Lotus Elan

Bobbin style Polybush install on Front A-arms

PostPost by: 74Twincam » Mon May 11, 2020 7:02 pm

OK- maybe there's another trick someone's used for installing the poly bushes in the front links... I read up on the post about the anti-sway bar bushings, but have exhausted by curse word vocabulary and almost popped a blood vessel in my forehead fighting these things.

The bushings have the small flange on each end, and I just can't seem to compress the damn thing enough to "just pop the bushing right in" like I've been instructed. I'm not the world's strongest man, but I'm not a wimp either, yet these are kicking my ass right now. They get caught up with the flange on the bushing folding over and not getting squeezed into the collar on the link.

Is it OK to split these things with a razor knife and install them from each end like the other top-hat style bushings? WTF? I tried to fabricate a clamp, like that used for compressing piston rings- no go, everything's too slippery to hold still in the tool, also a funnel to squeeze them down to the proper ID, still no go.

Any tips?
Bill
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PostPost by: mbell » Mon May 11, 2020 7:21 pm

I just used my vice to press the poly bushed into the links. One of them took a fair bit and deformed but it did pop in in the end.
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PostPost by: SENC » Mon May 11, 2020 7:54 pm

I seem to recall pressing them into something slightly larger than the wishbone then on through into the wishbone, but won't swear to it. I definitely used mechanical advantage either with my press or more likely with a bolt through the bushing to pull it through with a hammer drill.
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PostPost by: 74Twincam » Mon May 11, 2020 8:50 pm

Ahah- inserting the bolt and pulling through is one I didn't think of- ! I may try a combo of the two, hadn't resorted to the vice/press yet. Good to get confirmation to keep going, and I was thinking these just HAD to be split...
Thanks guys!
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PostPost by: Chrispy » Mon May 11, 2020 9:09 pm

I just did all my front wishbones. Bit of a prick of a job.

I used a big machine vice and pushed them in, they deform a bit, but doesn't seem to hurt them.
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PostPost by: 74Twincam » Tue May 12, 2020 2:12 am

Thanks Gents-
After letting off some steam there, thinking about your replies and using my brain, I came up with a fairly decent technique to share now.
I started the bushing into the collar as best I could (with the silicone grease applied), then ran a long bolt through the center with a washer that is larger than the face of the bushing. Fastening a nut and similar washer to the opposite side, I then tightened them up to pull the bushing into the collar. A little extra squeeze applied as necessary with the channel lock pliers, and in total, about 2 minutes a piece!
Attachments
Bushing5.jpg and
Step 5
Bushing4.jpg and
Step 4
Bushing3.jpg and
Step 3
Bushing2.jpg and
Step 2
Bushing1.jpg and
Step 1
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PostPost by: vstibbard » Tue May 12, 2020 9:57 am

I'm interested in who the manufacturer of the poly bushes is please?

Also has anyone used the Kelvedon 30% harder original style bushes? I have a S1 26R wishbone setup thats going on my S1 Shapecraft which is essentially a GTS build.

Cheers

Vaughan
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PostPost by: alanr » Tue May 12, 2020 11:02 am

The advantage of using Poly bushes versus the original bushes on a road car is a little lost on me.
I can perhaps understand on the rear inners which may get oil contamined from the diff and degrade quicker the metalastik type bushes but not on the front wishbones. They are not that difficult to change anyway and surely the ride will be compromised for little gain with polybushes?

Alan.
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PostPost by: 74Twincam » Tue May 12, 2020 12:06 pm

I can’t speak to the manufacturer, I sourced mine from RD Enterprises here in the US.

As far as poly vs. standard it’s a personal choice.

Cheers
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PostPost by: Roland » Tue May 12, 2020 2:31 pm

I am in the process of fitting polybushes/PU bushes to my Elan Sprint front wishbones. The wishbones are original to the car and have a 27mm (1 1/16") bore which I believe is correct.

I purchased a set of Superflex bushes and they were really hard to fit, I almost gave up to be honest. I managed to fit them but only using a load of silicone spray (you should really only use soap, the bush was softened with hot water) Unfortunately once the SS tube was inserted the bush had elongated 0.8mm longer than the SS tube. When fitted to the car the wishbones locked solid, in my view too much resistance to put into service. I measured up the Superflex bush diameter before fitting to the wishbone and fitting the SS tube, it is 27.5mm diameter. This seems too large to fit the 27mm wishbone without significant elongation and radial crush. I did discuss matters with Superflex but they couldn't supply a reduced diameter bush, re-tooling is expensive. Superflex didn't tell me what diameter of wishbone bore their design was based on.

I have talked with Autobush this morning, their PU bush diameter before fitting the SS tube and installing in the wishbone is 26.8 mm which much smaller than the Superflex bush. Autobush advised if the SS tube is inserted (without the bush in the wishbone) the diameter goes up to 27.1mm which will be an interference fit in the wishbone.

I have just ordered a set of Autobush bushes and hope they will be easier to fit in my wishbones and importantly will not lock solid. Personally I think the diameter of the bare bush before fitting should ideally be 27.2 mm but I can't find anyone who makes that diameter. Autobush confirmed their bush design is based on 1 1/16" wishbone bore.

My conclusion so far is that not all PU manufacturers bushes are the same dimensionally and
different manufacturers bushes may suit different Elans. I have read posts indicating wishbone bore variations. I have also read posts by Ceejay and he makes his own bushes from solid PU bar, I suspect to get it really correct this is what I need to do but I have no lathe.

Regards

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PostPost by: Roland » Tue May 12, 2020 6:39 pm

Apologies i didn’t actually answer the question on how I fitted the bushes. I used a vice pushing the PU bush into the wishbone, with a piece of metal to stop the vice jaws marking the bush. The first Superflex bush took 2 hours before I developed a technique. I found that:

1. Hot water to soften bush is needed
2. The bush must be centred well on the wishbone
3. Wind the vice slowly sine the PU takes time to sort of react
4. In the early stages when under light load you can sort of re-centre the bush if it starts going off centre
5 if the bush skews a little bit keep going but slowly on winding the vice
6. If it skews a lot abandon and start again.

As explained previously my Superflex bushes were very tight and I used spray silicone for the last 2 which did make things even easier. I have removed all the Superflex’s since they lock up and I am awaiting Autobush product. I hope these will be easier to fit.

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PostPost by: mark030358 » Tue May 12, 2020 6:54 pm

I tried to fit a set 15 years ago and binned them. They were as thee other poster just too tight. I even made longer crush tubes, but as I said, I binned them. The ones for the rear A arms by the way, were perfect. Just my 2p worth.

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PostPost by: 74Twincam » Tue May 12, 2020 7:25 pm

Thanks for the additional tip on the install process, seems like a similar approach. Sorry to hear you're struggling through with finding bushings you're happy with.

For the sake of discussion (not trying to be contrarian here, just asking so I might learn something)-
I'm not too sure I follow that there's really an issue or not with the poly bushes being a tight fit once installed, is there?
With stock rubber bushings, there's a rotational resistance around the axis of the pin, because the rubber and the steel inner and outer sleeves are mechanically bonded to each other, which is why I understand it's a requirement to torque the A-arm bolts once the car's on the ground at ride height with stock parts.
I believe that the polyurethane bushing will provide the required resistance and rotation when in use, i.e. when the car is on the ground, weight of engine, etc. on the suspension. These parts are not bonded to each other and will therefore move/rotate in use.
I have installed a full polybush kit in a Land Rover and they were very tight, squeezed a bit axially when I pressed in the steel inner sleeve, but once the vehicle was on it's own wheels, no issues. The bushings settled into place and everything rotates just fine. It's a huge improvement in ride, and for that vehicle, I won't have to tear the entire suspension apart in 60k miles to replace everything- longevity was a goal for that swap.

Are you hoping to achieve a slip-fit after installation? The urethane is going to give, not like another plastic- it is an elastomer. Is there a specification that you are trying to meet that I just am not aware of?
Also, you mention a slight difference in ID of the suspension arm, and a difference in OD of the various bushings, but note the final installed diameter (once the inner sleeve is installed) and hence a variance in installed OD, therefore interference. Are all the steel sleeves and bushing ID's comparable, or different as well? Does it matter?
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PostPost by: Roland » Tue May 12, 2020 9:23 pm

Bill,

The PU bushes are meant to work as a bearing with the PU bush rotating around the SS tube, at least that is my understanding. The problem is my PU bush is so tight in the wishbone that it has elongated and the pin hole closed up. I don’t expect the SS tube to slide in but it is a really tight fit and I get an further elongation of the bush when fitted. The SS tube is then 0.8 mm shorter than the bush.

Once this is bolted up on the car I can move the wishbone with a breaker bar but the movement is jerky not progressive. Obviously the real suspension forces are large and this arrangement may move smoother but I think it would result in harshness. My conclusion is that this is due to me getting clamping forces on the PU bush rather than the SS tube. I don’t disagree with you that perhaps this will all work fine but I am fitting new TTR fast road springs and dampers and don’t want to risk spoiling this set up.

The guys who make their own bushes seem to say fit is critical on PU bushes and seem to aim for the SS tube being 5 to 10 thou longer than the bush installed in the wishbone. I can see that this results in virtually all the clamping force going onto SS tube and the whole arrangement acting as a bearing with progressive movement.

I think the two bush manufacturers I quoted internal bush hole diameters are the same before the bush is installed in the wishbone.However once installed the internal holes diameters will be different because the external diameters are different and the holes will close to different extents. The SS tube diameter size are the same.

I am just not convinced the fitted Superflex bushes will work well on my car and will remove them and fit the Autobush bushes. Notte the Superflexes have smooth internal bores but the Autobush ones are knurled to hold the grease, for me this is also better design feature.

R
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PostPost by: 74Twincam » Tue May 12, 2020 9:52 pm

Ok, I understand a bit better, thank you.
I’ll see how mine end up when complete, you have me curious now. There’s some difference between them as a set after installing in the arms, I’ll have to take a closer look.
Good luck, I’ll be interested to see how it goes for you!
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