Topic: Hardtail jig for cb frame, any ideas??

[dergs713]

Any tips on jigging up a frame for hard tail weld up? Modifying my 73 cb500. Looking like I'm going to use the tc bros universal kit. If anyone has measurements or pics it would be greatly appreciated!!!!
Matt

[lucky]

Any tips on jigging up a frame for hard tail weld up? Modifying my 73 cb500. Looking like I'm going to use the tc bros universal kit. If anyone has measurements or pics it would be greatly appreciated!!!!
Matt

You won't need a jig because you are not building the frame from scratch ,but you will need a flat surface and measuring tools and some clamps.

First get the surface you are going to put the frame on LEVEL in both directions.
Take your time on this.
NEXT...

Draw a centerline down the table. Center the frame on that line by dropping a string downwards from the steering head or other part of the frame to that line you drew on the table.

Strap the frame down. And on the CB750 that kick stand bracket sticks downwards so you will have to put some EQUAL height blocks under the frame.
I would use some steel tubes or other metal bars that are consistent and equal.
Then screw the frame down to the surface with plumbers tape or what ever you have. Re check that the frame is still centered on that line you drew on the table.

Make sure that the parts of the frame are equal length where you made your cuts.
Measure.

Then clamp the hard tail portion in place leaving room for tack welding at the joints of attachment.

Put the axle or metal rod through the rear axle bracket and tie a string around it and bring the string up to the steering head and tie  it so it is centered. Tight.

Then recheck your table and make sure it is still level.
Now stand behind the motorcycle frame and make sure that string goes right down the backbone of the motorcycle and is centered.

Make sure the angle of the axle is perpendicular to that string. If it is not then adjust the rear add on frame until the axle is perpendicular to that string.
The axle should be all the way forward in its slot.

Now stand behind the motorcycle and look at the rear axle and make sure it is level by measuring from the surface up to the top of the axle. The add on hard tail could be twisted so check the rear axle for level to the table.

Make as many measurements as is necessary before you put the first tack weld on.
Make sure it is all clamped when tack welding. Welding can cause shrinkage and movement so just use small tacks until it is all tacked.

Then go back and measure it all again before you do the finished welding.
Weld equally on both sides so you reduce warpage. Do not weld one side completely, and then weld the other side. You would get warpage. Weld a little on one side then weld on the opposite side, 2 inch long welds.

BTW...If you have never welded a frame, this is not the time to practice.

If you hire a welder ,make sure they have motorcycle experience.
Not just ANY welder who welded pipes or buildings.

[754]

 If you got to ask, you may not be ready for this..
 Will add something, I would level the frame by putting a level on a straight bar thru a rear motor mount. then level the axle same way, and make sure it stasys there.

[Nick_701]

He said is is using the universal kit and I believe that is just pre bent tubing and axle plates. 
 http://www.tcbroschoppers.com/store/index.php?main_page=product_info&products_id=10

So he will be needing a jig, and that's ten times the project compared to a weld on kit.  Great write up by the way on how to put on hardtail, very detailed.

I built a jig, but can't upload pictures right now, ill do my best to get back on her an add some

[Eddie]

Ardcore Choppers in Indiana will hard tail your CB for $500 last I checked...seems worth it...

[dergs713]

Thanks guys, I think I found someone locally, old motorcycle gear head that's been in the business. Since 1960's. Learned a lot talking to him today, showed me pics of his Honda chop back in the old days with tons of bling and all custom stuff. So cool running into people like this.
Matt

[lucky]

If you got to ask, you may not be ready for this..
 Will add something, I would level the frame by putting a level on a straight bar thru a rear motor mount. then level the axle same way, and make sure it stasys there.

Good suggestion 754. I agree.
 And that is in addition to measuring the height of the axle on each side of the axle from the table.

[lucky]

He said is is using the universal kit and I believe that is just pre bent tubing and axle plates. 
 http://www.tcbroschoppers.com/store/index.php?main_page=product_info&products_id=10

So he will be needing a jig, and that's ten times the project compared to a weld on kit.  Great write up by the way on how to put on hardtail, very detailed.

I built a jig, but can't upload pictures right now, ill do my best to get back on her an add some

Thanks Nick 701 for that information. So he actually has two different welding projects. Or like you said, build a jig and make it all one project.

[dergs713]

I understand what I have ahead of me.. been doing machinist work for 6yrs now.  There is a lot of measuring and minimal welding if done correctly.  I understand that there is a lot of math involved.  I was just trying to see what people were doing before I made my universal jig.  Just because I am asking q's, doesn't mean I am not ready.  A smart person would do as much research as they could, to make sure its done correctly.  I see there are some people out there that are just shooting down other people's ideas before they even get a chance to try. Not everyone has the money to have work done for them, and everyone can agree by saying you wont learn unless you get your hands dirty.  If your an "older gent" that has been in the game a while, us "younger guys" are not all punks.  Remember that some of us will listen, but we also choose whom we may be listening to. Thank you to the helpful replies, as for the rest...
Matt 

[754]

Matt, nothing wrong with getting as much info as you can. Its hard to tell by your post starting out this thread that you have a general idea of how to do it.
 More often than not when its asked like that, they often should not be doing work of that scope..
 When I hear welding on a hardtail, if its only once, you can get away with  a lot less than an actual frame jig.

 Good luck with it..

[Nick_701]

Im gonna have to agree with you, not everyone has the money to have work done, and not all of us younger guys are punks.  With that said it was a learning experience with me and im still learning and making progress.  I am trying to do my project on the cheap so i came up with making a jig frame with what i got.  I happened to get a computer server rack (frame) and as i looked at it standing vertical i thought to my self, "hmm lay that flat and i could make a jig from that".  So i did, i knew the rack was square and strong, so i measured a lot and started building supports for front forks, factory frame tubes, and rear axle plates.  Got the stock axle to axle length and added six.  mounted it down and spend a few months finding people to bend tubing for me for 5 bucks here and 5 bucks there.  anyway here are a few pictures of what i came up with, ill add more to my build thread later.  its nothing wild but it worked and im now the proud owner of a six inch streched squared ridgid frame.  Good luck to you, im sure if i can do it you can.

 
 
 

[lucky]

I understand what I have ahead of me.. been doing machinist work for 6yrs now.  There is a lot of measuring and minimal welding if done correctly.  I understand that there is a lot of math involved.  I was just trying to see what people were doing before I made my universal jig.  Just because I am asking q's, doesn't mean I am not ready.  A smart person would do as much research as they could, to make sure its done correctly.  I see there are some people out there that are just shooting down other people's ideas before they even get a chance to try. Not everyone has the money to have work done for them, and everyone can agree by saying you wont learn unless you get your hands dirty.  If your an "older gent" that has been in the game a while, us "younger guys" are not all punks.  Remember that some of us will listen, but we also choose whom we may be listening to. Thank you to the helpful replies, as for the rest...
Matt

Yes I understand.
I was not being condescending I was just covering all the bases in case you were a beginner. I am sure your experience will help a lot on this project.

[dergs713]

Nick great idea man.  Using what you have lying around, lets you spend a little bit more on bike parts and gas.  Id like to see it when its all done. Thanks!
Matt