New guy and A7 landspeed record build

[muskrat]

G'day Charlieb,
                    yep, my seals used to blow out as well. In a rush for a fix I replaced the seal with a bronze bush  . Worked OK.
 The through bolts stopped the barrels parting company with the barrels, then she started snapping SJ cranks. Too much comp (13:1) and revs (7500-8000). I toyed with the idea of an A65 crank but retired the project due to lack of $$$ (out of work). 10 years later she is now my cafe.
I PM'd Dan my method. If he still has it he might pass it on with my blessing.
Cheers

[trickytree]

Hi Charlie, your A7 motor sounds interesting. How smoth does your motor run with the smaller pistons?...I have a fresh A65 crank that I'm considering using in some plunger cases myself.

[charlieb1954]

very smooth, had it balanced before final assembly, next time i will find `a50 flywheel. the crank was us as on -040 and scored, i reground to triumph size std and fitted t120 rods, better then the all alloy ones as had the steel rear half of conrod, the trident pistons had pins higher up so the 1/2 longer rod only pushed piston 3mm through top of barrel.  worked out well really
another project i am on with, is a7 with std crank, and a7 barrel to take a10 pistons, so being more square engine should rev better, got spitfire cam, twin carb head, in a royal enfield frame, should be running april may

[olev]

Gday Charlie,
Can you bore A7 barrels out to take A10 pistons?
The second last paragraph of the link makes interesting reading.
Its about an American gentleman who may have bent the rules slightly.
http://pages.prodigy.net/dukie/_import/pages.prodigy.net/dukie/index5.html
If you can bore an A7, I'm not sure why he went to the trouble of shaving a fin off the A10 barrels and making a special piston.
Another part of this site shows different rods, pumps and timing side bushes - interesting.
cheers

[muskrat]

G'day again Charlie,
                          I used the trident pistons in my A7 and shortened A10 rods by 2.5mm at the big end. Never had a rod let go.
 All this is starting me to think of building another motor. Doh !!!
Cheers

[dan daughenbaugh]

Thought I would update you guys on my build progress. Im still waiting on a ruling from the AMA on running the a50/65 crank in my class. In the meantime I've fitted my cub tank and made some mounts for it recessed into the frame. Put the fork stops on to limit the steering to 15 degrees each way. My hardtail came in from the fab shop. Just doing some mocking up on it. Made some spacers for the front wheel. I've been working on my suzuki clutch, getting the bearing sorted and fitting the basket. Ill get some pictures up for you guys soon.

[dan daughenbaugh]

A few update pics
Hard tail jigged up and finished welded, pipes made up and tacked together. Still waiting to hear back from the ama about using the a65 crank. maybe they will tell me the day of the race

[dan daughenbaugh]

Better quality

[dan daughenbaugh]

Well Gents, I just got off the phone with the head tech steward of the AMA event for which I am running and after a lot of debate the 65.5x74 combo will be allowed to be run in the vintage class. This will give me the better crank and a bit more stroke. Now to decide wether to run this combo or the stock stroke and crank with up to .050 pistons or maybe even the a65 crank offset ground to 72.6 with triumph rods and .020 triple pistons. This would all be legal? Thoughts?

[muskrat]

G'day Dan,
              I'd go for the A65 crank & rods at it's std stroke. Sleeve back the A7 barrels to 65.5 and use a 1mm compression plate under them. The only stumbling block would be the pin height of the pistons. I don't know if A7 and A50 are the same height. And you still have thin flange barrels. The push rods will need to be lengthened the same amount as the comp plate.
 When you say off set ground do you mean just taking off the outside of the crank pin which will make it smaller or would you take some off the inside as well and weld up and regrind to std size?
 Triple pistons have a different pin height which is why I had to shorten A10 rods by 2.5mm.
Cheers

[dan daughenbaugh]

yes Muskrat, thats exactly what i mean. Ive got a a65 crank thats 30 under, did the math and i could offset grind it to move the crankpin centerline in. Then fit it with the triumph 650 rods that are 6.5 inches long with .010 under bearings. The triumph rod is a bit better having a steel cap on the end. I would also fit a 3mm compression plate under the barrel and remove some material out of the lifters to allow them to drop down as described elsewhere in this thread. I'd use the through bolting method we discussed to keep the thin flange barrel on this planet. Seems like this would alleviate the need for high dollar custom pistons and rods. The only somewhat expensive part will be the extra machining the of the crank.

[muskrat]

Another option would be to grind it a little more then have it built back up to the std large journal size and use A10 rods.
 I have a LJ A10 crank that someone lengthened the stroke by building up the outside then reground. The trouble is they didn't build up all the way round before grinding, so I can see a definite line where the old meets new. One day I'll get it done properly and turn the cafe into a 800cc 
Cheers

[dan daughenbaugh]

 why the a50 flywheel? Lighter and therefore quicker to accelerate?

very smooth, had it balanced before final assembly, next time i will find `a50 flywheel. the crank was us as on -040 and scored, i reground to triumph size std and fitted t120 rods, better then the all alloy ones as had the steel rear half of conrod, the trident pistons had pins higher up so the 1/2 longer rod only pushed piston 3mm through top of barrel.  worked out well really
another project i am on with, is a7 with std crank, and a7 barrel to take a10 pistons, so being more square engine should rev better, got spitfire cam, twin carb head, in a royal enfield frame, should be running april may

[dan daughenbaugh]

Hello Gents
I was wondering a bit more about the a65 crank in the a7 plunger cases as Charlie did. I was measuring some cranks in the garage last night and it appears that the drive side of the crank on the a65 where the bearing rides was much smaller than the lj a10 crank i was measuring. I couldn't compare to an a7 crank as all of mine are in motors right now. I also noticed the a65 cranks I had on hand were about 1mm larger in width than the a10 these were all roller bearing cranks. I seem to recall reading somewhere that the ball bearing cranks were the same width as the a10/7 cranks. Do the ball bearing cranks have the same size journal for the bearing to sit on as the a7/10?
Thanks

[muskrat]

G'day Dan,
               All the A7/10 cranks have the same main bearings. The A65/50 is smaller on the drive side and I think larger on the timing side. I'm not 100% on the width but I thought they were the same. I have an A65 crank that I was playing with years ago and made a sleeve to go on the drive side to take the A7/10 bearing. That's as far as I got.
Cheers.