Topic: Frame stiffening/reinforcement

[Doctor_D]

I've stripped the brackets from my frame and am ready to add gussets.

On page IIIA-22 of Mark Paris' (Hondaman) book there are some suggestions listed, but I'm having a hard time visualizing the one regarding adding a second triangular plate at the right rear top engine mount.  If someone has pictures, it'd be a tremendous help.

Thanks in advance,
David

 

[Sam Green Racing]

Ya mean yav bought a book with no pictures in it

Sam.

[voxonda]

I've stripped the brackets from my frame and am ready to add gussets.

On page IIIA-22 of Mark Paris' (Hondaman) book there are some suggestions listed, but I'm having a hard time visualizing the one regarding adding a second triangular plate at the right rear top engine mount.  If someone has pictures, it'd be a tremendous help.

Thanks in advance,
David

 

What Mark means is to double up the triangular plate. You will have to grind off the two weldnuts at the back. I have a somewhat different approach.



Cheers, Rob

[wannabridin]

i will be ordering one of your engine mount kits when i get closer to that point Rob, so just you wait!!  could you further elaborate on the front mount you make and it's advantages??  thanks!

[voxonda]

Hey G,

The basic principle is that I am making the mounts rigid in construction, and not by using heavy material, so the mounting bolts are released of the bendingforce that are quided into the frame. Hope it is understandable, my technical English is not that good.


The latest is made of a high-grade aluminium:

Cheers, Rob

[turboguzzi]

done to my 500

[turboguzzi]

some more...

[kos]

The best thing we found to do on SOHC 750's was to incorporate a top engine mount into the mix of frame strengthening pieces. Using the top cover modified for camshaft holder, hold down bolts we then added a "bolt on" piece that allowed us to tie into a boss we had welded onto the lower frame rails. I'll try find the photos I have here somewhere. Tom Faulds told me about this trick way prior to me even racing one of these and he was right on. Worked very well, as the steering head was no allowed to move about under braking and high g-load cornering.

Also, as they did with Kaw Z1's...  bore out engine case mounting holes and corresponding frame mounting holes to next size American bolts and end up with an interference fit. Made those monsters a bit easier to ride.

A easier way to do it, is go to hobby shop and buy some of that very thin brass tubing for model aeroplane making that just slides over the engine mounting bolts and slip inside frame holes. You'd be surprised how much room there is between OD of frame hole and OD of bolt.

I have a funny story about why Honda has such great clearances on the engine mounts of this period of making motorbikes. For another day.

KOS


Pics of top frame mount and bronze tubing for engine bolt "slop" reduction shown.

[turboguzzi]

nice Kos

look like we think along the same lines 

[Howell]

nice Kos

look like we think along the same lines  

Hi TG,

Did you race with the stock frame or only with the reinforced one ?
Was there a difference ?
We didn't reinforce our Cb500 frame , because I think mostly the roadholding problem is the suspension by these old bikes.
Because of that we went to a suspension specialist ,  YSS shocks Europe , to buy good shockabsorbers and to adjust by them and also to adjust the Yamaha RD350 frontfork.
This fork  has stock internal teflon gliding rings and I put dampervalves in it and by YSS Europe they put in the right springs and oil and adjust it.
The swingarm is a CB750 Dresda type with tapered bearings also we use those bearings in the steering stem.
These Dresda type swingarms makes also a big difference , stiff and light.
My CB750 (820cc) has also a stock frame , last year we were on the circuit of Spa with this bike without roadholding problems.
Even not in the very fast corners with a speed of 220 km.
The only things I did with this bike , steering stem tapered bearings, a Dresda type swingarm with tapered bearings, Koni adjustable shock absorbers.
In the F2 frontfork I put dampervalves , progressive springs , the right capacity of sae20 forkoil and preload adjusters and a forkbrace.
The suspension is working very well.

[kos]

nice Kos

look like we think along the same lines 

Exactly...looks great.

KOS

[turboguzzi]

nice Kos

look like we think along the same lines  

Hi TG,

Did you race with the stock frame or only with the reinforced one ?
Was there a difference ?
We didn't reinforce our Cb500 frame , because I think mostly the roadholding problem is the suspension by these old bikes.
Because of that we went to a suspension specialist ,  YSS shocks Europe , to buy good shockabsorbers and to adjust by them and also to adjust the Yamaha RD350 frontfork.
This fork  has stock internal teflon gliding rings and I put dampervalves in it and by YSS Europe they put in the right springs and oil and adjust it.
The swingarm is a CB750 Dresda type with tapered bearings also we use those bearings in the steering stem.
These Dresda type swingarms makes also a big difference , stiff and light.
My CB750 (820cc) has also a stock frame , last year we were on the circuit of Spa with this bike without roadholding problems.
Even not in the very fast corners with a speed of 220 km.
The only things I did with this bike , steering stem tapered bearings, a Dresda type swingarm with tapered bearings, Koni adjustable shock absorbers.
In the F2 frontfork I put dampervalves , progressive springs , the right capacity of sae20 forkoil and preload adjusters and a forkbrace.
The suspension is working very well.

I race with it but have to say that I never did a back to back comparison on the same day. maybe i should try and do a season with and one without and then see. My feeling is that the bike is more stable on fast kinks, like in the main straight of Vallelunga. it weights very little, so its kind of cheap insurance  I am moving to RD forks this season. lets see... 

[754]

Vox, I was looking at that motor mount, and thinking, about something that looks lighter yet is very stiff, billet and 1 piece..

 And I think I came up with something... hopefully making chips tomorrow...... will post a pic when its done...

[voxonda]

Hey 754,

Yes you're right it 'looks' heavier than it actually is. but I like the 'sturdy' look. The steel one, when it is painted blends in with the frame. but am very interested in what you come up with.

cheers, Rob

[Doctor_D]

nice Kos

look like we think along the same lines 

Yes, they're called "headsteadies" and we brit-bikers know them well.  Thinking about integrating one, but there are a lot of bits to get sorted before I cross that bridge. Does it require the valve-cover/cam tower mods to provide enough stiffness to make it viable?

All, thanks for the other guidance.  Rob's upgraded engine mounts look like winners. Bushing the bolts seems like a cheap and easy enhancement as well.

Thanks again.

[MCRider]

nice Kos

look like we think along the same lines  

Yes, they're called "headsteadies" and we brit-bikers know them well.  Thinking about integrating one, but there are a lot of bits to get sorted before I cross that bridge. Does it require the valve-cover/cam tower mods to provide enough stiffness to make it viable?

All, thanks for the other guidance.  Rob's upgraded engine mounts look like winners. Bushing the bolts seems like a cheap and easy enhancement as well.

Thanks again.

Cool stuff. I'll be looking into a top motor mount on next project.

On this project, I have Rob's upper rear double mount with his bolt which fits tighter than stock. For the two lower my machinist drilled out the frame and motor, turned down bolts from stainless for interference fit, then turned down the threaded ends to match the stock nut sizes.  I have no machinist skills, but I have the next best thing... a checkbook.   

Can't wait to get it running.

[754]

The top rear mount, I think is 10mm, you can try a 7/16 fastener, or as MC suggested turn a 1/2 in down to fit, or try 12mm bolt.(may need reaming)

 The head steadies should fit on standard 750 valvecovers, with spacers, longer bolts, and some fabbed brackets..

[1080]

754's version of the rear engine mount.
Info to follow.

[Pinhead]

Very interesting subject, indeed.

[754]

Ok there it is, my first prototype, quickly whipped up from a chunk of billet. I will probably make a few changes(only thoought about making this 4 days ago), get it a bit lighter.. it will need nuts on the backside, and may not fit stock tank and lines..

 Weight so far is, 167 grams vs stock piece at 129.5 grams

[Doctor_D]

Ok there it is, my first prototype, quickly whipped up from a chunk of billet. I will probably make a few changes(only thoought about making this 4 days ago), get it a bit lighter.. it will need nuts on the backside, and may not fit stock tank and lines..

 Weight so far is, 167 grams vs stock piece at 129.5 grams

That's a good looking piece (no offense intended Rob).  So good, in fact, that I'd be happy to test one of them on my bike.

Why use nuts though? Why not just thicken the mount on the inside of the inside of the frame, and tap and heli-coil it?  Then one could use dome-head stainless allens to complete a pretty clean looking piece.

[voxonda]

Certainly no offense taken, it looks very good. Mine are copies of the ones that I made back in the 70's. Had no mill back then, and they still worked too.

[kos]

One of things we might be missing here is the issue of making the engine frame nice and firmly mounted to each other, but running standard swing arm and leaving steering head out there... with lack of support and or direct bracing. Add super sticky  racing rubber on the new tires on wider widths...one must treat these modifications as a package. Don't let the tail of the dog...do the wagging! Or the head, do it's thing up front and cause some much unnerving shaking.  We have been there and done that and there will be surprises if not all areas are addressed.

Then when you get this all dialed in and figured out... you will start breaking the frame tubes below steering head due to the great big braking forces you are certain to introduce with all the options in braking components and friction materials available these days.

Be Carefull

KOS

[MCRider]

One of things we might be missing here is the issue of making the engine frame nice and firmly mounted to each other, but running standard swing arm and leaving steering head out there... with lack of support and or direct bracing. Add super sticky  racing rubber on the new tires on wider widths...one must treat these modifications as a package. Don't let the tail of the dog...do the wagging! Or the head, do it's thing up front and cause some much unnerving shaking.  We have been there and done that and there will be surprises if not all areas are addressed.

Then when you get this all dialed in and figured out... you will start breaking the frame tubes below steering head due to the great big braking forces you are certain to introduce with all the options in braking components and friction materials available these days.

Be Carefull

KOS

Points well taken. My project is gussetted beyond the motormounts discussed, including steering head and swingarm areas. And in my case, its mostly for looks. My racing days, pitiful as they were, are far behind me.  at that time, I had done some things which make me cringe now and thank the racing gods I'm still here.

Good luck with your most serious endeavors and thanks for sharing. I at least enjoy the vicarious thrill!
Ron

[kos]

754's version of the rear engine mount.
Info to follow.

A good looking well designed piece. Nice!

KOS