded ribs onto the frame tube, they would surely not have smoothed them down to the extent of making them "disappear" I mean, this can be done but it would take a lot of work, not the kind of thing you would see on a production unit. and also if that where the case, I would think that the rib would have a nice clean smooth edge since there would be no reason for it to have a rough edge like in these pics , unless that is in fact the weld, which I think it certainly is... When I think of welded on ribs, I think of what you would see on a late 450 scr. frame, where they added ribs to stiffen the frame, and also the swing arm. Trust me those welds are definitely not pretty, and are very visible... Kind of what you would expect on a production bike of that era though. Strong welds, just not pretty, or smoothed over or anything.

Also, Im not an engineer, but I can tell you that constructing the down tube like you have depicted here is a HUGE improvement over a simple round tube, much stronger and stiffer no doubt (also a lot harder to fabricate though) Maybe thats why the later production ducatis didnt use this design, strictly because of cost ?

Joe

[Rick]

Phil,
I would like to see a picture that shows a different angle or lighting, I'll send you a PM with my email address in case your pictures are too big to load on the forum site. And, if you were paid by the amount of time someone spent looking at your photographs, my bank account would have been emptied long ago- really great photography.

To anyone else who's interested,
I've started modifying my cad drawing of a Mach1 frame to give me someplace to start with the 175 project- I've made the obvious changes, but the swingarm pivot area is going to take some real measurements- scaling from a photo won't do. The rear motor mounting plates may be considerably different also- need to do more digging around. Here's the preliminary print, with changes from the Mach1 in red:

175mods.jpg

And here is my blueprint overlaid onto Phil's photo:

overlay.jpg

My drawing is in yellow, and it's close, but there are some areas that don't match too well- for now, I'm going to call it parallax error and not change my Mach1 drawing- I spent a lot of time carefully measuring the frame, and am not ready to say it's off.
The deer in the backyard are driving my dogs crazy, so it's time for a walk- more later.
Rick

[double diamond]

Sure looks to me like a weld bead where the two stampings meet (Phil's pic 3/8). Also looks like a rubber bushing pressed into the frame where it bolts to the engine plate? Saw that 175 at the San Jose British/Euro show last March among a number of other interesting bikes. My pics aren't as good as Phil's... MW

[PhilA]

Any help?

[Rick]

Thanks. Yes- not much doubt in my mind that it's a pressed steel/pinch welded downtube.
Rick