Author Topic: My '59 Enfield /Indian 750cc Chief High Compression Build  (Read 161230 times)

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Offline wobblywalrus

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #225 on: February 09, 2014, 08:57:42 PM »
Scottie, sometimes you can put spacers on the damping rods to limit fork extension.

Offline Scottie J

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #226 on: February 09, 2014, 09:59:42 PM »
Scottie, sometimes you can put spacers on the damping rods to limit fork extension.

I was actually doing a bit of research on Race Techs website today.  I found these "VINTAGE FORK VALVING with GOLD VALVE CARTRIDGE EMULATORS" on their website that basically turn vintage damping style forks into a cartridge style fork.  I was also reading how you can dial them in and fine tune them with damping rod spacers.  $399 for a complete kit including springs.

http://racetech.com/page/id/56

Offline JimL

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #227 on: February 09, 2014, 11:27:54 PM »
You can probably adapt the Zuki forks into your frame.  I adapted FZR1000 forks onto my old GS frame head.  You can do a lot of mixing and matching with bearings and spacers, easier and cheaper than reworking your Brit forks.

The cheaper part is the best part. :-)

Offline Stainless1

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #228 on: February 10, 2014, 12:17:28 AM »
Yep, for a lot less money you can buy a late model busa or gsxr front end, or any other sport bike.   Lots of those get wrecked, just need to find one that went down on its side, and didn't hit the car in front of it.  Ebay is full of them.  I think modern forks would be better than the stock alternative, with any amount of work or money thrown at them.
I'll be in Denver visiting Johnboy on our way to Portland for Freuds reunion, if you know of a spot to get a good beer, we might have time for that.  PM me if you want to talk over a decent brew.
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Offline Scottie J

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #229 on: February 10, 2014, 08:33:58 AM »
I'm not going to lie guys, those Zuki forks are not in very good shape.  When I owned the bike previously, that was my biggest gripe about it.  They leaked really bad and won't hold any pressure.  They were so bad that they actually caused the front tire to wear very oddly.  Not to mention that about half of the parts for the forks have been discontinued including the brake lines which are totally shot.

http://www.bikebandit.com/1983-suzuki-gs550ese/o/m21344#sch240474

After reviewing what IS available, do you still think it's worth trying to save?  I can completely rebuild the original fork into a better fork for about $400 and not have to modify anything.

Scottie J

Offline Scottie J

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #230 on: February 10, 2014, 10:55:00 AM »
I changed the angle of the rear and took a few more pics this morning.  Looking at it now I think I can get away with just mounting a bung to the bottom of the frame to mount the shock.  I feel it is at a good angle and in a position to have ample travel without bottoming the frame out on the ground.  Also it looks like a good lowered height that should keep me close to the ground.  Thoughts?









Scottie J
« Last Edit: February 10, 2014, 10:57:02 AM by Scottie J »

Offline JimL

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #231 on: February 10, 2014, 11:49:17 AM »
One of the struggles, if you plan to run both SCTA and AMA events, is tire selections.  SCTA rulebook has tire rating requirements which affect your wheel choices.  Costwise, any class that might have over 151 mph records to run against is cheaper and simpler to build on 17" tubeless wheels.  ZR rating tires are mostly 17", especially DOT Race rated as is spelled out for 200+ sit-on bikes (Bridgestone BT-003 for example).

That is why so many of us use some of the sportbike components for front and rear suspension.  Its just one less question-mark taken off of the tech inspection list.

JimL

Offline Koncretekid

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #232 on: February 10, 2014, 03:54:23 PM »
If your swing arm is at that negative angle (relative to horizontal), you will lose the advantage that a chain driven swing arm offers for better traction.  If the swing arm pivot is lower than the axle (like you're showing) the chain tension will pull upward on the swing arm.  If the swing arm pivot is higher than the axle, the chain tension will pull the swing arm down as it tries to pull the wheel forward and hence improve traction.  Using a smaller wheel will allow you to raise the frame as well as the swingarm pivot up to improve this situation.  As Jim said, 17" high speed rubber is the easiest to find.  This is probably not significant on bikes under 100 hp (that' just a guess) but high hp bikes need all the help they can get.

Another thing you need to check with whatever wheel you chose is the sprocket offset from the centerline of the wheel.  Typical British transmissions put the drive sprocket closer to the wheel centerline than more modern designs that take the drive off the layshaft and usually further from the centerline.
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Offline wobblywalrus

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #233 on: February 11, 2014, 12:08:38 AM »
The entire chassis should have a similar modulus of elasticity.  In other words, no part of the chassis should be significantly stiffer or weaker than any other.  Those old brit bikes work fairly well 'cause everything is weak.  Things get really interesting when a strong set of forks and a stiff rear arm is bolted onto those bicycle type frames.

A Rex McCandless design frame, like those found on the Norton featherbeds, will give you period authenticity and be a heck of a lot stronger.  That motor should fit.  They are made new and can be purchased in a variety of geometries, steel alloys, and wall thicknesses.  Try Unity Equipe.  The BSA A-50 or A-65 frame was a "poor boy's featherbed" in those days.  It would be a lot stronger than the Enfield frame but not a strong as the McCandless.

 

Offline Scottie J

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #234 on: February 11, 2014, 07:01:57 AM »
The entire chassis should have a similar modulus of elasticity.  In other words, no part of the chassis should be significantly stiffer or weaker than any other.  Those old brit bikes work fairly well 'cause everything is weak.  Things get really interesting when a strong set of forks and a stiff rear arm is bolted onto those bicycle type frames.

A Rex McCandless design frame, like those found on the Norton featherbeds, will give you period authenticity and be a heck of a lot stronger.  That motor should fit.  They are made new and can be purchased in a variety of geometries, steel alloys, and wall thicknesses.  Try Unity Equipe.  The BSA A-50 or A-65 frame was a "poor boy's featherbed" in those days.  It would be a lot stronger than the Enfield frame but not a strong as the McCandless.

 

I agree and beg to differ at the same time.  the new Enfield that come out of Chennai, India do have weak frames that are prone to cracking and breaking under extreme stress.  The Redditch model frames are much stronger and made with stronger steel.  I'm not sure what exact gauge it is, but it looks to be close to 1/4" thick walls.  If I decide to run a custom frame, Rickman makes Enfield chassis in a variety of metals for a good price.  I believe Don Sliger was using a custom Rickman frame for his dual engine Interceptor.

I believe I have a plan of attack today.  I spent most of my free time yesterday developing a gusset template that I can weld to the bottom of the frame and make it so it has 3 different height positions I can set it to.  My problem is that I'm cutting the shock gusset out of 3/4" plate steel and I don't know how to cut it cleanly.  I'm thinking of just going back to the steel shop and have them cut it for me, though any suggestions are greatly welcomed.  I also picked up 8' of 1 1/8" steel tubing to fabricate a new seat area.  i have some ideas floating around in my head.   :-D

Position 1 (Lowest Position)



Position 2 (Middle Position)


Position 3 (Highest Position)





Scottie

Offline Scottie J

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #235 on: February 12, 2014, 06:29:46 AM »
After looking at what I had going on for another half hour or so yesterday, I decided to do away with the "3-way adjustable gusset".  After a closer look I realized that the shock mount bracket was actually damn near bottoming out on the gusset in any position other than the highest.  So I opted to go with just a simple triangle gusset  (2 1/4" H x 4"W) with a single mounting hole.  I started welding it place and called it a day before I got any pics taken, I will get some posted up by this afternoon.  I did "test" the articulation of the swing arm/shock (without the pre-load damper connected) and it seems very smooth and fluent, no binding anywhere.  And even with the pre-load damper not being installed I couldn't get the frame to hit the floor, so that's a good thing.

For the record, I did follow up on Koncrete Kid's last post about swing arm angle to the swing arm pivot point and he is correct about it's relativity to traction.  Now, I didn't read anywhere that said how the forces will pull the wheel different directions (upward or downward force) depending on where the axle/pivot point is located, but it did go into detail on how the higher the pivot of the swing arm, the more downward force can be transferred to the wheel.  So, in a nut shell, basically the same concept.  Though, it also stated that the chain/sprocket position/s have more influence on squat and anti-squat than any other factor.  It was a good read BTW.

http://www.sportrider.com/tech/146_0404_motorcycle_traction_geometry/

So I took this into consideration, and also did some close observation of my stock '58.  When looking at the '58 I noticed that the OE swing arm sits almost completely parallel with the ground, assembled without rider, so I obviously had a little room for improvement.  I ended up jacking up the swing arm as high as I could go with the jack I was using and took a step back and looked at it.  The swing arm had a nice positive stance without being to far over the top.  I was also reliant on the fact that I know when the pre-load is cranked all the way up on this shock, it gets very stiff and doesn't move much without some work.  From the measurements I took, the swing arm should be a few degrees positive fully loaded up and the pre-load at about 3 where I used to keep it at.

Scottie

Offline Interested Observer

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #236 on: February 12, 2014, 03:22:34 PM »
Think about it.  The ground contact load at the rear wheel is purely a function of the weight distribution and whatever aero load redistribution occurs.  Monkeying with the swing arm geometry only affects whether the chassis rises or lowers when load is applied to the chain.

Offline Koncretekid

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #237 on: February 12, 2014, 04:49:29 PM »
Yes, I.O., and I think you are smart enough to determine the downward component of the chain force that tries to pull the rear axle forward when it is below the swing arm pivot on the frame.  If the chassis moves upward, is there not an equal and opposite force acting downward?
We get too soon oldt, and too late schmart!
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Offline Briz

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #238 on: February 12, 2014, 05:54:10 PM »
Thats an interesting thought, but given that LSR racing is often a battle between drag and traction, maybe jacking up the back of the bike might cause more aero problems than the possible traction advantage might be worth?

Offline Interested Observer

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Re: My '59 Enfield /Indian 750cc Chief High Compression Build
« Reply #239 on: February 12, 2014, 07:25:04 PM »
Quote
If the chassis moves upward, is there not an equal and opposite force acting downward?

When the chassis moved upward it unloaded the suspension spring by just that amount--no net change.  Try drawing and analyzing a free body diagram.  There is nothing there to cause an increase in the tire contact load.  The sprockets, chain, swingarm, chassis, springs etc. are all a self-contained force system. No external forces are affected by their internal changes. 

If the contact load at the ground was increased, it would then be more than the weight originally acting on the wheel and the wheel would come off the ground!  An external load (weight/aero) has to be applied to change the wheel load.