Harris mag3 homebrew project

[nlovien]

whats your thoughts on best solution for this ??? - i've cut out as much as can be ref: the swing arm cross member but i'm still not getting enough arm droop - needing another 5 deg s - what's my options

1) I can make another bell crank and move the shock mount another 10mm in to give more clearance - negative ? - that will be a 20 mm shift from the original harris bell crank - my ratios will be out to lunch, can review this using Mr Tony Foale program - it will tell me whats going to happen - not make it right - maybe we can find a workable bellcrank ratio

2) I can cut a portion out of the centre fwd face of the swing arm cross brace and weld in a recessed plate - seems to me there is plenty beef in this arms cross brace to enable me to do this - negative ? arm weaker - will it really make a difference ?? positive = I can revert to the bellcrank ratios Harris used

3) looking at the original Harris arm - note the two plates that brace the cross beam to the swing arm axle sleeve - i'm liking this, the load from the bellcrank tie rods goes to these plates - this would add back in some strength if I cut out a part of the cross beam between where I would weld in these plates

so my present directions is 2 with maybe 3 - but my reasoning is based on thought versus actual experience - easiest solution is 1 but my sense is my rear suspension could be bollocks due to wrong bellcrank ratios - do you agree with my logic ???

[grebo]

Cant tell if you have a top shock  mount sorted If not why not modify bottom shock mount moving holes forward to gain clearance in arm .

Couple of plate brackets and spacers to see if it works , then alter the mount you have

 

[Gammaboy]

Chop the brace, keep the ratios. Unless you want to go all tony foale and design a bellcrank that gives a more linear rising rate...

[nlovien]

14 hours ago, grebo said:

Cant tell if you have a top shock  mount sorted If not why not modify bottom shock mount moving holes forward to gain clearance in arm .

Couple of plate brackets and spacers to see if it works , then alter the mount you have

 

thanks - top mount is set - moving it doesn't really help  - moving the bottom mount  - this is my option 1 - i'd prefer not to move it any further as this will change the suspension ratio's - should have added, before I crashed the bike I spent a bit of time with Maxton getting the rear shock "tuned" to match the original rear suspension rate 

Gammaboy - took a good look at this last night, there's plenty strength in this brace - recon i'm heading this way, even if I were to do a tony ( and that is a future option) I wouldn't know what rate or rate profile to go for - the bloomin manufacturer's can't agree on this - I'll go this route after I get bum on seat - so best I keep as near to as was to give a decent base line

thanks - your feedback does  really help 

[Cluffy]

Awesome build mate. Where are ya? I'd love to pop in n have a gander if I'm passing.

[nlovien]

more than welcome sir  - a  wee bit Northwest of Huntly - could use another set of eye's for this cosmetic stuff - its easy to stick a seat on her, dam't difficult to do this such that it looks right - some folks just have an eye for it - me? I need a mild stimulant to see it, problem is, once it wears off the next day - it's gone  - so what i'm seeing is - if you follow the blue scribble that could be the lower frame rail - at the same angle dictated by the centre seat line, the black bits are where I could cut out ( don't want the blended in tank to seat unit fit) and the angle of this cut could follow the frame top rail back --  but does it look right ?

[Gammaboy]

Seat unit looks to be sitting at a good height/angle, and the trim off the bottom that's parallel looks about right - just needs some tweaking on the shaping at the front of it.

[nlovien]

thanks - got a fresh set of artyfarty eye's on it today and the other person pointed out the obvious that I didn't see - but now pointed out - I can't now miss it, the seat and frame tube line is driven by the Engine side case - take the average line through this case top 4 bolts and project it to the moulded line mid section on the seat - make the frame rail match this to join it together - bingo!, its almost where i'm at anyway, but didn't know why-  in hindsight looks obvious - probably best seen by - what if these didn't line up - tried it - and it looks crap, all goes to proove, this 2nd person who spent 4 yrs at art college, obvious it wasn't a totally wasted education

 

[markfoggy]

Scallop the arm. 3mm plate in there properly welded and you will lose next to no strength. IMO.

[nlovien]

2 hours ago, markfoggy said:

Scallop the arm. 3mm plate in there properly welded and you will lose next to no strength. IMO.

brill, thanks - right where i'm thinking - make a half tube with an ID a few mm larger than the shock spring diameter and - as you say - scallop it in - got an added bonus in doing this

at the moment I tapped through the bottom plate of this brace to bolt up the mounts for the bellcrank tie rods - not happy with this as a final solution - was going to weld up once confirmed - but now I'm cutting into the box = I can put in an additional internal brace plate to achieve a decent bolt thread and spread this load = strong brace either side of the scallop

[nlovien]

been a while for an update - have made a bit of progress - never as quick as you wish though, however I came up with a neat thing to solve a pain  - getting the seat sitting square on - argh!!, tried x 3 times with the frame  mount that picks up on the seat mount bobbins on the side behind the bum rest - you working blind to it when you fit the seat - just needs to be out by a few mm and the seat just isn't right - ok, so I left one side with the tapped bush on centre to pick up on the matching seat mount, on the other side I made a bush thats a nice sliding fit into the frame mount hollow tube, then I tapped this bush off centre at two different places ( to get two different cams from it)

OK so 1st attach this bush with the off centre tapping to the seat, then you offer the seat up to the frame and let this bush socket into the frame tube - ok, then add your  spacer to the other side and make up the mount to the centred tapping ( this will space the seat  - horizontal @ 90deg to bike axis) as the other side bush can slide out of the frame tube as you tighten up the opposing side, now you just turn the allen bolt that mounts the sliding bush with the off centre tapping, because of this, as you turn the seat moves up and down and pivots  left to right relative to the bike axis - find the sweet spot / mark up the bush relative to the frame tube - remove and weld in place - job done 

bollocks - next time - make a jig and do it properly 

 

[nlovien]

right that's the seat subframe tacked up - done the wrong way - free hand versus making a jig creating a rod for my back getting it all aligned but after a few bits of scrap bin manufacture i've got it close enough. The smaller OD top tubes are an ingenious technical development - saving aprox 20grams in weight  - yea - bollocks, I ran out of the larger dia. chrome moly tube  - hayho - it enabled sliding the seat support back and forth to aid locating the seat - right, next is all the tabs and mounts needed for mounting things - got to do a bit more seat shaping at the front - not sure yet how to finish this - the original Harris body work = the tank sat into the seat - hence why i've made a tank support and why the bottom of the tank looks like it needs to sit into something, going to live with the tank and seat being seen as two separate parts - i've also modified the swing arm = now getting the droop I was looking for

[Fugly]

Coming on nicely

[Swiss Toni]

Bloody hell! You're certainly getting stuck in! Great post! 

[nlovien]

thanks - had to take it off the bench to go fix another bike, but before I did i've sorted a bit thats been bugging me - to trim the front of the seat in an attempt to get a shape that works - metal is easy - you can put back on what you take off but thin fibreglass - once its off, its off - not an exciting picture but it reflects a good few hrs with a bit of mental intoxication ( whisky ) - perfect - nope, happy yes

whilst i'm otherwise focussed would be a good time to get it painted - can anybody advise on the right colours for the XR69 red/black and yellow ? - its the trident XR69 i'm using as a guide - thanks 

[fatblokeonbandit]

Niice seat unit

 

I did my magum in sort of heron colours not sure it its right but I liked the look

 

[nlovien]

been a while for an update because i've got other projects on the go however my good friend who is just brilliant when it comes to sorting bodywork delivered this back to me. The petrol tank was so badly twisted and bashed i'd presumed it was scrap but he's worked his magic on it pulled it back into shape with only a light skim of filler where required - he's also pritty good at applying paint - I know - XR69 rep colours done to death, but not by me and I love it - well happy  - now going to carefully take it off and hide away upstairs and let the paint cure - ok, not yet - maybe keep it in the garage for a few days for inspiration 

 

[vizman]

looking good

[RUSSP]

I agree got to be those colours bike is looking great 

[nlovien]

thanks, pissed me off this morning looking at a GPZ9 project on my bench and this one sitting idle, daft bugger taking on the gpz but i'll get back to this one in a few months, should see it finished over the winter - definitely on the road next yr, got a date at Spa for it 

[SiBag]

Coming together nicely,

Colour scheme suits the shape of the tank and seat unit perfectly.. Top job..

Edited December 9, 2017 by SiBag

[Swiss Toni]

Yup! Agree with all above. Great choice with the colour scheme! 

 

[bluedog59]

That looks mighty fine.

PS. like the homemade blast cabinet in the background ( unless it's some kinky bondage s+m device ).

[nlovien]

On 07/08/2017 at 6:29 PM, bluedog59 said:

That looks mighty fine.

PS. like the homemade blast cabinet in the background ( unless it's some kinky bondage s+m device ).

 this comment now distracts me when I go into the garage however, my good lady says - no -no no - NO! 

[bandit750]

On 07/08/2017 at 6:29 PM, bluedog59 said:

 

like the homemade blast cabinet in the background ( unless it's some kinky bondage s+m device ).

Proper blind mans blast cab so you could be right.