Precious Metal Silver Brazed Frames?

[HarleyCreation]

Since there isn't a dedicated K Model forum, I hope you guys don't mind if I ask a K question here.

For a Model K & Sportster story (yes) I reviewed an interview with old Harley engineer who said that the K model frame was silver brazed. He even told the name of the company/guys in Chicago who supplied the materials and that it had been Spexarth's idea to use silver braze.

Of course earlier frames were brass brazed and later (Panhead) frames welded, but silver brazed?

The only other reference I have found so far is from the "Harley Data Book" (p.86) that gives official specs for the 1952 K including: "frame is double-loop and silver brazed tubular steel." Later year entries don't say that.

Okay, so apparently at least the 1952 K frame was silver-brazed, but how about later Ks? How about early Sportster frames? When did the silver-brazing process drop out of production?

Anyone know about these "precious metal" frames that Harley built?

PS: I found 2 more references to 1952 silver-brazed K frames: 1952 brochure info quoted in David Wright's book and a 1952 H-D ad in "American Motorcycling" mag (May 1952): "Silver-brazed double-loop frame."

How long was this process used?

[pete reeves]

I have a 56 KH as the bike is togeather I can only see some of the frame joints, the two tubes going up in to the head stock and the reinforcement (buted ) tubes are not welded, I have scratched the joints and can not see a yellow/brass color only silver color.

Pete.

[HarleyCreation]

Originally posted by pete reeves
I have a 56 KH as the bike is togeather I can only see some of the frame joints, the two tubes going up in to the head stock and the reinforcement (buted ) tubes are not welded, I have scratched the joints and can not see a yellow/brass color only silver color.

Pete.

I know it's an obvious (dumb) question but do you think 100% your frame is original 1956 production to your 56KH motor/bike?

What else could a silver color be but the above described "silver-brazed" precious metal frame?

If silver-brazing was still used in 1956 it seems likely that it continued into the Sportster (1957+) era.

Very interesting and thanks for the reply!

[pete reeves]

It is a 56 frame it has the late K frame features in preparation for the OHV motor.

Pete.

[HarleyCreation]

Originally posted by pete reeves
It is a 56 frame it has the late K frame features in preparation for the OHV motor.

Pete.

Good. That would seem to clinch it as a gen-u-whine 1956 frame.

What features were added/differed for the OHV motor?

Now we need somebody with a authentic '57 frame and later and see if they are still silver-brazed and for how much longer.

PS: I have never owned a K or Sportster and don't know the parts but have divined the rather wacky background of these models which is interesting indeed.

Thanks!

[pete reeves]

I cant remember exactly what the change was now And I dont have a 55 to compare it with ,When I bought the bike about 5 years ago I did some research and was satisfied that it was the correct frame for a 56 perhaps other members on this forum can remind me what I should be looking for?
I am fairly positive that this bike has always been togeather.

[Kojack]

You may have a tough time seeing the difference if they did change. Silver brazing rod is usually no more than 40% silver and still has a yellow color. Not necessarily the same as straight brazing but it can be close. Pete, you said that you couldn't see anything but silver in the joint and I believe you. I have a '52 frame in my junk collection and I went out to check it. The yellow color is visible at the top tube to headstock joint but it's very small. I'd estimate the actual width of the braze showing to be about .015" wide. I had to polish it with a scotchbrite pad to see it. There's a little more showing at the top motor mount joint but not much. This is extremely fine brazing that was done on this frame. Silver brazing can flow better than regular brazing so the capillary action would allow this. You won't always have a fillet of brass at the joint. Then again, you might. I've done some silver brazing and if you get everthing right this stuff will flow like solder, or, it can end up a little thick.

[JohnR]

Question?

Would a Silver braze be superior to Bronze?

[Kojack]

It's claimed to be but I'm no expert on this. Advertised tensile strengths of brazing rods are usually in the 60-70,000psi range. For silver brazing it's supposedly 120,000 for the one brand I found on-line. A lot is going to depend on the design of the joint. Here are a couple of interesting links.
This ESAB site has good info on brazing and bronze welding:
http://www.esabna.com/euweb/oxy_handbook/589oxy14_2.htm

This silver brazing rod looks to be the same as the type I used to use:
http://www.tinmantech.com/html/silver_brazing_rod.php

We used the silver brazing rod at my workplace. We did a lot of work with stainless steel and the silver brazing rod was very easy to use on stainless and very strong.

[HarleyCreation]

Being "silver" braze I assumed it would be a white or silver color, although I didn't think it would be 100% silver but some alloy.

Good info all around, thanks!

Here is more info supplied by "Patrick" over on the Flatheadpower forum in answer to the same question. He has a nice KR website of his own and while I can't say how much of this is correct it sounds right.

Hi All,

Not only were K frames silver brazed, they were also made in thin chrome-moly extruded (not seam welded) tubing. I think the practise ended with the 56 KH frame when it was made of thicker std tubes and bigger castings all round in view of the incoming Sportster engine. All KR frames were the same as early K/KH when they had cast junctions. This is somehow implied in the KR parts books, the race shop recommended and listed the Sportster frame as the Daytona frame after 1958, a bit stronger for all the sand ruts... So much for H-Ds built like tractors!!!

My 54 KHK frame is about half the weight of a later 58/69CH frame, itself a bit lighter than 60's XL/XLH frames.

I can also say it was not a lone practice, all Velocette frames are silver brazed. It allows lower temps during bazing and the penetration is better than with bronze rods and the resulting strengh is better as well.

Patrick

[mmoore]

years ago I cleaned a 57 frame up that needed painting. One thing I did was to grind off some excess brass by the castings as a drop stuck to the frame about a half inch below the casting. it was brass . I do believe the frame was original as the bike was mostly stock. just a few weeks ago I started cleaning my 68 frame fron my ironhead. it also has globs of brass stuck on it below the head casting which I ground off. now the bracket that the foot pegs mount on was electrically welded. not sure but maybe they coulnt or didnt want to electrically weld the cast parts. anyway welcome to all the k's here, without you we probaly would not have our ironheads

[Powerlifter626]

Ok I am restoring a 1957 Sportster.....I blasted the frame down to bare metal and I did not see any silver. There was brass in a few spots including around the top motor mount, just underneath the backbone of the frame. However, my bike had been apart before, and the neck was cut with a torch the raised portion where the crash bars mount to make it smooth, so there is no telling what else was messed with when they did that nightmare. I got a replacement neck and swapped that for my original neck that was destroyed. Like I said I saw no silver on the frame, all other numbers tell me that this is a 57 frame.