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Discussion Starter #1 (Edited)
I have been working with my local garage on an insight Mk 1 rear axle assembly after I recently replaced one in one of my cars.

The axle contains two large rubber bushes which are not available from honda as seperate items. ASFAIK You have to buy the complete axle assembly at a cost of over £500.

Anyway to cut a long story short with the help of their press I mananged to get the one good bush out of my old axle and this was sent to a well known UK poly bush manufacturer for evaluation.

I now have a rough price and tooling costs for a run of 10 poly bushes, which works out at around £150 a pair. This is a massive saving and they should be much harder wearing and give more feeling to the rear suspension setup.

If anyone is interested in a pair e-mail me asap at [email protected]

I intend to place an order next week, they will carry no guarantee whatsoever as this is the first run. I'm prepared to put the money up for the first ten as a calculated gamble.

If they work out I may well approach them with a sample bush from the front suspension arms which wear/dry out as we know giving the well known scrunching noise problem.

I'll try an post some pics of my disasembled rear axle to illustrate.

Peter
 

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Nice work Pete.

Just out of interest what sort of dimensions was the original bush? If it one bush or is there a seperate thrush washer? I think one of the issues with the Insight stability is the sideways motion of the beam isnt controlled by the bushes and relies on the damper, the Jazz, Civic, Insight II and CRZ all now feature angled beam bush axis.

Do you have any pictures of it stripped down at the rear end?

Sounds good for cost, my only concern would be uniform compliance due to the poly is X and Z and then possibly more stiffness if there any toe change that occurs when only one side is in bump. Trailing arm bushes on other Hondas can make them a bit more prone to oversteer, which in mine is terrible (probably tyres), although that was on the far more complicated setups with the passive rear steer and toe changing independant rear setups.

The Insight rear suspension is quite agricultural so noise from stiffer bushes could be quite marked?

What shore rating are you looking at going for? This could be a really good mod to connect the rear end though :)

Thanks
 

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Discussion Starter #3
Too many technical questions for me at the moment jonny. I'll pass them onto my partner in this. My knowledge is minimal in this area. I'll post some pics in due course but don't have the bush to photograph as it is with the poly man as a pattern. be a few weeks before we get any more updates I expect. Peter
 

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Discussion Starter #4 (Edited)
This project is still ongoing and the manufacturer Powerflex is starting on our first prototype batch of 5 pairs of bushes next week. I'll be testing a pair and so will the Rally chap, that leaves three pairs. PM if interested.
 

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Discussion Starter #6
50mm if I remember correctly. Powerflex are being slow but I hope we get them eventually! I'll keeps us posted.
 

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Discussion Starter #7
Sadly Powerflex UK failed to deliver any bushes after having our pattern for over six months!!! Useless and continualy lied on the phone that they were nearly finished. So we are back to square one looking for an alternative supplier :roll: Any ideas?
 

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Bushings

There is a company called Smooth-on that makes pourable polyurethanes. One called PMC-790 might work. It is 90 Shore A which is about as hard as a typewriter roller if you are old enough to remember those. Just pour your own. PMC®-790 Urethane Rubber Product Information | Smooth-On
Jim
 

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Machinable Polyurethane Bar Stock

Once the durometer and sections of the existing bushings have been determined, it should be possible to machine a suitable replacement from readily obtainable polyurethane bar stock that is available from a die maker's supply house. This material is used in place of metal coil springs in stamping and forming dies. Assembling the outer housing, the rubber, and the inner steel bushing may require some simple tooling.

These Insight bushings employ the rubber in shear and compression similar to most automotive/truck spring shackle isolator bushings which are available in many, many sizes at very reasonable prices. It is possible that the Insight bushing is a standard size and is available at your friendly auto supply store. If the exact size is not found, suitable press on/in sleeves could make up a fit.
 

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....Once the durometer and sections of the existing bushings have been determined, it should be possible to machine a suitable replacement from readily obtainable polyurethane bar stock that is available from a die maker's supply house.....
Hugh,

How would you machine the poly material???

Over the years I have machined rubber in a small South Bend lathe, but it involved the use of dry-ice to "freeze" the rubber and make it hard enough to actually "cut" material from the rubber.

At room temperature, the only practical way I know of to machine rubber is by high speed grinding, which creates a lot of dust and is slow.

Jim.
 

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Thats disappointing Peter,

I want to look at the European Ford KA rear bushes. Same as the Puma and Fiesta I belive and come in 49 or 58mm size? The 49mm could work with the Insight and the beam hinges in the same manner of the insight (no angle)



I like metalastic rubber like OEM, no moving parts that wear out like poly with a sleeve and also they tend to be tuned such that are difference stiffnesses in different axis. Plenty of poly options for the Fords though.

We really could do with a Honda bush sized up and dimensioned.







 

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Discussion Starter #12
Jonny I can send you the bush if you want to measure it up see if you can find a supplier.

I think i posted some dimensions earlier in this thread though.

Peter
 

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Machining and assembling polyurethane bushings

Jim: Rubber-like materials are best machined on a wood turning lathe. Your South Bend metal cutting lathe, unless modified, is not capable of the 3000 SFM plus needed for proper wood turning or polyurethane machining. You would use a light feed to avoid melting and use standard wood cutting tools.

See McMaster-Carr for chart showing how to determine/guess at the hardness of the material you want to order. The material will need to be pressed into a metal sleeve and have a metal insert: jonnyvtec's photo shows flutes and a chamfer on the bushing's O.D. to facilitate assembly and a shoulder/flange to limit insertion and/or sidewards movement of the axle beam assembly when in place. Without the flutes and chamfer, some type of funnel-like fixturing might be needed for assembly.

The Insight bushings appear to have the elastomer adhered to both the outer sleeve and the insert and probably depend on both lateral and diametrical shear to maintain location of the rear axle beam assembly. This dual function requirement, especially the lateral/axial shear could be the reason for failure of the existing bushing. Therefore, if the replacement bushings rely on a simple press fit, the flange/shoulder or a thrust washer will be required (appropriately located) to absorb lateral thrust and change of dimension as the Insight's torsion rear beam assembly flexes and rocks.

The type of bushing shown in jonnyvtec's photo as a replacement may well outlast the the Insight's OEM bushing but will probably yield a stiffer less supple ride. The ride of the rear end probably will change.

The cast bushing suggested by jimrm has a good chance for simple duplication of the OEM bushing if 1.) the proper durometer elastomer is used 2.) the material adheres sufficiently to the sleeve and bushing 3.) the contours and sections of the OEM bushing can be accurately replicated in the mold.
 

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I see you stated 50mm Peter, but from your 'I think' comment Im only taking that as an estimate and of course we would need to know the length. :) If you send me one Im happy to order some Ford parts to compare them.

I certainly would be concerned about the NVH impact of pure poly as shown but it would be interested in trying the OEM bushes, The Ka, Puma and Fiesta that use this arrangement and bush are praised for their handling as they come from a time as Ford were finding their sweet spot with vehicle ride attributes



This is a pair of Ford replacments that typically sell between £10-£15!

Difference stiffness qualities in the primary axis's so we can get a ride comfort and control tradeoff in the Ford engineered area and the Ford Ka is a sub 1000kg so certainly the right ball park for comparison to an I1.

The front bush could also find a replacement appropriate from a similar parts bit. Most the parts on the I1 are lightly loaded, ie ball joints. But I think we have a life of rubber issues on the bushes that cant be masked by the Insights light weight, we summer approaching those tell tale dry rubber splits creaking will be more frequent.
http://ecx.images-amazon.com/images/I/41qDo2ppp-L._SL500_AA300_.jpg
 

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Discussion Starter #16
I'll post some better pics of the bush when I get home about 10 days. I'll bring bush to the UK day so people can take measurements etc.

At the moment only option is to buy the rear crossmember costg around £600
 

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Discussion Starter #17

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Thanks for posting the pictures of the bushings. So would a bushing that is basically a cylinder like the Ka's even close to fitting this application? Seems like the extra "wing" on the Insight makes it significantly more complex.

I keep hearing you can machine urethane, maybe that's a direction to consider. Another would be to make up a mold and cast new ones using whatever hardness & color you like.

Speaking of the "wings", my assumption is that they allow a certain amount of lateral deflection and thus some passive rear steering effect but are limited by the steel bit that's a similar shape. I haven't gotten under mine to look at this aspect in detail yet. If indeed the car was built to have some amount of passive rear steering, I'm curious whether going stiffer in the bushing department would help or hurt the handling. In any case, having dead bushings in there couldn't be good. :)

Joel
 

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Bummer! they look a far more complicated deal.

Tempted to try a spacer from a normal bush though. I think the metal travel stopper would explain why at anything about low steering angles results in more rear tyre noise, the metal to metal contact within the bush.
 

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Discussion Starter #20
I've sent the bush details to another supplier so we shall have to wait and see for a bit now.
 
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