Doug Heim's Cuda Build

[Doug Heim]

This will be my newest thread of my newest build. Even though I have already spent alot of time since the Plans came out gathering parts, machining the smaller items, bending tube, and putting together weldments such as PIRCV and control arms, I would like to announce that the offocial build is now on its way as of October 7th.

I started off clamping the lower frame to my table and fitting the PIRCV to it. I then proceded to position the engine in front of the PIRCV. I also positioned the main roll bar to see what type of engine clearance I had between the roll bar and PIRCV. Keep in mind I did not weld anything at this point so I am able to make changes before I am commited. That is why I started at this point instead of building the chassis first like most builders do.

I was very unhappy with the clearance I had behind the engine and I knew if i could get at least another 1" (25mm), the benifits would be huge as far as clearance with the main roll bar and being able to get the engine in and out.

I always had the idea in my mind of the possibility of creating more rear engine clearance on the Honda RC-51 and I put it to the test today with great results! As some of you know and for those of you that dont, the RC-51 engine is a supporting member. The rear A-arm pivot on the Swing Arm is mounted through the engine casting. I always wondered if I could machine it down without tearing down the engine to give me that clearance I was looking for in past builds. The main thing holding me back was the fact that castings have many voids in them for weight reduction or clearance for internal parts. I have never seen a bare casting so I had no idea what was on the inside. I felt I needed the clearance so much to the point that It was worth the risk. I clamped the engine down to the Horizontal Mill and started to carfully remove material. There is a hardend steel sleeve that needed to be pressed out because it was too hard to machine efficently. I did plan on just cutting it along with the casting but I tore up the ends of my endmill relizing it was too hard. After I removed the sleeve it revealed the voids in that area of the engine casting and I was able to shine a flashlight through the pivot hole and see where my safe points were. The voids did not expose the internals of the engine. I was very happy to be able to remove in excess of 1 1/2" from the case. Needless to say I have zero clearance issues and I am happy as hell. Next step is to add the idler. I also will be dropping the engine 1 1/2" below the lower chassis and making a new oil sump from billet that will sit the 1 1/2" higher than stock. Doing this helps with the little remaining main hoop clearance but does not eliminate it. I will notch one of the cross bars to eliminate it completly. The main benefit to lowering the motor is now I will not have to notch the PIRCV Housing for the chain completly. i will keep you posted as the work progresses. Here is my new link.

http://s39.photobucket.com/albums/e162/ ... a%20Build/





I have spent the last 2 evenings mocking up the idler and positioning and repositioning. I am happy with the progress. It took me a few hours brainstorming about how I wanted to mount the idler as well as it being strong and look like it was well thought out. All I have to do to complete the idler set up is bore the blank sprocket out to fit the double row ball bearing and make up the correct spacers. I temporary set a used (stretched) chain into the set up to see where my full link comes out to. Tomorrow I will fit a brand new chain and I will reposition the engine front or back (can only go back 1/8" from where it currently is) for optimum chain adjustment. The PIRCV does not allow enough adjustment to be able to do without a half link unless great care is taken to where the motor is mounted in the optimum position. A different # of teeth of the front sprocket will also affect it. I am running the same gearing as on my Piranha (14-60) and have that fit as well. If I ever do need more or less adjustment I can fit a different diameter idler if need be but the idler at a 15 tooth is already pretty tight. You can see the huge benifits from not building the chassis first at this point. I was able to unclamp the PIRCV from the jig table and fixture it to my milling machines to notch the housing for chain clearance as well as the fabrication of the idler mounts. The next step is finalizing the position of the engine and then to notch out the main roll bar hoop before making engine mounts. ENJOY!












Here is a thought... I cycled my adjuster today now with the engine attached to it's first mount so it is quite ridged to the housing now and was not before. While cycling it and all the turning I had to do to the adjuster made me think... Hell if the chain stretches so much that I have to remove the 2 links, being the short chain it is I would think the chain would be junk at that point and need replacing rather than the removal of the links. The chain I will be runnung is 74 links. Thats 1/2 of a normal bike chain's length. I have never had to, or even heard of ever removing 4 links from a bike through its entire life. If it had I would think the same would apply. Chain = Junk. What are your thoughts?

Here are some pics of the progress tonight. I fitted the rear main hoop and it is welded solid @ 90 degrees. I have the upswept nose tacked on and tomorrow I will fit the main cockpit / upper frame Rail. I wanted to fit this so I can continue on the same plane for the rear upper frame. Then I will know where the structure points all are so I can button up the engine mounts. The engine did end up moving forward about 1/4" (6mm) than where I first just set it for mock up. This is now what I figure to be the best position for the engine in relation to the PIRCV. Moving the Engine forward scraped my idea of only notching one of the cross tubes in the main hoop. Instead I now had to completly remove it. If I hadnt, the removal and install of the Engine would be a battle. I do want to add the strength and protection back into the main hoop somehow. look at my Pics below to share your ideas with me and if anyone thinks the will help, or really just add weight with zero strength attributes. Thanks for viewing... Doug Heim

Yellow = proposed bracing
Red = pointless or necessary?


Engine mount



I made up the opposing engine mount to the one that ties into the idler boss. I wanted to continue with the upper rear but decided I shold see where all the bracing ends up so I made headway on that. I added an X that ties into the front of the PIRCV because I was unable to tie the front in as suggested in the plans because of my exhaust. The V-twin shure is tight for getting the exhaust out but once I make the tight bend it is all open for whatever my imagination can come up with. I mocked up the exit for the header on the rear cylinderso I cold see where that ended up to avoid any fouling on bracing. I still will be tieing the PIRCV housing's front into the uprights somehow. Ill get to that next. Seems like Im doing all the hard stuff first. Hopfully once this is all sorted out it wll go much quicker. Hell you guys probably already think this is moving along quite fast. Im only 1 week into the build and I have not even devoted all my time to just this project. Hope to have more to show you soon. later Doug

Have to do witout the bar in red...


Extra X-bar to replace the absence of the above pic...

[plkracer]

Looks great doug. Thanks again for the arms. I mounted my engine in a similar way, but didn't mill off the back side. that must have been a job! my idler will be in my mount, although it wasn't intentional. I found that the chain will slightly rub the shifter shaft, so i put the idler shaft in one of the lightening holes on the mount. should work out excellent. did you add the x bracing on the front side of the pircv? Did you think it was necessary? Thanks.

[plkracer]

Oh, I see now, you couldn't put the cross bar in, so you used the x brace. My 750 was also pretty tight. The lower motor mount is about 2 inches from the pircv and the airbox would hit if i didn't cut off the front mount tab. There is a couple inches between the headers and the bracing.

[K-fab]

Fantastic write up Doug! *

Thanks for sharing it on the board.

[Doug Heim]

.I had to remove the one cross bar because of the Engine placment and I do want to build the new bracing around the engine. I do not want to go too tight to the motor though as I want to make it a less of effort to install or remove the engine. The RC 51 is a long engine. Probably one of the longest V-twins because of the 90 degree configuration. I actually thing fitting a Busa engine to this frame would be easier.

I made some great progress today but almost got ahead of myself. I tacked up the rear upper frame with the uprights that connect it to the PIRCV housing. As things were moving along so smoothly, I fully welded the uprights. Then I stood back and noticed how crooked they were. To the untrained eye it would probably go unnoticed *but as I am picky I took out the sawzall, cutoff wheel, and 3 ratchet straps to trim & pull it all straight again then reweld. I am very happy now and the cause was I accidently left one end of my main frame about 3/16" longer than the other. It was about a 1/2 hr set back. I could have stared at it a bit longer but the more I did all it did was piss me off. I figure... I could stare at it all day but why stare and woder what went wrong when I could just start cutting and grinding untill it is fixed. It is perfect now and all is right on track. I hate it when one bar is off. It is so easy for everythingelst to get off course then.

After fixing that issue I started to make the uprights that attach to the lower frame in front of the PIRCV Housing. I knew I was going to have to add a X-tube for the install and removal of my Idler bolt so I got that sorted out. I also knew that my Engine would foul on the right side so somthing was going to have to be done there. I marked it out and found that the best way was a long narrow notch in the tube that contours the engine. Tomorrow I will begin more engine mounts. Thanks for your input guys. Please keep checking back.




This Tube is not as week as it appears! The circular notch is only half the depth into the tube and what you cant see is that the engine actually straddles this part of the notch. I know that does not make much sence to some of you so I will try and get pics of this tomorrow. There is also more clearance on the bolt lug than the picture showes. Must be the angle.


Compare this picture to the above one.



The red line represents where the origianl tube was.
The yellow line represents the notching for the engine toward the camera.
The blue line is where the notch is behind the bolt lug in the casting that is difficult to see. Hope you can make sence of it. I just dont want anyone thinking this may be a weak spot. I may brace the back sides of the tubes in these areas.



I also wanted to point out my little idea to help those of you who dont have a 3rd hand in the shop. I decided to tack on these little pieces of angle iron to create a pocket for the upper frame to sit in at the main hoop. This way it was easier to handle by myself.

[plkracer]

Doesn't that radius rod want to roll the upright, and pull it forward as it goes up or down past level? Or is there soe trick in the heims so they aren't already solid mounted?

[Doug Heim]

I have some time to talk about my build so I thought I would take the time to post. I didnt get a chance to work on the buggy tonight as I had another project to work on but I hope to get the other side of the rod end's mounts cut out and tacked in place. I also would like to tack up the other upright as I only got the one side tacked for experimenting with the Trailing Link system. I first started off by drawing it all up on CAD. I am unfamiliar with 3-D CAD so I had to really work to try and figure out the notch for the cross bar on the main hoop on the chassis mount of the trailing link. I printed it out at full scale and then transfered it to cardboard and then to 1/4" thick press board (wood) refining the pattern each time. You can see this below...


I then scribed the locations on the mount points as the top view has showed on my CAD work...


Placed the plate into position and tacked in place...


I tacked up a new upright so I could also tack on the new mount point for the Trailing Link to attach to the Upright...



I can move it through full travel with zero binding and plenty of engine clearance which was my main concern!




Now all I have to do is make up the other plates so that the rod end mount's are double shear. Also have to do the other side now that it is proven out. Thanks for looking guys... Doug

[plkracer]

Wow, that's kind of crazy, i guess if the arms are long enough, you can get a decent amount before it binds. BTW, did you get my email? Thanks. Also, is that brace necessary? Will the arms actually tweak?

[Doug Heim]

No the arms will not tweak and the deflection if built to the CAD work is less than .001" through full travel. Hardly able to even call it a bind.

[RickS.]

Hey it turned out great Doug,
It's true there is no bind anywhere throughout the travel once you've determined the sweet spot. The double a arm suspension geometry creates an arc, and that arc simulates a pivot point in space. In most cases this point in space is actually a very tiny arc. The arc is so small that you can just position the point midway along this tiny arc without creating a bind.
Now I’ve called it a point, but really it’s an axis that travels the full length of the buggy. The link can be as long or short as you want as long as the end is placed on this axis.
The same method is used when determining the length of your steering rack pivots on a double a arm front suspension. Determine where this point is and design your rack length accordingly. If the arms are swept up the axis will be traveling up on this angle also.