RUMCars Forum
General Category => Unusual Microcar Discussion => Topic started by: Bob Purton on February 17, 2014, 12:47:32 PM
-
A few vintage microcars use rubber silent blocks as bearings in the steering system like Isetta and Nobel /Fulda Etc. Has anyone here replaced those with rod ends? I ask as I have a theory that the silent blocks were used for cheapness rather than serving a useful purpose. I could be entirely wrong. What do you think?
-
Well, they were probably cheaper but they did serve a useful purpose, which most likely was to supply the function of a rod end with a lower cost at the expense of long term reliability. Given the choice of either with no budget constraints, I would choose the rod ends for a more positive road handling. The Isetta steering is a bit "spongy" even with new silent blocs.
also- you have currently have a hypothesis, not a theory. ::)
-
also- you have currently have a hypothesis, not a theory. ::)
Sounds nasty; do you need a rubber ring to sit on with one of these? ;D
-
Do you tighten the silent blocks up (pointing straight ahead) or leave the pin to rotate? If I remember, it's not a shoulder screw that goes through the silent block. A shoulder screw would give a precise clearance.
-
Barry did you mean is it not rather than it's not ? Why shouldn't bob have a hypothesis ? Like himself they are largely vegetarian and with all this flooding what an ideal pet , though best kept outside and mind those big teeth ;D
-
also- you have currently have a hypothesis, not a theory. ::)
Sounds nasty; do you need a rubber ring to sit on with one of these? ;D
I have some ointment for that somewhere!
-
Silent blocks verses rod ends.
Sounds like someone needs a lot of help with their toilet pan ;D
-
Do you tighten the silent blocks up (pointing straight ahead) or leave the pin to rotate? If I remember, it's not a shoulder screw that goes through the silent block. A shoulder screw would give a precise clearance.
With both isettas and Nobels the pin is tightened down so as to lock the centre tube, as you say, done with the wheels facing straight ahead. All the movement takes place in the rubber. Now, with the Nobel there are six of these silent blocks in the steering system so assuming the pins are not rotating in the centre tubes[they usually end up doing this] there is quite a lot of resistance when you turn the steering wheel. No wonder the steering racks wear out! I raised this issue because I have replaced four out of the six in my Nobel with rod ends and just wondered if anyone else had done this. I know a few guys have used rod ends on the Isetta tie rod with no ill effect. Any thoughts?
As silent blocks were cheaper than rod endsin the 1950's the hypotheses becomes tested and is theory although as we all know a theory can be disproved. That's my argument and I'm sticking to it! ::) Just for the record.
-
With both isettas and Nobels the pin is tightened down so as to lock the centre tube, as you say, done with the wheels facing straight ahead.
Are they? I seem to recall both have shouldered steering bush bolts, like the Trienkel. The Trienkel has a castellated nut and split pin. I used to be certain of buying high quality silent blocks - readily available size on the Trienkel (For some reason the Club refused to believe this and made the part, badly, for three times the price. I bought in the real thing for a few quid. Somebody made a few bob there. Eventually they sold those off at a loss, as no one wanted them, and Dave and I, who used the right ones, bought the lot as we new what else they fitted and some installations needed no great accuracy, so I made a few bob there. Plus continuing to sell the correct bush the club still did not stock). The center tube is slightly longer and mounted with washers the bolt was done up to kiss the bloc. It therefore rotated about the shoulder bolt and center of the bloc in grease. One finger steering. Two sets of replaceable parts that were cheap to make. It works well. The Schmitt is similar, but uses a plastic material, latterly, that is more sacrificial in favour of the bolt.
If the steering bolts are shouldered and longer than the block depth and the bolt locked in some way it would suggest it should have a silent block that has a longer center than outer and the same rules apply. If the center is not proud then the washer will probably foul as the rubber flexes in use. Without the washers it will work, but I have them if I can as any failure of the rubber insert is not going to see a fast loss of the bushing material and a potential accident as I chose one large enough to cover the outside of the insert, if room. Of course if the steering is aligned badly by design than a free rotating system will not work since the excess flex will be upset. If really poor it will effect the steering and suspension geametry - see Tri Tech, despite ball joints. That is called crap engineering.
To lock up the steering and drive through rubber in torsion sound a pretty crap idea and might go part way to explain why I fail to enjoy driving Nobs and Isettas. In neither case did I ever get as far as pulling the steering apart to effect a result I wanted. I realized I did not like them and moved on. Stock came in, and went out, to MOT standard if on the road. Thereby showing the advantage, and extra asking price, of a car I have been using as such things get sorted out so they work.
Secondly by having rigid steering the input from caster settings, tracking, tyres and trike instability must be awful - thinks - yep, it was. The Nobel that went straight on at the Mini Roundabout being the worst case.
The Trienkel had two issues. The rubber mounted engine frame could move on cornering. The rear drums tended to work loose, in a bad case the short axle would have worn splines and need stuffing with compound (Again a problem the Club could simply resolve by supplying a hard steel bearing spacer, in place of the soft steel one that deforms under the loading. Its a design and materials fault that can be resolved for pennies. To date this has not happened). So resolving the issues mentioned and setting the steering up well the Trienkel handles as well as its front dampers will allow, which is fast at the risk of having an emergency and asking to much of the front suspension and rolling. So driver skill and risk assessment, but they are better than many think. The cure for that front suspension is whole other problem.
-
yes with both cars the centre tube locks tight, the tube is not a bearing fit and should not rotate on the loosely fitting pin. Centre tubes are longer than the outer. I agree about the parts alignment though. This is why I left silent blocks on the Nobel steering arm linkage as the angles created look a little iffy! I have only replaced the four on the track rods. With all new bushes, rod ends, steering centre pin and an adjustment of the rack and pinion my car now has zero free play in the system. More than I can say for the Isetta! I wasn't even aware that the rack was adjustable but the bushes that the pinion rotate in have an off centre hole so if you rotate the bushes you can lower or raise the pinion onto or away from the rack. I think this is done and then set in the manufacturing process as the two grub screws that lock the bushes have pointed ends that drop into dimples on the side of the bushes. I made new bushes using a four jaw chuck then adjusted them up before drilling the dimples in the new position. This took all the loose play out of the rack.
-
Great dialogue going here!
However, Bob, a picture is worth a thousand words, and would help me see what I should do next to improve the steering on my Nobels.
I bumped into their intended non user adjustable steering racks adjustment setting by accident once. After dissembling, inspecting, cleaning, and reassembling my Nobel's rack, for the first time- I noticed to my horror that the rack movement had mysteriously become fully bound.
I eventually figured out by process of elimination, that the apparent symmetry of the center bushe's bore was a lie as revealed by my vernier caliper with dial indicator's measurements, and got it back to working.
I did, however, achieve a huge degree of steering improvement by building a simple bracket that kept the rack from counter rotating when the steering wheel was turned hard. This was most noticeable at low or no speed, as a non rotating tire's contact patch could resist steering input en mass, whilst a more rapidly rotating road wheel would more easily yield to steering input of smaller increment per rotation. Prior to installing my simplistic bracket, the effect was so strong, that at standstill the steering wheel could be suddenly turned to full lock without continuing to effect the steering angles of the road wheels.
You show me your fixes, and then I will show you mine.
-
I should have pointed out that the Trienkel info is the way I did it. I forget what the manual says. When you actually use these things you find the best way by experience and it is not always the prescribed way in a book. It was good enough for Mick Leeson, so good enough for me.
-
Steve, was the whole pedal box moving or just the rack and pinion? I have not encountered that problem on any of the Nobels I have owned.
-
Just the rack would counter rotate to the direction of turning the steering wheel when at standstill.
This was no doubt related to the fact that the rack was only clasped by a more central mount that was easier to twist upon than turning the road wheels about their pivot axis.
-
Well I rebuilt my pedal box as it was half rotted away and may have used stouter steel for the brackets holding the R&P. Whilst about it I modified how the pedals attach and move in the pedal box. I never liked how the pedals were just bolted individually to a plate and found they would always flop from side to side a little which was disconcerting when driving. My mod involved having all the pedals move on one shaft using pieces of tube as baring's. see pic.
-
Good work!
Got pictures of your rod ends?
-
I'm not the worlds neatest welder but nothing has ever dropped off! Here is a shot of the rod ends although a rod end is a rod end.. I intend to fit the rubber boots that McGill Motor sport sell to keep the dirt out of them.
You may not recognize the track rods [Americans call them tie rods I think] Again, the ones I had were very badly corroded and as the eyes on each end are lightly welded on I didn't want to trust them so made new ones.. I used some new earthing rods I spotted in the local scrap metal yard, what you drive into the ground for electrical systems. They are half inch diameter mild steel solid rods with a copper coating which is easily turned off on the lathe. I then bought a pair of short turn buckles which I cut in half and welded to either end of the rods to get the left and right hand threads, it was cheaper to do this than buy a left handed M10 tap! I didn't just weld them end to end you understand, I bored them and turned the end of the rods down to insert then welded around the shoulder. Much stronger that way. The new set up will weigh a little more but at least I'm confident they are strong enough for the job. Despite all the afore mentioned I'm not really one for modifications and like my cars original but as its a project car and I'm using all the rubbish left overs it kind of lends its self to some artistic license.
-
Bot pic is the item I fought most on Nobs. The transfer of the steering from inside to outside. Every car I had suffered play here. It takes a lot of strain, especially if the working system is winding up several rubbers. It would appear not to have been man enough for the job.
The rack was not such a source of issues as it is, as you point out, adjustable. Bit like the Heinkel, with offset bushings. In the Heinkel these are carried in rubbers and the insert rotates inside these. A very neat steering rack results, few parts, light and accurate. Then you look at other manufacturers efforts and have to snigger and the complex things they cam up with. Think Ernst wins this one even over my beloved Goggo, which does have a flaw to trap the unwary. If I had been doing the Bobette I would have been tempted to ditch the Nob system for the Heinkel one as long is it mounted in the correct place outside. Half the joints are gone directly. The top bush is a better job too.
Hmm, all the best bits of microdesign in one car. What would that look like? No, it would not be a Messerschmitt Tiger before its said! AC Type 70? ;D ;D ;D
-
Well you know what owners of microcars were like in the 60's. Nobody ever serviced there cars! That transfer arm and bushes have a nice big grease nipple on them but how many of them ever saw a grease gun? Mine in the picture is a whole new steel tub with new bushes and pin. I used oilite bushes , don't know if they will fare any better but at least they will not be tugging against six silent blocks! I was considering a different rack until I sorted this one out. Lets start a new thread on the ideal parts microcar.
-
Indeed composite car elsewhere.
Likewise renewing the system gives it a chance to show what it can do. Maybe regular servicing will find it live long, maybe it is a weak design. There is interest in proving it on its own account despite the rest of the vehicle. I am sure you have enjoyed the rebuild as well.
Wish Dad had schooled me on machine tools, but he was very reluctant, despite being good in his younger days before management and an MSc called after the war. That generation who did wartime reserved occupation were very skilled. To the extent that when a part of Fairey went on strike he, and the other managers, all time served, went into the machine shop to finish a rush order and turned it round faster and to a higher quality than the men. Needless to say the strike was somewhat undermined by that and the immediate man management taken much more seriously. Several of those guys become some of Dad's 'young men' and built good carriers off the floor. Clearly he considered I had not the natural ability. Humph.
-
Its not too late Al. I'm self taught and that's why I'm not that good truth be known. With me its more craft based as a carry over from restoration work. Going back to Nobel steering lever bearings, with that massive pin and fossy bronze bushes its hard to see why they did wear out, one reason could be road grit getting into the grease as it open to the elements under the car. I was going to say "just a theory" but I dont want to tempt Jims pedantic side.
-
You are right.
Both you and Al are blessed with a similarly high degree of intuitive engineering sense.
I have often wished to have enough space in the garage for a compact lathe/ mill/ drill, as my sharing of your perfectionism (blessing or curse that it be), leads me to believe that respectable machining would be an inevitable eventual result of such an arrangement.
-
It is often assumed that rod ends are a superior product but they don't have a very long lifespan if used under a car in a British winter with salt, grit, etc. Possibly no problem for a hobby car if it will mostly see only fair days.
There are sealed rod ends available that overcome the problem but they tend to be very expensive if engineering products or to have appalling levels of friction if they are automotive track rod ends. They were used in motorcycle 'funny front ends' where the friction caused a serious weave, and the back yard mechanic technique was to put the taper pin in a drill chuck and 'run them in' until the friction dropped.