Frame Dimension - - help?

[Rooster]

My '52 BT frame is at the restorers shop, and nearing completion. We just have one minor issue left to deal with, looking for a difinitive answer. We are replacing the horn mount blocks with replicas, and they measure just 3/16" thick. Yes, they have the correct #12-24 thread pitch, and have 'rounded' corners. The earlier horn blocks appear to be closer to 5/16" thick. Can anyone tell me what the thickness of the '52 horn mount blocks should be?
Thanks in advance.

[exeric]

Wow, that's a good question Rooster. I got the reproduction horn blocks for my '51FL and even though I welded them on, I thought they looked a bit thin. I just figured they must be right since the company I got them from charged $20 for the pair. I can easily make the horn blocks but I assumed that original H-D blocks would be typical H-D odd-ball dimensions and that a company that had the audacity to charge $20 of two dinky pieces of steel would get them exactly right. I would be very upset if they are wrong. I'm using the square horn blocks. I hope someone replys.

[Rooster]

We may have sourced our parts from the same place.

I have measured the horn mounting bolts and the spacers on the 'floating' side of the bracket. The bolts have about 3/8" of thread on them, and the spacers are about 3/16" thick. If the mount block is also 3/16" thick, the bolts would be about right. HOWEVER----- on the 'non-spacer' side, the 3/8" long bolts will be too long. I suspect the mount blocks need to be 5/16" thick, but I'll wait for someone who can actually go out in the shop and put an eyeball on one.
Incidentally--- the mount blocks that I removed from the frame are 5/16" thick, have #10-24 threads, and also have rounded corners. I believe these would not technically be correct, I think Palmer says they should be more 'squared' in shape if they have the #10-24 threads. But this frame has more stories to tell than a retired sailor, and who can tell what is original to the frame or not? (Quite certain the horn blocks are not.)

[Rooster]

Just an update/correction.

On the non-spacer side, when the lock-washer is placed on the bolt, then the bolt inserted through the mount hole on the horn bracket itself, there is exactly 3/16" thread protruding. I will have to surmise that the 3/16" thick horn block is correct, unless someone here can tell me otherwise.

[bmh]

How late is your 52? All the original 52's I have examined have had square horn mount blocks. The white police 52 FL in the spring magazine is in the 5200's for serial number and has square blocks as shown in this photo. this is the latest original 52 I have found so far. The square blocks are just a fuzz over 5/16" thick.

[exeric]

That's what I was afraid of. My reproductions are 3/16" thick. I have also taken a fair number of pictures of '50-'52 panheads and I always took pictures of the horn area because I knew I would need to address that on my '51 when I got around to restoring it. Visually, the horn blocks on original bikes looked thicker than the ones I got from my aftermarket source. Well, I can't blame this one on V-Twin.

[Rooster]

How late is your 52? All the original 52's I have examined have had square horn mount blocks. The white police 52 FL in the spring magazine is in the 5200's for serial number and has square blocks as shown in this photo. this is the latest original 52 I have found so far. The square blocks are just a fuzz over 5/16" thick.

Thanks very much for the reply. I have no way of knowing the actual production number of this frame, or even if it is for sure a '52. I bought it by itself, just the frame. It came with a combination of features that would have identified it as either a '48-'51 or a '52. Certainly no later than a '52, based on the lower front motor mount. It was in need of extensive restoration, which I am glad to say was just completed this afternoon. Unfortunately, I did not see you reply until now. My restorer and I decided to go ahead with the 'rounded' blocks, 3/16" thick, with #12-24 thread pitch.
Palmer says that this is correct for '52, but I wonder if that wouldn't have been one of the 600 or so corrections he has been trying to get the publisher to incorporate in future printings.

bmh, can you tell me what size the mounting bolts are on this original '52 you show? I was of the understanding that the square blocks have #10-24 threads.

It's not the end of the world, my restorer is just 40 miles away. I will look for the square blocks, if I knew what thread pitch to look for.

Thanks again for the helpful information and excellent photo, bmh. Greatly appreciated.

[Chris Haynes]

Mine measures 0.0325".

[Steve Little]

Hi.
I am still researching this subject for my own records but I think it went like this... Early 1949 to....later 49...not sure when... has no pressing in front down tubes and fitted with 0.177" thick (just under 3/16) square end horn blocks that are welded all way around. Terrible welding with holes and slag impregnation.
I have not defined when the change was made but I know a guy with a very late unrestored 1949 who's frame has the depression in the down tubes and 0.329" (lets call it 5/16" for ease of conversation") thick horn blocks with welds on the ends only. So the change was somewhere in 49.
1950 has the same 5/16 square end horn blocks with weld either end
51 is same. I have an unrestored.... late 1951...51FL91XX... that has the square end 5/16" horn blocks.
I think all horn blocks from here on, are 5/16 thick but with a thread change.

[Rooster]

Steve, thanks very much for the info!

It seems that I'll need to make a little change to my horn blocks. At the very least, they should be thicker, at a fuzz over 5/16" (0.325"). Dammit. Just welded them up yesterday.

[bmh]

Rooster, you can't tell what size the threads are unless you remove the mount bolts as both the -48 set and the -51 set have the same size head. As far as I can find out the thread change occurred in mid 51. Just make sure you use the correct spacer for which ever size threads you have and all should be fine.

[Rooster]

Thank-you. Duly noted.

[Rooster]

(OOps, double-post)

[bmh]

How late is your 52? All the original 52's I have examined have had square horn mount blocks. The white police 52 FL in the spring magazine is in the 5200's for serial number and has square blocks as shown in this photo. this is the latest original 52 I have found so far. The square blocks are just a fuzz over 5/16" thick.

I would like to correct my previous statement, in going through my photos and notes I found that 52FL255X did have the rounded mounts. Here is a pic of that, they appear to be the same thickness as the square variety.

[Rooster]

Thanks, bmh. I cut a set of round mounts off this frame, they had #10-24 thread pitch. I replaced them with round mounts, #12-24 threads. Appreciate the correction, that's good for everyone.