Topic: Frame mod cb 750

[mysta2]

I just did this a couple of weeks ago so I figured my two cents might be worthwhile



I've never really understood the purpose of the nut on Gordon's kit, and if you're paying someone for machining, omitting that will save a good chunk of change. I cut mine on our lathe and 4axis mill but someone who really knows what they're doing could probably knock it out on a Bridgeport in 2 or 3 hours. I also plan on bolting some plates behind the cross brace, but haven't gotten to that yet.

I've already had the head off the bike three times since I built the frame kit, so I can promise you that it works.

There's a little more info on my blog if you're interested www.dropbars.com

[KrautKoffin]

I just did this a couple of weeks ago so I figured my two cents might be worthwhile



I've never really understood the purpose of the nut on Gordon's kit, and if you're paying someone for machining, omitting that will save a good chunk of change. I cut mine on our lathe and 4axis mill but someone who really knows what they're doing could probably knock it out on a Bridgeport in 2 or 3 hours. I also plan on bolting some plates behind the cross brace, but haven't gotten to that yet.

I've already had the head off the bike three times since I built the frame kit, so I can promise you that it works.

There's a little more info on my blog if you're interested www.dropbars.com

You're a damn cock tease! I was hoping you'd crank out a few kits!

[MCRider]

I think the nut is to fine tune the clearance between the slug and the end of the frame cut.  Did you weld your slug in place or do they float? Pressed into the frame cuts?

[754]

 Hey at least you got the machining done properly, not like the flaw on the Gordon kit.
 The part that threaded in on some kits, I suspect may not have been as rigid as the other joints.

[mysta2]

I bolted the whole thing together and welded all the slugs in place. There should be no need for fine tuning if you bolt it all together before tacking it. I've read several explinations by Gordon to explain that front nut and it sounded like it had more to do with not being able to see the bolt on pieces when the tank's on (maintain stock appearance)

But I still don't understand how that would work as you'd be able to see at least the nut (which is absolutely not to say that I am disparaging his kit in any way, it's very well crafted and thought out, I would have been happy to buy one and put it on his bike had I the opportunity)

I just put the bolt on slug as far forward as possible because I don't care about it showing. This bike is far from a restoration, and I'm proud of my fabrication.

[Terry in Australia]

Nice!

[taggat]

What do you guys think about ditching the bottom triple rails and just making a gusset plate on each end?

[Terry in Australia]

What do you guys think about ditching the bottom triple rails and just making a gusset plate on each end?

Not a good idea mate, unless you replace the top tube with something beefier than what's there now. The factory frame is pretty rigid in standard form, but if you remove those support rails you're weakening the design significantly. Cheers, Terry.

[Rookster]

With any of the kits I don't understand why the frame tubes are discarded in favor of new tubes.  It would seem more economical to reuse the cut pieces since they are already tied together at the bottom anyway.  No need to add new bracing.  Just connect the upper triangles back together using a flat plate and some bolts and nuts.  The sleeve kits like Carpy and Cycle X sell can be made much cheaper.  Get a section of steel tubing with an id of 1" and reuse the cut sections of frame.  Drill holes and bolt together. 

Scott

[Terry in Australia]

G'Day Scott, the "Gordon Kits" do just that, they just include the inner slugs and the flat plates to tie the braces back together, and it's up to the installer to ensure that he "measures twice and cuts once".

Personally I think that the kits with sliding tubes are rubbish, but the gordon kits (and better still, the "Mysta 2" kit) are a much better answer, maintaining the rigidity and integrity of the original design. Cheers, Terry.

[KrautKoffin]

So who's got one of these laying around they want to sell?

[Phoenix]

Given:
    Pulling the engine is a pain in the *ss
    "Gordon" needs the engine pulled and joints welded
    "Gordon" system is expensive but properly addresses the situation
    "sliders" are too tight and skin paint off
    Hednut, 754 and Kraut Killer look like they can make ANYTHING     
             and appear to be interested
I would hope we could come up with a "Gordon" type and one that involves keeping the bars that are cut out and providing the "sliders"  that would properly fit, to be bolted on.  Would you agree that would give us the best weld and no-weld products.                                                                                                           

[KrautKoffin]

Given:
    Pulling the engine is a pain in the *ss
    "Gordon" needs the engine pulled and joints welded
    "Gordon" system is expensive but properly addresses the situation
    "sliders" are too tight and skin paint off
    Hednut, 754 and Kraut Killer look like they can make ANYTHING     
             and appear to be interested
I would hope we could come up with a "Gordon" type and one that involves keeping the bars that are cut out and providing the "sliders"  that would properly fit, to be bolted on.  Would you agree that would give us the best weld and no-weld products.                                                                                                           

Don't say I can make anything, I effed up making toast this morning.

[Terry in Australia]

Actually you don't need to pull the engine to install the Gordon kit, there was a post somewhere here from someone who carefully installed it with their engine in place, but sure, it'd be much easier with the engine out.

There are a lot of guys here who like the Gordon kit but aren't keen on welding it in, so I reckon a kit that allowed you to tap the joints in with a hammer then drill a hole thru the frame and the "slug" end of the joint to bolt the items together would be "do-able"? Of course, drilling thru an inch of solid steel might be a PITA, so maybe machining the joints from 6061 Aircraft grade aluminum might be a better idea?

It might not be quite as good as the Gordon kit or the Mysta 2 kit, but stll much nicer engineering than the other crapola out there. Cheers, Terry.

[Rookster]

There are a lot of guys here who like the Gordon kit but aren't keen on welding it in, so I reckon a kit that allowed you to tap the joints in with a hammer then drill a hole thru the frame and the "slug" end of the joint to bolt the items together would be "do-able"? Of course, drilling thru an inch of solid steel might be a PITA, so maybe machining the joints from 6061 Aircraft grade aluminum might be a better idea?

Hi Terry,

This is the same as the sleeve kits but the sleeves run inside the frame tubes rather than outside. 

The sleeve kits like Ape, Carpy, and Cycle X sell aren't as bad as they first sound.  I have been doing some research into making my own version of this kit since this thread was brought back to life.  The fit between the sleeves and the frame tubes is what makes all the difference.  A loose interference fit of between .0012 and .0055 would provide quite enough stiffness to the original tubes.  The bolt that holds the sleeves in place is essentially window dressing as the interference fit is what is providing the strength.  Couple the sleeves with plates that reconnect the triangle and I think the original integrity of the frame would be pretty much preserved. 

A sloppy fit between the sleeves and the frame tubes would be like Terry says, junk.  If the bolts are the only thing holding the frame back together without either welding in the slugs or creating a nice tight sleeve, then it would be for looks only.

I would be interested in hearing from someone like Frank who has alot of machining experience about the sleeves and fit?

Scott

[754]

 I know a method that will be even stiffer will start on it soon.

[KrautKoffin]

I know a method that will be even stiffer will start on it soon.

Frank, send me one with a set of front motor mounts 

[754]

Let me get them done first.

[Terry in Australia]

There are a lot of guys here who like the Gordon kit but aren't keen on welding it in, so I reckon a kit that allowed you to tap the joints in with a hammer then drill a hole thru the frame and the "slug" end of the joint to bolt the items together would be "do-able"? Of course, drilling thru an inch of solid steel might be a PITA, so maybe machining the joints from 6061 Aircraft grade aluminum might be a better idea?

Hi Terry,

This is the same as the sleeve kits but the sleeves run inside the frame tubes rather than outside. 

The sleeve kits like Ape, Carpy, and Cycle X sell aren't as bad as they first sound.  I have been doing some research into making my own version of this kit since this thread was brought back to life.  The fit between the sleeves and the frame tubes is what makes all the difference.  A loose interference fit of between .0012 and .0055 would provide quite enough stiffness to the original tubes.  The bolt that holds the sleeves in place is essentially window dressing as the interference fit is what is providing the strength.  Couple the sleeves with plates that reconnect the triangle and I think the original integrity of the frame would be pretty much preserved. 

A sloppy fit between the sleeves and the frame tubes would be like Terry says, junk.  If the bolts are the only thing holding the frame back together without either welding in the slugs or creating a nice tight sleeve, then it would be for looks only.

I would be interested in hearing from someone like Frank who has alot of machining experience about the sleeves and fit?

Scott

Yeah mate, by the time I finished typing that post I'd just about talked myself out of it. I still think the sliding tubes are crap though, any slop, however small, weakens the integrity and rigidity of the frame.

What I'm thinking about now though, is a tight fitting clamp made from oversize tube split horizontally that clamps over the removable and fixed frame tube sections with a couple of bolts either side of the cuts, that would hold it a lot more rigidly.

Probably not as pretty as the Gordon kit or the Mysta 2 kit, but if you don't have access to a welder, probably the closest you'll get to original rigidity. Cheers, Terry.

[754]

You got mail..

[Phoenix]

Are we still alive here?

[KrautKoffin]

Are we still alive here?

I just checked, I think so.


The problem is no one can make the kit for what it was originally sold at without taking a major loss or not charge labor (taking a loss). Unless someone out of the kindness of their heart wants to make these, we won't be seeing these any time soon.

[MRieck]

I have that basic design on my bike but we machined a crown on one of the mating surfaces and a matching trough in the other. It truely locks the pieces together when the bolts are tightened. We also drilled 2 holes in the frame so a couple of blind welds could be added (about 3/4" below the cut) besides the welding where the adapter meets the frame.

[KrautKoffin]

I have that basic design on my bike but we machined a crown on one of the mating surfaces and a matching trough in the other. It truely locks the pieces together when the bolts are tightened. We also drilled 2 holes in the frame so a couple of blind welds could be added (about 3/4" below the cut) besides the welding where the adapter meets the frame.

Got pics?

I had a reason to PM you a few days ago but forgot..

[MRieck]

I have that basic design on my bike but we machined a crown on one of the mating surfaces and a matching trough in the other. It truely locks the pieces together when the bolts are tightened. We also drilled 2 holes in the frame so a couple of blind welds could be added (about 3/4" below the cut) besides the welding where the adapter meets the frame.

Got pics?

I had a reason to PM you a few days ago but forgot..

There may be some more sets at my friends shop....he made a few of them. I can't get there until early next week though.